On 13 March 2025, Swissmint issued a special "CERN" coin symbolising Swiss and global innovation.

Swissmint is the company mandated by the Swiss Confederation to mint Switzerland's standard coins, the ones you use for everyday payments. It also produces special-edition coins to mark important historical and cultural events or to honour eminent Swiss personalities or organisations.

The special, limited-edition CERN coin is made of silver and weighs 20 grams. A particle collision is depicted on the “heads” side (known as “obverse” in numismatic jargon), while the “tails” (or “reverse”) side depicts the cross-section of an LHC magnet.

The coin is worth 20 Swiss francs and is on sale on Swissmint’s website.

A luxury “burnished flan” version will be presented at the International Coin Fair in Bern in mid-May and will then go on sale in a display box at the CERN shop.

More information can be found on the Swissmint and the Swiss Government websites.

A "laser pointer" is a small, hand-held laser device that emits laser radiation to indicate objects and locations.

From 1 June 2019, only class 1 laser pointers will be allowed for display purposes in Switzerland: it is forbidden to import, possess and use laser pointers of classes 1M, 2, 2M, 3R, 3B and 4, as well as unclassified or incorrectly labelled laser pointers (Articles 22 and 23 of the Ordinance to the Federal Law on Protection against Non-Ionising Radiation and Sound (NISRV)).

All CERN contributors must comply with these regulations. Failure to do so may result in criminal prosecution in Switzerland.

To avoid any incidents related to the use of laser pointers, their use is also restricted to class 1 equipment throughout the CERN site, including the French part.

Laser pointers must be disposed of as electronic waste after removing the batteries.

If you are in possession of a laser pointer of class 1M or higher, you can return it for proper disposal by placing it in one of the blue containers reserved for electronic equipment provided by the Storage, Recovery and Sales Service of the SCE department or return it directly to building 133.

Host State Relations service
www.cern.ch/relations
relations.secretariat@cern.ch
Tel.: 72848 / 75152

Spring has arrived and the lure of the great outdoors grows as the days get longer and warmer. This also means the return of ticks: little parasitic mites, whose bites can have severe consequences for our health through the transmission of various infectious agents. The most common infections caused by tick bites are Lyme disease (Lyme Borreliosis), generally treatable with antibiotics, and tick-borne encephalitis (TBE), which is rarer than Lyme disease with 5000 to 13 000 cases reported globally each year. Although there is no vaccine against Lyme disease, one does exist against TBE and it is recommended for anyone, including children residing in or travelling to areas where the disease is prevalent. In Europe, the TBE vaccination is recommended in Switzerland as well as Austria, Czech Republic, Estonia, Finland, Germany, Latvia, Lithuania, Poland, Slovakia, Slovenia, Sweden and Western Russia.

If you are bitten by a tick, you can go to the CERN Medical Service infirmary to have it removed and to get advice and guidance.

Find out more about ticks and tick-borne diseases, vaccination possibilities, how to protect yourself and what to do if you are bitten by a tick on the dedicated Medical Service webpage: https://hse.cern/ticks.

24 Mar 14:00 | Knowledge Sharing | Online | CERN Venture Connect | EN
CVC Deep Tech Talks #1 – Single Frequency Raman Laser with Lisa Glöggler

25 Mar 08:30 | At CERN | Building 29 | HSE | EN & FR
Blood donation at CERN

26 Mar 14:00 | At CERN | 54/R-037 | HSE | EN & FR
Stress Check-up Workshop / Atelier "Stress Check-up" – part of CERN’s new stress check-up programme

26 Mar 16:00 | Knowledge Sharing | 40/S2-C01 - Salle Curie | Early career community | EN
LHC Soft Skills Workshop: Presenting Science – How to prepare a scientific presentation with impact!

27 Mar 12:00 | Knowledge Sharing | IdeaSquare | IdeaSquare | EN
Prototyping at CERN

27 Mar 16:30 | Knowledge Sharing | Main Auditorium | CERN Colloquium | EN
Physics in the abyss with KM3NeT: from cosmic rays to neutrino oscillations

27 Mar 18:00 | Knowledge Sharing | Cinélux | CERN Public events partnership | FR
Première du documentaire Segnali di vita de Leandro Picarella en présence du protagoniste du film – l’astrophysicien Paolo Calcidese – et du physicien Michael Doser, CERN

1 Apr 12:30 | At CERN | Council Chamber & online | Association du personnel/Staff Association | FR & EN
La protection sociale au CERN / Social protection at CERN

2 Apr 11:00 | Knowledge Sharing | Main Auditorium | Academic Training Lectures | EN
Fresh results (and surprises) from the James Webb Space Telescope (1/2)

3 Apr 11:00 | Knowledge Sharing | Main Auditorium | Academic Training Lectures | EN
The other side of cosmology: what we learn from first galaxies and black holes (2/2)

3 Apr 16:30 | Knowledge Sharing | Main Auditorium & online | CERN Colloquium | EN
Superintelligent Agents Pose Catastrophic Risks: Can Scientist AI Offer a Safer Path?

4 Apr 10:30 | At CERN | Council Chamber & online | Association du personnel/Staff Association | FR & EN
Réunion publique Association du personnel / Public meeting Staff Association

4 Apr 14:00 | Knowledge Sharing | Council Chamber | KT Seminars | EN
Symposium to celebrate Ugo Amaldi’s 90th birthday

8–11 Apr | Accelerators | Globe of Science and Innovation | ICFA | EN
5th ICFA Beam Dynamics Mini-Workshop on Machine Learning for Particle Accelerators

9 Apr 11:00 | Knowledge Sharing | CERN Library | Archives, Library and Open Science events | FR
Meet the author of "Quantix", "Infinix" and "Cosmix"

9 Apr 13:30 et 15:30 | Knowledge Sharing | CERN Science Gateway | CERN Public events | FR
Les super-pouvoirs de l’Univers - Ateliers BD et sciences au CERN – part of CERN's Quantum! season

9 Apr 20:00 | Knowledge Sharing | CERN Science Gateway | CERN Public events | FR
Super Quantum! – part of CERN's Quantum! season

9–13 Apr | Knowledge Sharing | Palexpo | CERN Local engagement | FR
CERN Workshops (Wed, Sat & Sun) at the Salon of Inventions

10 Apr 18:00 | Knowledge Sharing | Online | CERN Alumni | EN
News from the Lab | Introduction and Status Report on the HL-LHC Project

14 Apr 11:00 | Knowledge Sharing | CERN Library | Archives, Library and Open Science events | FR
Meet the authors of "New Frontiers in Science in the Era of AI"

26 Apr | Knowledge Sharing | CERN Science Gateway | CERN Public events | FR
Girls in ICT 2025 – Découverte de l’informatique au CERN

29 Apr 10:00 | At CERN | 14/5-022 | HSE | EN
Stress Check-up Workshop / Atelier "Stress Check-up" – part of CERN’s new stress check-up programme

6 May 11:00 | Physics | Main Auditorium | EP Seminar | EN
Latest results from the KATRIN experiment

13 May 14:00 | At CERN | 73/1-031 | HSE | FR
Stress Check-up Workshop / Atelier "Stress Check-up" – part of CERN’s new stress check-up programme

14 May 12:00–16:00 | At CERN | Meyrin site | Running Club & Staff Association | EN & FR
Annual relay race followed by a celebration for the 70th anniversary of the Staff Association / Course relais annuelle suivie d'une célébration des 70 ans de l'Association du personnel

14–18 May | Knowledge Sharing | CERN Science Gateway | CinéGlobe | EN & FR
CinéGlobe Film Festival 2025 – Interwoven / Festival de films CineGlobe 2025 – Entrelacé

Registration now open

20–23 May | Engineering | CERN | FPGA Developers' Forum | EN
2nd FPGA Developers' Forum (FDF) meeting

23 May 14:00 | Knowledge Sharing | Online | Micro-Talks | EN
#16 Self-Care: Why should you care?

28 May | Knowledge Sharing | EPFL, Lausanne | Famelab | EN, FR or DE
Famelab Switzerland 2025 local heats, open to 18–35-year-olds

15–27 Jun | Accelerators | Bulgaria | CERN Accelerator School | EN
Pushing the Limits: Intensity Limitations in Hadron Beams

23–27 Jun | Physics | Venice, Italy | Update of the European Strategy for Particle Physics | EN
Open Symposium of the 2026 Update of the European Strategy for Particle Physics

23–28 Jun | Physics | Deadwood, South Dakota, USA | The Institute for Underground Science at SURF | EN
PPC 2025: XVIII International Conference on Interconnections between Particle Physics and Cosmology

6–19 Jul | Computing | Lund, Sweden | CERN School of Computing | EN
46th CERN School of Computing (CSC 2025)

8 Jul 10:30 | At CERN | 13/3-005 | HSE | EN
Stress Check-up Workshop / Atelier "Stress Check-up" – part of CERN’s new stress check-up programme

15–24 Jul | Physics | CICG, Geneva | ICRC | EN
ICRC 2025: 39th International Cosmic Ray Conference

1–13 Sep | Physics | Pisa, Italy | INFIERI | EN
INFIERI 2025: Intelligent signal processing for frontier research and industry

21 Sep–4 Oct | Accelerators | Spain | CERN Accelerator School | EN
Introduction to Accelerator Physics

This is a curated list of events relevant to the CERN community.
More events are available here: home.cern/events
Indico also shows ALL events happening today, this week and in a calendar view. 

If you would like your event to appear on an upcoming Bulletin events list, please contact bulletin-editors@cern.ch

Do you have questions about fire safety, emergency response or first aid?

The CERN Fire and Rescue Service is here to help!

Join us at our pop-up stands for interactive discussions, live demonstrations, hands-on experience with emergency equipment (e.g. fire extinguishers), and expert advice on:

• Fire safety at CERN and at home
• How to react in the event of an emergency
• Basic first-aid techniques
• Prevention

Two or three sessions will be held each month, rotating around CERN’s three restaurants. For the full programme, see: https://hse.cern/BeReadyBeSafe. Pop by, get involved and be prepared!

And, if you haven’t done so yet, why not complete your first-aid knowledge by attending the Life-Saving Actions training course? Find out more about course content and dates on the CERN learning hub.

Yesterday, at the annual Rencontres de Moriond conference taking place in La Thuile, Italy, the LHCb collaboration at CERN reported a new milestone in our understanding of the subtle yet profound differences between matter and antimatter. In its analysis of large quantities of data produced by the Large Hadron Collider (LHC), the international team found overwhelming evidence that particles known as baryons, such as the protons and neutrons that make up atomic nuclei, are subject to a mirror-like asymmetry in nature’s fundamental laws that causes matter and antimatter to behave differently. The discovery provides new ways to address why the elementary particles that make up matter fall into the neat patterns described by the Standard Model of particle physics, and to explore why matter apparently prevailed over antimatter after the Big Bang.

First observed in the 1960s among a class of particles called mesons, which are made up of a quark–antiquark pair, the violation of “charge-parity (CP)” symmetry has been the subject of intense study at both fixed-target and collider experiments. While it was expected that the other main class of known particles – baryons, which are made up of three quarks – would also be subject to this phenomenon, experiments such as LHCb had only seen hints of CP violation in baryons until now.

“The reason why it took longer to observe CP violation in baryons than in mesons is down to the size of the effect and the available data,” explains LHCb spokesperson Vincenzo Vagnoni. “We needed a machine like the LHC capable of producing a large enough number of beauty baryons and their antimatter counterparts, and we needed an experiment at that machine capable of pinpointing their decay products. It took over 80 000 baryon decays for us to see matter–antimatter asymmetry with this class of particles for the first time.”

Particles are known to have identical mass and opposite charges with respect to their antimatter partners. However, when particles transform or decay into other particles, for example as occurs when an atomic nucleus undergoes radioactive decay, CP violation causes a crack in this mirror-like symmetry. The effect can manifest itself in a difference between the rates at which particles and their antimatter counterparts decay into lighter particles, which physicists can log using highly sophisticated detectors and data analysis techniques. 

The LHCb collaboration observed CP violation in a heavier, short-lived cousin of protons and neutrons called the beauty-lambda baryon Λ_b, which is composed of an up quark, a down quark and a beauty quark. First, they sifted through data collected by the LHCb detector during the first and second runs of the LHC (which lasted from 2009 to 2013 and from 2015 to 2018, respectively) in search of the decay of the Λ_b particle into a proton, a kaon and a pair of oppositely charged pions, as well as the corresponding decay of its antimatter counterpart, the anti-Λ_b. They then counted the numbers of the observed decays of each and took the difference between the two.

The analysis showed that the difference between the numbers of Λ_b and anti-Λ_b decays, divided by the sum of the two, differs by 2.45% from zero with an uncertainty of about 0.47%. Statistically speaking, the result differs from zero by 5.2 standard deviations, which is above the threshold required to claim an observation of the existence of CP violation in this baryon decay.

While it has long been expected that CP violation exists among baryons, the complex predictions of the Standard Model of particle physics are not yet precise enough to enable a thorough comparison between theory and the LHCb measurement.

Perplexingly, the amount of CP violation predicted by the Standard Model is many orders of magnitude too small to account for the matter–antimatter asymmetry observed in the Universe. This suggests the existence of new sources of CP violation beyond those predicted by the Standard Model, the search for which is an important part of the LHC physics programme and will continue at future colliders that may succeed it.

“The more systems in which we observe CP violations and the more precise the measurements are, the more opportunities we have to test the Standard Model and to look for physics beyond it,” says Vagnoni. “The first ever observation of CP violation in a baryon decay paves the way for further theoretical and experimental investigations of the nature of CP violation, potentially offering new constraints for physics beyond the Standard Model.”

“I congratulate the LHCb collaboration on this exciting result. It again underlines the scientific potential of the LHC and its experiments, offering a new tool with which to explore the matter–antimatter asymmetry in the Universe,” says CERN Director for Research and Computing, Joachim Mnich.

On the evening of Friday, 11 April, CERN will participate in the fifth edition of “La nuit est belle !” . The aim of this initiative is to make turning off or reducing the intensity of public lighting in the middle of the night commonplace.

The theme of the fifth edition is “The culture… of the night.” The founding and organising partners chose this due to the power of culture to raise awareness and change practices.

CERN will join this initiative by switching off the lights all evening and night, of the Globe, the Science Gateway Portal, Gate E, the roads and car parks on the Meyrin and Prévessin sites, and the SPS and LHC sites, except where lighting is required for safety reasons.

If you are working at CERN, you can contribute by switching off your computers, monitors and lights when you go home. Please remember that switching off computers and lights is good practice in general to save energy and favour biodiversity at night, read more at https://hse.cern/content/energy-management.

During the evening and over the weekend, many activities will be organised in the local area.Visit https://lanuitestbelle.org for more information and to register for activities. You can also follow the event live on social media via the hashtag #lanuitestbelle.

Cyclists and pedestrians – make sure that you can be seen in the dark! Car-drivers – stay alert!

HSE recommends that you wear light-coloured clothing, preferably with reflectors, if you are out when it is dark. 

• People wearing dark clothes will be seen by a car from a distance of about 25 metres
• People wearing light-coloured clothes will be seen from a distance of about 40 metres
• People wearing reflectors will be seen from a distance of about 125 metres

The popular Bike to Work challenge is back for its 2025 edition. This Switzerland-wide initiative encourages us all to grab our handlebars throughout May and June. So, whether you’re a cycling pro or a beginner, it’s time for pedal power.

How to join:

1. Form a team of four and register on the Bike to Work website. No team? No problem – you can request to join an incomplete one.
2. Flexible rules: No registration fee, no minimum distance, and part of your commute can include public transport. One teammate can even walk, skateboard or use any non-motorised transport.

In this edition, CERN is once again joining forces with the State of Geneva and more than 40 local entities, including Geneva municipalities, public organisations and other international institutions. Together, we’ll make a bold statement promoting active mobility and well-being across Geneva. Winners will be rewarded with special prizes offered by participating organisations.

For more details and tips, check out the Bike to Work FAQ and Bike to CERN web pages. Stay safe by completing the Road Traffic – Bike Riding online course and reviewing CERN’s cycling safety tips.

Let’s hope for sunshine, safe roads and enjoyable cycling!

Last week, on 19 March, the first beam-based physics of the year began when protons from the PS hit the n_TOF target, producing the neutrons required for the n_TOF experiments. On that same day, physics was also scheduled to start in the PS East Area, but had to be delayed after an issue with a collimator in one of the four East Area beamlines was identified: the collimator was found to be partially closed and obstructing the beam path.

Collimators are key components used to remove unwanted halo particles from the beam. They consist of movable parts that can be adjusted electro-mechanically to set the beam’s aperture. In this case, the faulty collimator required replacement.

Under the coordination of the Experimental Areas (BE-EA) group, a team of experts from various domains quickly devised a plan for the replacement. However, accessing the collimator required the removal of the thick concrete shielding blocks above the beamline.

Initial estimates projected a delay of three to four days to the start of physics in the East Area, with hopes of resuming beam operations over the weekend. Thanks to the efficiency and excellent collaboration of the teams involved, the collimator was successfully replaced and the shielding reinstated in the early afternoon of 22 March. Beam for physics was delivered to the East Area at 4 p.m. that same day, just in time for the weekend and only two days behind the original schedule.

Meanwhile, beam commissioning in the SPS is progressing well. A high-intensity LHC-type beam, containing more protons per bunch than usual, is currently being used to “scrub” the vacuum chamber. This scrubbing process helps reduce the emission of secondary electrons, which in turn lowers the formation of electron clouds. Minimising electron-cloud effects is essential for stable beam conditions and quality when the LHC-type beam is eventually delivered to the LHC.

In parallel, SPS experts have been setting up the beam and its slow extraction for the SPS North Area. Slow extraction is a technique in which the accelerated beam is gradually extracted from the SPS over millions of turns. During each turn, only a small fraction of the beam is extracted, allowing the entire extraction process to span approximately 4.5 seconds.

In the coming weeks, beamline physicists will use this extracted beam to set up the various beamlines in the North Area, delivering the beam to the experiments. Physics in the North Area is scheduled to begin on 14 April.

In my previous report, I mentioned the presence of a small vacuum leak in the SPS. The opening and closing of this leak appear to be synchronised with the pulsing of the magnets, but the leak remains too small to be precisely located, making it impossible to determine with certainty which magnet needs to be replaced.

Depending on how one looks at it, the leak has fortunately or unfortunately not evolved; it remains present but stable. As time goes on, however, it is increasingly likely that a one-day stop during the physics run may be required to replace a magnet. That said, this decision will depend on whether the leak worsens and becomes easier to localise. We continue to monitor the situation closely and will keep you informed as it develops.

On the LHC side, testing of all power converters, electrical circuits, magnets and other systems is progressing well and is even slightly ahead of schedule. On the machine side all remains on track for the first beam injection, originally planned for 4 April.

However, we recently received some unfortunate news from the ATLAS experiment. A water leak was discovered in the cooling system of their argon calorimeter (detector), which now requires repair. To access the affected components, the detector must be opened on one side, which is usually a complex and time-consuming operation.

Despite the complexity of the operation, the resulting delay to the overall LHC schedule is expected to be limited to just two weeks. This situation highlights a key difference between the LHC and the rest of the accelerator complex: in the LHC, the experiments are fully integrated into the machine itself, meaning that an intervention in ATLAS directly affects the ability to inject and circulate beam. In contrast, experiments in the injector complex operate on separate beamlines and are therefore independent of accelerator operation.

The LHC machine teams are working closely with the ATLAS collaboration to develop a plan that makes most efficient use of the available time and keeps the delay to a minimum.

Originally, first beam was scheduled for 4 April, comfortably ahead of the Easter weekend. Many were pleased, as LHC beam commissioning has traditionally, though unintentionally, coincided with Easter. Now, if the two-week delay holds, the 2025 commissioning may once again fall during the Easter weekend. Have we discovered a new constant of nature? We’ll see in the coming days when the details become clearer…

Recently, the Computer Security Office reported on a cybersecurity incident at a remote Tier 2 site of the Worldwide LHC Computing Grid (WLCG). Compromised to the backbone, dozens of servers deeply infiltrated by the attackers, taken over and abused for cryptocurrency mining. For months. While the attackers’ earnings in dollars might reach five digits, the costs to that Tier 2 site are also significant. Let’s look at the ledger:

• Instead of performing physics computing, some nodes were mining cryptocurrency. This implies Tier-2-sponsored electricity being converted into Bitcoin and pocketed by the attackers. And computing resources were blocked from doing physics analysis.
• Since the detection in October 2024, the site has been taken offline. Hence, with their compute nodes down for four months now, this equates to about 5% of the investment in their computing power (assuming a hardware lifetime of eight years).
• On top of that comes the cost of reputational damage due to bad publicity and criticism in the media.
• The whole sysadmin team has since been occupied with incident response, delaying any software development. A team of five people occupied for four months results in twenty months of personpower (PM) in salaries paid for nothing productive. In addition, the CERN Computer Security Office has invested about 0.5 PM in recent months to help out with guidance, forensics and consultancy.
• Re-establishing full functionality will take even more time and resources and will require money for external consultancy, reviews and possibly training to avoid it happening again.

Given that we cannot disclose the local currency and the average salaries, of course, we cannot share a quantitative figure. But in abstract numbers over the whole time span of 6–8 months (detection, response and reinstallation) this adds up to 30–40 PM and 10% of their investment in compute. Or 10% of their committed computing power. Either number is non-negligible.

Compare that with the costs of implementing proper security measures prior to any incident. Actually, “prior” doesn’t even matter anymore as the same security measures will definitely need to be implemented in the aftermath. Any auditor, any incident responder and, in this particular case, even the attackers(!) pushed for such proper measures. And with 40 PM and 10% of the operating expenses of a computer centre, you can already put some decent security mechanisms in place. Firewalls. Monitoring. Better configurations. So, what about you? Ready to act prior to or after an incident?

______

Do you want to learn more about computer security incidents and issues at CERN? Follow our Monthly Report. For further information, questions or help, check our website or contact us at Computer.Security@cern.ch.

Particle physics is all about data, but so too is mobility at CERN. The data shows that we feel strongly about how we get to work and how we get around the CERN sites – on foot, by car, bike, shuttle and more. We see this in the large number of responses to CERN mobility surveys over the last decade. Interesting trends are emerging, and the Site and Civil Engineering (SCE) department is responding to them within CERN and in collaboration with our Host States.

Mobility masterplan

CERN’s first CERN mobility survey was conducted in 2014 following a request by Geneva’s Office cantonal des transports (OCT) that Geneva-based international organisations survey their populations about travel habits. This led to a joint mobility plan, drawn up between international organisations, the State of Geneva and the Swiss Mission, which included raising awareness about mobility issues. The launch of CERN’s first mobility survey marked the beginning of the mobility adventure and of concrete plans to improve parking management, communication and infrastructure.

CERN’s mobility plan was updated in 2024 to include action on motorised transportation, alternative mobility and accessibility, with a strong focus on sustainability. For the many new initiatives, SCE has taken the particle physics approach: we conduct a pilot, we test and analyse data, and then we go with the best solution. This has seen us step up efforts to support soft mobility across the CERN sites: increasing the bike fleet to 600, gradually installing more bike shelters, setting up bike repair points and charging points for e-bikes, and many more as explained in detail at the recent SCE seminar.

Host State collaboration

Our mobility plan has also seen CERN work closely with the French and Swiss authorities to improve mobility in the areas surrounding the CERN sites. CERN played a decisive role in the planning and construction of the Route de l’Europe cycle path linking the Meyrin and Prévessin sites. Improvements to cycle paths around Meyrin Entrance A and the Prévessin entrance are under development and are expected later this year.

Public transport has continued to be reinforced over the years, with more frequent buses and trams. This is set to continue to improve in the years to come. 

Sustainable transport

In September 2025, the SCE department will be launching a Mobility Week for the CERN community with the aim of encouraging alternative, sustainable transport through challenges, games and prizes (more details to come).

In the meantime, mobility survey data shows that bicycle use at CERN increased by 8% between 2017 and 2023. With spring now beginning and thousands of bicycle parking spaces available across the CERN sites, it’s time to get ready for this year’s Bike2Work challenge in May and June – let’s see if we can beat last year’s records.

Join CERN on Friday, 4 April to celebrate the achievements and long career of Ugo Amaldi as he turns 90.

Ugo Amaldi joined CERN as a fellow in September 1961. He then spent 10 years at the Italian health institute Istituto Superiore di Sanità in Rome, performing experiments in nuclear and particle physics alongside radiation physics and radiotherapy. Returning to CERN, he helped to discover the rise in energy in the proton–proton cross-section at the Intersecting Storage Rings, and later led the DELPHI collaboration at the Large Electron–Positron Collider (LEP). In the early 1990s, he founded the TERA Foundation, introducing hadron therapy to Italy. Today, he continues to promote the use of accelerators in cancer treatment and is president emeritus of the National Centre for Oncological Hadrontherapy (CNAO) in Pavia.

Hear all about his outstanding contributions to physics and society on Friday, 4 April, from 2 p.m. in the Main Auditorium. Distinguished scientists will present and discuss his major achievements, including his contributions to particle physics while at CERN, the creation of the TERA Foundation, the design of novel particle accelerators for hadron therapy and his role in setting up an international network for cancer treatment with proton and ion beams. The celebrations will then continue with a drinks reception.

Register now to attend in person. The event is open to all, but registration is required for organisational purposes and to issue CERN access cards for non-CERN attendees. A webcast will also be available for the event.

Read more in an interview with Ugo Amaldi in the latest CERN Courier that draws on his childhood memories and his distinguished career at CERN to offer deeply personal insights into his father Edoardo’s foundational contributions to international cooperation in science. See also his contribution to the CERN70 feature series: From physics to medicine.

Spring is in the air! As the accelerator complex starts to awaken, so too does the biodiversity on the CERN site. But it’s not just blossom on the trees and sheep returning to graze – the vast CERN sites are home to a plethora of species.

To celebrate spring, we’re launching an online nature-themed scavenger hunt, using the “biodiversity walk” website. Created by SCE’s Geographic Information System team, the biodiversity walk takes you on a comprehensive virtual tour of CERN’s biodiversity around Meyrin, Prévessin and beyond.

Participants in the scavenger hunt will have a chance to win two CAGI Choco Passes courtesy of Geneva Tourism and the International Geneva Welcome Centre (CAGI), which runs a cultural kiosk at CERN. The Choco Passes are for two people to spend a day exploring Geneva and sampling chocolates from a range of different chocolate shops.

Here’s how to enter the scavenger hunt:

• Open the biodiversity walk website at cern.ch/biodiversity-walk.
• Use the information you find there to answer the questions below.
• Send your answers to bulletin-editors@cern.ch by Monday, 14 April, 11.59 p.m. CEST from your CERN email address.

All entries will go into a prize draw and the winner of the two Choco Passes will be announced in the next edition of the Bulletin. Good luck!

Questions:

1. Eighteen species of which type of plant can be found across the CERN sites?
2. Which snake can be seen slithering near LHC Point 6? No need to worry, it is harmless and, if threatened, will play dead. 
3. Which species has yellow translucent wings and can be found near Crozet? It is not a dragonfly, even if it may look like one.
4. Which bird, found on the Prévessin site, has the impressive multitasking skills of eating, sleeping and even mating in mid-flight?
5. Which common bird sings alongside a beautiful experiment?

In late 2023, Wojciech Brylinski was analysing data from the NA61/SHINE collaboration at CERN for his thesis when he noticed an unexpected anomaly – a strikingly large imbalance between charged and neutral kaons in argon–scandium collisions. He found that, instead of being produced in roughly equal numbers, charged kaons were produced 18.4% more often than neutral kaons. This suggested that the so-called “isospin symmetry” between up and down quarks might be broken by more than expected due to the differences in their electric charges and masses – a discrepancy that existing theoretical models would struggle to explain. Known sources of isospin asymmetry only predict deviations of a few percent.

“When Wojciech got started, we thought it would be a trivial verification of the symmetry,” says Marek Gaździcki, who was spokesperson of NA61/SHINE at the time of the discovery. “We expected the symmetry to be closely obeyed – although we had previously measured these types of discrepancies at the NA49 experiment, they had large uncertainties and were not significant.”

Isospin symmetry is one facet of flavour symmetry, whereby the strong interaction treats all quark flavours identically. This means that all types of quarks should behave the same under the strong interaction, except for kinematic differences arising from their different masses. Isospin is not a symmetry of the electromagnetic interaction as up and down quarks have different electric charges. According to isospin symmetry, strong interactions in heavy-ion collisions should generate nearly equal amounts of charged kaons (comprising either an up quark and a strange antiquark or an up antiquark and a strange quark) and neutral kaons (comprising either a down quark and a strange antiquark or a down antiquark and a strange quark), given the similar masses of the up and down quarks. NA61/SHINE’s data contradicts the hypothesis of equal yields with a 4.7σ significance.

“I see two ways to interpret the results,” says Francesco Giacosa, a theoretical physicist working with NA61/SHINE. “First, we might be substantially underestimating the role of electromagnetic interactions in creating quark–antiquark pairs. Second, these results could mean that strong interactions do not obey flavour symmetry. If this is true, it would contradict physicists’ current understanding of quantum chromodynamics (QCD), that is, how quarks and gluons (carriers of the strong interaction) combine.”

While the experiment routinely measures particle yields in nuclear collisions, finding a discrepancy in isospin symmetry was not something the researchers were actively looking for. NA61/SHINE’s primary focus is studying properties of the production of hadrons in the production of hadrons when beams from CERN’s Super Proton Synchrotron collide with a variety of fixed nuclear targets. This data is also shared with neutrino and cosmic ray experiments, such as T2K, to help them to refine their models.

The collaboration is now planning additional studies on this new result, using different projectiles, targets and collision energies to determine whether this effect is unique to certain heavy-ion collisions or is a more general feature of high-energy interactions. It has also put out a call to theoretical physicists to help explain what might have caused such an unexpectedly large asymmetry.

“We tried to fit the data into the current, existing models, but it didn’t work at all — it was just not possible,” says Giacosa. “We need more experimental data and more theoretical predictions to fill our gap in knowledge of the strong interaction. So the real question is: what’s next?”

Read more:

• Paper: Evidence of isospin-symmetry violation in high-energy collisions of atomic nuclei
• CERN Courier article: Isospin symmetry broken more than expected

After several years of intense work, CERN and international partners have completed a study to assess the feasibility of a possible Future Circular Collider (FCC). Reflecting the expertise of over a thousand physicists and engineers across the globe, the report presents an overview of the different aspects related to the potential implementation of such a project.

The FCC is a proposed particle collider with a circumference of about 91 km that could succeed CERN’s current flagship instrument – the 27-km Large Hadron Collider (LHC) – in the 2040s. Its scientific motivation stems from the discovery of the Higgs boson in 2012, along with other crucial outstanding questions in fundamental physics.

The Higgs boson is the simplest yet most perplexing particle discovered so far, with properties that have far-reaching implications for our existence. It is related to the mechanism that enabled elementary particles such as electrons to gain mass a fraction of a nanosecond after the Big Bang, allowing atoms and thus structures to form. It may also be connected to the fate of the Universe and could potentially shed light on the many unsolved mysteries of modern physics.

As described in Feasibility Study Report, the FCC research programme outlines two possible stages: an electron–positron collider serving as a Higgs, electroweak and top-quark factory running at different centre-of-mass energies, followed at a later stage by a proton–proton collider operating at an unprecedented collision energy of around 100 TeV. The complementary physics programmes of each stage match the highest priorities set out in the 2020 update of the European Strategy for Particle Physics.

The report covers wide-ranging aspects related to the potential implementation of such a project. These include physics objectives, geology, civil engineering, technical infrastructure, territorial and environmental dimensions, R&D needs for the accelerators and detectors, socioeconomic benefits, and cost.

The estimated cost of construction of the FCC electron–positron stage, including the tunnel and all the infrastructure, is 15 billion Swiss francs. This investment, which would be distributed over a period of about 12 years starting from the early 2030s, includes the civil engineering, technical infrastructure, electron and positron accelerators and four detectors for operation. As was the case for the construction of the LHC, the majority of the funding would come from CERN’s current annual budget.

CERN has made a commitment that any new project at the Laboratory would be an exemplar of a sustainable research infrastructure, integrating ecodesign principles into every phase of the project, from design to construction, operations and dismantling. The report details the concepts and paths to keep the FCC’s environmental footprint low while boosting new technologies to benefit society and developing territorial synergies such as energy reuse.

A major component of the FCC Feasibility Study has been the layout and placement of the collider ring and related infrastructure, which have been diligently studied to maximise the scientific benefit while taking into account territorial compatibility, environmental and construction constraints and cost. No fewer than 100 scenarios were developed and analysed before settling on the preferred option: a ring circumference of 90.7 km at an average depth of 200 m, with eight surface sites and four experiments.

Throughout the Feasibility Study process, CERN has been accompanied by its two Host States, France and Switzerland, working with entities at the local, regional and national levels. Engagement processes with the public are being prepared in line with the Host States’ respective frameworks to ensure a constructive dialogue with territorial stakeholders.

The report, which does not imply any commitments by the CERN Member and Associate Member States to build the FCC, will be reviewed by various independent expert bodies before being examined by the CERN Council at a dedicated meeting in November 2025. The Council may take a decision on whether or not to proceed with the FCC project around 2028.

Particle colliders play a unique role in physics exploration. They also enable the development of unprecedented technologies in many fields of relevance for society, ranging from superconducting materials for medical applications, fusion energy research and electricity transmission to advanced accelerators and detectors for medical and many other applications.

The FCC Feasibility Study was launched following the recommendations of the 2020 update of the European Strategy for Particle Physics and will serve as input for the ongoing update of the Strategy, along with studies of alternative projects proposed by the scientific community.

Further information: 

• Future Circular Collider Feasibility Study Report Volume 1: Physics and Experiments is here
• Future Circular Collider Feasibility Study Report Volume 2: Accelerators, technical infrastructure and safety is here
• Future Circular Collider Feasibility Study Report Volume 3: Civil Engineering, Implementation and Sustainability is here 
• The media kit about the FCC Feasibility Study is here. 

Quantum entanglement is a fascinating phenomenon where two particles’ states are tied to each other, no matter how far apart the particles are. In 2022, the Nobel Prize in Physics was awarded to Alain Aspect, John F. Clauser and Anton Zeilinger for groundbreaking experiments involving entangled photons. These experiments confirmed the predictions for the manifestation of entanglement that had been made by the late CERN theorist John Bell. This phenomenon has so far been observed in a wide variety of systems, such as in top quarks at CERN’s Large Hadron Collider (LHC) in 2024. Entanglement has also found several important societal applications, such as quantum cryptography and quantum computing. Now, it also explains the famous herd mentality of sheep.

A flock of sheep (ovis aries) has roamed the CERN site during the spring and summer months for over 40 years. Along with the CERN shepherd, they help to maintain the vast expanses of grassland around the LHC and are part of the Organization’s long-standing efforts to protect the site’s biodiversity. In addition, their flocking behaviour has been of great interest to CERN's physicists. It is well known that sheep behave like particles: their stochastic behaviour has been studied by zoologists and physicists alike, who noticed that a flock’s ability to quickly change phase is similar to that of atoms in a solid and a liquid. Known as the Lamb Shift, this can cause them to get themselves into bizarre situations, such as walking in a circle for days on end.

Now, new research has shed light on the reason for these extraordinary abilities. Scientists at CERN have found evidence of quantum entanglement in sheep. Using sophisticated modelling techniques and specialised trackers, the findings show that the brains of individual sheep in a flock are quantum-entangled in such a way that the sheep can move and vocalise simultaneously, no matter how far apart they are. The evidence has several ramifications for ovine research and has set the baa for a new branch of quantum physics.

“The fact that we were having our lunch next to the flock was a shear coincidence,” says Mary Little, leader of the HERD collaboration, describing how the project came about. “When we saw and herd their behaviour, we wanted to investigate the movement of the flock using the technology at our disposal at the Laboratory.”

Observing the sheep’s ability to simultaneously move and vocalise together caused one main question to aries: since the sheep behave like subatomic particles, could quantum effects be the reason for their behaviour?

“Obviously, we couldn’t put them all in a box and see if they were dead or alive,” said Beau Peep, a researcher on the project. “However, by assuming that the sheep were spherical, we were able to model their behaviour in almost the exact same way as we model subatomic particles.”

Using sophisticated trackers, akin to those in the LHC experiments, the physicists were able to locate the precise particles in the sheep’s brains that might be the cause of this entanglement. Dubbed “moutons” and represented by the Greek letter lambda, l, these particles are leptons and are close relatives of the muon, but fluffier.

The statistical significance of the findings is 4 sigma, which is enough to show evidence of the phenomenon. However, it does not quite pass the baa to be classed as an observation.

“More research is needed to fully confirm that this was indeed an observation of ovine entanglement or a statistical fluctuation,” says Ewen Woolly, spokesperson for the HERD collaboration. “This may be difficult, as we have found that the research makes physicists become inexplicably drowsy.”

“While entanglement is now the leading theory for this phenomenon, we have to take everything into account,” adds Dolly Shepherd, a CERN theorist. “Who knows, maybe further variables are hidden beneath their fleeces. Wolves, for example.”

Did you know that the camera sensor in your smartphone could help unlock the secrets of antimatter? The AEgIS collaboration, led by Professor Christoph Hugenschmidt’s team from the research neutron source FRM II at the Technical University of Munich (TUM), has developed a detector using modified mobile camera sensors to image in real time the points where antimatter annihilates with matter. This new device, described in a paper just published in Science Advances, can pinpoint antiproton annihilations with a resolution of about 0.6 micrometres, a 35-fold improvement over previous real-time methods.

AEgIS and other experiments at CERN’s Antimatter Factory, such as ALPHA and GBAR, are on a mission to measure the free-fall of antihydrogen within Earth’s gravitational field with high precision, each using a different technique. AEgIS’s approach involves producing a horizontal beam of antihydrogen and measuring its vertical displacement using a device called a moiré deflectometer that reveals tiny deviations in motion and a detector that records the antihydrogen annihilation points.

“For AEgIS to work, we need a detector with incredibly high spatial resolution, and mobile camera sensors have pixels smaller than 1 micrometre,” says Francesco Guatieri, the principal investigator on the paper. “We’ve integrated 60 camera sensors into our detector, enabling it to achieve a resolution of 3840 mega pixels – the highest pixel count of any imaging detector to date.”

Previously, photographic plates were the only option, but they lacked real-time capabilities,” added Guatieri. “Our solution, demonstrated for antiprotons and directly applicable to antihydrogen, combines photographic-plate-level resolution, real-time diagnostics, self-calibration and a good particle collection surface, all in one device.”

The researchers used commercial optical image sensors that had previously been shown to be capable of imaging low-energy positrons in real time with unprecedented resolution. “We had to strip away the first layers of the sensors, which are made to deal with the advanced integrated electronics of mobile phones,” says Guatieri. “This required high-level electronic design and micro-engineering.”

A key factor in achieving the record resolution was an unexpected element: crowdsourcing. “We found that human intuition currently outperforms automated methods,” says Guatieri. The AEgIS team asked their colleagues to manually determine the position of the antiproton annihilation points in each of the more than 2500 detector images, a procedure that turned out to be far more accurate and precise than any algorithm. The only downside: it took up to 10 hours for each colleague to plough through every annihilation event.

“The extraordinary resolution also enables us to distinguish between different annihilation fragments,” says AEgIS spokesperson Ruggero Caravita. By measuring the width of tracks of different annihilation products, the researchers can investigate whether the tracks are produced by protons or pions.

“The new detector paves the way for new research on low-energy antiparticle annihilation, and is a game-changing technology for the observation of the tiny shifts in antihydrogen caused by gravity,” says Caravita.

Read more:

Paper: Real-time antiproton annihilation vertexing with sub-micron resolution

The CMS collaboration at CERN has observed an unexpected feature in data produced by the Large Hadron Collider (LHC), which could point to the existence of the smallest composite particle yet observed. The result, reported at the Rencontres de Moriond conference in the Italian Alps this week, suggests that top quarks – the heaviest and shortest lived of all the elementary particles – can momentarily pair up with their antimatter counterparts to produce an object called toponium. Other explanations cannot be ruled out, however, as the existence of toponium was thought too difficult to verify at the LHC, and the result will need to be further scrutinised by CMS’s sister experiment, ATLAS.

High-energy collisions between protons at the LHC routinely produce top quark–antiquark pairs (tt-bar). Measuring the probability, or cross section, of tt-bar production is both an important test of the Standard Model of particle physics and a powerful way to search for the existence of new particles that are not described by the 50-year-old theory. Many of the open questions in particle physics, such as the nature of dark matter, motivate the search for new particles that may be too heavy to have been produced in experiments so far.

CMS researchers were analysing a large sample of tt-bar production data collected in 2016–2018 to search for new types of Higgs bosons when they spotted something unusual. Additional Higgs-like particles are predicted in many extensions of the Standard Model. If they exist, such particles are expected to interact most strongly with the singularly massive top quark, which weighs in at 184 times the mass of the proton. And if they are massive enough to decay into a top quark–antiquark pair, this should dominate the way they decay inside detectors, with the two massive quarks splintering into “jets” of particles.

Observing more top–antitop pairs than expected is therefore often considered to be a smoking gun for the presence of additional Higgs-like bosons. The CMS data showed just such a surplus. Intriguingly, however, the collaboration observed the excess top-quark pairs at the minimum energy required to produce a pair of top quarks. This led the team to consider an alternative hypothesis long considered difficult to detect: a short-lived union of a top quark and a top antiquark, or toponium.

While tt-bar pairs do not form stable bound states, calculations in quantum chromodynamics – which describes how the strong nuclear force binds quarks into hadrons – predict bound-state enhancements at the tt-bar production threshold. Though other explanations – including an elementary boson such as appears in models with additional Higgs bosons – cannot be ruled out, the cross section that CMS obtains for a simplified toponium-production hypothesis is 8.8 picobarns with an uncertainty of about 15%. This passes the “five sigma” level of certainty required to claim an observation in particle physics, and makes it extremely unlikely that the excess is just a statistical fluctuation.

If the result is confirmed, toponium would be the final example of quarkonium – a term for unstable quark–antiquark states formed from pairings of the heavier charm, bottom and perhaps top quarks. Charmonium (charm–anticharm) was discovered simultaneously at Stanford National Accelerator Laboratory in California and Brookhaven National Laboratory in New York in the November Revolution in particle physics of 1974. Bottomonium (bottom–antibottom) was discovered at Fermi National Accelerator Laboratory in Illinois in 1977. Charmonium and bottomonium are approximately 0.6 and 0.4 femtometres in size respectively, where one femtometre is a millionth of a nanometre. Bottomonium is thought to be the smallest hadron yet discovered. Given its larger mass, toponium is expected to be far smaller – qualifying it as the smallest known hadron.

For a long time, it was thought that toponium bound states were unlikely to be detected in hadron–hadron collisions. The top quark decays into a bottom quark and a W boson in the time it takes light to travel just 0.1 femtometre – a fraction of the size of the particle itself. Toponium would therefore be unique among quarkonia in that its decay would be triggered by the spontaneous disintegration of one of its constituent quarks rather than by the mutual annihilation of its matter and antimatter components.

CMS and ATLAS are now working closely to study the effect, which remains an open scientific question.

For further details, consult the full report in CERN Courier magazine or visit the CMS website.

On 28 March, the CERN Council concluded an intense week of presentations and discussions covering the full range of CERN’s activities. The delegates congratulated CERN and its personnel on a spectacular year in 2024, with the accelerators, detectors and computing breaking new performance records and with the release of beautiful physics results from across our scientific programme. This was demonstrated by the depth and breadth of the 2024 Annual Progress Report.

Highlights from CERN’s knowledge transfer activities showed the far-reaching impact of particle physics research across environmental, aerospace, healthcare, digital and other applications. The Member States also approved the use of isotopes produced at CERN’s MEDICIS facility for clinical treatment, reinforcing CERN's commitment to translating scientific research and innovation into societal benefits.

The Council approved the admission of Chile and Ireland as new Associate Member States, subject to completion of the necessary accession and ratification processes in the countries. I hope that the agreements can be signed soon so that we can welcome these countries into the CERN family in the near future.  The Council also endorsed CERN’s management structure for the period 2026–2030, as proposed by the Director-General designate, Professor Mark Thomson.

The process for the update of the European Strategy for Particle Physics is in full swing, with input from the community submitted by the deadline of 31 March. The Physics Preparatory Group and the European Strategy Group are preparing to review the contributions, which will then be extensively discussed at the Open Symposium that will be held in Venice in June.

Throughout the week, the Council’s discussions highlighted the strong and sustained support of our Member and Associate Member States for CERN’s mission and personnel, for which we are very grateful. I would also like to take this opportunity to express, on behalf of the Directorate, our heartfelt thanks to you, the CERN community, for your hard work and dedication to the Organization.

In my first months as Director-General Designate, I’ve been privileged to have enriching discussions with the current Management and have consulted widely across the Organization. Meeting so many brilliant and committed colleagues has been a real inspiration, and I wish to take this opportunity to thank you all for such a warm welcome to CERN.

The input that I have received over the past months has helped me to define CERN’s Directorate structure for 2026–2030, which was endorsed at the March CERN Council session. Here, I would like to explain briefly what is going to change from 2026 and, just as importantly, what is not.

The endorsed structure outlines the different sectors, but I have not yet taken any decisions on the future Directors themselves. I intend to present the nominations for the Directors to the CERN Council in June, and the nominations for the Department Heads at the Council session in September. I would like to thank all members of CERN Council for their support and endorsement of this first step.

CERN priorities for 2026–2030

In considering the new structure, I felt it important to avoid making changes for the sake of change, and my reflections for my upcoming mandate are as much about management culture and practices as they are about structure. Ultimately, the new structure is motivated by the Organization’s key priorities for the coming years.

I believe that CERN’s main scientific priorities for 2026–2030 will be:

• Completing the High Luminosity LHC (HL-LHC) and the timely completion of the upgrades of the ATLAS and CMS experiments. This must be our collective top priority.
• Building consensus through the European Strategy for Particle Physics (ESPP) process for the Future Circular Collider (FCC) or an alternative flagship project for CERN.
• Proactively engaging with key stakeholders to consolidate the collective sense of ownership and build political consensus for CERN’s long-term future.
• Progressing with the planning and decision making for proposed upgrades of the ALICE and LHCb experiments.
• Developing a long-term vision and roadmap to exploit the CERN injector complex, in order to deliver an exciting, diverse programme of experiments for Physics Beyond Colliders.

Beyond the HL-LHC, many other activities will, of course, be taking place during the coming Long Shutdown (LS3), including consolidation and operation of the injector complex.

Management structure for 2026–2030

As Director-General, I will be supported by a team of five Directors, each responsible for a sector:

• The Accelerators and Technology sector will remain largely unchanged, with the current four departments remaining, as I firmly believe that the risk of introducing delays due to disruption from restructuring outweighs any potential gains. Nonetheless, some increased priority will need to be given to support the installation of the ATLAS and CMS upgrades.
• The Research and Computing sector will also remain largely unchanged, but with an enhanced focus on supporting the installation of the ATLAS and CMS upgrades.
• The Stakeholder Relations sector will replace the current International Relations sector, with a somewhat broader scope to reflect key activities towards the realisation of the FCC, should it be prioritised by the ESPP. For example, increased emphasis will be placed on our Member States, the Host States and the European Union.
• The Finance and Human Resources sector will see some changes in scope, the main one being that the Site and Civil Engineering (SCE) department will move to a new Site Operations sector.
• The Site Operations sector will be a new sector and the Director’s role will be similar to that of a traditional Chief Operation Officer (COO), focusing on those operational activities, such as SCE, that span multiple sectors. Some fine details of the full scope of this new sector will be developed when the new Director is selected.

In addition, I will introduce a new non-departmental role of Chief Information Officer (CIO), reporting directly to the Director-General. This strongly aligns with the recommendations from the Audit Committee concerning cross-organisational authority for governance of IT-related activities. Nevertheless, as is the case now, the resources for these IT-related activities and the responsibility for their delivery will remain within the relevant sectors.

Looking beyond the structure

The broad range of the activities that will take place in LS3 should not be underestimated. Success will rely upon CERN’s incredible personnel, the wider scientific community and other partners. With many LS3 activities running in parallel, how we work together will be at least as important as the management structure. I always strive to lead collaboratively and intend to further embed the culture of trust and empowerment at CERN, with decisions being systemically delegated to, and taken at, the appropriate level. I have always found it important to provide clarity and transparency in decision making and in setting organisational priorities, with effective internal communication. This will ensure that we have a clear collective understanding of the main priorities for CERN so that we can work together as a community to deliver our main goals.

Building on the solid foundation of the current CERN management objectives, we will continue the Organization’s commitment to address imbalances in industrial and personnel return to the Member States for CERN’s long-term future. I also want to strengthen support for CERN users, other associated members of the personnel, and the major experiment collaborations to foster the best possible environment to ensure the success of the HL-LHC, including the experiment upgrades.

Next steps

Over the coming months, I will be fine-tuning my plans and will continue discussions with the current Management and with colleagues across the Organization. We have an exciting time ahead of us and I am looking forward to working together with colleagues across CERN and with our key stakeholders to deliver our priorities.