Merci à vous de suivre le flux Rss de www.sospc.name.

Je vous ai présenté ce lecteur en 2019 lorsqu'il était encore en version bêta, puis en 2020 lors de la sortie de la version officielle, et plus récemment en 2022.

Il est développé depuis Janvier 2017, est disponible pour Windows, Linux et Mac et existe aussi en version portable. :good: 

Ce lecteur de streaming extrait des contenus de sources gratuites.

Cet article Un lecteur de contenus musicaux incroyable est apparu en premier sur votre site préféré www.sospc.name

Merci à vous de suivre le flux Rss de www.sospc.name.

Je vous ai présenté ce lecteur en 2019 lorsqu'il était encore en version bêta, puis en 2020 lors de la sortie de la version officielle, et plus récemment en 2022.

Il est développé depuis Janvier 2017, est disponible pour Windows, Linux et Mac et existe aussi en version portable. :good: 

Ce lecteur de streaming extrait des contenus de sources gratuites.

Cet article Un lecteur de contenus musicaux incroyable est apparu en premier sur votre site préféré www.sospc.name

Lia Merminga has resigned as director of Fermilab – the US’s premier particle-physics lab. She stepped down yesterday after a turbulent year that saw staff layoffs, a change in the lab’s management contractor and accusations of a toxic atmosphere. Merminga is being replaced by Young-Kee Kim from the University of Chicago, who will serve as interim director until a permanent successor is found. Kim was previously Fermilab’s deputy director between 2006 and 2013.

Tracy Marc, a spokerperson for Fermilab, says that the search for Merminga’s successor has already begun, although without a specific schedule. “Input from Fermilab employees is highly valued and we expect to have Fermilab employee representatives as advisory members on the search committee, just as has been done in the past,” Marc told Physics World. “The search committee will keep the Fermilab community informed about the progress of this search.”

The departure of Merminga, who became Fermilab director in August 2022, was announced by Paul Alivisatos, president of the University of Chicago. The university jointly manages the lab with Universities Research Association (URA), a consortium of research universities, as well as the industrial firms Amentum Environment & Energy, Inc. and Longenecker & Associates.

“Her dedication and passion for high-energy physics and Fermilab’s mission have been deeply appreciated,” Alivisatos said in a statement. “This leadership change will bring fresh perspectives and expertise to the Fermilab leadership team.”

Turbulent times

The reasons for Merminga’s resignation are unclear but Fermilab has experienced a difficult last two years with questions raised about its internal management and external oversight. Last August, a group of anonymous self-styled whistleblowers published a 113-page “white paper” on the arXiv preprint server, asserting that the lab was “doomed without a management overhaul”.

The document highlighted issues such as management cover ups of dangerous behaviour including guns being brought onto Fermilab’s campus and a male employee’s attack on a female colleague. In addition, key experiments such as the Deep Underground Neutrino Experiment suffered notable delays. Cost overruns also led to a “limited operations period” with most staff on leave in late August.

In October, the US Department of Energy, which oversees Fermilab, announced a new organization – Fermi Forward Discovery Group – to manage the lab. Yet that decision came under scrutiny given it is dominated by the University of Chicago and URA, which had already been part of the management since 2007. Then a month later, almost 2.5% of Fermilab’s employees were laid off, adding to portray an institution in crisis.

The whistleblowers, who told Physics World that they still stand by their analysis of the lab’s issues, say that the layoffs “undermined Fermilab’s scientific mission” and claim that it sidelined “some of its most accomplished” researchers at the lab. “Meanwhile, executive managers, insulated by high salaries and direct oversight responsibilities, remained unaffected,” they allege.

Born in Greece, Merminga, 65, earned a BSc in physics from the University of Athens before moving to the University of Michigan where she completed an MS and PhD in physics. Before taking on Fermilab’s directorship, she held leadership posts in governmental physics-related institutions in the US and Canada.

The post Fermilab seeks new boss after Lia Merminga resigns as director appeared first on Physics World.

An international team of physicists has used the principle of entanglement entropy to examine how particles are produced in high-energy electron–proton collisions. Led by Kong Tu at Brookhaven National Laboratory in the US, the researchers showed that quarks and gluons in protons are deeply entangled and approach a state of maximum entanglement when they take part in high-energy collisions.

While particle physicists have made significant progress in understanding the inner structures of protons, neutrons, and other hadrons, there is still much to learn. Quantum chromodynamics (QCD) says that the proton and other hadrons comprise quarks, which are tightly bound together via exchanges of gluons – mediators of the strong force. However, using QCD to calculate the properties of hadrons is notoriously difficult except under certain special circumstances.

Calculations can be simplified by describing the quarks and gluons as partons in a model that was developed in late 1960s by James Bjorken, Richard Feynman, Vladimir Gribov and others. “Here, all the partons within a proton appear ‘frozen’ when the proton is moving very fast relative to an observer, such as in high-energy particle colliders,” explains Tu.

Dynamic and deeply complex interactions

While the parton model is useful for interpreting the results of particle collisions, it cannot fully capture the dynamic and deeply complex interactions between quarks and gluons within protons and other hadrons. These interactions are quantum in nature and therefore involve entanglement. This is a purely quantum phenomenon whereby a group of particles can be more highly correlated than is possible in classical physics.

“To analyse this concept of entanglement, we utilize a tool from quantum information science named entanglement entropy, which quantifies the degree of entanglement within a system,” Tu explains.

In physics, entropy is used to quantify the degree of randomness and disorder in a system. However, it can also be used in information theory to measure the degree of uncertainty within a set of possible outcomes.

“In terms of information theory, entropy measures the minimum amount of information required to describe a system,” Tu says. “The higher the entropy, the more information is needed to describe the system, meaning there is more uncertainty in the system. This provides a dynamic picture of a complex proton structure at high energy.”

Deeply entangled

In this context, particles in a system with high entanglement entropy will be deeply entangled – whereas those in a system with low entanglement entropy will be mostly uncorrelated.

In recent studies, entanglement entropy has been used to described how hadrons are produced through deep inelastic scattering interactions – such as when an electron or neutrino collides with a hadron at high energy. However, the evolution with energy of entanglement entropy within protons had gone largely unexplored. “Before we did this work, no one had looked at entanglement inside of a proton in experimental high-energy collision data,” says Tu.

Now, Tu’s team investigated how entanglement entropy varies with the speed of the proton – and how this relationship relates to the hadrons created during inelastic collisions.

Matching experimental data

Their study revealed that the equations of QCD can accurately predict the evolution of entanglement entropy – with their results closely matching with experimental collision data. Perhaps most strikingly, they discovered that if this entanglement entropy is increased at high energies, it may approach a state of maximum entanglement under certain conditions. This high degree of entropy is evident in the large numbers of particles that are produced in electron–proton collisions.

The researchers are now confident that their approach could lead to further insights about QCD. “This method serves as a powerful tool for studying not only the structure of the proton, but also those of the nucleons within atomic nuclei.” Tu explains. “It is particularly useful for investigating the underlying mechanisms by which nucleons are modified in the nuclear environment.”

In the future, Tu and colleagues hope that their model could boost our understanding of processes such as the formation and fragmentation of hadrons within the high-energy jets created in particle collisions, and the resulting shift in parton distributions within atomic nuclei. Ultimately, this could lead to a fresh new perspective on the inner workings of QCD.

The research is described in Reports on Progress in Physics.

The post Entanglement entropy in protons affects high-energy collisions, calculations reveal appeared first on Physics World.

This year marked the 70th anniversary of the European Council for Nuclear Research, which is known universally as CERN. To celebrate, we have published a bumper crop of articles on particle and nuclear physics in 2024. Many focus on people and my favourite articles have definitely skewed in that direction. So let’s start with the remarkable life of accelerator pioneer Bruno Touschek.

Bruno Touschek: the physicist who escaped the Nazi Holocaust to build particle colliders

Born in Vienna in 1921 to a Jewish mother, Bruno Touschek’s life changed when Nazi Germany annexed Austria in 1938. After suffering antisemitism in his hometown and then in Rome, he inexplicably turned down an offer to study in the UK and settled in Germany. There he worked on a “death ray” for the military but was eventually imprisoned by the German secret police. He was then left for dead during a forced march to a concentration camp in 1945. When the war ended a few weeks later, Touschek’s expertise came to the attention of the British, who occupied north-western Germany. He went on to become a leading accelerator physicist and you can read much more about the extraordinary life of Touschek in this article by the physicist and biographer Giulia Pancheri.

Nuclear clock ticks ever closer

Today, the best atomic clocks would only be off by about 10 ms after running for the current age of the universe. But, could these timekeepers soon be upstaged by clocks that use a nuclear, rather than an atomic transition? Such nuclear clocks could rival their atomic cousins when it comes to precision and accuracy. They also promise to be fully solid-state, which means that they could be used in a wide range of commercial applications. This year saw physicists make new measurements and develop new technologies that could soon make nuclear clocks a reality. Click on the headline above to discover how physicists in the US have fabricated all of the components needed to create a nuclear clock made from thorium-229. Also, earlier this year physicists in Germany and Austria showed that they can put nuclei of the isotope into a low-lying metastable state that could be used in a nuclear clock. You can find out more here: “Excitation of thorium-229 brings a working nuclear clock closer”.

Physics World Live: the future of particle physics

In 2024 we launched our Physics World Live series of panel discussions. In September, we explored the future of particle physics with Tara Shears of the UK’s University of Liverpool, Phil Burrows at the University of Oxford in the UK and Tulika Bose at the University of Wisconsin–Madison in the US. Moderated by Physics World’s Michael Banks, the discussion focussed on next-generation particle colliders and how they could unravel the mysteries of the Higgs boson and probe beyond the Standard Model of particle physics. You can watch a video of the event by clicking on the above headline (free registration) or read an article based on the discussion here: “How a next-generation particle collider could unravel the mysteries of the Higgs boson”.

‘Sometimes nature will surprise us.’ Juan Pedro Ochoa-Ricoux on eureka moments and the future of neutrino physics

Neutrinos do not fit in nicely with the Standard Model of particle physics because of their non-zero masses. As a result some physicists believe that they offer a unique opportunity to do experiments that could reveal new physics. In a wide-ranging interview, the particle physicist Juan Pedro Ochoa-Ricoux explains why he has devoted much of his career to the study of these elusive subatomic particles. He also looks forward to two big future experiments – JUNO and DUNE – which could change our understanding of the universe.

Using Minecraft to get young people interested in particle physics: Çiğdem İşsever on the importance of science in the early years

“Children decide quite early in their life, as early as primary school, if science is for them or not,” explains Çiğdem İşsever – who is leads the particle physics group at DESY in Hamburg, and the experimental high-energy physics group at the Humboldt University of Berlin. İşsever has joined forces with physicists Steven Worm and Becky Parker to create ATLAScraft, which creates a virtual version of CERN’s ATLAS detector in the hugely popular computer game Minecraft. In this profile, the science writer Rob Lea talks to İşsever about her passion for outreach and how she dispels gender stereotypes in science by talking to school children as young as five about her career in physics. İşsever also looks forward to the future of particle physics and what could eventually replace the Large Hadron collider as the world’s premier particle-physics experiment.

CERN celebrates 70 years at the helm of particle physics in lavish ceremony

This year marked the 70th anniversary of the world’s most famous physics laboratory, so the last two items in my list celebrate that iconic facility nestled between the Alps and the Jura mountains. Formed in the aftermath of the Second World War, which devastated much of Europe, CERN came into being on 29 September 1954. That year also saw the start of construction of the Geneva-based lab’s proton synchrotron, which fired-up in 1959 with an energy of 24 GeV, becoming the world’s highest-energy particle accelerator. The original CERN had 12 member states and that has since doubled to 24, with an additional 10 associate members. The lab has been associated with a number of Nobel laureates and is a shining example of how science can bring nations together after a the trauma of war. Read more about the anniversary here.

CERN at 70: how the Higgs hunt elevated particle physics to Hollywood status

When former physicist James Gillies sat down for dinner in 2009 with actors Tom Hanks and Ayelet Zurer, joined by legendary director Ron Howard, he could scarcely believe the turn of events. Gillies was the head of communications at CERN, and the Hollywood trio were in town for the launch of Angels & Demons. The  blockbuster film is partly set at CERN with antimatter central to its plot, and is based on the Dan Brown novel. In this Physics World Stories podcast, Gillies looks back on those heady days. Gillies has also written a feature article for us about his Hollywood experience: “Angels & Demons, Tom Hanks and Peter Higgs: how CERN sold its story to the world”.

The post Particle and nuclear physics highlights in 2024: celebrating the past and looking to the future appeared first on Physics World.

A cutting-edge experiment that probes the internal structure of the neutron has been done at Jefferson Lab in the US. An international collaboration used the CEBAF Large Acceptance Spectrometer (CLAS12) to study the scattering of high-energy electrons from a deuterium target. The team measured generalized parton distributions, which provide a detailed picture of how the neutron’s constituent quarks contribute to its momentum and spin. A key innovation was the use of the Central Neutron Detector, a specialized instrument enabling the direct detection of neutrons ejected from the target.

“The theory of the strong force, called quantum chromodynamics [QCD], that describes the interaction between quarks via the exchange of gluons, is too complex and cannot be used to compute the properties of bound states, such as nucleons [both protons and neutrons],” explains Silvia Niccolai, a research director at the French National Centre for Scientific Research, who proposed the idea for the new detector. “Therefore, we need to use unknown but experimentally measurable functions called generalized parton distributions that help us connect the properties of the nucleons (for instance their spin) to the dynamics of quarks and gluons.”

The parton model assumes that a nucleon contains point-like constituents called partons – which represent the quarks and gluons of QCD.  By measuring parton distributions, physicists can examine correlations between a quark’s longitudinal momentum — how much of the nucleon’s total momentum it carries — and its transverse position within the nucleon. By analyzing these relationships for varying momentum values, scientists create a tomographic-like scan of the nucleon’s internal structure.

“This experiment is important because it directly accesses the structure of the neutron,” says Gerald Miller at the University of Washington, who was not involved in the study. “A neutron [outside of a nuclei] will decay in about 15 min, so it is difficult to study. The experiment in question used a novel technique to directly examine the neutron. They measured the neutron in the final state, which required new detection techniques.”

Separating quark contributions

Protons and neutrons consist of distinct combinations of up and down quarks: up-up-down for protons and down-down-up for neutrons. Each type of quark is associated with its own set of generalized parton distributions, and the overarching aim of the experimental effort is to determine distributions for both protons and neutrons. This would enable researchers to disentangle the distributions by quark type, offering deeper insights into the contributions of individual quark flavours to the properties of nucleons.

While these distributions are vital for understanding the strong interactions within both protons and neutrons, our understanding of protons is significantly more advanced. This disparity arises from the electric charge of protons, which facilitates their interaction with other charged particles, unlike electrically neutral neutrons. Additionally, proton targets are simpler to prepare, consisting solely of hydrogen atoms. In contrast, neutron experiments target deuterium nuclei, which comprise a neutron and a proton. The interaction between these two nucleons within the nucleus complicates the analysis of scattering data in neutron experiments.

To address these problems, the CLAS12 collaboration utilized the Central Neutron Detector, which was developed at France’s Laboratory of the Physics of the Two Infinities Irène Joliot-Curie (IJCLab). This allowed them to detect neutrons ejected from the deuterium target by high-energy electrons for the first time.

By combining neutron detection with the simultaneous measurement of scattered electrons and energetic photons produced during the interactions, the team gathered comprehensive data on particle momenta. This was used to calculate the generalized parton distributions of quarks inside neutrons.

Spin alignment

The CLAS12 team used electron beams with spins aligned both parallel and antiparallel to their momentum. This configuration resulted in slightly different interactions with the target, enabling the team to investigate subtle features of the generalized parton distributions related to angular momentum. By analyzing these details, they successfully disentangled the contributions of up and down quarks to the angular momentum of the neutron.

The team believes their findings could help address the longstanding “spin crisis“. This is the large body of experimental evidence suggesting that quarks and gluons contribute far less to the total spin of nucleons than initially expected.

“The sum of both the intrinsic spin of the quarks and gluons still doesn’t add up to the total spin,” says Adam Hobart, a researcher at IJCLab who led the data analysis for this experiment. “The only missing piece to complement the intrinsic spin of the quarks and the gluons is the orbital angular momentum of the quarks.”

The team plan to do a new and more accurate experiment that will involve firing electrons at a polarized target in which the nuclear spins of the deuterium all point in the same direction. This should allow the physicists to extract all possible generalized parton distributions from the scattering data.

“More data are needed to get a fuller picture, but this experiment can be thought of as a big step in a huge experimental program that is needed to get a complete understanding,” concludes Miller. “I think that this work will clearly influence future studies. Others will try to build on this experiment to expand the kinematic reach.”

The research is described in Physical Review Letters.

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When I was asked to review Unfinished Nature: Particle Physics at CERN, a new ethnography of CERN by Arpita Roy, an anthropologist at the University of California Berkeley, US, I was excited. Having recently completed a PhD in science communication where I studied the researchers at CERN – albeit from a very different, quantitative‐heavy, perspective – the subject is close to my heart.

Roy spent two and a half years doing fieldwork at CERN, around the time of the discovery of the Higgs boson in 2012. The book examines this event through an anthropological lens, asking questions such as how are scientific advances made and how do scientists understand their work? Unfortunately, although I read many books and papers of a similar nature for my doctoral studies, I struggled with Unfinished Nature.

A good book makes you pause to reflect. You may find yourself enlightened by the author’s perspectives or disagree with their arguments, but comprehension is key in either case. A book that has you stumbling through the pages without clarity, re-reading sentences over and over again in an effort to make sense of them, is frustrating. I may lack the expertise to appreciate the finer points of the subject, but I struggled despite repeated, earnest attempts to read the book with the care and attention the topic deserves.

Take the following snippet from the first page of the introduction, which sets the tone for what is to come: “But what has been lost to sight is the elucidation of how a science like particle physics may incorporate elements into its domain beyond what its epistemic assumption would lead us to expect, which deepens the mystery of what logic of classification it obeys. It is far from easy, however, to explicate the notion of classification, if only for the reason that it engenders notions of system, category, or context whose lucidity is hard to pinpoint in the scientific realm.” While I eventually understood (or at least think I did) what Roy is trying to say, the phrasing is unnecessarily convoluted.

None of this is criticism of Roy as a researcher but reflects the seemingly intentionally confusing language that academics – and my fellow social scientists in particular – are expected to use, despite increased calls to make research more accessible to those without specialist knowledge.

The ideas and stories Roy covers are no doubt interesting, even if the book itself isn’t an easy read. Unfinished Nature is more suited to the invested social scientist familiar with the particular flavour of academic prose adopted by anthropologists than physicists or physics enthusiasts indulging a more superficial interest in the lives of researchers at CERN.

• 2024 Columbia University Press 296pp £30.00

The post Unclear nature: anthropological study of CERN is a missed opportunity to bridge physics and social sciences appeared first on Physics World.

All eyes were on the election of Donald Trump as US president earlier this month, whose win overshadowed two big appointments in physics. First, the particle physicist Jun Cao took over as director of China’s Institute of High Energy Physics (IHEP) in October, succeeding Yifang Wang, who had held the job since 2011.

Over the last decade, IHEP has emerged as an important force in particle physics, with plans to build a huge 100 km-circumference machine called the Circular Electron Positron Collider (CEPC). Acting as a “Higgs factory”, such a machine would be hundreds of times bigger and pricier than any project IHEP has ever attempted.

But China is serious about its intentions, aiming to present a full CEPC proposal to the Chinese government next year, with construction staring two years later and the facility opening in 2035. If the CEPC opens as planned in 2035, China could leapfrog the rest of the particle-physics community.

China’s intentions will be one pressing issue facing the British particle physicist Mark Thomson, 58, who was named as the 17th director-general at CERN earlier this month. He will take over in January 2026 from current CERN boss Fabiola Gianotti, who will finish her second term next year. Thomson will have a decisive hand in the question of what – and where – the next particle-physics facility should be.

CERN is currently backing the 91 km-circumference Future Circular Collider (FCC), several times bigger than the Large Hadron Collider (LHC). An electron–positron collider designed to study the Higgs boson in unprecedented detail, it could later be upgraded to a hadron collider, dubbed FCC-hh. But with Germany already objecting to the FCC’s steep £12bn price tag, Thomson will have a tough job eking extra cash for it from CERN member states. He’ll also be busy ensuring the upgraded LHC, known as the High-Luminosity LHC, is ready as planned by 2030.

I wouldn’t dare tell Thomson how to do his job, but Physics World did once ask previous CERN directors-general what skills are needed as lab boss. Crucial, they said, were people management, delegation, communication and the ability to speak multiple languages. Physical stamina was deemed a vital attribute too, with extensive international travel and late-night working required.

One former CERN director-general even cited the need to “eat two lunches the same day to satisfy important visitors”. Squeezing double dinners in will probably be the least of Thomson’s worries.

Fortuantely, I bumped into Thomson at an Institute of Physics meeting in London earlier this week, where he agreed to do an interview with Physics World. So you can be sure we’ll get Thomson put his aims and priorities as next CERN boss on record. Stay tuned…

• For more about the future of particle colliders, check out our feature interview with Tulika Bose, Philip Burrows and Tara Shears.

The post Mark Thomson and Jung Cao: a changing of the guard in particle physics appeared first on Physics World.

In a groundbreaking study, scientists in the STAR Collaboration have unveiled a pioneering method for investigating the shapes of atomic nuclei by colliding them at near light-speed in particle accelerators like the Relativistic Heavy Ion Collider (RHIC) and the Large Hadron Collider (LHC). Their innovative approach offers unprecedented insight into nuclear structure and promises to deepen our understanding of strong nuclear forces and their role in the composition of neutron stars and the evolution of the early universe.

Understanding the properties of nuclei is daunting, largely due to the complexities of quantum chromodynamics (QCD), the fundamental theory governing the strong interaction. Calculations in QCD are notoriously difficult at low relative velocities, typical for nucleons within nuclei. Given these challenges, experimental methods in this area are even more crucial than usual.

Historically, scientists relied on two primary techniques to study nuclear shapes. The first involves exciting a nucleus to a higher energy state, often by colliding it with a fixed target. By measuring how long it takes the nucleus to return to its ground state, researchers can gather information about its shape. However, this relaxation process unfolds over much longer timescales than typical nuclear interactions, thus providing only an averaged image of the nucleus and missing finer details.

Another popular method is to bombard nuclei with high-energy electrons, analysing the scattering data to infer structural details. However, this technique only reveals localized properties of the nucleus, falling short in capturing the overall shape, which depends on the coordinated movement of nucleons across the entire nucleus.

Smashing nuclei

The STAR collaboration’s approach circumvents these limitations by smashing nuclei together at extremely high energies and analysing the collision products. Since these high-energy collisions occur on timescales much shorter than typical nuclear processes, the new method promises a more detailed snapshot of nuclear shape.

When two nuclei collide at near-light speeds, they annihilate, turning into an expanding ball of plasma made of quarks and gluons – which are the fundamental building blocks of nuclear matter. This plasma lasts only about 10⁻²³ s before forming thousands of new composite particles, which are then caught by detectors. By studying the speeds and angles at which these particles are ejected, scientists can infer the shape of the colliding nuclei.

“You cannot image the same nuclei again and again because you destroy them in the collision,” explains Jiangyong Jia, a professor at Stony Brook University and one of lead authors of a paper describing the study. “But by looking at the whole collection of images from many different collisions, scientists can reconstruct the subtle properties of the 3D structure of the smashed nuclei.”

Verifying the results

To verify the reliability of this method, STAR researchers compared their findings with those obtained through established techniques on nuclei with well-known shapes. Specifically, they analysed two types of head-on collisions. These were gold–gold collisions, involving slightly oblate (flattened sphere) gold nuclei; and uranium–uranium collisions, featuring highly prolate (elongated sphere) uranium nuclei. The shapes of these nuclei are well-documented, providing benchmarks for assessing the accuracy of the high-energy approach.

The results from both types of collisions aligned remarkably well with established findings, validating the precision of this high-energy method.

Paul Garrett, who is at Canada’s University of Guelph and was not involved in the research, tells Physics World, “The fact that the high-energy collisions occur over an extraordinarily short time scale – effectively capturing the nucleus with the equivalent of an extremely high-speed camera – opens possibilities for us to see the effects of fluctuations in the nuclear shape that are very difficult to determine using low-energy probes”.

Future directions

The initial success of this new method paves the way for more extensive applications, especially with nuclei whose shapes are not as well understood. The high-energy approach holds potential for exploring finer details beyond the basic prolate or oblate characterizations. For example, it could reveal complex triaxial shapes or capture rapid, transient fluctuations in soft nuclei, offering unprecedented insights into the dynamic interactions among nucleons.

Moreover, this technique could enhance our understanding of the quark–gluon plasma, a state of matter not only produced in high-energy particle collisions but also found in the cores of neutron stars and in the universe’s earliest moments. During that primordial phase, temperatures were so extreme that protons and neutrons could not form, leaving all strongly interacting matter in a quark-gluon state.

“Indeed, I think this study is the tip of the iceberg of what the technique can do, and will ultimately be one of the groundbreaking studies in nuclear physics,” said Garrett. “Sitting on the border of traditional nuclear physics and high-energy physics, it will bring the communities together and clearly demonstrates that we have much to learn from each other.”

The research is described in Nature.

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The UK particle physicist Mark Thomson has been selected as the 17th director-general of the CERN particle-physics laboratory. Thomson, 58, was chosen today at a meeting of the CERN Council. He will take up the position on 1 January 2026 for a five-year period succeeding the current CERN boss Fabiola Gianotti, who will finish her second term next year.

Three candidates were shortlisted for the job after being put forward by a search committee. Physics World understands that the Dutch theoretical physicist and former Dutch science minister Robbert Dijkgraaf was also considered for the position. The other was reported to have been Greek particle physicist Paris Sphicas.

With a PhD in physics from the University of Oxford, Thomson is currently executive chair of the Science and Technology Facilities Council (STFC), one of the main funding agencies in the UK. He spent a significant part of career at CERN working on precise measurements of the W and Z boson in the 1990s as part of the OPAL experiment at CERN’s Large Electron-Positron Collider.

In 2000 he moved back to the UK to take up a position in experimental particle physics at the University of Cambridge. He was then a member of the ATLAS collaboration at CERN’s Large Hadron Collider (LHC) and between 2015 and 2018 served as co-spokesperson for the US Deep Underground Neutrino Experiment. Since 2018 he has served as the UK delegate to CERN’s Council.

Thomson was selected for his managerial credentials in science and connection to CERN. “Thomson is a talented physicist with great managerial experience,” notes Gianotti. “I have had the opportunity to collaborate with him in several contexts over the past years and I am confident he will make an excellent director-general. I am pleased to hand over this important role to him at the end of 2025.”

“Thomson’s election is great news – he has the scientific credentials, experience, and vision to ensure that CERN’s future is just as bright as its past, and it remains at the absolute cutting edge of research,” notes Peter Kyle, UK secretary of state for science, innovation and technology.“Work that is happening at CERN right now will be critical to scientific endeavour for decades to come, and for how we tackle some of the biggest challenges facing humanity.”

‘The right person’

Dirk Ryckbosch, a particle physicist at Ghent University and a delegate for Belgium in the CERN Council, told Physics World that Thomson is a “perfect match” for CERN. “As a former employee and a current member of the council, Thomson knows the ins and outs of CERN and he has the experience needed to lead a large research organization,” adds Ryckbosch.

The last UK director-general of CERN was Chris Llewellyn Smith who held the position between 1994 and 1998. Yet Ryckbosch acknowledges that within CERN, Brexit has never clouded the relationship between the UK and EU member states. “The UK has always remained a strong and loyal partner,” he says.

Thomson will have two big tasks when he becomes CERN boss in 2026: ensuring the start of operations with the upgraded LHC, known as the High-Luminosity LHC (HL-LHC) by 2030, and securing plans for the LHC’s successor.

CERN has currently put its weight behind the Future Circular Collider (FCC), which will cost about £12bn and be four times as large as the LHC with a 91 km circumference. The FCC would first be built as an electron-positron collider with the aim of studying the Higgs boson in unprecedented detail. It could later be upgraded as a hadron collider, known as the FCC-hh.

The construction of the FCC will, however, require additional funding from CERN member states. Earlier this year Germany, which is a main contributor to CERN’s annual budget, publicly objected to the FCC’s high cost. Garnering support from the FCC, if CERN selects it as its next project, will be a delicate balancing act for Thomson. “With his international network and his diplomatic skills, Mark is the right person for this,” concludes Ryckbosch.

That view is backed by particle theorist John Ellis from King’s College London, who told Physics World that Thomson has the “ideal profile for guiding CERN during the selection and initiation of its next major accelerator project”. Ellis adds that Thomson “brings to the role a strong record of research in collider physics as well as studies of electron-positron colliders and leadership in the DUNE neutrino experiment and also extensive managerial experience”.

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