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Searching for matter–antimatter asymmetry with the Higgs boson

Wed, 22/06/2022 - 17:47
Searching for matter–antimatter asymmetry with the Higgs boson

Symmetries make the world go round, but so do asymmetries. A case in point is an asymmetry known as charge–parity (CP) asymmetry, which is required to explain why matter vastly outnumbers antimatter in the present-day universe even though both forms of matter should have been created in equal amounts in the Big Bang.

The Standard Model of particle physics – the theory that best describes the building blocks of matter and their interactions – includes sources of CP asymmetry, and some of these sources have been confirmed in experiments. However, these Standard Model sources collectively generate an amount of CP asymmetry that is far too small to account for the matter–antimatter imbalance in the universe, prompting physicists to look for new sources of CP asymmetry.

In two recent independent investigations, the international ATLAS and CMS collaborations at the Large Hadron Collider (LHC) turned to the Higgs boson that they discovered ten years ago to see if this unique particle hides a new, unknown source of CP asymmetry.

The ATLAS and CMS teams had previously searched for – and found no signs of – CP asymmetry in the interactions of the Higgs boson with other bosons as well as with the heaviest known fundamental particle, the top quark. In their latest studies, ATLAS and CMS searched for this asymmetry in the interaction between the Higgs boson and the tau lepton, a heavier version of the electron.

To search for this asymmetry, ATLAS and CMS first looked for Higgs bosons transforming, or “decaying”, into pairs of tau leptons in proton–proton collision data recorded by the experiments during the second run of the LHC (2015–2018). They then analysed this decay’s motion, or “kinematics”, which depends on an angle, called the mixing angle, that quantifies the amount of CP asymmetry in the interaction between the Higgs boson and the tau lepton.

In the Standard Model, the mixing angle is zero and thus the interaction is CP symmetric, meaning that it remains the same under a transformation that swaps a particle with the mirror image of its antiparticle. In theories that extend the Standard Model, however, the angle may deviate from zero and the interaction may be partially or fully CP asymmetric depending on the angle; an angle of -90 or +90 degrees corresponds to a fully CP-asymmetric interaction, whereas any angle in between, except 0 degrees, corresponds to a partially CP-asymmetric interaction.

After analysing their samples of Higgs boson decays into tau leptons, the ATLAS team obtained a mixing angle of 9 ± 16 degrees and the CMS team −1 ± 19 degrees, both of which exclude a fully CP-asymmetric Higgs boson­–tau lepton interaction with a statistical significance of about three standard deviations.

The results are consistent with the Standard Model within the present measurement precision. More data will allow researchers to either confirm this conclusion or spot CP asymmetry in the Higgs boson–tau lepton interaction, which would have a profound impact on our understanding of the history of the universe.

With the third run of the LHC set to start soon, the ATLAS and CMS collaborations won’t need to wait too long before they can feed more data into their analysis kits to find out whether or not the Higgs boson hides a new source of CP asymmetry.

abelchio Wed, 06/22/2022 - 16:47 Byline Ana Lopes Publication Date Thu, 06/23/2022 - 12:00

Environmental awareness: exploring CERN’s biodiversity

Wed, 22/06/2022 - 14:42
Environmental awareness: exploring CERN’s biodiversity

It’s morning. You’re walking to your workplace. The sun is shining, and you look down at the greenery along the path. What do you see? Is that wild thyme? Sorrel? And look, a pyramidal orchid! You might know that CERN has several sites, but what you might not know is that the Organization spans 625 hectares, 415 of which are non-built environments. This land hosts a variety of species and ecosystems, including endangered species of wild orchid.

Over time, the Laboratory has implemented several measures to promote biodiversity on its land, with an approach based on low-intensity maintenance to foster biodiversity preservation, keeping watering to a minimum and eliminating fertilisers and chemicals wherever possible. CERN delays grass mowing and uses sheep grazing to allow the flora’s full life cycle to complete. In addition to its fenced sites, CERN also owns 136 hectares of woodland, mainly located along the surface path of the SPS accelerator. These forests, most of which are located in France, are jointly managed by CERN and the French forestry commission (Office National des Forêts – ONF). To ensure minimum mechanical intervention, be more respectful of the land and reduce damage to woodland soil, horse logging is used to remove fallen trees, a forest management measure in regular use since 2012.

In 2020, the Organization set up a working group on biodiversity with four key objectives: conserving and protecting natural spaces in the CERN domain; developing biodiversity in fenced and unfenced areas; establishing measures for biodiversity for new development projects on CERN sites; and defining indicators to monitor biodiversity at CERN. The proposed action plan for 2021–2025 identified several measures to be approved, funded and implemented by the CERN Environmental Protection Steering board (CEPS), two of which have already been set in motion.

The first one is to draw up guidelines for biodiversity considerations concerning new construction at CERN. These 11 guidelines aim to align CERN with the French and Swiss regulations on biodiversity protection. They cover a range of subjects, such as new plantations, invasive species, green roofs and tree compensation. An example of the latter is the recent planting of 200 trees on the Meyrin site over three years, compensating for previously felled trees due to ageing and construction work. This measure is aligned with CERN’s Masterplan 2040, released at the end of 2021, which adopts principles and standards to promote biodiversity when developing the site. Specific measures have been developed not only to preserve CERN’s natural heritage, but also to strengthen biodiversity on the land managed by CERN.

The second measure that has been launched involves surveys of various species of fauna and flora on the CERN sites. Conducting surveys is crucial to monitor populations and will enable CERN to identify zones of biological interest and their importance and help put in place concrete protection measures. Based on expert recommendations, the inventories will focus on flora, amphibians, insects and birds. The first surveys have already started: during the inventory of amphibians, two species of frog as well as two protected species of newt were found. A first inventory of the flora led to the identification of a new orchid species on the CERN site, the burnt-tip orchid. The inventory of birds is still under way.

CERN’s biodiversity working group will continue to investigate other issues, such as light pollution, which can negatively impact night wildlife, as well as urban heat islands. Planting more trees and vegetation on site will help mitigate this phenomenon, which occurs in areas with high artificial infrastructure and little to no greenery. While concrete and asphalt absorb heat, vegetation helps cool the air and thus keeps the temperature stable.

The Organization is also committed to improving biodiversity downstream of its activities. In 2020, CERN co-signed a charter initiated by WWF Geneva for the revitalisation of the Nant d’Avril, the second largest affluent to the Rhône in the Geneva basin. In addition to improving water quality, the project will boost the biodiversity of the entire watershed. The project will run until 2033 and the actions taken will promote recolonisation by some target species, namely the brown trout, the fire salamander and the grass snake.

Next time you take a walk on the CERN site, engage your senses and notice the many species that surround you. Meanwhile, you can catch a glimpse of CERN’s biodiversity in this short video.

(Video: CERN)


This article is a part of the series “CERN’s Year of Environmental Awareness”.

thortala Wed, 06/22/2022 - 13:42 Publication Date Wed, 06/22/2022 - 13:35

Fire and rescue service newcomers successfully complete their induction

Tue, 21/06/2022 - 13:07
Fire and rescue service newcomers successfully complete their induction

In the past few weeks, you might have noticed some of our firefighter colleagues wearing a red T-shirt that reads “Firefighter in induction”. The red T-shirt feature – to distinguish firefighters in induction from established colleagues – was proposed by former firefighter newcomers themselves to ensure that their status was duly marked and clear to the CERN community.

On Friday, 10 June, a special ceremony was held at the CERN Fire and Rescue Service (FRS) to mark the completion of the nine-week long induction process for the seven newcomers, who joined the FRS on 1 April 2022. The induction comprises training on all the different risks and specificities of the CERN sites and activities, delivered by both FRS colleagues and external trainers. During the ceremony, the newcomers were formally presented with their official uniform, characterised by a dark blue T-shirt, as well as their full equipment for intervention in any situation on the CERN sites. It was the first such ceremony following the many months of COVID-19 pandemic restrictions, which made it a particularly special event.

anschaef Tue, 06/21/2022 - 12:07 Byline HSE unit Publication Date Tue, 06/21/2022 - 12:05

Higgs10: Big Bang Day

Tue, 21/06/2022 - 09:58
Higgs10: Big Bang Day

It was at 9.30 a.m. on 10 September 2008 that the LHC’s first beam was injected, in the full glare of the global media spotlight. Just under one hour later, a beam had been successfully steered all the way around the ring, to scenes of great emotion at the Laboratory. A long wait was over, LHC page 1 became the focus of everyone’s attention around the Lab, and a new era of research seemed about to get under way, but the sense of euphoria was to be short-lived.

In the days that followed, things went well, but then disaster struck: during a ramp to full energy, one of the 10 000 superconducting joints between the magnets failed, causing extensive damage that took more than a year to recover from.

Image of a LHC beam screen recorded on 10 September 2008, showing two spots corresponding to the successful circulation of protons once around the machine. (Image: CERN)

It was unheard of to start a machine like the LHC in the public eye, but I’m assured we had little choice. In the months and weeks before the start-up, particle physics had never seen so much media attention. A small number of individuals on social media had managed to stir up the myth that the LHC would create a world-eating black hole, and the newspapers were full of it. They were going to come to CERN whether we asked them or not, so we invited them in on the basis that it would be better to have them inside the Lab than outside, telling the world that CERN was starting up the “black hole machine” behind locked doors. Over 300 media outlets came, BBC Radio 4 did an unprecedented full day of outside broadcast from CERN, and an estimated billion people watched as I gave the countdown to that first beam. I thought I was just talking to physicists in the main auditorium!

Those joyful events of 10 September firmly established CERN’s place in the public eye, while the failure of a magnet interconnection just over a week later ensured the Laboratory would stay there. There was, and there remains, fascination with the human endeavour that particle physics represents, and the media were kind to us on the whole. But for me, the most important part of the story was somewhat lost.

The LHC is unique. Like any energy-frontier accelerator, it is its own prototype, and building it was a learning experience from the start. Despite the serious nature of the setback in September 2008, it was really just another step, albeit a big one, on a long learning curve. As with previous setbacks, the LHC team was hard at work the next day to ensure that we could recover as fast as possible. We soon understood the problem, and we had all the spares we needed. It took a year to put right, but we knew straight away what we had to do.

It’s a great tribute to the global particle physics community that setbacks are confronted with a confident, positive approach. In 2004, after we’d installed a full sector of the cryogenic distribution line (QRL), it failed and had to be removed from the tunnel. To me, this was a much bigger issue than the 2008 event, since it required the whole LHC installation schedule to be rearranged while the contractor made good the problem with considerable help from CERN. Our Director-General at the time, Robert Aymar, was an engineer, and he understood the magnitude of the problem perfectly. He was the unsung hero in liberating the resources needed to get it fixed. It’s also thanks to him that we have Linac4, a key part of the HL-LHC project, whose construction began during his mandate. Later, in 2007, one of the so-called inner triplets, which perform the final focus of the beams, failed a high-pressure test in the LHC tunnel. It was remarkable how quickly CERN staff came up with an innovative and elegant solution, and implemented it with the help of colleagues from Fermilab, KEK and the Lawrence Berkeley National Laboratory.

Following repairs and consolidation, on 29 November 2009 there were beams circulating again in the LHC, and full commissioning could get under way. The experiments had had an extra year to prepare, and although I’m sure they’d have preferred beam in 2008, they were in perfect shape to start data taking. Every cloud has a silver lining. This time, start-up went very quickly. The injector chain worked beautifully, as always, with even higher performance than we’d anticipated: a great tribute to our predecessors who built those machines from the 1950s onwards. We’d also learned a lot from LEP, and instrumentation was very much improved. The LHC physics programme, at an initial energy of 3.5 TeV per beam, began in earnest in March 2010.

I’m an accelerator physicist, but I want to finish by talking about the experiments. It’s not only the LHC that took technology way beyond anything that had ever been done before. Like the accelerator team, the experimental collaborations had also learned much from their predecessors. The previous generation of hadron collider experiments had luminosities two orders of magnitude lower to deal with, they had around a million readout channels compared with the LHC experiments’ up to 100 million, and their data rates and volumes were also much smaller. It’s thanks to the efforts of a global, multidisciplinary collaboration that the LHC project delivered so well on its promise right from the moment data taking began, re-measuring everything we’d learned before about the Standard Model of particle physics in the first few months of operation, and then going on to new discoveries. But that’s a story for another day.

thortala Tue, 06/21/2022 - 08:58 Byline Lyn Evans Publication Date Mon, 06/20/2022 - 17:18

The CERN Library gets a facelift

Mon, 20/06/2022 - 17:23
The CERN Library gets a facelift

The Library is at the heart of CERN and plays a key role in supporting scientific research in the Organization. It offers a range of services, including a quiet space to study and think. Since its conception in the 1950s, the use of its space has changed dramatically, and the time has come for a makeover to meet the requirements of a modern library in terms of furniture quality and ergonomics and to address environmental and safety concerns.

To achieve these goals, the CERN Library is going to be renovated soon. Work will start in autumn 2022 and is due to end one year later. This makeover is the final stage of a long process, including an in-depth reflection, surveys and stakeholders’ interviews to get feedback on the use of Library premises and services and to learn about readers’ expectations.

You can find the guiding style of some areas of the renovated Library in the pictures below, as designed by the architecture firm Bisset Adams, which worked closely with the Site and Civil Engineering department and in accordance with the requirements of the Scientific Information service.

Library collections and the Bookshop will remain accessible during the renovation work. Practical information on the organisation of library services as well as regular updates about the progress of the work will follow in the coming months.

In recognition of the crucial importance of library services for scientific research, measures will be taken to minimise any inconvenience caused by the renovation.

If you have any feedback or questions, please contact us at

thortala Mon, 06/20/2022 - 16:23 Byline SCE department CERN Library Publication Date Mon, 06/20/2022 - 16:20

Don’t miss the live stream of the launch of Run 3!

Mon, 20/06/2022 - 15:45
Don’t miss the live stream of the launch of Run 3!

A mere day after the 10th anniversary of the discovery of the Higgs boson celebrations at CERN, the LHC will make the promise of a bright future for Higgs research a reality, breaking a new energy world record of 13.6 trillion electron volts (13.6 TeV) in its first stable-beam collisions. These collisions will mark the start of data taking for the new physics season, called Run 3.

The launch of the LHC Run 3 will be streamed live on CERN’s social media channels and by high-quality Eurovision satellite link on 5 July starting at 4 p.m. Live commentary in five languages (English, French, German, Italian and Spanish) from the CERN Control Centre will walk you through the operation stages that take proton beams from their injection into the LHC to collision points. A live Q&A session with experts from the accelerators and experiments will conclude the live stream.

Fitted out to cope with the more intense beam, the LHC will allow physicists to collect more data during Run 3 (which will last until the end of 2025) than they did in the first two runs combined. The upcoming physics season will be focused on the study of the properties of the Higgs and the search for physics beyond the Standard Model of particle physics.

Join us for this historic event: connect on FacebookYouTubeInstagram or LinkedIn


Visit this page for a list of events surrounding the start of Run 3 and the anniversary of the discovery of the Higgs boson. 

(Video: CERN)


thortala Mon, 06/20/2022 - 14:45 Publication Date Mon, 06/20/2022 - 14:30

Join CERN in a historic week for particle physics

Mon, 20/06/2022 - 15:12
Join CERN in a historic week for particle physics

CERN is set for jam-packed, exciting and ecstatic days starting on 3 July with the first celebrations of the ten-year anniversary of the discovery of the Higgs boson, a scientific symposium on 4 July and ending on a high note on 5 July, with collisions at unprecedented energy levels at the Large Hadron Collider (LHC) marking the launch of the new physics season at CERN’s flagship accelerator. Be it physically at CERN or online from around the world, we invite you to join us in celebrating past and present achievements for particle physics and science, as well as looking ahead to how CERN is preparing future research.


Marking the anniversary of the discovery of the Higgs boson

Ten years ago, on 4 July 2012, a packed CERN Auditorium watched the ATLAS and CMS collaborations present compelling evidence for the discovery of the Higgs boson, thus confirming the existence of the Brout-Englert-Higgs mechanism, first predicted by theorists in the 1960s.  The subsequent 10 years have seen impressive advances in our understanding of the Higgs boson's properties, and how they determine the features of the universe. There is much more still to be learned. On 3 and 4 July 2022, we look back at where a decade of Higgs science has brought the field and look forward to exciting new prospects. 

(Image: CERN)

A special evening is planned at the Globe of Science and Innovation, on 3 July, at 5 p.m. After a discussion with Mark Levinson, film Director, and Walter Murch, film editor and Academy Awards Oscar winner, you are invited to watch their documentary “Particle Fever”, which follows particle physicists on their hunt for the Higgs boson. The screening will be followed by a discussion with CERN Director-General Fabiola Gianotti and other CERN characters in the movie. Registration is needed to reserve a seat inside the Globe. A live webcast of both the film and discussion will be available online and screened outside the Globe.

The most scientifically oriented amongst you will without a doubt enjoy the centrepiece of the celebrations surrounding the anniversary of this historical discovery: a full-day (9.00 a.m.–6.00 p.m.) scientific symposium from CERN’s main auditorium on 4 July. Eminent speakers, ranging from CERN Director-Generals to theorists, will share their recollections of the discovery, look at what’s been learned since, present the latest results and take a look ahead at what’s still to come.

Remote attendance from around the world is possible as the full symposium will be webcast with live English captions. The morning session will also be webcast in French.


Follow the start of a new season of physics data-taking live

No time will be wasted to make the promises of a bright future for Higgs research a reality: the day after the celebrations, the LHC, which restarted on April 2022, will reach a new energy world-record of 13.6 trillion electronvolts (13.6 TeV) in stable-beam collisions, marking the start of data-taking for the new physics season, called Run 3. The event, which will be streamed live on multiple platforms, is the culmination of more than three years of work to push the performances of the collider and its four main detectors to their limit. The larger and higher-quality data samples collected by the LHC experiments will allow scientists to continue stress-testing the Standard Model of Particle Physics, further understand the properties of the Higgs boson and advance in cracking some of the outstanding mysteries of the universe.

(Video: CERN)

The start of Run 3 of the LHC will be streamed live on CERN’s social media channels and high quality Eurovision satellite link on 5 July starting at 4 p.m.. Live commentary in five languages (English, French, German, Italian, Spanish) from the CERN Control Centre will walk you through the stages that take proton beams from their injection into the LHC to the collision points. A live Q&A session with experts from the accelerators and experiments, and questions from the audience, will conclude the livestream.

While biding your time until the excitement starts, browse our article series on the history of Higgs research, from the theorisation of the Higgs boson in 1964 to its discovery and beyond. New articles coming up!


thortala Mon, 06/20/2022 - 14:12 Byline Thomas Hortala Publication Date Mon, 06/20/2022 - 13:55

I.FAST launches a new fund to support innovation in accelerator technologies

Mon, 20/06/2022 - 12:07
I.FAST launches a new fund to support innovation in accelerator technologies

Since 2021, the EU-funded I.FAST project has been developing innovative technologies that are common to multiple accelerator platforms and defining strategic roadmaps for their future development. Coordinated by CERN, the project brings together 49 participants who are helping to prepare for the next step of particle physics research, improve the sustainability of accelerator-based science and meet the specific needs of applications for society.

The project’s Internal Innovation Fund (IIF) was created to stimulate innovation in accelerator technologies. The fund’s primary objective is to encourage I.FAST partners to identify innovative solutions with viable industrial or commercial potential. This fast-track, competitive process will finance emerging technologies and innovative processes, research, business models and other solutions, at both the development and the prototype stages.

Technologies supported by the IIF must be capable of advancing the state of the art in fields related to the I.FAST thematic areas. They must also contribute to improving the sustainability of particle accelerator facilities by reducing their electricity consumption or footprint, improving their performance without increasing their environmental impact, or directly serving the environment.

The project’s thematic areas include:

  • Novel particle accelerator concepts and technologies
  • High-luminosity accelerators for light sources
  • Innovative superconducting magnets
  • Innovative superconducting thin-film-coated cavities
  • Advanced accelerator technologies and materials
  • Sustainable concepts and technologies
  • Societal applications
  • Technology infrastructure

Individual projects will receive from 100 to 200 kEUR in funding until the available funds (1 MEUR) have been exhausted. To qualify for support, the projects’ consortia must include at least one I.FAST beneficiary and one industrial partner.

To submit your proposal, complete the submission form on the I.FAST website by 15 September 2022.

Find out more about the application process by visiting the I.FAST website or by contacting Marcello Losasso, the fund manager.

thortala Mon, 06/20/2022 - 11:07 Byline Antoine Le Gall Publication Date Mon, 06/20/2022 - 11:02

The ARIES project, a promoter of innovation and accessibility for accelerators, comes to a close

Mon, 20/06/2022 - 11:53
The ARIES project, a promoter of innovation and accessibility for accelerators, comes to a close

Over the past five years, the ARIES (Accelerator Research and Innovation for European Science and Society) project has brought together 41 partners from academia and industry from 18 different European countries with the aim of developing key accelerator technologies to make present and future machines more efficient, affordable, reliable and sustainable.

Coordinated by CERN, this Horizon-2020-funded project has broken new ground for the accelerator community, and leaves an impressive legacy: the European ecosystem of accelerator centres is now stronger than ever, with easily accessible facilities, well-highlighted synergies and new plans to improve current technologies and infrastructures.

One of the project’s main endeavours was to facilitate transnational access. With the aim of providing a wide range of European researchers and industry with access to top-class accelerator research and test infrastructures, ARIES set up a network of 14 accelerator test facilities across Europe. Users can carry out tests within five separate domains: magnet, material, electron and proton beam, radiofrequency, and plasma beam. With over 23 000 hours of testing for 307 users, the scheme generated interesting new science and expanded the project’s user community.

Video presentation of the ARIES project in its early days as a new initiative to improve particle accelerators and make them more compact and easier to use outside research. (Video: CERN)

ARIES played a critical role in investigating and promoting new prospects for accelerator research and development. It was a breeding ground for research in plasma and laser-based acceleration, a field now driven in Europe by EuPRAXIA, another promising EU-funded project. Furthermore, ARIES support was key in ensuring the continuation of initiatives such as studies on high-temperature superconductivity and the revival of the studies on muon colliders. In 2022, a prototype electron gun for electron lenses was assembled and tested by four ARIES collaborators, and breakthrough results were achieved in the fields of thin superconducting films and materials for extreme thermal management.

One of ARIES’s key objectives was strong interaction with industry. The project benefited from enhanced industrial participation, with the involvement of seven industries and one association, and ran three new co-innovation programmes with industry. It also identified and supported a wealth of technologies with societal and environmental applications, such as a particle accelerator system to remove harmful emissions from ship exhausts.

With its mission fulfilled, ARIES is now coming to a close. However, its succession is ensured thanks to two new projects. I.FAST, started in April 2021, will continue and build on ARIES’s legacy of joint R&D activities with industry to develop ideas and technologies for the next generation of particle accelerators. In parallel, EURO-LABS will further the transnational access tradition of ARIES, forging even closer ties between research centres by creating a new, synergetic network of research facilities for accelerator, detector and nuclear technologies.

thortala Mon, 06/20/2022 - 10:53 Byline Antoine Le Gall Publication Date Mon, 06/20/2022 - 10:49

CMS on the lookout for new physics

Fri, 17/06/2022 - 15:18
CMS on the lookout for new physics

With Run 3 of the LHC just around the corner, the LHC experiments are still publishing new results based on the previous runs’ data. Despite no new discoveries being announced, small deviations from expectations are appearing in a small number of analyses. At the current level these deviations can still be attributed to random fluctuations in data, but they indicate regions that need to be investigated closely once the new stream of collisions arrives. Below are a few examples published recently by the CMS collaboration.

In 2017 CMS recorded a spectacular collision event containing four particle jets in the final state. The invariant mass of all four jets was 8 TeV and the jets could be divided into two pairs with a 1.9 TeV invariant mass each. Such a configuration could be produced if a new particle with an 8 TeV mass was created in the collision of proton beams, and subsequently decayed into a pair of – again, new – particles, with masses of 1.9 TeV. In a new analysis recently published by CMS, a search for such twin pairs of jets with matching invariant masses is performed for data collected up to the end of LHC Run 2. Surprisingly, a second event with similarly striking properties was found, with a 4-jet mass of 8.6 TeV and 2-jet masses of 2.15 TeV. These two events can be clearly seen in the plot below, where the 4-jet events are plotted as a function of the 2-jet and 4-jet mass.

Number of events observed (colour scale), plotted as a function of four-jet mass and the average mass of the two dijets. The two points in the top right correspond to the two interesting events. (Image: CMS)

While nearly all observed events with two pairs of jets are produced by strong interactions between the colliding photons, events with such high invariant masses are extremely unlikely. The probability of seeing two events at these masses without any new phenomena being present is of the order of 1 in 20 000, corresponding to a local significance of 3.9σ. While this may appear to be a very strong signal at first, given that the area of masses that are being analysed is large it is important to also look at global significance, which indicates the probability of observing an excess anywhere in the analysed region. For the two events the global significance is only 1.6σ.

Two other searches for new heavy particles are reporting small excesses in data. In a search for high mass resonances decaying into a pair of W bosons (that then decay into leptons) the highest deviation corresponds to a signal hypothesis with a mass of 650 GeV, with local significance at 3.8σ and global significance of 2.6σ. In a search for heavy particles decaying into a pair of bosons (WW, WZ or other combinations, also including Higgs bosons) that subsequently decay into pairs of jets, the data diverge from expectations in two places. The signal hypothesis is a W’ boson with a mass of 2.1 or 2.9 TeV, decaying into a WZ pair and the highest local significance is 3.6σ, with a global significance of 2.3σ.

Another new result comes from searches looking for extra Higgs boson particles decaying into tau pairs. For a new particle with a 100 GeV mass there is a small excess seen in the data with 3.1σ local and 2.7σ global significance. Interestingly, this coincides with a similar excess seen by CMS in a previous search for low-mass resonances in the two-photon final state. Another excess is visible in the high-mass range, with the largest deviation from the expectation observed for a mass of 1.2 TeV with a local (global) significance of 2.8σ (2.4σ).

The tau pair final state was also used to look for hypothetical new particles called leptoquarks. This is of particular interest since leptoquarks could potentially explain the flavour anomalies that have been observed by the LHCb experiment, so if the anomalies are indeed a manifestation of some new phenomena, this would be a way to independently look at these phenomena from a different angle. No excess has been found by CMS so far, but the analysis is only just beginning to be sensitive to the range of leptoquark parameters that could fit the flavour anomalies, so more data is needed to fully explore the leptoquark hypothesis.

The new LHC data-taking period is set to start in July, at higher energy and with significantly upgraded detectors, promising a fresh stream of data for searches for new phenomena.

Read more in the CERN Courier and CMS publications here, here and here

ptraczyk Fri, 06/17/2022 - 14:18 Byline Piotr Traczyk Publication Date Fri, 06/17/2022 - 14:13

CERN Council declares its intention to terminate cooperation agreements with Russia and Belarus at their expiration dates in 2024

Fri, 17/06/2022 - 12:03
CERN Council declares its intention to terminate cooperation agreements with Russia and Belarus at their expiration dates in 2024 CERN Council statement

At its 208th meeting yesterday, the CERN Council reiterated its denunciation of the continuing illegal military invasion of Ukraine by the Russian Federation with the involvement of the Republic of Belarus, which has resulted in a widespread humanitarian crisis and significant loss of life. CERN was established in the aftermath of World War II to bring nations and people together for the peaceful pursuit of science. Member States recalled that the core values of the Organization have always been based upon scientific collaboration across borders as a driver for peace, and stressed that the aggression of one country against another runs counter to these values.

The Council declared that it intends to terminate CERN’s International Cooperation Agreements (ICAs) with the Russian Federation and the Republic of Belarus at their expiration dates in 2024. However, the situation will continue to be monitored carefully and the Council stands ready to take any further decision in the light of developments in Ukraine.

CERN’s International Cooperation Agreements, ICAs, normally run for five years, and are tacitly renewed for the same period unless a written notice of termination is provided by one party to the other at least six months prior to the renewal date. The ICA with the Russian Federation expires in December 2024, that with the Republic of Belarus in June 2024.

These measures follow those already adopted at an extraordinary meeting of the Council on 8 March, and at the Council’s regular meeting on 25 March. The Council reaffirmed that all decisions taken to date, along with the actions undertaken by the Management, which have had a marked impact on the involvement of the Russian Federation and the Republic of Belarus in the scientific programme of the Organization, remain in force.

The Council also decided to review CERN’s future cooperation with the Joint Institute for Nuclear Research (JINR) well in advance of the expiration of the current ICA in January 2025.

The full text of the Council’s resolutions can be found here.

mailys Fri, 06/17/2022 - 11:03 Publication Date Fri, 06/17/2022 - 13:10

Harnessing a supercomputer for ATLAS

Thu, 16/06/2022 - 11:04
Harnessing a supercomputer for ATLAS

The ATLAS collaboration uses a global network of data centres – the Worldwide LHC Computing Grid – to perform data processing and analysis. These data centres are generally built from commodity hardware to run the whole spectrum of ATLAS data crunching, from reducing the raw data coming out of the detector down to a manageable size to producing plots for publication.

While the Grid’s distributed approach has proven very successful, the computing needs of the LHC experiments keep expanding, so the ATLAS collaboration has been exploring the potential of integrating high-performance computing (HPC) centres in the Grid’s distributed environment. HPC harnesses the power of purpose-built supercomputers constructed from specialised hardware, and is used widely in other scientific disciplines. 

However, HPC poses significant challenges for ATLAS data processing. Access to supercomputer installations are typically subject to more restrictions than Grid sites and their CPU architectures may not be suitable for ATLAS software. Their scheduling mechanisms favour very large jobs using many thousands of nodes, which is atypical of an ATLAS workflow. Finally, the supercomputer installation may be geographically distant from storage hosting ATLAS data, which may pose network problems.

Despite these challenges, ATLAS collaborators have been able to successfully exploit HPC over the last few years, including several near the top of the famous Top500 list of supercomputers. Technological barriers were overcome by isolating the main computation from the parts requiring network access, such as data transfer. Software issues were resolved by using container technology, which allows ATLAS software to run on any operating system, and the development of “edge services”, which enables computations to run in an offline mode without the need to contact external services.

The most recent HPC centre to process ATLAS data is Vega – the first new petascale EuroHPC JU machine, hosted in the Institute of Information Science in Maribor, Slovenia. Vega started operation in April 2021 and consists of 960 nodes, each of which contains 128 physical CPU cores, for a total of 122 800 physical or 245 760 logical cores. To put this in perspective, the total number of cores provided to ATLAS from Grid resources is around 300 000.

Due to close connections with the community of ATLAS physicists in Slovenia, some of whom were heavily involved in the design and commissioning of Vega, the ATLAS collaboration was one of the first users to be granted official time allocations. This was to the benefit of both the ATLAS collaboration, which could take advantage of a significant extra resource, and Vega, which was supplied with a steady, well-understood stream of jobs to assist in the commissioning phase. 

Vega was almost continually occupied with ATLAS jobs from the moment it was turned on, and the periods where fewer jobs were running were due to either other users on Vega or a lack of ATLAS jobs to submit. This huge additional computing power – essentially doubling ATLAS’s available resources – was invaluable, allowing several large-scale data-processing campaigns to run in parallel. As such, the ATLAS collaboration heads towards the restart of the LHC with a fully refreshed Run 2 data set and corresponding simulations, many of which have been significantly extended in statistics thanks to the additional resources provided by Vega.

It is a testament to the robustness of ATLAS’s distributed computing systems that they could be scaled up to a single site equivalent in size to the entire Grid. While Vega will eventually be given over to other science projects, some fraction will continue to be dedicated to ATLAS. What’s more, the successful experience shows that ATLAS members (and their data) are ready to jump on the next available HPC centre and fully exploit its potential.

ndinmore Thu, 06/16/2022 - 10:04 Byline ATLAS collaboration Publication Date Thu, 06/16/2022 - 09:50

Five CERN apprentices received their diplomas in 2021

Thu, 09/06/2022 - 12:02
Five CERN apprentices received their diplomas in 2021

In 2021, four CERN technical apprentices(1) completed their training. Two electronics technicians, Lois Gonnon and Adrian Grosclaude, and two physics laboratory technicians, Lenny Emmenegger and Florian Jenny, received their certificat fédéral de capacité (CFC) after four years of training at CERN. No mean feat, given the global health crisis over the last two years!

Lois Gonnon and Florian Jenny were also among the winners of the Union Industrielle Genevoise (UIG) prizes awarded in each field of industrial mechatronics. In addition, Florian Jenny won the Socorex Science Merit prize for his excellent results in the end-of-apprenticeship exams.

More than 300 students have benefited from the technical apprentice programme – CERN’s oldest professional training programme – since it began in 1966. It was launched by the Geneva authorities, which were keen to collaborate with CERN, and quickly took off. The records below show how the programme evolved over the years.

Records of technical apprentice recruitment between 1966 and 1990. (Image: CERN)

Since 1999, the apprentice programme has included library apprentices(2) as well as technical apprentices. 25 young people have obtained their diploma in this field at CERN since the programme was launched. The most recent graduate, Laurène Come, received hers in 2021, after three years of training. Since the start of the 2021 academic year, CERN has also been hosting a commercial apprentice(3).

Since 2020, all CERN apprentices have taken part in various workshops designed to raise their awareness of different topics within their specialism and help them to develop their personal skills and to network with their peers. The 2020 “resilience” workshop and the 2021 workshop on “data protection and the dangers associated with the digital world” were organised by CERN’s Learning and Development group, in collaboration with the leaders of the various apprentice programmes. These events are run by expert trainers and their content has been specially developed for apprentices.

In 2021, apprentices were hosted by the EN-MME, TE-VSC, TE-MPE, SY-BI, SY-RF, TE-MSC, SY-EPC, BE-CEM, EP-ESE and EP-DT groups and, outside CERN, by the Hôpitaux universitaires de Genève (HUG) and the Haute école du paysage, d'ingénierie et d'architecture de Genève (HEPIA).

CERN’s apprentice programme team wishes to thank the host groups and, in particular, the supervisors, for the high quality of teaching and support provided througout the training period, without which the programme would not be possible.


(1) The CERN technical apprentice programme trains mechanical technicians, electronics technicians and physics laboratory technicians. It is coordinated by the recently created RAS-APP section within the TE department. For more information on the programme, see its new website:! Alternatively, you can contact Virginia Prieto Hermosilla (TE-RAS-APP).

(2) The library apprentice programme is coordinated by the Scientific Information service (SIS) in the Research and Computing sector (RCS). For more information, please contact Anne Gentil-Beccot (RCS-SIS-LB).

(3) CERN’s commercial apprentice programme is coordinated by the HR department. For more information, please contact Fanny Cantin (HR-CBS-B).

anschaef Thu, 06/09/2022 - 11:02 Byline Cristina Coman Publication Date Thu, 06/09/2022 - 10:53

Computer Security: Wrong link, wrong login, and BOOM

Wed, 08/06/2022 - 15:46
Computer Security: Wrong link, wrong login, and BOOM

Clicking on a malicious link or attachment, or disclosing your password in reply to a malignant email or on a fake and nasty CERN Single Sign-On page, are two major attack vectors for the evil side to infiltrate CERN. That’s why the Computer Security team is testing you again (see here) and again (see here) with its clicking campaigns (and see here). The aim of these campaigns is to introduce you to the drawbacks of the email protocol (“E-mail is broken and there is nothing we can do”), make you aware of the threats of so-called social engineering (“Got a call from "Microsoft"? The social way of infecting your PC”), and enable you to detect the less sophisticated emails designed by attackers to make you click and infect your computer or lose your password (“Click and infect”).

While we have had lots of positive feedback –

– and also some good, constructive – and sometimes less constructive – feedback, it seems that you’re getting used to these campaigns.


Some special species at CERN even impatiently look forward to our campaigns, race to be the first to click and get in touch with us :) or disclose their discovery via internal communication channels :(.


These clicking campaigns may be “predictable” and “annoying”. Still, they follow the recommendations of the French government and good industry practices. Importantly, the vast majority of the feedback we got was positive. People who identified the spam emails correctly were glad and pleased to have succeeded. And those who did click appreciated the reminder that the online world can be evil. Hopefully, they won’t click next time! Remember what’s at stake: CERN’s operations and reputation! After all, a security report shows that about 24% of incidents have a malicious email as the initial vector. And attachments are a very common way to pown multimillion companies (see here and here). It would be great if, together, we could spare CERN from such nasty surprises.

So, please watch out and check any email before answering, opening attachments or clicking on embedded links:


Similarly, make sure that you enter your CERN password only on either the new or old CERN Single Sign-On pages, and, respectively:


Help us to protect the Organization. STOP – THINK – DON’T CLICK. And, ideally, opt into our multi-factor authentication pilot, which provides the silver bullet to protect your account. And, if you happen to have received a suspicious email, just delete it and/or report it to us at For more information on how to recognise malicious emails, check out our general recommendations.


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

anschaef Wed, 06/08/2022 - 14:46 Byline Computer Security team Publication Date Thu, 05/26/2022 - 14:36

What will the future LHC beam dumps be made of?

Wed, 08/06/2022 - 13:02
What will the future LHC beam dumps be made of?

The HiRadMat-56 (HRMT-56) experiment was designed and set up in barely a year, during the period from October 2020 to October 2021, in order to answer a question that was as urgent as it was crucial: how should the future HL-LHC beam dumps and the new spare LHC beam dumps be designed? The autopsy performed on one of the accelerator’s old beam dumps had revealed that one of its components, namely extruded graphite, had cracked under the repeated impact of the beam (see the corresponding article entitled “Autopsy of an LHC beam dump”). But what could be used instead of extruded graphite? How could the resistance of the materials that might one day absorb the beams of the LHC and the future HL-LHC be assessed? “We wanted to understand, quantitatively, how various materials would behave under the impact of a high-energy beam,” explains Pablo Andreu Munoz, an engineer in the SY-STI group. “So we designed a custom test station at HiRadMat.”

The HRMT-56 experiment installed on its beamline at HiRadMat. (Image: CERN)

The HRMT-56 experiment consists of an aluminium vessel under a controlled atmosphere, where some targets are under vacuum and others under nitrogen gas; the vessel contains 20 target trains, each of which can hold several different samples. By means of a “lift” system, the target trains pass one after another into the 440-GeV/c proton beam supplied by the SPS. The beam hits each sample around four times. The dimensions of the beam and targets are selected such that the energy density generated on impact is comparable to that generated when a 7-TeV beam collides with a beam dump. Moreover, the experiment is equipped with “beam diluters”: titanium tubes containing cylinders made of denser materials, which are located upstream of the targets and allow the amount of energy that hits them to be increased. It is thus possible to reach energy density values close to those that are anticipated during Run 3, and even at the future HL-LHC. On the menu: various types of low- and high-density graphite, silicon carbide reinforced with carbon fibres, and “carbon–carbon”, a material made of woven carbon fibres in a graphic matrix that is notably used in space shuttles.

The targets are inserted into the aluminium vessel. (Image: CERN)

“The targets are fitted with various sensors, notably temperature probes and laser Doppler accelerometers, which provide live information on the effect of the beam on the samples,” explains François-Xavier Nuiry, head of the HRMT-56 experiment. “We also compare the target trains, in a radiation bunker, before and after irradiation. The samples are analysed from all perspectives, before and after impact, using various means, including metrology, microtomography, mass measurements and surface studies.”

The SY-STI-TCD team analyses samples after irradiation, in the radiation bunker. (Image: CERN)

The first data, obtained in January 2022, confirmed the results of the autopsy: the low- and high-density graphites are fit for use in the spare LHC beam dumps. The carbon–ؘcarbon also produced very promising results, notably for various HL-LHC beam dumps. It will also replace extruded graphite in the spare dumps.

During the second phase of the HRMT-56 experiment, which will take place in 2024, the samples will be massively irradiated – to the tune of several hundred impacts per target – by the SPS beams.

anschaef Wed, 06/08/2022 - 12:02 Byline Anaïs Schaeffer Publication Date Wed, 06/08/2022 - 11:40

Autopsie d’un absorbeur de faisceaux du LHC

Wed, 08/06/2022 - 12:48
Autopsy of an LHC beam dump

During LS2, the LHC’s two external beam dumps were removed from the tunnel and replaced with spare ones. After ten years of operation, they were showing signs of degradation, notably nitrogen leaks. Before being installed, the spare dumps were modified and upgraded to prevent the same problems from occurring during Run 3 (see this Bulletin article published in 2020).

To find out more about the cause of the nitrogen leaks, an endoscopy was carried out in July 2020. It revealed unexpected cracks in the beam dump’s two extruded graphite discs (see box). An action plan was drawn up by the SY-STI (Sources, Targets and Interactions) group as more information was needed with Run 3 on the horizon, especially with a view to designing new spare beam dumps for the LHC and, beyond that, beam dumps for the HL-LHC. To access the dump’s three main components – high-density, low-density and extruded graphite (see box) – there was only one possible solution: perform an “autopsy” on one of the dumps. Given its radioactivity levels, this was easier said than done.

“To reach the heart of the beam dump, we needed to be able to open it…,” says project leader Ana-Paula Bernardes. “But its duplex-stainless-steel-alloy housing was extremely difficult to cut. The first attempt, in January 2021, under a framework contract, was unsuccessful: it was impossible to cut through it manually without exceeding the radiation dose limits. We considered outsourcing the job to a specialised external company with the right equipment for the task, but the costs and time frames were incompatible with the project.”

Thanks to the expertise and versatility of CERN’s teams, a solution was eventually found in house: the SY-STI and BE-CEM (Controls, Electronics and Mechatronics) groups worked together to develop two techniques that would allow the dump’s housing to be cut remotely. The first involved an automated circular saw mounted on a rail, and the second a robot arm equipped with a cutter. Several trial runs were carried out on a mock-up in order to “choreograph” the operation and thus limit, as far as possible, the time spent in close proximity to the dump. The circular saw was ultimately used to make five cuts, in a sealed radiation chamber created specially for the job: two radial cuts to separate the low-density graphite block and three longitudinal cuts to remove the stainless-steel-alloy housing.

Longitudinal test cut with the circular saw, performed by the SY-STI group. Solution chosen for the cutting of the radioactive dump. (Image: CERN)


Longitudinal test cut with the robot arm, performed by the BE-CEM group. (Image: CERN) Positioning of the automated, rail-mounted circular saw for the first radial cut, performed by the SY-STI group. (Image: CERN) The first longitudinal cut. (Image: CERN)



The highly radioactive stainless-steel-alloy housing is removed by the EN-HE (Handling Engineering) group to allow access to the low-density graphite.(Image: CERN)

“As the endoscopy had already shown, both extruded graphite discs were cracked. Against all expectations, the low-density graphite was generally in good condition, as were the high-density-graphite blocks,” says Ana-Paula Bernardes.

The upstream extruded graphite disc (the first to be hit by the beam) is cracked. (Image: CERN)

“It was important to check the condition of the various components of the dump and establish how resistant they were, for various reasons,” explains Marco Calviani, leader of the Targets, Collimators and Dumps (STI-TCD) section in the SY department. “First of all, we needed to be sure that the dumps currently installed in the LHC – which are built from the same components as the autopsied dump – would withstand the energy levels of Run 3; next, we wanted to know what strategy to adopt for the two new spare dumps, which we need to design and manufacture by 2023, and especially for the dumps for the future HL-LHC.”

The results of the autopsy validated the use of low-density and high-density graphite for Run 3, but ruled out the use of extruded graphite for the design of the spare dumps. Other studies are under way at the HiRadMat facility (see the corresponding article entitled “What will the future LHC beam dumps be made of?”) to confirm these results and to test new materials, notably for the HL-LHC beam dumps. What about the dumps that are already in place? “The modifications made before their installation should greatly improve their resistance for Run 3, even though the energy to be dissipated is set to increase from 320 MJ to 540 MJ,” says Marco Calviani. “Don’t forget that the previous dumps withstood the onslaught for ten years!”

What are the current LHC beam dumps made of? (Image: CERN)

The LHC’s external beam dumps comprise a graphite dump measuring 8.5 metres in length and 722 mm in diameter, contained in a 12-mm-thick 318LN stainless-steel-alloy tube. In total, each dump weighs 6.2 tonnes.

Each beam dump is made of several graphite blocks of varying density: high-density isostatic graphite; a stack of 1700 2-mm-thick low-density expanded graphite discs; and two extruded graphite discs (the black bands), which hold the low-density graphite stack together.

anschaef Wed, 06/08/2022 - 15:56 Byline Anaïs Schaeffer Publication Date Wed, 06/08/2022 - 11:43

Burotel: Sharing common space at CERN

Fri, 03/06/2022 - 17:40
Burotel: Sharing common space at CERN

“Burotel” is an innovative space management software tool through which colleagues without a fixed office can have a desk and office space assigned to them for a limited time and in a flexible way.

Burotel offices come in different shapes and sizes, and desks booking is easy and straightforward. Whether you need a desk in an open space or in a smaller, closed office space, the procedure is the same: visit the Burotel booking website, fill in the requested time period, check desk availability on an interactive map of CERN and book it. You will then receive confirmation from the room owner (e.g., the experimental secretariat).

The Burotel concept was presented to the Working Group on Strengthening the Support for Users at CERN, chaired by Manfred Krammer, head of the Experimental Physics (EP) department. It generated a lot of interest and the members suggested that the concept be shared with the CERN community.

The EP department has been making extensive use of the tool for years to support its large user community. This concept is in line with the CERN General Conditions Applicable to the Execution of Experiments, which state that an office space equipped with standard furniture and infrastructure should be provided to anyone involved in the fulfilment of CERN’s scientific mission.

Now, as work practices evolve, the Burotel concept is spreading to other departments at CERN. As we all know, office space is an important factor when it comes to feeling included in the workplace. The Burotel concept was developed within the EP department, initially by the ALICE and CMS experiments, to meet the challenge of appropriately welcoming the ever-growing number of CERN users. Following a collaboration with the Indico team in the IT-CDA (Collaboration, Devices and Applications) group, a reservation system based on the Indico Room Booking tool was deployed in April 2019, and the concept is now used throughout EP.

While the EP department used to be the only client of this software, the Beams (BE) department and the Occupational Health & Safety and Environmental Protection (HSE) unit have also adopted the Burotel solution to facilitate the management of their office space, and the International Relations (IR) sector is currently investigating its usage. As of today, CERN has more than 700 Burotel desks, and the EP department intends to set up more on the CERN sites.

The “Burotel” tool has recently been enhanced with new features, such as the automatic cancellation of unconfirmed desks bookings to ensure that the latter are made again available. In addition, Burotel offices that are equipped with electronic locks, the access is automatically granted through ADaMS. This new feature was implemented with the support of the Engineering Access & Alarms (EN-AA) group.

Future integrations are currently under discussion, including an option to filter desks by suitability for people with disabilities (with support from the Diversity Office), and the automatic reporting of each Burotel user’s temporary internal address in all platforms, such as the phonebook.

A feasibility study called “Labotel” is also under way to examine whether this booking model could be extended to technical areas (laboratories, clean rooms, etc.).

Find out more about Burotel by writing to:

thortala Fri, 06/03/2022 - 16:40 Byline IT department EP department Publication Date Fri, 06/03/2022 - 16:35

Environmental awareness: Energy at CERN

Thu, 02/06/2022 - 09:53
Environmental awareness: Energy at CERN

This infographic provides food for thought about CERN’s energy consumption and invites you to submit your ideas for its optimisation through an idea box. Take part!


This infographic is part of the series “CERN’s Year of Environmental Awareness”

thortala Thu, 06/02/2022 - 08:53 Publication Date Thu, 06/02/2022 - 08:51

Higgs10: The dramatic last year of CERN’s flagship LEP collider

Tue, 31/05/2022 - 15:28
Higgs10: The dramatic last year of CERN’s flagship LEP collider

The year 2000 was set to be the last year of running for CERN’s Large Electron–Positron (LEP) collider, and it ended in dramatic fashion. Luciano Maiani was Director-General and Roger Cashmore Research Director as the new millennium dawned.

Roger Cashmore :

The final year of LEP operation, 2000, had been agreed on at CERN by all of the relevant committees. By this time, the LEP experiments – ALEPH, DELPHI, L3 and OPAL – had established the Standard Model of particle physics with great precision. LEP had achieved its mission, and the only thing missing from the Standard Model was the elusive Higgs particle. Nobody knew whether the Higgs was within LEP’s reach, but detailed analysis suggested that its mass might be not much more than 100 GeV and that it would be produced in electron–positron collisions in association with a Z particle. In other words, the LEP experiments might have a chance of crowning their achievements with a spectacular discovery to start the new millennium.

There was nothing to lose and, as the 2000 run got underway, the machine was pushed to its limits. A cut-off date of 1 September had been set, and a closing celebration planned for the following month. Throughout the year, regular reports were made to the LEP Experiments Committee (LEPC), but there was no sign of a Higgs up to a mass of about 110 GeV. The decision was taken to push the beam energy beyond the limits through July and August: at this stage, if something broke, it really didn’t matter. And that was when the situation became exciting. A small excess of events was observed by the ALEPH experiment at a mass of about 114 GeV, but with no supporting evidence from the other experiments. Nevertheless, I telephoned Luciano to keep him informed that we might have an exciting time on our hands, and potentially a very difficult one! As a result of the ALEPH candidates, LEP’s final run was extended through to the end of October.

Luciano Maiani : 

I remember Roger’s call like it was yesterday. Whatever happened next was going to require some difficult decisions. In October, we celebrated the conclusion of the LEP programme in the presence of eminent representatives of the Member States, even though the machine was still running. ALEPH’s excess was still there so, after the speeches were done, we discreetly started to work out the cost of running LEP for another year, and the repercussions it would have on the construction of the LHC.

The problem was that LHC excavations would soon reach the LEP tunnel, so an extra year of running would mean that work would have to stop, contracts be terminated and penalties paid to the companies involved, not to mention the extra running costs that had not been budgeted for. In total, we worked out that it would cost some 120 MCHF, and deal a major psychological blow to the LHC community. We had no way of anticipating how the LHC experiments’ funding agencies would react to the news of a year’s delay.

As October progressed, the other LEP experiments did not see anything, and ALEPH did not find any more candidates. LEP’s illustrious career seemed to be coming to an uneventful end, but there was to be one final twist: towards the end of month, the L3 experiment announced an event that seemed to change everything. It was a two-jet event. Each jet contained a b quark, and there was missing energy corresponding to the mass of a Z particle. Significantly, the jets had the fateful energy of around 114 GeV.

L3’s event could be interpreted as the production of the same particle that ALEPH seemed to see decaying into a b-anti-b quark pair, with the accompanying Z decaying into two invisible neutrinos. In short, it could be another trace of the existence of the Higgs boson.

We discussed the L3 event thoroughly with LEPC Chair Michel Spiro and concluded that it was inconclusive. It could be a Higgs, but it could equally well be something much more mundane: there was no imbalance in transverse energy as there had been in the 1980s when Carlo Rubbia had announced the discovery of the Z boson. Without that, the missing energy could have been lost down the beam pipes and so gone undetected and, importantly, there were well-known electromagnetic processes that would produce just such an outcome.

Michel Spiro (left) and Roger Cashmore speaking at the LEP Fest, a celebration of the achievements of LEP on 10 October 2000. (Image: CERN)

The L3 event was not a smoking gun after all, and we were left at the end of the month with a very difficult decision to take. Whatever we decided, some part of the community would be disappointed. Events proceeded quickly. On 3 November, LEPC delivered its verdict: not conclusive. Similar verdicts were then delivered by the Research Board and the Scientific Policy Committee (SPC). The decision was left to us and, along with Roger and the whole Directorate, we made our decision. For us, LEP was over; the LHC was the best machine to tell us whether there was a Higgs at 114 GeV, or whether LEP had been chasing phantoms.

By 4 November I had already written to George Kalmus, the Chair of the SPC. “The idea that we may find ourselves in September 2001 with 3.5–4 sigma, CERN’s financial position aggravated, LHC delayed and LHC people disbanded is not very encouraging. I am not going to go this way.” On 17 November, we recommended no additional year of LEP running to the Committee of Council. Faced with the alternative of betting 120 MCHF on the roulette wheel of a few anomalous events, the Council wisely accepted our advice. LEP’s final year had been an emotionally charged rollercoaster ride. The lights never went out at CERN as analyses were refined around the clock and, when our decision became known, it was greeted with relief, shock and disbelief in equal measure. At the end of 2000, the Council’s decision moved us firmly into the LHC era, ready to fully explore the Higgs and much more.


thortala Tue, 05/31/2022 - 14:28 Byline Luciano Maiani Roger Cashmore Publication Date Tue, 05/31/2022 - 14:18

Arts at CERN celebrates its 10th anniversary

Mon, 30/05/2022 - 15:05
Arts at CERN celebrates its 10th anniversary

For the past decade, Arts at CERN has fostered the dialogue between art and physics through art residencies, commissions and exhibitions. Artists across all creative disciplines have been invited to CERN to experience how the big questions about our universe are pursued by fundamental science.

Since its foundation in 1954, CERN has been a place of inspiration to many artists. Before the arts programme was officially launched, several highly regarded artists visited the Laboratory, drawn to physics and fundamental science. As early as 1972, James Lee Byars was the first artist to visit the Laboratory and the only one, so far, to feature on the cover of the CERN Courier. Mariko Mori, Gianni Motti, Cerith Wyn Evans, John Berger and Anselm Kiefer are among the artists who came to CERN in the years that followed.

In 2022 we celebrate the 10th anniversary of the first artistic residency organised by Arts at CERN, and the beginning of the programme’s activities. More than 200 artists have participated in the residencies, benefiting from the involvement of 400 scientists. Around 600 applications from 80 different countries are received every year. Over 20 new artworks have been commissioned since the residency programme began, and numerous education and outreach events take place every year.

The celebration of the 10th anniversary begins with the launch of the Arts at CERN podcast series. In each of the six episodes, one artist and one scientist will explore a theme that has inspired their artistic practice and their scientific research, respectively. Together, the podcast guests will look back at the artist’s residency and the creative encounters that it facilitated within the vibrant CERN community. The six themes selected for the anniversary podcast series are time, the invisible, nature, broken symmetries, extra dimensions and black holes. The first episode will feature the work of the very first artist in residence, Julius von Bismarck, who arrived at CERN in early 2012. He explores the topic of “extra dimensions”, in conversation with physicist Michael Doser. Both are introduced by Mónica Bello, curator and head of Arts at CERN, and Ana Prendes, content producer of Arts at CERN. In the following episodes, scientists John Ellis, Alessandra Gnecchi, Dorota Grabowska, Helga Timko and Tamara Vázquez-Schroeder converse with artists Rasheedah Phillips, Ruth Jarman and Joe Gerhardt (Semiconductor), SU Wen-Chi, Suzanne Treister and Rosa Menkman. At the end of 2022, the anniversary celebrations with culminate in the publication of a collection of essays by artists, scientists and authors. This publication will be the fruit of Arts at CERN’s goal to inspire significant exchanges between art and physics, and to participate in an international cultural community eager to connect with CERN.

The anniversary marks ten years since the first artistic residency at CERN in spring 2012. However, CERN has a history of welcoming artists to its premises ever since the Lab’s foundation. Explore a non-comprehensive timeline of the history of arts engagement at CERN on Arts at CERN’s website.

Listen to Arts at CERN on Spotify, Google Podcasts, Apple Podcasts.


thortala Mon, 05/30/2022 - 14:05 Publication Date Tue, 05/31/2022 - 08:50