ProtoDUNE begins liquid argon filling (Image: CERN)

This will be a significant step towards testing ProtoDUNE for the next era of neutrino research

CERN’s Neutrino Platform houses a prototype of the Deep Underground Neutrino Experiment (DUNE) known as ProtoDUNE, which is designed to test and validate the technologies that will be applied to the construction of the DUNE experiment in the United States.

Recently, ProtoDUNE has entered a pivotal stage: the filling of one of its two particle detectors with liquid argon. Filling such a detector takes almost two months, as the chamber is gigantic – almost the size of a three-storey building. ProtoDUNE’s second detector will be filled in the autumn.

ProtoDUNE will use the proton beam from the Super Proton Synchrotron to test the detecting of charged particles. This argon-filled detector will be crucial to test the detector response for the next era of neutrino research. Liquid argon is used in DUNE due to its inert nature, which provides a clean environment for precise measurements. When a neutrino interacts with argon, it produces charged particles that ionise the atoms, allowing scientists to detect and study neutrino interactions. Additionally, liquid argon's density and high scintillation light yield enhance the detection of these interactions, making it an ideal medium for neutrino experiments.

Interestingly, the interior of the partially filled detector now appears green instead of its usual golden colour. This is because when the regular LED light is reflected inside the metal cryostat, the light travels through the liquid argon and the wavelength of the photons is shifted, producing a visible green effect.

The DUNE far detector, which will be roughly 20 times bigger than protoDUNE, is being built in the United States. DUNE will send a beam of neutrinos from Fermi National Accelerator Laboratory (Fermilab) near Chicago, Illinois, over a distance of more than 1300 kilometres through the Earth to neutrino detectors located 1.5 km underground at the Sanford Underground Research Facility (SURF) in Lead, South Dakota.

Watch a short time-lapse video of protoDUNE being filled with liquid argon: https://youtu.be/FweOvhKsqaM

Planet-forming discs in three clouds of the Milky Way - image credit: ESO

ESO, 5th March 2024. In a series of studies, a team of astronomers has shed new light on the fascinating and complex process of planet formation. The stunning images, captured using the European Southern Observatory's Very Large Telescope (ESO’s VLT) in Chile, represent one of the largest ever surveys of planet-forming discs. The research brings together observations of more than 80 young stars that might have planets forming around them, providing astronomers with a wealth of data and unique insights into how planets arise in different regions of our galaxy.

“This is really a shift in our field of study,” says Christian Ginski, a lecturer at the University of Galway, Ireland, and lead author of one of three new papers published today in Astronomy & Astrophysics. “We’ve gone from the intense study of individual star systems to this huge overview of entire star-forming regions.”

To date more than 5000 planets have been discovered orbiting stars other than the Sun, often within systems markedly different from our own Solar System. To understand where and how this diversity arises, astronomers must observe the dust- and gas-rich discs that envelop young stars — the very cradles of planet formation. These are best found in huge gas clouds where the stars themselves are forming.

Much like mature planetary systems, the new images showcase the extraordinary diversity of planet-forming discs. “Some of these discs show huge spiral arms, presumably driven by the intricate ballet of orbiting planets,” says Ginski. “Others show rings and large cavities carved out by forming planets, while yet others seem smooth and almost dormant among all this bustle of activity,” adds Antonio Garufi, an astronomer at the Arcetri Astrophysical Observatory, Italian National Institute for Astrophysics (INAF), and lead author of one of the papers.

The team studied a total of 86 stars across three different star-forming regions of our galaxy: Taurus and Chamaeleon I, both around 600 light-years from Earth, and Orion, a gas-rich cloud about 1600 light-years from us that is known to be the birthplace of several stars more massive than the Sun. The observations were gathered by a large international team, comprising scientists from more than 10 countries.

The team was able to glean several key insights from the dataset. For example, in Orion they found that stars in groups of two or more were less likely to have large planet-forming discs. This is a significant result given that, unlike our Sun, most stars in our galaxy have companions. As well as this, the uneven appearance of the discs in this region suggests the possibility of massive planets embedded within them, which could be causing the discs to warp and become misaligned.

While planet-forming discs can extend for distances hundreds of times greater than the distance between Earth and the Sun, their location several hundreds of light-years from us makes them appear as tiny pinpricks in the night sky. To observe the discs, the team employed the sophisticated Spectro-Polarimetric High-contrast Exoplanet REsearch instrument (SPHERE) mounted on ESO’s VLT. SPHERE’s state-of-the-art extreme adaptive optics system corrects for the turbulent effects of Earth’s atmosphere, yielding crisp images of the discs. This meant the team were able to image discs around stars with masses as low as half the mass of the Sun, which are typically too faint for most other instruments available today. Additional data for the survey were obtained using the VLT’s X-shooter instrument, which allowed astronomers to determine how young and how massive the stars are. The Atacama Large Millimeter/submillimeter Array (ALMA), in which ESO is a partner, on the other hand, helped the team understand more about the amount of dust surrounding some of the stars.

As technology advances, the team hopes to delve even deeper into the heart of planet-forming systems. The large 39-metre mirror of ESO’s forthcoming Extremely Large Telescope (ELT), for example, will enable the team to study the innermost regions around young stars, where rocky planets like our own might be forming. 

For now, these spectacular images provide researchers with a treasure trove of data to help unpick the mysteries of planet formation. “It is almost poetic that the processes that mark the start of the journey towards forming planets and ultimately life in our own Solar System should be so beautiful,” concludes Per-Gunnar Valegård, a doctoral student at the University of Amsterdam, the Netherlands, who led the Orion study. Valegård, who is also a part-time teacher at the International School Hilversum in the Netherlands, hopes the images will inspire his pupils to become scientists in the future.

More information

This research was presented in three papers to appear in Astronomy & Astrophysics. The data presented were gathered as part of the SPHERE consortium guaranteed time programme, as well as the DESTINYS (Disk Evolution Study Through Imaging of Nearby Young Stars) ESO Large Programme.

1. “The SPHERE view of the Chamaeleon I star-forming region: The full census of planet-forming disks with GTO and DESTINYS programs” (https://www.aanda.org/10.1051/0004-6361/202244005)

The team is composed of C. Ginski (University of Galway, Ireland; Leiden Observatory, Leiden University, the Netherlands [Leiden]; Anton Pannekoek Institute for Astronomy, University of Amsterdam, the Netherlands [API]), R. Tazaki (API), M. Benisty (Univ. Grenoble Alpes, CNRS, IPAG, France [Grenoble]), A. Garufi (INAF, Osservatorio Astrofisico di Arcetri, Italy), C. Dominik (API), Á. Ribas (European Southern Observatory, Chile [ESO Chile]), N. Engler (ETH Zurich, Institute for Particle Physics and Astrophysics, Switzerland), J. Hagelberg (Geneva Observatory, University of Geneva, Switzerland), R. G. van Holstein (ESO Chile), T. Muto (Division of Liberal Arts, Kogakuin University, Japan), P. Pinilla (Max-Planck-Institut für Astronomie, Germany [MPIA]; Mullard Space Science Laboratory, University College London, UK), K. Kanagawa (Department of Earth and Planetary Sciences, Tokyo Institute of Technology, Japan), S. Kim (Department of Astronomy, Tsinghua University, China), N. Kurtovic (MPIA), M. Langlois (Centre de Recherche Astrophysique de Lyon, CNRS, UCBL, France), J. Milli (Grenoble), M. Momose (College of Science, Ibaraki University, Japan [Ibaraki]), R. Orihara (Ibaraki), N. Pawellek (Department of Astrophysics, University of Vienna, Austria), T. O. B. Schmidt (Hamburger Sternwarte, Germany), F. Snik (Leiden), and Z. Wahhaj (ESO Chile).

2. “The SPHERE view of the Taurus star-forming region: The full census of planet-forming disks with GTO and DESTINYS programs” (https://www.aanda.org/10.1051/0004-6361/202347586)

The team is composed of A. Garufi (INAF, Osservatorio Astrofisico di Arcetri, Italy [INAF Arcetri]), C. Ginski (University of Galway, Ireland), R. G. van Holstein (European Southern Observatory, Chile [ESO Chile]), M. Benisty (Laboratoire Lagrange, Université Côte d’Azur, Observatoire de la Côte d’Azur, CNRS, France; Univ. Grenoble Alpes, CNRS, IPAG, France [Grenoble]), C. F. Manara (European Southern Observatory, Germany), S. Pérez (Millennium Nucleus on Young Exoplanets and their Moons [YEMS]; Departamento de Física, Universidad de Santiago de Chile, Chile [Santiago]), P. Pinilla (Mullard Space Science Laboratory, University College London, UK), A. Ribas (Institute of Astronomy, University of Cambridge, UK), P. Weber (YEMS, Santiago), J. Williams (Institute for Astronomy, University of Hawai‘i, USA), L. Cieza (Instituto de Estudios Astrofísicos, Facultad de Ingeniería y Ciencias, Universidad Diego Portales, Chile [Diego Portales]; YEMS), C. Dominik (Anton Pannekoek Institute for Astronomy, University of Amsterdam, the Netherlands [API]), S. Facchini (Dipartimento di Fisica, Università degli Studi di Milano, Italy), J. Huang (Department of Astronomy, Columbia University, USA), A. Zurlo (Diego Portales; YEMS), J. Bae (Department of Astronomy, University of Florida, USA), J. Hagelberg (Observatoire de Genève, Université de Genève, Switzerland), Th. Henning (Max Planck Institute for Astronomy, Germany [MPIA]), M. R. Hogerheijde (Leiden Observatory, Leiden University, the Netherlands; API), M. Janson (Department of Astronomy, Stockholm University, Sweden), F. Ménard (Grenoble), S. Messina (INAF - Osservatorio Astrofisico di Catania, Italy), M. R. Meyer (Department of Astronomy, The University of Michigan, USA), C. Pinte (School of Physics and Astronomy, Monash University, Australia; Grenoble), S. Quanz (ETH Zürich, Department of Physics, Switzerland [Zürich]), E. Rigliaco (Osservatorio Astronomico di Padova, Italy [Padova]), V. Roccatagliata (INAF Arcetri), H. M. Schmid (Zürich), J. Szulágyi (Zürich), R. van Boekel (MPIA), Z. Wahhaj (ESO Chile), J. Antichi (INAF Arcetri), A. Baruffolo (Padova), and T. Moulin (Grenoble).

3. “Disk Evolution Study Through Imaging of Nearby Young Stars (DESTINYS): The SPHERE view of the Orion star-forming region” (https://www.aanda.org/10.1051/0004-6361/202347452)

The team is composed of P.-G. Valegård (Anton Pannekoek Institute for Astronomy, University of Amsterdam, the Netherlands [API]), C. Ginski (University of Galway, Ireland), A. Derkink (API), A. Garufi (INAF, Osservatorio Astrofisico di Arcetri, Italy), C. Dominik (API), Á. Ribas (Institute of Astronomy, University of Cambridge, UK), J. P. Williams (Institute for Astronomy, University of Hawai‘i, USA), M. Benisty (University of Grenoble Alps, CNRS, IPAG, France), T. Birnstiel (University Observatory, Faculty of Physics, Ludwig-Maximilians-Universität München, Germany [LMU]; Exzellenzcluster ORIGINS, Germany), S. Facchini (Dipartimento di Fisica, Università degli Studi di Milano, Italy), G. Columba (Department of Physics and Astronomy "Galileo Galilei" - University of Padova, Italy; INAF – Osservatorio Astronomico di Padova, Italy), M. Hogerheijde (API; Leiden Observatory, Leiden University, the Netherlands [Leiden]), R. G. van Holstein (European Southern Observatory, Chile), J. Huang (Department of Astronomy, Columbia University, USA), M. Kenworthy (Leiden), C. F. Manara (European Southern Observatory, Germany), P. Pinilla (Mullard Space Science Laboratory, University College London, UK), Ch. Rab (LMU; Max-Planck-Institut für extraterrestrische Physik, Germany), R. Sulaiman (Department of Physics, American University of Beirut, Lebanon), A. Zurlo (Instituto de Estudios Astrofísicos, Facultad de Ingeniería y Ciencias, Universidad Diego Portales, Chile; Escuela de Ingeniería Industrial, Facultad de Ingeniería y Ciencias, Universidad Diego Portales, Chile; Millennium Nucleus on Young Exoplanets and their Moons).

The European Southern Observatory (ESO) enables scientists worldwide to discover the secrets of the Universe for the benefit of all. We design, build and operate world-class observatories on the ground — which astronomers use to tackle exciting questions and spread the fascination of astronomy — and promote international collaboration for astronomy. Established as an intergovernmental organisation in 1962, today ESO is supported by 16 Member States (Austria, Belgium, Czechia, Denmark, France, Finland, Germany, Ireland, Italy, the Netherlands, Poland, Portugal, Spain, Sweden, Switzerland and the United Kingdom), along with the host state of Chile and with Australia as a Strategic Partner. ESO’s headquarters and its visitor centre and planetarium, the ESO Supernova, are located close to Munich in Germany, while the Chilean Atacama Desert, a marvellous place with unique conditions to observe the sky, hosts our telescopes. ESO operates three observing sites: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope and its Very Large Telescope Interferometer, as well as survey telescopes such as VISTA. Also at Paranal ESO will host and operate the Cherenkov Telescope Array South, the world’s largest and most sensitive gamma-ray observatory. Together with international partners, ESO operates ALMA on Chajnantor, a facility that observes the skies in the millimetre and submillimetre range. At Cerro Armazones, near Paranal, we are building “the world’s biggest eye on the sky” — ESO’s Extremely Large Telescope. From our offices in Santiago, Chile we support our operations in the country and engage with Chilean partners and society. 

The Atacama Large Millimeter/submillimeter Array (ALMA), an international astronomy facility, is a partnership of ESO, the U.S. National Science Foundation (NSF) and the National Institutes of Natural Sciences (NINS) of Japan in cooperation with the Republic of Chile. ALMA is funded by ESO on behalf of its Member States, by NSF in cooperation with the National Research Council of Canada (NRC) and the National Science and Technology Council (NSTC) in Taiwan and by NINS in cooperation with the Academia Sinica (AS) in Taiwan and the Korea Astronomy and Space Science Institute (KASI). ALMA construction and operations are led by ESO on behalf of its Member States; by the National Radio Astronomy Observatory (NRAO), managed by Associated Universities, Inc. (AUI), on behalf of North America; and by the National Astronomical Observatory of Japan (NAOJ) on behalf of East Asia. The Joint ALMA Observatory (JAO) provides the unified leadership and management of the construction, commissioning and operation of ALMA. 

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• Research papers: Chamaeleon, Taurus, Orion
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At the Joint European Torus (JET) in the UK, a European research team has succeeded in generating 69 megajoules of energy from 0.2 milligrams of fuel. This is the largest amount of energy ever achieved in a fusion experiment.

Fusion power plants are designed to fuse light atomic nuclei, following the example of the sun, in order to harness huge amounts of energy for humanity from very small amounts of fuel. The European research consortium EUROfusion is pursuing the concept of magnetic fusion, which is considered by experts to be the most advanced. With the large-scale experiments ASDEX Upgrade and Wendelstein 7-X, the Max Planck Institute for Plasma Physics (IPP) is driving forward research into this in Germany.

For experiments with the fuel of future power plants (deuterium and tritium), Europe's scientists operated the JET research facility near Oxford together with the UK Atomic Energy Authority (UKAEA). A new world record was set there on 3 October 2023: 69 megajoules of fusion energy were released in the form of fast neutrons during a 5.2 second plasma discharge. 0.2 milligrams of fuel were required for this. The same amount of energy would have required about 2 kilograms of lignite – ten million times as much. JET thus beat its own record from 2021 (59 megajoules in 5 seconds).

"This world record is actually a by-product. It was not actively planned, but we were hoping for it," explains IPP scientist Dr Athina Kappatou, who worked for JET as one of nine Task Force Leaders. "This experimental campaign was mainly about achieving the different conditions necessary for a future power plant and thus testing realistic scenarios. One positive aspect, however, was that the experiments from two years ago could also be successfully reproduced and even surpassed." The latter was the case with the record-breaking experiment. The entire campaign is essential for the future operation of the international fusion plant ITER, which is currently being built in southern France, as well as for the planned European demonstration power plant DEMO. Over 300 scientists and engineers from EUROfusion contributed to these landmark experiments.

The JET record did not achieve a positive energy balance – in other words, more heating energy had to be invested in the plasma than fusion energy was generated. In fact, an "energy gain" is physically impossible with JET and all other current magnetic fusion experiments worldwide. For a positive energy balance, these fusion plants must exceed a certain size, which will be the case with ITER.

The record-breaking experiment (JET pulse #104522) in the autumn was one of the last ever at JET. After four decades the facility ceased operations at the end of 2023.

Review in Nature Review Physics discusses major challenges in the field of superheavy elements and their nuclei and provides an outlook on future developments

Since the turn of the century, six new chemical elements have been discovered and subsequently added to the periodic table of elements, the very icon of chemistry. These new elements have high atomic numbers up to 118 and are significantly heavier than uranium, the element with the highest atomic number (92) found in larger quantities on Earth. This raises questions such as how many more of these superheavy species are waiting to be discovered, where – if at all – is a fundamental limit in the creation of these elements, and what are the characteristics of the so-called island of enhanced stability. In a recent review, experts in theoretical and experimental chemistry and physics of the heaviest elements and their nuclei summarize the major challenges and offer a fresh view on new superheavy elements and the limit of the periodic table. One of them is Professor Christoph Düllmann from the GSI Helmholtzzentrum für Schwerionenforschung in Darmstadt, Johannes Gutenberg University Mainz, and the Helmholtz Institute Mainz (HIM). In its February issue, the world's leading high-impact journal Nature Review Physics presents the topic as its cover story.

Visualizing an island of stability of superheavy nuclei

Already in the first half of the last century, researchers realized that the mass of atomic nuclei is smaller than the total mass of their proton and neutron constituents. This difference in mass is responsible for the binding energy of the nuclei. Certain numbers of neutrons and protons lead to stronger binding and are referred to as “magic”. In fact, scientists observed early on that protons and neutrons move in individual shells that are similar to electronic shells, with nuclei of the metal lead being the heaviest with completely filled shells containing 82 protons and 126 neutrons – a doubly-magic nucleus. Early theoretical predictions suggested that the extra stability from the next “magic” numbers, far from nuclei known at that time, might lead to lifetimes comparable to the age of the Earth. This led to the notion of a so-called island of stability of superheavy nuclei separated from uranium and its neighbors by a sea of instability.

There are numerous graphical representations of the island of stability, depicting it as a distant island. Many decades have passed since this image emerged, so it is time to take a fresh look at the stability of superheavy nuclei and see where the journey to the limits of mass and charge might lead us. In their recent paper titled "The quest for superheavy elements and the limit of the periodic table", the authors describe the current state of knowledge and the most important challenges in the field of these superheavies. They also present key considerations for future development.

Elements up to oganesson (element 118) have been produced in experiments, named, and included in the periodic table of elements in accelerator facilities around the world, such as at GSI in Darmstadt and in future at FAIR, the international accelerator center being built at GSI. These new elements are highly unstable, with the heaviest ones disintegrating within seconds at most. A more detailed analysis reveals that their lifetimes increase towards the magic neutron number 184. In the case of copernicium (element 112), for example, which was discovered at GSI, the lifetime increases from less than a thousandth of a second to 30 seconds. However, the neutron number 184 is still a long way from being reached, so the 30 seconds are only one step on the way. Since the theoretical description is still prone to large uncertainties, there is no consensus on where the longest lifetimes will occur and how long they will be. However, there is a general agreement that truly stable superheavy nuclei are no longer to be expected.

Revising the map of superheavy elements

This leads to a revision of the superheavy landscape in two important ways. On the one hand, we have indeed arrived at the shores of the region of enhanced stability and have thus confirmed experimentally the concept of an island of enhanced stability. On the other hand, we do not yet know how large this region is – to stay with the picture. How long will the maximum lifetimes be, with the height of the mountains on the island typically representing the stability, and where will the longest lifetimes occur? The Nature Reviews Physics paper discusses various aspects of relevant nuclear and electronic structure theory, including the synthesis and detection of superheavy nuclei and atoms in the laboratory or in astrophysical events, their structure and stability, and the location of the current and anticipated superheavy elements in the periodic table.

The detailed investigation of the superheavy elements remains an important pillar of the research program at GSI Darmstadt, supported by infrastructure and expertise at HIM and Johannes Gutenberg University Mainz, forming a unique setting for such studies. Over the past decade, several breakthrough results were obtained, including detailed studies of their production, which led to the confirmation of element 117 and the discovery of the comparatively long-lived isotope lawrencium-266, of their nuclear structure by a variety of experimental techniques, of the structure of their atomic shells as well as their chemical properties, where flerovium (element 114) represents the heaviest element for which chemical data exist. Calculations on production in the cosmos, especially during the merging of two neutron stars, as observed experimentally for the first time in 2017, round off the research portfolio. In the future, the investigation of superheavy elements could be even more efficient thanks to the new linear accelerator HELIAC, for which the first module was recently assembled at HIM and then successfully tested in Darmstadt, so that further, even more exotic and therefore presumably longer-lived nuclei will also be experimentally achievable. An overview of the element discoveries and first chemical studies at GSI can be found in the article “Five decades of GSI superheavy element discoveries and chemical investigation,” published in May 2022.

Geneva, January 25, 2024. Today CERN, the European Laboratory for Particle Physics, announced a programme to celebrate its 70th anniversary in 2024. This landmark year honours CERN's remarkable contributions to scientific knowledge, technological innovation and international collaboration in the field of particle physics. Throughout the year, a variety of events and activities will showcase the Laboratory’s rich past as well as its bright future.

Leading up to an official high-level ceremony on 1 October, the preliminary anniversary programme, spanning the entire year, offers a rich array of events and activities, aimed at all types of audiences, at CERN and in the Organization’s Member States and Associate Member States and beyond. The first public event, scheduled for 30 January, will combine science, art and culture, and will feature a panel of eminent scientists discussing the evolution of particle physics and CERN’s significant contributions in advancing this field. On 7 March and 18 April, special events will showcase the practical applications of high-energy physics research in everyday life. Mid-May will see a focus on the importance of global collaboration in scientific endeavours, while the events in June and July will explore the current unanswered questions in particle physics and the facilities being planned for future breakthroughs. From talks by distinguished scientists and exhibitions showing CERN’s cutting-edge research and the diversity of its science and its people, to public engagement initiatives worldwide, everyone will find something to enjoy in this programme.

“CERN’s achievements over the 70 years of its history show what humanity can do when we put aside our differences and focus on the common good”, says Fabiola Gianotti, CERN Director-General. “Through the celebrations of CERN’s 70^thanniversary, we will demonstrate how, over the past seven decades, CERN has been at the forefront of scientific knowledge and technological innovation, a model for training and education, collaboration and open science, and an inspiration for citizens around the world. This anniversary is also a great opportunity to look forward: CERN’s beautiful journey of exploration into the fundamental laws of nature and the constituents of matter is set to continue into the future with new, more powerful instruments and technologies.”

CERN came to life in 1954, in the aftermath of the Second World War, to bring excellence in scientific research back to Europe and to foster peaceful collaboration in fundamental research. This collective effort has pushed back the frontiers of human knowledge and of technology. As more powerful accelerators and experiments were built, foundational discoveries and innovations were made: among others, Georges Charpak revolutionised detection with his multiwire proportional chamber in 1968, the neutral currents were discovered in the 1970s, the W and Z bosons were discovered in 1983, the precision measurement of the Z boson and of other parameters of the electroweak theory was made in the 1990s thanks to the Large Electron Positron (LEP) collider, the Large Hadron Collider started up in 2009, and the Higgs boson was discovered in 2012. CERN is also the birthplace of the World Wide Web and has generated technologies that are used in other fields, including medical diagnostics and therapy and environmental protection.

Today, CERN counts 23 Member States, 10 Associate Member States and a vibrant community of 17,000 people from all over the world, with more than 110 nationalities represented. Currently, the Laboratory is home to the Large Hadron Collider, the world’s most powerful particle accelerator. Building on its remarkable legacy of research and technological development, CERN is already looking to the future, in particular by studying the feasibility of a Future Circular Collider.

“This anniversary year is for everyone and should engage and inspire scientists, policy makers and the public. We are looking forward to welcoming everyone at CERN for the many events being planned, but also to the celebrations in our Member States, Associate Member States and beyond”, says Luciano Musa, coordinator of the CERN 70^thanniversary. “These international events are a testament to CERN's impact on scientific knowledge, technological development and worldwide collaboration.”

CERN extends an invitation to everyone to take part in these inspiring events, which aim to kindle scientific curiosity, honour scientific progress and collaborative efforts, and underscore the role of science in society.

Join us in this year of celebration as we honour our glorious past and shape a bright future for CERN and its community.

For the complete CERN70 anniversary events and programme of activities, please visit: cern.ch/cern70. 

The deadline for nominations is 31st January 2024.

Statement by the Executive Committee of the European Physical Society about the organisation of the 2024 International Physics Olympiad in Tehran, Iran

14th December 2023

"The European Physical Society (EPS) supports the International Physics Olympiad, which provides a wonderful opportunity to gather promising young physicists from around the world to discuss physics and solve physics problems in a safe, peaceful, and collaborative atmosphere.

Nevertheless, the EPS asks the organisers of the upcoming International Physics Olympiad in 2024 to reconsider Tehran, Iran, as a suitable location. The EPS is deeply concerned about the actions of the Iranian regime, particularly its ongoing repression of women and girls, as well as the recent violent crackdowns on political protests. Such circumstances, the EPS believes, create an environment where the safety of future physicists cannot be assured and where the diversity found among physicists is not respected.

Supporting the International Physics Olympiad in Iran is an endorsement of the actions of the Iranian government. Consequently, the EPS cannot endorse the event if it is held in Iran and recommends relocating it to a country where democratic ideals are respected and all participants will be welcomed regardless of their nationality, religion, or gender identity."

Details about the position and the application procedure can be found at: https://fr.indeed.com/job/responsable-de-conf%C3%A9rences-hf-bef63c86a3a8b539

The ISOLDE set-up used to study the exotic nucleus of aluminium. (Image: CERN)

Geneva, 28th November 2023

Experiments at CERN and the Accelerator Laboratory inJyväskylä, Finland,haverevealed that the radius of an exoticnucleus ofaluminium,^26mAl, is much larger than previously thought. The result, described in a paper just published inPhysical Review Letters, sheds light on the effects of the weak force onquarks–the elementary particles that make upprotons,neutronsand other composite particles.

Among thefourknown fundamental forcesof nature–the electromagnetic force, the strong force, the weak force and gravity –the weakforcecan,with a certain probability, change the“flavour”ofaquark. The Standard Model of particle physics, which describes all particles and their interactions with one another, does not predict the value of this probability, but, for a given quark flavour, does predict thesum of allpossibleprobabilitiesto be exactly1. Therefore, the probability sum offers a way to test the Standard Model and search for new physics: if theprobabilitysum is found to be different from 1, itwould imply new physicsbeyond the Standard Model.

Interestingly, the probability sum involving the up quark is presently in apparent tension with the expected unity, although the strength of the tension depends on the underlying theoretical calculations.This sum includes the respective probabilities of the down quark, the strange quark and the bottom quark transforming into the up quark.

The first of these probabilities manifests itselfinthebeta decayof an atomic nucleus, in which a neutron (made of one up quark and two down quarks)changes into a proton (composed of two up quarks and one down quark)or vice versa.However, due to the complex structure of the atomic nuclei that undergo beta decays, an exact determination of this probability is generally not feasible. Researchers thus turn to a subset of beta decays that are less sensitive to the effects of nuclear structure to determine the probability. Among the several quantities that are needed to characterise such “superallowed” beta decays is the (charge) radius of the decaying nucleus.

This is where the new result for the radius of the^26mAlnucleus, which undergoes a superallowed beta decay, comes in. The result was obtained by measuring the response of the^26mAlnucleus to laser light in experiments conducted at CERN’s ISOLDE facility and the AcceleratorLaboratory’s IGISOL facility. The new radius, a weighted average of the ISOLDE and IGISOL datasets, is much larger than predicted, and the upshot is a weakening of the current apparent tension inthe probability sum involving the up quark.

“Charge radii of other nuclei that undergo superallowed beta decays have been measured previously at ISOLDE and other facilities, and efforts are under way to determine the radius of⁵⁴Co at IGISOL,”explains ISOLDE physicist and lead author of the paper, Peter Plattner. “But^26mAlis a rather unique case as, although it is the most precisely studied of such nuclei, its radius has remained unknown until now, and, as it turns out, it is much larger than assumed in the calculation of theprobability of the down quark transforming into the up quark.”

“Searches for new physics beyond the Standard Model, including those based on the probabilities of quarks changing flavour, are often a high-precision game,” says CERN theorist Andreas Juttner. “This result underlines the importance of scrutinising all relevant experimental and theoretical results in every possible way.”

Past and present particle physics experiments worldwide, including the LHCb experiment at the Large Hadron Collider, have contributed, and are continuing to contribute, significantly to our knowledge of the effects of the weak force on quarks through the determination ofvarious probabilities of a quarkflavour change. However,nuclear physics experiments onsuperallowed beta decays currently offer the best way to determine theprobability of the down quark transforming into the up quark, and this may well remain the case for the foreseeable future.

Illustration of two types of long-lived particles decaying into a pair of muons, showing how the signals of the muons can be traced back to the long-lived particle decay point using data from the tracker and muon detectors. / Représentation graphique de deux types de particules à vie longue se désintégrant en paires de muons ; les signaux correspondant aux muons peuvent être associés au point où la particule à vie longue s'est désintégrée, à l’aide des données provenant du trajectographe et des détecteurs de muons. (Image: CMS/CERN)

Geneva, 13th november 2023

The CMS experiment has presented its first search for new physics using data from Run 3 of the Large Hadron Collider. The new study looks at the possibility of “dark photon” production in the decay of Higgs bosons in the detector. Dark photons are exotic long-lived particles: “long-lived” because they have an average lifetime of more than a tenth of a billionth of a second – a very long lifetime in terms of particles produced in the LHC – and “exotic” because they are not part of the Standard Model of particle physics. The Standard Model is the leading theory of the fundamental building blocks of the Universe, but many physics questions remain unanswered, and so searches for phenomena beyond the Standard Model continue. CMS’s new result defines more constrained limits on the parameters of the decay of Higgs bosons to dark photons, further narrowing down the area in which physicists can search for them.

In theory, dark photons would travel a measurable distance in the CMS detector before they decay into “displaced muons”. If scientists were to retrace the tracks of these muons, they would find that they don’t reach all the way to the collision point, because the tracks come from a particle that has already moved some distance away, without any trace.

Run 3 of the LHC began in July 2022 and has a higher instantaneous luminosity than previous LHC runs, meaning there are more collisions happening at any one moment for researchers to analyse. The LHC produces tens of millions of collisions every second, but only a few thousand of them can be stored, as recording every collision would quickly consume all the available data storage. This is why CMS is equipped with a real-time data selection algorithm called the trigger, which decides whether or not a given collision is interesting. Therefore, it is not only a higher volume of data that could help to reveal evidence of the dark photon, but also the way in which the trigger system is fine-tuned to look for specific phenomena.

“We have really improved our ability to trigger on displaced muons,” says Juliette Alimena from the CMS experiment. “This allows us to collect much more events than before with muons that are displaced from the collision point by distances from a few hundred micrometres to several metres. Thanks to these improvements, if dark photons exist, CMS is now much more likely to find them.”

The CMS trigger system has been crucial to this search, and was especially refined between Runs 2 and 3 to search for exotic long-lived particles. As a result, the collaboration has been able to use the LHC more efficiently, obtaining a strong result using just a third of the amount of data as previous searches. To do this, the CMS team refined the trigger system by adding a new algorithm called a non-pointing muon algorithm. This improvement meant that even with just four to five months of data from Run 3 in 2022, more displaced-muon events were recorded than in the much larger 2016–18 Run 2 dataset. The new coverage of the triggers vastly increases the momentum ranges of the muons that are picked up, allowing the team to explore new regions where long-lived particles may be hiding.

The CMS team will continue using the most powerful techniques to analyse all data taken in the remaining years of Run 3 operations, with the aim of further exploring physics beyond the Standard Model.

Statement by the Executive Committee of the EPS about the current situation in the Middle-East

2nd November 2023

We remain convinced of the fundamental importance of the free exchange of scientific ideas, transcending national boundaries, as a key vector for the progress of civilization. This progress is hindered by acts of violence which the EPS will always oppose. Fostering peaceful international cooperation, EPS played a founding role in the SESAME facility where both Israel and Palestine are represented and it created Young Minds sections in Palestine (Bethlehem) and Israel (Jerusalem).

We stand with our colleagues of the Israeli Physical Society, a Member Society of the EPS, and extend our heartfelt support to our Palestinian colleagues suffering in these dark times.

The experiment was conducted at the Radioactive Ion Beam Factory (RIBF) at the RIKEN research center in Japan. The ²⁸O nuclei were produced in collisions of accelerated ions of the radioactive fluorine isotope ²⁹F with a hydrogen target, in which a proton was shot out of the fluorine. Subsequently, the decay of the ²⁸O into ²⁴O and four neutrons had to be measured. Thanks to the utilization of the NeuLAND neutron detector setup, four neutrons could be observed in coincidence with the charged remnant nucleus for the first time.

“NeuLAND is being developed at GSI/FAIR and built with the participation of German university groups for the R3B experiment at the FAIR facility. For the current experiment, we flew the detector to RIKEN in Japan and recommissioned it on site,” explains Professor Thomas Aumann, who heads the Research department Nuclear Reactions at GSI/FAIR and holds a professorship for experimental nuclear physics with exotic ion beams at TU Darmstadt. “The realization required an extraordinary effort, in which the Darmstadt groups at GSI/FAIR and the TU Darmstadt made a central contribution.”

The most stable oxygen isotope is composed of eight protons and eight neutrons, while ²⁸O has eight protons and 20 neutrons. Understanding the properties of such extremely neutron-rich nuclei is of great importance for the further development and for tests of modern nuclear theories. These, in turn, form the basis for predicting and understanding properties of neutron-rich nuclei and neutron-rich nuclear matter, which play a major role in our universe, for example in the synthesis of the heavy elements. They are for example produced in collisions of neutron stars, which have recently been detected by multi-messenger astronomy using the measurement of gravitational waves.

“The result impressively highlights the relevance and contribution of the detector setups developed for FAIR, such as in this case the NeuLAND detector, which was essential to conduct the experiment,” says Professor Paolo Giubellino, Scientific Managing Director of GSI and FAIR. “Together with our Japanese colleagues, with whom we have a long-standing successful collaboration, and in an international team of top researchers, we were able to achieve this outstanding result, of which all involved can be very proud.”

The participation of German universities in the development and construction of the R3B NeuLAND detector was substantially supported through the BMBF's collaborative research program. The experiment was funded by the DFG through the collaborative research center SFB 1245 “Atomic nuclei: From Fundamental Interactions to Structure and Stars” at the TU Darmstadt.

Imagte credit: Niklas Elmehed © Nobel Prize Outreach

3rd October 2023 - Press release Nobel Prize Foundation

The Royal Swedish Academy of Sciences has decided to award the Nobel Prize in Physics 2023 to

Pierre Agostini
The Ohio State University, Columbus, USA

Ferenc Krausz
Max Planck Institute of Quantum Optics, Garching and Ludwig-Maximilians-Universität München, Germany

Anne L’Huillier
Lund University, Sweden

“for experimental methods that generate attosecond pulses of light for the study of electron dynamics in matter”

Experiments with light capture the shortest of moments

The three Nobel Laureates in Physics 2023 are being recognised for their experiments, which have given humanity new tools for exploring the world of electrons inside atoms and molecules. Pierre Agostini, Ferenc Krausz and Anne L’Huillier have demonstrated a way to create extremely short pulses of light that can be used to measure the rapid processes in which electrons move or change energy.

Fast-moving events flow into each other when perceived by humans, just like a film that consists of still images is perceived as continual movement. If we want to investigate really brief events, we need special technology. In the world of electrons, changes occur in a few tenths of an attosecond – an attosecond is so short that there are as many in one second as there have been seconds since the birth of the universe.

The laureates’ experiments have produced pulses of light so short that they are measured in attoseconds, thus demonstrating that these pulses can be used to provide images of processes inside atoms and molecules.

In 1987,Anne L’Huillier discovered that many different overtones of light arose when she transmitted infrared laser light through a noble gas. Each overtone is a light wave with a given number of cycles for each cycle in the laser light. They are caused by the laser light interacting with atoms in the gas; it gives some electrons extra energy that is then emitted as light. Anne L’Huillier has continued to explore this phenomenon, laying the ground for subsequent breakthroughs.

In 2001,Pierre Agostini succeeded in producing and investigating a series of consecutive light pulses, in which each pulse lasted just 250 attoseconds. At the same time,Ferenc Krausz was working with another type of experiment, one that made it possible to isolate a single light pulse that lasted 650 attoseconds.

The laureates’ contributions have enabled the investigation of processes that are so rapid they were previously impossible to follow.

“We can now open the door to the world of electrons. Attosecond physics gives us the opportunity to understand mechanisms that are governed by electrons. The next step will be utilising them,” says Eva Olsson, Chair of the Nobel Committee for Physics.

There are potential applications in many different areas. In electronics, for example, it is important to understand and control how electrons behave in a material. Attosecond pulses can also be used to identify different molecules, such as in medical diagnostics.

From left to right: President of the CERN Council, Eliezer Rabinovici, President of the Swiss Confederation, Alain Berset, CERN Director-General, Fabiola Gianotti, Chair of Stellantis, John Elkann, and architect, Renzo Piano, right after cutting the ribbon of Science Gateway, officially declaring the project open.

Geneva, 7 October 2023. Today, CERN inaugurated its new state-of-the-art facility for science education and outreach. In a day-long inauguration event, CERN debuted Science Gateway to the President of the Swiss Confederation, ministers and other high-level authorities from CERN’s Member and Associate Member States, the project’s donors and partners in CERN’s research, education and outreach. Designed by world-renowned Renzo Piano Building Workshop, the new facility is open to visitors from around the world, from the age of five and upwards. It will allow CERN to significantly expand its portfolio of educational and outreach activities. CERN Science Gateway will be open to the public as of tomorrow, 8 October 2023.

The inauguration ceremony began with an address by Fabiola Gianotti, the CERN Director-General, who stressed the value of education and outreach with the public. “Sharing CERN’s research and the beauty and utility of science with the public has always been a key objective and activity of CERN, and with Science Gateway, as of tomorrow, we can expand significantly this component of our mission. We want to show the importance of fundamental research and its applications to society, infuse everyone who comes here with curiosity and a passion for science, and inspire young people to take up careers in Science, Technology, Engineering and Mathematics (STEM)” she said. “Science Gateway will be a place where scientists and the public can interact daily. For me, personally, Science Gateway is a dream that has become a reality and I am deeply grateful to all the people who have contributed, starting with our generous donors.”

CERN, the European Laboratory for Particle Physics, is the home of the Large Hadron Collider, the world’s largest and most powerful particle accelerator.

In his address, the President of the Swiss Confederation, Alain Berset, said: “Those familiar with Venn diagrams will agree that this invisible circle puts CERN at the intersection between Switzerland, France and Europe, thus symbolising its commitment to shared scientific and political values. CERN truly is an exceptional facility and one that enables Switzerland and Geneva to shine on the world stage.”

The iconic building, inspired by the tubular structure of CERN’s accelerators, comprises five areas housing exhibitions, laboratories and an auditorium that can be flexibly configured into different spaces depending on requirements, as well as a shop and a restaurant. 

The transparent glass panels and bridges further represent CERN’s commitment to collaboration across borders and culture and open science that is accessible to all.

Renzo Piano, chief architect of the project, said: “This will be a place where people meet: kids, students, adults, teachers and scientists, everybody attracted by the exploration of the Universe, from the infinitely vast to the infinitely small. It is a bridge, in both a metaphorical and a real sense. This building is fed by the energy of the Sun, landed in the middle of a newly grown forest.”

Not only is the building visually striking, but CERN and the architects committed to it being fully carbon neutral, and almost 4000 square metres of solar panels supply more power than the building’s needs. Over 400 trees have been planted, situating the whole campus in a living forest. 

While the full project was launched in 2018, construction of the Science Gateway campus took just over two years, with the first stone of the building being laid on 21 June 2021.

This new facility would not have been possible without the generous support of the CERN Science Gateway sponsors, who share the same values and, through their contributions, want to pay tribute to education and knowledge for the benefit of society. The overall cost of Science Gateway was about 100 million Swiss francs, and this was funded exclusively through donations. In particular, the Stellantis Foundation is the largest single donor and contributed 45 million Swiss francs towards the project. John Elkann, Chairman of Stellantis, said: “CERN is an example of how we can work together in harmony, using scientific knowledge and ingenuity for the greater good. Stellantis Foundation is proud to partner with such an institution as it opens to the public the new Science Gateway, which also celebrates a great innovator like Sergio Marchionne. My family and I strongly believe in the power of education, which is the mission of the Fondazione Agnelli : a commitment we reinforce today with conviction and passion.”

As part of wider society, Stellantis takes action to advance human achievement. Stellantis, through its philanthropic activities and its Foundation, invests in individuals through education projects that spark innovation and excellence. 

The Fondation Hans Wilsdorf is also a major donor. Other donors are the LEGO foundation, the Loterie Romande, Ernst Göhner Stiftung, Rolex, the Carla Fendi Foundation, the Fondation Gelbert, Solvay, the Fondation Meyrinoise du Casino and the town of Meyrin. CERN thanks the République et Canton de Genève and the CERN and Society Foundation for their support.

The ceremony took place in the new 900-seat auditorium, named after Sergio Marchionne, former CEO of Fiat Chrysler Automobiles, who recently passed away. Guests visited the education laboratories and the unique immersive exhibitions and enjoyed the Big Bang Café, the Collider Circle square and other areas of the Science Gateway campus.

Throughout the day, guided by CERN scientists and children of CERN personnel, visitors were able to experience first-hand the range of Science Gateway’s opportunities, from interactive exhibitions to laboratories for hands-on experiments and immersive spaces. They also had the opportunity to appreciate CERN’s scientific breakthroughs and technologies, learn about the history of the Universe and admire the mysteries of the quantum world. Teenagers guided guests through various enquiry-based laboratory activities throughout the afternoon. 

Eliezer Rabinovici, President of the CERN Council, speaking on behalf of CERN’s Member and Associate Member States, said: “Today we celebrate the courage and passion to innovate that CERN has always demonstrated and the commitment to share the fruits of its research with people from all countries and of all ages. May the science leaders of tomorrow come from among the curious children who will fill this wonderful place with joy in the coming years.”

The new centre is expected to host up to 500 000 visitors a year from across the world. Science Gateway will be free of charge and open 6 days a week, from Tuesday to Sunday.

Rendering of the southern array site, CTAO-South, located in Chile. Credit: CTAO

Bologna, Italy – On 6 September 2023, the Cherenkov Telescope Array Observatory’s (CTAO’s) two governing bodies, the Board of Governmental Representatives (BGR) and the CTAO gGmbH Council, gathered to agree on the significant forthcoming measures to advance the Observatory to its construction phase. During the meeting, both bodies unanimously certified their commitment to the progress of the CTAO, including a foreseen endorsement of up to approximately 30 million euro for 2024. This represents a significant increase in annual funding, which will enable the Observatory to not only move forward with substantial infrastructure development but also to double its workforce.

The CTAO is in the process of a two-step application to transition from a gGmbH (under the German law) to a European Research Infrastructure Consortium (ERIC, under the European law). While the first step has been completed, discussions with the European Commission concerning the second step are still ongoing. The agreement between the BGR, comprised of representatives of the future legal entity’s member countries, and the CTAO gGmbH Council, allows the project to proceed in the meantime.

“While we continue to work towards obtaining the ERIC status, the member countries and organisations within the BGR are prepared to advance the project to its next phase,” explains Aldo Covello, Chair of the BGR. Markus Schleier, Chair of the CTAO gGmbH Council, stated: “The pledge of the BGR and the agreement we have reached in the Council will not only ensure the stability of the project but will undoubtedly help the CTAO attract new talent and investment as it continues to grow.”

The current legal entity of the CTAO, the CTAO gGmbH, and its partners have carried out extensive design and pre-construction activities, including the advancement of telescopes, such as the LST-1, the prototype of the Large-Sized Telescope under commissioning on the CTAO-North site in La Palma, Spain. In 2024, the Observatory plans to open at least 30 new positions and start major infrastructure development including building roads, power systems, and foundations for its southern array site in the Atacama Desert (Chile). Together with the very important developments in the northern array site, this represents a major milestone for the project.

These steps will bring the Observatory closer to realizing its planned 64 telescopes, which will deliver an unprecedented sensitivity in the quest to unveil new discoveries in the high-energy gamma-ray Universe.

The European Commission and the United Kingdom reached a political agreement on 7th September 2023 on the UK's participation in Horizon Europe, the EU's research and innovation programme, and Copernicus, the EU's world-leading Earth observation programme.

President of the European Commission, Ursula von der Leyen, said: “The EU and UK are key strategic partners and allies, and today's agreement proves that point. We will continue to be at the forefront of global science and research.”

This mutually agreed solution follows in-depth discussions between the EU and the UK and will be beneficial to both. It will allow the EU and UK to deepen their relationship in research, innovation and space, bringing together research and space communities.

Today's agreement remains fully in line with the EU-UK Trade and Cooperation Agreement. The UK will be required to contribute financially to the EU budget and is subject to all the safeguards of the Trade and Cooperation Agreement. Overall, it is estimated that the UK will contribute almost €2.6 billion per year on average for its participation to both Horizon Europe and the Copernicus component of the Space programme.

In more detail

As of 1 January 2024, researchers and organisations in the UK will be able to participate in Horizon Europe on par with their counterparts in EU Member States and will have access to Horizon Europe funding. This will reinforce the opportunity to be part of a worldwide network of researchers and innovators aimed at tackling global challenges in climate, energy, mobility, digital, industry and space, health, and more.

Association to Copernicus will enable the UK's contribution to a strategically important space programme with a state-of-the art capacity to monitor the Earth and to access its services. Copernicus makes an essential contribution in reaching our European Green Deal and net-zero objectives.

The UK will also have access to services from the EU Space Surveillance and Tracking, a component of the EU Space Programme.

Next steps

Today's political agreement must now be approved by the Council before being formally adopted in the EU-UK Specialised Committee on Participation in Union Programmes.

Background

The UK association to certain EU programmes is governed by the Trade and Cooperation Agreement. The agreement on the Windsor Framework earlier this year allowed the EU and the UK to open a new chapter in their partnership, based on mutual trust and full cooperation.

For more information

• Joint statement by the European Commission and UK Government
  
• Questions and Answers
  
• Horizon Europe
  
• Copernicus
  
• EU SST – EU Space Surveillance and Tracking
  

University of Mainz, 7th September 2023. Important milestone reached in "Project 8" experiment to measure neutrino mass

Neutrinos are ubiquitous elementary particles that interact only very weakly with normal matter. Therefore, they usually penetrate it unhindered and are therefore also called ghost particles. Nevertheless, neutrinos play a predominant role in the early universe. In order to fully explain how our universe evolved, we need above all to know their mass. But so far, it has not been possible to determine this mass.

The international Project 8 collaboration wants to change this with its new experiment. For the first time, Project 8 is using a completely new technology to determine the neutrino mass, the so-called "Cyclotron Radiation Emission Spectroscopy" - CRES for short. In a recent publication in the renowned journal Physical Review Letters, the Project 8 collaboration has now been able to show that the CRES method is indeed suitable for determining the neutrino mass and has already set an upper limit for this fundamental quantity in a first measurement – an important milestone has thus been reached. From Johannes Gutenberg University Mainz (JGU), the research groups of Prof. Dr. Martin Fertl and Prof. Dr. Sebastian Böser are involved, both researchers at the Cluster of Excellence PRISMA⁺. Dr. Christine Claessens, former PhD student of Sebastian Böser and now postdoc at the University of Washington in Seattle (USA), made a crucial contribution to the current publication as part of her PhD thesis.

Electrons as the key to neutrino mass

The Project 8 experiment uses the beta decay of radioactive tritium to track neutrino mass. Tritium is a heavy relative of hydrogen – a so-called isotope. It is unstable and consists of one proton and two neutrons. By converting one of these neutrons into a proton, tritium decays to helium while emitting an electron and an antineutrino. "And here's the kicker," says Martin Fertl. "Since neutrinos and their antiparticles have no electric charge, they are very difficult to detect. Therefore, we don't even try to detect them. Instead, we measure the energy of the resulting electrons via their orbital frequency in a magnetic field. Based on the shape of the energy spectrum of the electrons, we then determine the neutrino mass, or set an upper limit on that mass in this way."

Very precise measurement of electron energy is necessary

To obtain reliable results, the energy of the electrons must be measured extremely precisely. This is because the resulting (anti)neutrino is incredibly light, at least 500,000 times lighter than an electron. "When neutrinos and electrons are produced simultaneously, the neutrino mass has only a tiny effect on the electron's motion. And we want to see this small effect," explains Sebastian Böser. The method that makes this possible is called "Cyclotron Radiation Emission Spectroscopy" (CRES). It registers the microwave radiation emitted by the nascent electrons when they are forced into a circular path in a magnetic field. The frequency of the emitted radiation can be determined extremely precisely and then the mass of the neutrino can be inferred from the electron energy.

To make this work, Christine Claessens has made a decisive experimental contribution: "As part of my doctoral thesis, I developed, among other things, an event detection system consisting of a real-time trigger and an offline event reconstruction. This system searches for the characteristic CRES features in the continuously digitized and processed radio frequency signal. Reconstruction of the start frequency of each electron event enables high-precision recording of a tritium decay spectrum." On this basis, Christine Claessens succeeded in analyzing the first tritium spectrum recorded with CRES with respect to systematic uncertainties – and thus in calculating a first upper limit for the neutrino mass with this new technology, which has now found its way into the latest publication.

There, the Project 8 collaboration specifically reports 3,770 tritium-beta decay events that were registered over a period of 82 days in a sample cell the size of a single pea. The sample cell is cooled to very low temperatures and placed in a magnetic field that causes the escaping electrons to travel in a circular path long enough for the detectors to register a microwave signal. Crucially, no false signals or background events are registered that could be mistaken for or mask the "real signal". "The resulting first-time determination of the upper limit for the neutrino mass with a purely frequency-based measurement technique is a very promising result, since we can measure frequencies very accurately nowadays," Sebastian Böser and Martin Fertl conclude.

Next steps are already underway

After the successful proof of principle, the next step is ready: For the final experiment, the researchers need individual tritium atoms, which they create from the fission of tritium molecules. This is tricky because tritium, like hydrogen, prefers to form molecules. Developing such a source – first for atomic hydrogen and later for atomic tritium – is an important contribution of the Mainz team.

At the moment the Project 8 collaboration, which includes members from ten research institutions worldwide, is working on testing designs for scaling up the experiment from a pea-sized sample chamber to one a thousand times larger. This will allow far more beta decay events to be registered. At the end of a multi-year research and development program, the Project 8 experiment should eventually surpass the sensitivity of previous experiments – such as the current KATRIN experiment – to provide a value for neutrino mass for the first time.

ALMA view of the 9io9 galaxy - © ESO

ESO, 6th September 2023. Using the Atacama Large Millimeter/submillimeter Array (ALMA), astronomers have detected the magnetic field of a galaxy so far away that its light has taken more than 11 billion years to reach us: we see it as it was when the Universe was just 2.5 billion years old. The result provides astronomers with vital clues about how the magnetic fields of galaxies like our own Milky Way came to be.

Lots of astronomical bodies in the Universe have magnetic fields, whether it be planets, stars or galaxies. “Many people might not be aware that our entire galaxy and other galaxies are laced with magnetic fields, spanning tens of thousands of light-years,” says James Geach, a professor of astrophysics at the University of Hertfordshire, UK, and lead author of the study published today in Nature.

“We actually know very little about how these fields form, despite their being quite fundamental to how galaxies evolve,” adds Enrique Lopez Rodriguez, a researcher at Stanford University, USA, who also participated in the study. It is not clear how early in the lifetime of the Universe, and how quickly, magnetic fields in galaxies form because so far astronomers have only mapped magnetic fields in galaxies close to us.

Now, using ALMA, in which the European Southern Observatory (ESO) is a partner, Geach and his team have discovered a fully formed magnetic field in a distant galaxy, similar in structure to what is observed in nearby galaxies. The field is about 1000 times weaker than the Earth’s magnetic field, but extends over more than 16 000 light-years.

“This discovery gives us new clues as to how galactic-scale magnetic fields are formed,” explains Geach. Observing a fully developed magnetic field this early in the history of the Universe indicates that magnetic fields spanning entire galaxies can form rapidly while young galaxies are still growing.

The team believes that intense star formation in the early Universe could have played a role in accelerating the development of the fields. Moreover, these fields can in turn influence how later generations of stars will form. Co-author and ESO astronomer Rob Ivison says that the discovery opens up “a new window onto the inner workings of galaxies, because the magnetic fields are linked to the material that is forming new stars.”

To make this detection, the team searched for light emitted by dust grains in a distant galaxy, 9io9 [1]. Galaxies are packed full of dust grains and when a magnetic field is present, the grains tend to align and the light they emit becomes polarised. This means that the light waves oscillate along a preferred direction rather than randomly. When ALMA detected and mapped a polarised signal coming from 9io9, the presence of a magnetic field in a very distant galaxy was confirmed for the first time.

“No other telescope could have achieved this,” says Geach. The hope is that with this and future observations of distant magnetic fields the mystery of how these fundamental galactic features form will begin to unravel.

Notes

[1] 9io9 was discovered in the course of a citizen science project. The discovery was helped by viewers of the British BBC television programme Stargazing Live, when over three nights in 2014 the audience was asked to examine millions of images in the hunt for distant galaxies.

Links

• Research paper
  
• Photos of ALMA
  

Artist’s impression of HD 45166, the star that might become a magnetar - © ESO

Magnetars are the strongest magnets in the Universe. These super-dense dead stars with ultra-strong magnetic fields can be found all over our galaxy but astronomers don’t know exactly how they form. Now, using multiple telescopes around the world, including European Southern Observatory (ESO) facilities, researchers have uncovered a living star that is likely to become a magnetar. This finding marks the discovery of a new type of astronomical object — massive magnetic helium stars — and sheds light on the origin of magnetars.

Despite having been observed for over 100 years, the enigmatic nature of the star HD 45166 could not be easily explained by conventional models, and little was known about it beyond the fact that it is one of a pair of stars [1], is rich in helium and is a few times more massive than our Sun.

“This star became a bit of an obsession of mine,” says Tomer Shenar, the lead author of a study on this object published today in Science and an astronomer at the University of Amsterdam, the Netherlands. “Tomer and I refer to HD 45166 as the ‘zombie star’,” says co-author and ESO astronomer Julia Bodensteiner, based in Germany. “This is not only because this star is so unique, but also because I jokingly said that it turns Tomer into a zombie."

Having studied similar helium-rich stars before, Shenar thought magnetic fields could crack the case. Indeed, magnetic fields are known to influence the behaviour of stars and could explain why traditional models failed to describe HD 45166, which is located about 3000 light-years away in the constellation Monoceros. “I remember having a Eureka moment while reading the literature: ‘What if the star is magnetic?’,” says Shenar, who is currently based at the Centre for Astrobiology in Madrid, Spain.

Shenar and his team set out to study the star using multiple facilities around the globe. The main observations were conducted in February 2022 using an instrument on the Canada-France-Hawaii Telescope that can detect and measure magnetic fields. The team also relied on key archive data taken with the Fiber-fed Extended Range Optical Spectrograph (FEROS) at ESO’s La Silla Observatory in Chile.

Once the observations were in, Shenar asked co-author Gregg Wade, an expert on magnetic fields in stars at the Royal Military College of Canada, to examine the data. Wade’s response confirmed Shenar’s hunch: “Well my friend, whatever this thing is — it is definitely magnetic.”

Shenar's team had found that the star has an incredibly strong magnetic field, of 43 000 gauss, making HD 45166 the most magnetic massive star found to date [2]. “The entire surface of the helium star has a magnetic field almost 100,000 times stronger than Earth's,” explains co-author Pablo Marchant, an astronomer at KU Leuven’s Institute of Astronomy in Belgium [see edit]. 

This observation marks the discovery of the very first massive magnetic helium star. “It is exciting to uncover a new type of astronomical object,” says Shenar, ”especially when it’s been hiding in plain sight all along.”

Moreover, it provides clues to the origin of magnetars, compact dead stars laced with magnetic fields at least a billion times stronger than the one in HD 45166. The team’s calculations suggest that this star will end its life as a magnetar. As it collapses under its own gravity, its magnetic field will strengthen, and the star will eventually become a very compact core with a magnetic field of around 100 trillion gauss [3] — the most powerful type of magnet in the Universe.

Shenar and his team also found that HD 45166 has a mass smaller than previously reported, around twice the mass of the Sun, and that its stellar pair orbits at a far larger distance than believed before. Furthermore, their research indicates that HD 45166 formed through the merger of two smaller helium-rich stars. “Our findings completely reshape our understanding of HD 45166,” concludes Bodensteiner.

Edit [17 August]: the quote by Pablo Marchant was changed since a unit conversion mistake led to the previous version being incorrect.

Notes

[1] While HD 45166 is a binary system, in this text HD 45166 refers to the helium-rich star, not to both stars.

[2] The magnetic field of 43 000 gauss is the strongest magnetic field ever detected in a star that exceeds the Chandrasekhar mass limit, which is the critical limit above which stars may collapse into neutron stars (magnetars are a type of neutron star).

[3] In this text, a billion refers to one followed by nine zeros and a trillion refers to one followed by 12 zeros.

New result from the ATLAS experiment at CERN reaches the unprecedented precision of 0.09%

In the 11 years since its discovery at the Large Hadron Collider (LHC), the Higgs boson has become a central avenue for shedding light on the fundamental structure of the Universe. Precise measurements of the properties of this special particle are among the most powerful tools physicists have to test the Standard Model, currently the theory that best describes the world of particles and their interactions. At the Lepton Photon Conference this week, the ATLAS  collaboration reported how it has measured the mass of the Higgs boson more precisely than ever before.

The mass of the Higgs boson is not predicted by the Standard Model and must therefore be determined by experimental measurement. Its value governs the strengths of the interactions of the Higgs boson with the other elementary particles as well as with itself. A precise knowledge of this fundamental parameter is key to accurate theoretical calculations which, in turn, allow physicists to confront their measurements of the Higgs boson’s properties with predictions from the Standard Model. Deviations from these predictions would signal the presence of new or unaccounted-for phenomena. The Higgs boson’s mass is also a crucial parameter driving the evolution and the stability of the Universe’s vacuum.

The ATLAS and CMS collaborations have been making ever more precise measurements of the Higgs boson’s mass since the particle’s discovery. The new ATLAS measurement combines two results: a new Higgs boson mass measurement based on an analysis of the particle’s decay into two high-energy photons (the “diphoton channel”) and an earlier mass measurement based on a study of its decay into four leptons (the “four-lepton channel”).

The new measurement in the diphoton channel, which combines analyses of the full ATLAS data sets from Runs 1 and 2 of the LHC, resulted in a mass of 125.22 billion electronvolts (GeV) with an uncertainty of only 0.14 GeV. With a precision of 0.11%, this diphoton-channel result is the most precise measurement to date of the Higgs boson’s mass from a single decay channel.

Compared to the previous ATLAS measurement in this channel, the new result benefits both from the full ATLAS Run 2 data set, which reduced the statistical uncertainty by a factor of two, and from dramatic improvements to the calibration of photon energy measurements, which decreased the systematic uncertainty by almost a factor of four to 0.09 GeV.

“The advanced and rigorous calibration techniques used in this analysis were critical for pushing the precision to such an unprecedented level,” says Stefano Manzoni, convener of the ATLAS electron–photon calibration subgroup. “Their development took several years and required a deep understanding of the ATLAS detector. They will also greatly benefit future analyses.”

When the ATLAS researchers combined this new mass measurement in the diphoton channel with the earlier mass measurement in the four-lepton channel, they obtained a Higgs boson mass of 125.11 GeV with an uncertainty of 0.11 GeV. With a precision of 0.09%, this is the most precise measurement yet of this fundamental parameter.

“This very precise measurement is the result of the relentless investment of the ATLAS collaboration in improving the understanding of our data,” says ATLAS spokesperson Andreas Hoecker. “Powerful reconstruction algorithms paired with precise calibrations are the determining ingredients of precision measurements. The new measurement of the Higgs boson’s mass adds to the increasingly detailed mapping of this critical new sector of particle physics.”

Find out more on the ATLAS website.

Combined SPHERE and ALMA image of material orbiting V960 Mon - image credit: ESO

25th July 2023. A spectacular new image released today by the European Southern Observatory gives us clues about how planets as massive as Jupiter could form. Using ESO’s Very Large Telescope (VLT) and the Atacama Large Millimeter/submillimeter Array (ALMA), researchers have detected large dusty clumps, close to a young star, that could collapse to create giant planets.

“This discovery is truly captivating as it marks the very first detection of clumps around a young star that have the potential to give rise to giant planets,” says Alice Zurlo, a researcher at the Universidad Diego Portales, Chile, involved in the observations.

The work is based on a mesmerising picture obtained with the Spectro-Polarimetric High-contrast Exoplanet REsearch (SPHERE) instrument on ESO’s VLT that features fascinating detail of the material around the star V960 Mon. This young star is located over 5000 light-years away in the constellation Monoceros and attracted astronomers’ attention when it suddenly increased its brightness more than twenty times in 2014. SPHERE observations taken shortly after the onset of this brightness ‘outburst’ revealed that the material orbiting V960 Mon is assembling together in a series of intricate spiral arms extending over distances bigger than the entire Solar System.

This finding then motivated astronomers to analyse archive observations of the same system made with ALMA, in which ESO is a partner. The VLT observations probe the surface of the dusty material around the star, while ALMA can peer deeper into its structure. “With ALMA, it became apparent that the spiral arms are undergoing fragmentation, resulting in the formation of clumps with masses akin to those of planets,” says Zurlo.

Astronomers believe that giant planets form either by ‘core accretion’, when dust grains come together, or by ‘gravitational instability’, when large fragments of the material around a star contract and collapse. While researchers have previously found evidence for the first of these scenarios, support for the latter has been scant.

“No one had ever seen a real observation of gravitational instability happening at planetary scales — until now,” says Philipp Weber, a researcher at the University of Santiago, Chile, who led the study published today in The Astrophysical Journal Letters.

“Our group has been searching for signs of how planets form for over ten years, and we couldn't be more thrilled about this incredible discovery,” says team-member Sebastián Pérez from the University of Santiago, Chile.

ESO instruments will help astronomers unveil more details of this captivating planetary system in the making, and ESO’s Extremely Large Telescope (ELT) will play a key role. Currently under construction in Chile’s Atacama Desert, the ELT will be able to observe the system in greater detail than ever before, collecting crucial information about it. “The ELT will enable the exploration of the chemical complexity surrounding these clumps, helping us find out more about the composition of the material from which potential planets are forming,” concludes Weber.

More information

The team behind this work comprises young researchers from diverse Chilean universities and institutes, under the Millennium Nucleus on Young Exoplanets and their Moons (YEMS) research centre, funded by the Chilean National Agency for Research and Development (ANID) and its Millennium Science Initiative Program. The two facilities used, ALMA and VLT, are located in Chile’s Atacama Desert.

This research is presented in a paper to appear in The Astrophysical Journal Letters (doi: 10.3847/2041-8213/ace186).

Composition of the team: https://www.eso.org/public/news/eso2312/?lang

Links

• Research paper
  
• Photos of the VLT
  
• Photos of ALMA 
  
• Find out more about ESO's Extremely Large Telescope

The LHCb experiment (image: CERN)

Geneva 16th June 2023

The Big Bang is thought to have created equal amounts of matter and antimatter, yet the Universe today is made almost entirely of matter, so something must have happened to create this imbalance.

The weak force of the Standard Model of particle physics is known to induce a behavioural difference between matter and antimatter – known as CP symmetry violation – in decays of particles containing quarks, one of the building blocks of matter. But these differences, or asymmetries, are hard to measure and insufficient to explain the matter–antimatter imbalance in the present-day Universe, prompting physicists to both measure precisely the known differences and to look for new ones.

At a seminar held at CERN today, the LHCb collaboration reported how it has measured, more precisely than ever before, two key parameters that determine such matter–antimatter asymmetries.

In 1964, James Cronin and Val Fitch discovered CP symmetry violation through their pioneering experiment at Brookhaven National Laboratory in the US, using decays of particles containing strange quarks. This finding challenged the long-held belief in this symmetry of nature and earned Cronin and Fitch the Nobel Prize in Physics in 1980.

In 2001, the BaBar experiment in the US and the Belle experiment in Japan confirmed the existence of CP violation in decays of beauty mesons, particles with a beauty quark, solidifying our understanding of the nature of this phenomenon. This achievement ignited intense research efforts to further understand the mechanisms behind CP violation. In 2008, Makoto Kobayashi and Toshihide Maskawa received the Nobel Prize in Physics for their theoretical framework that elegantly explained the observed CP violation phenomena.

It its latest studies, using the full dataset recorded by the LHCb detector during the second run of the Large Hadron Collider(LHC), the LHCb collaboration set out to measure with high precision two parameters that determine the amount of CP violation in decays of beauty mesons.

One parameter determines the amount of CP violation in decays of neutral beauty mesons, which are made up of a bottom antiquark and a down quark. This is the same parameter as that measured by the BaBar and Belle experiments in 2001. The other parameter determines the amount of CP violation in decays of strange beauty mesons, which consist of a bottom antiquark and a strange quark.

Specifically, these parameters determine the extent of time-dependent CP violation. This type of CP violation stems from the intriguing quantum interference that occurs when a particle and its antiparticle undergo decay. The particle has the ability to spontaneously transform into its antiparticle and vice versa. As this oscillation takes place, the decays of the particle and antiparticle interfere with each other, leading to a distinctive pattern of CP violation that changes over time. In other words, the amount of CP violation observed depends on the time the particle lives before decaying. This fascinating phenomenon provides physicists with key insights into the fundamental nature of particles and their symmetries.

For both parameters, the new LHCb results, which are more precise than any equivalent result from a single experiment, are in line with the values predicted by the Standard Model.

“These measurements are interpreted within our fundamental theory of particle physics, the Standard Model, improving the precision with which we can determine the difference between the behaviour of matter and antimatter,” explains LHCb spokesperson Chris Parkes. “Through more precise measurements, large improvements have been made in our knowledge. These are key parameters that aid our search for unknown effects from beyond our current theory.”

Future data, from the third run of the LHC and the collider’s planned upgrade, the High-Luminosity LHC, will further tighten the precision on these matter–antimatter asymmetry parameters and perhaps point to new physics phenomena that could help shed light on what is one of the Universe’s best-kept secrets.

Find out more on LHCb's website: precise measurement of the CP-violating phase φs and precise measurement of the unitarity triangle angle β

Candidate events fromATLAS (left) and CMS (right) for a Higgs boson decaying into a Z bosonand a photon,with the Z bosondecayinginto a pair of muons. (Image: CERN)

The discovery of the Higgs boson at CERN’s Large Hadron Collider (LHC) in 2012 marked a significant milestone in particle physics. Since then, the ATLAS and CMS collaborations have been diligently investigating the properties of this unique particle and searching to establish the different ways in which it is produced and decays into other particles.

At the Large Hadron Collider Physics (LHCP) conference this week, ATLAS and CMS report how they teamed up to find the first evidence of the rare process in which the Higgs boson decays into a Z boson, the electrically neutral carrier of the weak force, and a photon, the carrier of the electromagnetic force. This Higgs boson decay could provide indirect evidence of the existence of particles beyond those predicted by the Standard Model of particle physics.

The decay of the Higgs boson into a Z boson and a photon is similar to that of a decay into two photons. In these processes, the Higgs boson does not decay directly into these pairs of particles. Instead, the decays proceed via an intermediate "loop" of “virtual” particles that pop in and out of existence and cannot be directly detected. These virtual particles could include new, as yet undiscovered particles that interact with the Higgs boson.

The Standard Model predicts that, if the Higgs boson has a mass of around 125 billion electronvolts, approximately 0.15% of Higgs bosons will decay into a Z boson and a photon. But some theories that extend the Standard Model predict a different decay rate. Measuring the decay rate therefore provides valuable insights into both physics beyond the Standard Model and the nature of the Higgs boson.

Previously, using data from proton–proton collisions at the LHC, ATLAS and CMS independently conducted extensive searches for the decay of the Higgs boson into a Z boson and a photon. Both searches used similar strategies, identifying the Z boson through its decays into pairs of electrons or muons – heavier versions of electrons. These Z boson decays occur in about 6.6% of the cases.

In these searches, collision events associated with this Higgs boson decay (the signal) would be identified as a narrow peak, over a smooth background of events, in the distribution of the combined mass of the decay products. To enhance the sensitivity to the decay, ATLAS and CMS exploited the most frequent modes in which the Higgs boson is produced and categorised events based on the characteristics of these production processes. They also used advanced machine-learning techniques to further distinguish between signal and background events.

In a new study, ATLAS and CMS have now joined forces to maximise the outcome of their search. By combining the data sets collected by both experiments during the second run of the LHC, which took place between 2015 and 2018, the collaborations have significantly increased the statistical precision and reach of their searches.

This collaborative effort resulted in the first evidence of the Higgs boson decay into a Z boson and a photon. The result has a statistical significance of 3.4 standard deviations, which is below the conventional requirement of 5 standard deviations to claim an observation. The measured signal rate is 1.9 standard deviations above the Standard Model prediction.

“Each particle has a special relationship with the Higgs boson, making the search for rare Higgs decays a high priority,” says ATLAS physics coordinator Pamela Ferrari. "Through a meticulous combination of the individual results of ATLAS and CMS, we have made a step forward towards unravelling yet another riddle of the Higgs boson."

“The existence of new particles could have very significant effects on rare Higgs decay modes,” says CMS physics coordinator Florencia Canelli. “This study is a powerful test of the Standard Model. With the ongoing third run of the LHC and the future High-Luminosity LHC, we will be able to improve the precision of this test and probe ever rarer Higgs decays.”