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SHiP lève l’ancre pour explorer le secteur caché
The SHiP (Search for Hidden Particles) collaboration was in high spirits at its annual meeting this week. Its project to develop a large detector and target to be installed in one of the underground caverns of the accelerator complex has been accepted by the CERN Research Board. Thus, SHiP plans to sail to explore the hidden sector in 2031. Scientists hope to capture particles that interact very feebly with ordinary matter – so feebly, in fact, that they have not yet been detected.
This group of hypothetical particles includes dark photons, axions and axion-like particles, heavy neutral leptons and others. These particles, which could be among the dark matter, particles, are predicted by several theoretical models that extend beyond the Standard Model, the current theory describing elementary particles and the forces that unite them.
Although very solid, the Standard Model does not explain certain phenomena. The particles predicted by the Model – in other words, the ordinary matter that we know – account for just 5% of the Universe. The rest is thought to be unknown matter and energy, which scientists refer to as dark matter and dark energy. Their effects can be observed in the Universe, but their nature is a mystery that a growing number of experiments are trying to uncover.
This is where SHiP comes in. The idea is simple: the more particles that are produced, the greater the chances of finding feebly interacting particles. A high-intensity proton beam from the Super Proton Synchrotron (SPS) accelerator will be repeatedly sent to a target, a large metal block, producing a vast number of particles. Among them, scientists hope to find particles from the hidden sector. Thanks to the very high beam intensity, SHiP will be more sensitive than the existing experiments.
Another special feature of SHiP is that its detectors will be placed several tens of metres away from the target in order to detect relatively long-lived particles and eliminate “background noise”, in other words, particles such as muons that could interfere with the detection of long-lived particles. The experiment is equipped with a magnet system to divert the flow of muons and a large 50 m-long chamber in which the particles of interest can decay into known particles.
The experiment therefore complements the large LHC experiments, whose detectors surround the collision point and are unable to study the feebly interacting particles that travel several tens of metres before transforming. Theoretical models predict that the lower their mass and the weaker their coupling (the intensity of the interaction), the longer the lifetime of these particles. SHiP will therefore be sensitive to particles with relatively low masses.
In their journey through the detector, these particles could either disintegrate into known particles or collide with an atom of ordinary matter, which would also produce particles. The SHiP detectors have been designed to detect their signals.
Beyond the hypothetical dark-matter particles, SHiP will also study neutrinos which, despite being known particles of the Standard Model, are difficult to intercept and still hold many mysteries.
The target and the experiment will be installed in an existing underground cavern at CERN and supplied by a beam line from the SPS, CERN’s second largest accelerator, which supplies several experiments and pre-accelerates particles for the LHC.
The target is a complex device that is more like a beam dump than a conventional fixed target. Under study for several years, it is a 1.5-metre-thick block made of several different metals in order to produce the specific particles required by SHiP and fitted with a cooling and shielding system.
Part of the SHiP collaboration during its annual meeting, which was held at CERN this week. (Image: Marina Cavazza/CERN)cmenard Thu, 04/18/2024 - 16:35 Byline Corinne Pralavorio Publication Date Fri, 04/19/2024 - 14:05
Blazing trails: CMS cavern evacuation paves the way for future safety design
CERN strives for excellence in safety matters, with a commitment to continuous improvement in the field. Emergency preparedness is a priority for the Organization as it is a key element in its aim to protect both people participating in its activities and its installations. In this context, regular evacuation exercises of all accelerator and experimental areas are a regulatory requirement and part of the CERN-wide safety objectives.
On a warm, sunny day in February 2024, 48 people were going about their daily work in the CMS cavern, unaware that an evacuation exercise, which had been carefully planned for several months, was about to take place. Such exercises are crucial for facility users and rescue teams to gain familiarity with emergency procedures in various contexts and settings. When the alarm sounded, all 48 people reacted calmly, reaching the assembly point quickly and safely. It was a pleasing result for CMS and, apart from the important lessons learned from the exercise, additional data was gathered to improve not only evacuation procedures but also the design of installations in order to make emergency plans even more effective.
This exercise was part of a pilot collaboration between CMS Safety, the HSE Fire Safety Engineering (FSE) team and the Fire Safety Engineering division of Lund University in Sweden, which took this opportunity to maximise the usefulness of the evacuation to study human behaviour in emergency situations.
Comprising reports by undercover observers, questionnaires and footage from security cameras (used in full compliance with Operational Circular No. 11 to ensure anonymity), the data collected provides many useful insights into evacuation dynamics, occupant characteristics and perceptions of safety procedures.
This information is essential for the design of and emergency planning for subterranean experimental areas. As opposed to the design of buildings located above ground, which follows national safety standards, the design of underground areas relies extensively on computer modelling. Using various parameters, it is possible to simulate human behaviours in the event of an emergency to predict the effectiveness of a real-life evacuation.
In this pilot study, the Lund and FSE teams will use the CMS evacuation data to identify unique human behaviours observed in emergencies in complex underground environments. This will expand the current knowledge base and help build a database of specific input parameters to fine-tune and/or validate existing evacuation models.
Ultimately, this methodology will be instrumental not only to improve CERN’s emergency response in the caverns, but also to influence the safety design across current and future complex facilities, at CERN and beyond.
anschaef Tue, 04/16/2024 - 23:45 Byline CMS collaboration HSE unit Publication Date Wed, 04/17/2024 - 08:43CERN donates computing equipment to South Africa
On 9 April 2024, a ceremony at CERN marked the donation of computing equipment to the Tshwane University of Technology in South Africa. The ceremony was attended by Mr. Curtis Singo, Political and Economic Counsellor at the South Africa Embassy in Bern, Joachim Mnich, CERN’s director for Research and Computing, and Bob Jones, deputy head of CERN’s IT department.
On this occasion, 21 servers and 4 network switches were sent to the Tshwane University of Technology, where the equipment will be used to support academic and research projects.
CERN regularly donates computing equipment that no longer meets its highly specific requirements but is still more than adequate for less demanding environments. To date, more than 2500 servers and 150 network switches have been donated by CERN to countries and international organisations, namely Algeria, Bulgaria, Ecuador, Egypt, Ghana, Mexico, Morocco, Nepal, Palestine, Pakistan, the Philippines, Senegal, Serbia, Jordan, Lebanon and now South Africa.
If you are a publicly funded research organisation, you can request computing equipment from CERN.
anschaef Tue, 04/16/2024 - 23:21 Byline Marina Banjac Publication Date Tue, 04/16/2024 - 23:20Fabiola Gianotti receives the 2024 prize from the “Fondation pour Genève”
The Fondation pour Genève will be presenting its 30th prize to Fabiola Gianotti, CERN Director-General, in recognition of her outstanding contribution to Geneva’s international reputation.
“I am extremely honoured to receive the Fondation pour Genève Prize. The development of science and technology, openness, collaboration across borders and the education of young people are fundamental values at CERN, which are also deeply rooted in international Geneva. The fact that these values, which are so dear to me, are being recognised is a particularly touching moment for me,” declared Fabiola Gianotti.
The award ceremony is open to everyone and will take place on Monday 13 May 2024 at 6.30 pm at the Victoria Hall in Geneva. To register, click here.
More information on the Fondation pour Genève website.
anschaef Tue, 04/16/2024 - 23:08 Publication Date Wed, 04/17/2024 - 10:05Handover at the CERN Ombud’s Office
The CERN Ombud’s Office was established in 2010 to provide the entire CERN community with support in resolving conflicts informally, in a consensual and impartial manner. Since then, several Ombuds have held the position, which is now firmly anchored at the Laboratory. On 1 May, Marie-Luce Falipou, the fifth CERN Ombud, will take up her duties. She takes over from Laure Esteveny, who has been in the role since April 2021 and is taking early retirement.
As they prepared for the handover, Laure and Marie-Luce agreed to answer the Bulletin team’s questions.
The Bulletin: Laure, what drove you to become Ombud?
Laure: I began my career as Ombud in 2021, after 35 years working in different departments of the Organization. I was attracted by the human side of the role, and I haven’t been disappointed. I’m extremely happy to have been able to serve out my career as CERN Ombud. It’s very rewarding to help people to overcome a conflict.
The Bulletin: What do you need to succeed in this role?
Laure: When they take up their duties, all new CERN Ombuds follow the training courses run by the International Ombuds Association (IAO) and also receive training in mediation. This is clearly essential, but the skills I acquired throughout my career at CERN have also been invaluable. You need to have good analytical skills and be very thorough to succeed in this role.
Pierre Gildemyn, my predecessor, also supported me a lot. He was always available to answer my questions and shared his own experience as Ombud with me. I, in turn, am available for Marie-Luce; I will be delighted to help her. I would also urge her to turn to the IAO for support and to all the professional ombud networks, especially that of the United Nations and Related International Organizations (UNARIO) – ombuds are very good at supporting each other.
The Bulletin: Have you encountered any difficulties?
Laure: The role of Ombud is very rewarding on the human level. If I had to name a difficulty, I would say that the isolation that inevitably comes with the role is not always easy to cope with. In addition, by definition, the Ombud is only exposed to problematic situations in which people are suffering – to the “Dark Side of the Force” – which can sometimes be a heavy burden.
The Bulletin: Marie-Luce, what brought you to this role?
Marie-Luce: I’ve known Pierre and Laure for a long time, and I’ve seen them thrive in the role of Ombud, for which they developed a real passion. It’s a privilege to be the next to take on this role.
I’ve spent my whole career at CERN, 35 years now, in the Human Resources department. I’ve held various positions, notably HRA (human resources adviser) for 13 years, so I’m very familiar with the workplace culture. I’ve also been trained in active listening – skills that will certainly be very useful in my new position. For me, becoming Ombud is really a natural evolution, even if the role is of course unique.
The Bulletin: You take up your duties on 1 May, but you don’t become Ombud overnight, I imagine?
Marie-Luce: Indeed, I’ll take the necessary time to prepare myself for this new role, which is really something out of the ordinary and something with which I need to familiarise myself. I’m aware of the importance and the impact that the Ombud can have, and I’m humbled and grateful to accept this responsibility.
Le Bulletin: As the new Ombud, what message would you like to send to the CERN community?
Marie-Luce: I want people to know that the Ombud’s office is a safe, calm place where they will be listened to in confidence and understood. The Ombud is there to serve all members of the CERN community, regardless of their role in the Organization. Questions, problems and conflicts are part and parcel of life, including in the workplace. Finding the best way to handle them can make a big difference, and that’s where the Ombud can help.
The Bulletin: Any final words?
Marie-Luce: I’d like to say a big thank you to Laure for sharing her experience with me and for offering me her support; it’s a precious resource to have someone experienced to turn to.
Laure: Thank you to all those who placed their trust in me, and I wish Marie-Luce all the best!
The Bulletin: A big thank you to you both!
_____
The Ombud is available from Monday to Friday in office B500/1-004 on the Meyrin site. To make an appointment, in person or online, contact the Ombud at ombuds@cern.ch.
More information can be found on the Ombud’s website: https://ombuds.web.cern.ch
anschaef Tue, 04/16/2024 - 22:37 Byline Internal Communication Publication Date Tue, 04/16/2024 - 22:31Accelerator Report: The LHC is well ahead of schedule
Almost the whole accelerator complex is now in “physics mode”, routinely delivering the various types of beam to the different physics facilities and experiments. Notably, the intensity ramp-up in the LHC is progressing remarkably well.
In particular, I am happy to start this report with the good news that, thanks to the excellent availability of the accelerator complex and the hard work of the LHC teams and experts, the LHC is now 12 days ahead of schedule, yielding a direct gain of integrated luminosity and thus physics and boding well for the 2024 run.
The first stable beams of 2024 in the LHC were initially scheduled for 8 April, but the teams working on the LHC beam commissioning managed to be ready earlier and declared first stable beams at 18.25 on 5 April, three days ahead of the official schedule. The first stable beams also mark the start of a period of intensity ramp-up interleaved with the completion of the final commissioning steps.
These final steps include the scrubbing of the LHC vacuum chamber to reduce the production of electron clouds that negatively impact the beam quality and put a strain on the cryogenics system. Usually, the scrubbing lasts two days, but this year an extra day was added since a new injection kicker and two TDIS (target dump injection systems) were installed during the YETS (the new TDIS replace the ones at Points 2 and 8 that suffered vacuum leaks in 2023). The scrubbing run was nevertheless completed in only 36 hours, resulting in another gain in the schedule.
The LHC availability during the recent intensity ramp-up was 85%, including stable beams for about 35% of the time, and the experts very efficiently signed off the checklists at each intensity step. This is why we are now about 12 days ahead of schedule, colliding beams of 1200 bunches and already producing a meaningful level of luminosity for physics. The next step is 1800 bunches, which, if all goes well, might be achieved before the end of this week.
On Tuesday, 16 April, at the end of the afternoon, the first 1.5 fb-1 of integrated luminosity was collected. More than 90 fb-1 are expected for 2024. (Image: CERN)Meanwhile, the injectors are providing the experiment facilities with beams for physics. The PS was the first to routinely provide beams for physics to the East Area, on 22 March, and n_TOF followed suit on 25 March. ISOLDE, located behind the PS Booster, started physics on 8 April. The SPS fixed-target physics in the North Area started on 10 April. On 15 April, the AWAKE facility located behind the SPS started the first of five two-week proton runs scheduled for 2024. The next in line is the Antimatter factory: the AD and ELENA decelerators should start providing the experiments with antiprotons for physics on 22 April.
The 2024 run has been extended by four weeks, until 25 November, for the LHC, and by five weeks, until 2 December, for the injectors. The YETS will start later this year, which will allow more physics to be done in 2024.
anschaef Tue, 04/16/2024 - 22:27 Byline Rende Steerenberg Publication Date Tue, 04/16/2024 - 22:10Mitigating the environmental impact of CERN procurement
Every year, CERN spends some 500 MCHF on goods and services to build, maintain and operate its infrastructure to fulfil its scientific objectives. These purchases not only come at a financial cost, but also have an impact on the environment through the indirect emissions arising from their procurement. In 2023, CERN reported its procurement-related indirect emissions in the CERN Environment Report for the first time. These amounted to 98 030 tCO2e and 104 974 tCO2e in 2021 and 2022 respectively. To put this in context, this represents more than 90% of CERN’s total indirect emissions, the rest being attributed to personnel mobility, duty travel and catering, and just over 30% of CERN’s total emissions.
CERN strives to be a model for environmentally responsible research by taking action on its most impactful domains, including energy and water consumption and emissions, and setting objectives to minimise its environmental footprint. Adopting measures to positively influence procurement-related emissions is a priority for which a comprehensive strategy has been set out that will commit CERN, its suppliers and each and every one of us to making conscious decisions when purchasing goods or services.
Underpinning this strategy, the Environmentally Responsible Procurement Policy was approved by the Enlarged Directorate in June 2023. Anchored in the principle of embedding environmental responsibility where appropriate throughout all phases of the procurement process, the Policy commits the Organization to environmentally responsible procurement and to achieving sustainable results both internally and throughout its supply chains, integrating relevant best practices in its processes, measuring their impact, and communicating with and raising the awareness of all stakeholders.
In December 2023, the Enlarged Directorate approved the implementation of the Policy, effective from 1 January 2024. This entails a one-year kick-off phase to identify suitable areas for policy implementation, including a comprehensive awareness-raising programme with tailored training for technical officers and workshops for the departments focusing on their purchasing activities.
Additionally, pilot projects will help evaluate the integration of environmental criteria into market surveys and invitations to tender. Procurement officers will have access to a supplier sustainability due diligence tool and guidelines outlining best practices. These resources will equip them with the knowledge they need to assess suppliers based on their sustainability efforts.
Furthermore, a supplier engagement programme will be launched in order to foster discussions on sustainability within our supply chains, aiming to collaborate with and encourage suppliers to adopt sustainable practices.
Overall, this comprehensive implementation plan is designed to ensure a smooth transition towards policy compliance and create a sustainable framework for all stakeholders involved. Successful implementation will depend on all actors in CERN’s supply chains challenging our choices and decisions, from CERN’s IPT department, to CERN personnel involved in purchasing, to the suppliers themselves spanning our 23 Member and 11 Associate Member States, while continuing to strive for balanced returns.
According to Chris Hartley, Head of the IPT Department: “It is of great importance that we have established an Environmentally Responsible Procurement Policy for CERN. All CERN stakeholders want to see CERN continue to minimise its environmental impact. This Policy, underpinned by our progressive commitment to responsible sourcing, waste reduction and supplier engagement, will contribute to a more sustainable future.”
ndinmore Mon, 04/15/2024 - 16:39 Byline IPT department Publication Date Mon, 04/15/2024 - 16:35ProtoDUNE’s argon filling underway
CERN’s Neutrino Platform houses a prototype of the Deep Underground Neutrino Experiment (DUNE) known as ProtoDUNE, which is designed to test and validate the technologies that will be applied to the construction of the DUNE experiment in the United States.
Recently, ProtoDUNE has entered a pivotal stage: the filling of one of its two particle detectors with liquid argon. Filling such a detector takes almost two months, as the chamber is gigantic – almost the size of a three-storey building. ProtoDUNE’s second detector will be filled in the autumn.
ProtoDUNE will use the proton beam from the Super Proton Synchrotron to test the detecting of charged particles. This argon-filled detector will be crucial to test the detector response for the next era of neutrino research. Liquid argon is used in DUNE due to its inert nature, which provides a clean environment for precise measurements. When a neutrino interacts with argon, it produces charged particles that ionise the atoms, allowing scientists to detect and study neutrino interactions. Additionally, liquid argon's density and high scintillation light yield enhance the detection of these interactions, making it an ideal medium for neutrino experiments.
Interestingly, the interior of the partially filled detector now appears green instead of its usual golden colour. This is because when the regular LED light is reflected inside the metal cryostat, the light travels through the liquid argon and the wavelength of the photons is shifted, producing a visible green effect.
The DUNE far detector, which will be roughly 20 times bigger than protoDUNE, is being built in the United States. DUNE will send a beam of neutrinos from Fermi National Accelerator Laboratory (Fermilab) near Chicago, Illinois, over a distance of more than 1300 kilometres through the Earth to neutrino detectors located 1.5 km underground at the Sanford Underground Research Facility (SURF) in Sanford, South Dakota.
Watch a short time-lapse video of protoDUNE being filled with liquid argon:
ckrishna Fri, 04/12/2024 - 10:15 Byline Chetna Krishna Publication Date Fri, 04/12/2024 - 10:30The next-generation triggers for CERN detectors
The experiments at the Large Hadron Collider (LHC) require high-performance event-selection systems – known as “triggers” in particle physics – to filter the flow of data to manageable levels. The triggers pick events with distinguishing characteristics, such as interactions or collisions of particles recorded in particle detectors, and make them available for physics analyses. In just a few seconds, the complex system can determine whether the information about a given collision event is worth keeping or not.
The ATLAS and CMS experiments use triggers on two levels. The first trigger runs in sync with the rate of particle bunches colliding in the detectors, deciding in less than 10 microseconds which data to keep. Events that pass the first-level trigger move on to the second high-level trigger for further selection. The selected events are then sent to the CERN Data Centre, where the data is copied, stored and eventually made available to scientists around the world for data analysis.
In preparation for the High-Luminosity LHC (HL-LHC), the ATLAS and CMS detectors are being upgraded with finer spatial and timing granularity, which will result in more data for each collision. The principle is the same as taking a picture with a camera with more pixels: the resulting file will be bigger because the image contains more detail, and the picture will be of higher quality. To prepare for the data deluge expected when the LHC enters the high-luminosity era, scientists need to develop new strategies for more sophisticated event processing and selection.
The key objective of the five-year Next-Generation Triggers (NextGen) project is to get more physics information out of the HL-LHC data. The hope is to uncover as-yet-unseen phenomena by more efficiently selecting interesting physics events while rejecting background noise. Scientists will make use of neural network optimisation, quantum-inspired algorithms, high-performance computing and field-programmable gate array (FPGA) techniques to improve the theoretical modelling and optimise their tools in the search for ultra-rare events.
The foundations of the NextGen project were laid in 2022 when a group of private donors, including former Google CEO Eric Schmidt, visited CERN. This first inspiring visit eventually evolved into an agreement with the Eric and Wendy Schmidt Fund for Strategic Innovation, approved by the CERN Council in October 2023, to fund a project that would pave the way for the future trigger systems at the HL-LHC and beyond: NextGen was born.
NextGen will collaborate with experts in academia and industry. The work builds on the open-science and knowledge-sharing principles embedded in CERN's institutional governance and modus operandi. The project includes a work package dedicated to education and outreach, a unique multi-disciplinary training programme for NextGen researchers and targeted events and conferences for the wider community of scientists interested in the field. The intellectual property generated as part of the NextGen Triggers project, owned by CERN, will be released and shared under open licences in compliance with the CERN Open Science Policy.
The NextGen Triggers project will mark a new chapter in in high-energy physics, leveraging upgraded event-selection systems and data-processing techniques to unlock a realm of discoveries.
ckrishna Thu, 04/11/2024 - 11:45 Byline Antonella Del Rosso Publication Date Thu, 04/11/2024 - 12:00Searching for new asymmetry between matter and antimatter
Once a particle of matter, always a particle of matter. Or not. Thanks to a quirk of quantum physics, four known particles made up of two different quarks – such as the electrically neutral D meson composed of a charm quark and an up antiquark – can spontaneously oscillate into their antimatter partners and vice versa.
At a seminar held recently at CERN, the LHCb collaboration at the Large Hadron Collider (LHC) presented the results of its latest search for matter–antimatter asymmetry in the oscillation of the neutral D meson, which, if found, could help shed light on the mysterious matter–antimatter imbalance in the Universe.
The weak force of the Standard Model of particle physics induces an asymmetry between matter and antimatter, known as CP violation, in particles containing quarks. However, these sources of CP violation are difficult to study and are insufficient to explain the matter–antimatter imbalance in the Universe, leading physicists to both search for new sources and to study the known ones better than ever before.
In their latest endeavour, the LHCb researchers have rolled up their sleeves to measure with unprecedented precision a set of parameters that determine the matter–antimatter oscillation of the neutral D meson and enable the search for the hitherto unobserved but predicted CP violation in the oscillation.
The collaboration had previously measured the same set of parameters, which are linked to the decay of the neutral D meson into a positively charged kaon and a negatively charged pion, using its full data set from Run 1 of the LHC and a partial data set from Run 2. This time around, the team analysed the full Run-2 data set and, by combining the result with that of its previous analysis, excluding the partial Run-2 data set, it obtained the most precise measurements of the parameters to date – the overall measurement uncertainty is 1.6 times smaller than the smallest uncertainty achieved before by LHCb.
The results are consistent with previous studies, confirming the matter–antimatter oscillation of the neutral D meson and showing no evidence of CP violation in the oscillation. The findings call for future analyses of this and other decays of the neutral D meson using data from the third run of the LHC and its planned upgrade, the High-Luminosity LHC.
Other neutral D meson decays of interest include the decay into a pair of two kaons or two pions, in which LHCb researchers observed CP violation in particles containing charm quarks for the first time, and the decay into a neutral kaon and a pair of pions, with which LHCb clocked the speed of the particle’s matter–antimatter oscillation. No avenue should be left unexplored in the search for clues to the matter–antimatter imbalance in the Universe and other cosmic mysteries.
Find out more on the LHCb website.
abelchio Thu, 04/11/2024 - 11:41 Byline Ana Lopes Publication Date Thu, 04/11/2024 - 17:00ATLAS provides first measurement of the W-boson width at the LHC
The discovery of the Higgs boson in 2012 slotted in the final missing piece of the Standard Model puzzle. Yet, it left lingering questions. What lies beyond this framework? Where are the new phenomena that would solve the Universe's remaining mysteries, such as the nature of dark matter and the origin of matter–antimatter asymmetry?
One parameter that may hold clues about new physics phenomena is the “width” of the W boson, the electrically charged carrier of the weak force. A particle’s width is directly related to its lifetime and describes how it decays to other particles. If the W boson decays in unexpected ways, such as into yet-to-be-discovered new particles, these would influence the measured width. As its value is precisely predicted by the Standard Model based on the strength of the charged weak force and the mass of the W boson (along with smaller quantum effects), any significant deviation from the prediction would indicate the presence of unaccounted phenomena.
In a new study, the ATLAS collaboration measured the W-boson width at the Large Hadron Collider (LHC) for the first time. The W-boson width had previously been measured at CERN’s Large Electron–Positron (LEP) collider and Fermilab’s Tevatron collider, yielding an average value of 2085 ± 42 million electronvolts (MeV), consistent with the Standard-Model prediction of 2088 ± 1 MeV. Using proton–proton collision data at an energy of 7 TeV collected during Run 1 of the LHC, ATLAS measured the W-boson width as 2202 ± 47 MeV. This is the most precise measurement to date made by a single experiment, and — while a bit larger — it is consistent with the Standard-Model prediction to within 2.5 standard deviations (see figure below).
This remarkable result was achieved by performing a detailed particle-momentum analysis of decays of the W boson into an electron or a muon and their corresponding neutrino, which goes undetected but leaves a signature of missing energy in the collision event (see image above). This required physicists to precisely calibrate the ATLAS detector’s response to these particles in terms of efficiency, energy and momentum, taking contributions from background processes into account.
However, achieving such high precision also requires the confluence of several high-precision results. For instance, an accurate understanding of W-boson production in proton–proton collisions was essential, and researchers relied on a combination of theoretical predictions validated by various measurements of W and Z boson properties. Also crucial to this measurement is the knowledge of the inner structure of the proton, which is described in parton distribution functions. ATLAS physicists incorporated and tested parton distribution functions derived by global research groups from fits to data from a wide range of particle physics experiments.
The ATLAS collaboration measured the W-boson width simultaneously with the W-boson mass using a statistical method that allowed part of the parameters quantifying uncertainties to be directly constrained from the measured data, thus improving the measurement’s precision. The updated measurement of the W-boson mass is 80367 ± 16 MeV, which improves on and supersedes the previous ATLAS measurement using the same dataset. The measured values of both the mass and the width are consistent with the Standard-Model predictions.
Future measurements of the W-boson width and mass using larger ATLAS datasets are expected to reduce the statistical and experimental uncertainties. Concurrently, advancements in theoretical predictions and a more refined understanding of parton distribution functions will help to reduce the theoretical uncertainties. As their measurements become ever more precise, physicists will be able to conduct yet more stringent tests of the Standard Model and probe for new particles and forces.
Comparison of the measured W-boson width with the Standard-Model prediction and with measurements from the LEP and Tevatron colliders. The vertical grey band illustrates the Standard-Model prediction, while the black dots and the associated horizontal bands represent the published experimental results. (Image: ATLAS/CERN) abelchio Wed, 04/10/2024 - 12:03 Byline ATLAS collaboration Publication Date Wed, 04/10/2024 - 11:57CMS releases Higgs boson discovery data to the public
As part of its continued commitment to making its science fully open, the CMS collaboration has just publicly released, in electronic format, the combination of CMS measurements that contributed to establishing the discovery of the Higgs boson in 2012. This release coincides with the publication of the Combine software – the statistical analysis tool that CMS developed during the first run of the Large Hadron Collider (LHC) to search for the unique particle, which has since been adopted throughout the collaboration.
Physics measurements based on data from the LHC are usually reported as a central value and its corresponding uncertainty. For instance, soon after observing the Higgs boson in LHC proton–proton collision data, CMS measured its mass as 125.3 plus or minus 0.6 GeV (the proton mass being about 1 GeV). But this figure is just a brief summary of the measurement outcome, a bit like the title of a book.
In a measurement, the full information extracted from the data is encoded in a mathematical function, known as the likelihood function, that includes the measured value of a quantity as well as its dependence on external factors. In the case of a CMS measurement, these factors encompass the calibration of the CMS detector, the accuracy of the CMS detector simulation used to facilitate the measurement and other systematic effects.
A likelihood function of a measurement based on LHC data can be complex, as many aspects need to be pinned down to fully understand the messy collisions that take place at the LHC. For example, the likelihood function of the combination of CMS Higgs boson discovery measurements, which CMS just released in electronic format, has nearly 700 parameters for a fixed value of the Higgs boson mass. Among these, only one – the number of Higgs bosons found in the data – is the physics parameter of interest, while the rest model systematic uncertainties.
Each of these parameters corresponds to a dimension of a multi-dimensional abstract space, in which the likelihood function can be drawn. It is hard for humans to visualise a space with more than a few dimensions, let alone one with many. The new release of the likelihood function of the CMS Higgs boson discovery measurements – the first likelihood function to be made publicly available by the collaboration – allows researchers to get around this problem. With a publicly accessible likelihood function, physicists outside the CMS collaboration can now precisely factor in the CMS Higgs boson discovery measurements in their studies.
The release of this likelihood function, as well as that of the Combine software, which is used to model the likelihood and fit the data, marks a new milestone in CMS’s decade-long commitment to fully open science. It joins hundreds of open-access publications, the release of almost five petabytes of CMS data on the CERN open-data portal and the publication of its entire software framework on GitHub.
Find out more on the CMS website.
abelchio Tue, 04/09/2024 - 14:29 Byline CMS collaboration Publication Date Tue, 04/16/2024 - 10:50Computer Security: Swipes vs PINs vs passwords vs you
What kind of person are you? An artist, like a painter? A credit card fanatic or just “in numbers”? Cerebral, a memoriser or even a genius? An influencer, like a peacock, or just prettily self-confident? A security buff or sufficiently security aware? Or just ignorant about security and your privacy? Let’s assume for a moment that the way you unlock your smartphone tells us which.
There are many different ways to unlock your smartphone: swiping patterns, PIN numbers, passwords, biometric fingerprints or face recognition. Some are more secure, some less so. But all are better than nothing. So, let’s look at some of them.
Swiping patterns: The obvious choice on Android phones. Your favourite pattern on a 3x3 matrix. But as it should be a continuous swipe, the number of actual possibilities are quite limited, boiling down to about 20 most-used swipes. If yours is listed there, it may be time to move to another, more secure swipe. In any case, your swiping can be spied on and then tried once your smartphone is stolen.
Worse ─ although it’s probably still academic ─ a small basic sonar system combining a local loudspeaker to emit acoustic signals inaudible to humans and a microphone to record them coming back again allowed researchers to use “the echo signal […] to profile user interaction with the device”, i.e. the way your finger swipes over and interacts with the screen. They’ve shown how this sonar can be employed to help identify the swipe pattern to unlock an Android phone – reducing the number of trials to be performed by an attacker by 70%. And that’s only their proof of concept… Maybe PINs and passwords are better?
PINs vs passwords: A common paradigm of computer security is linked to password complexity. Four-digit PIN numbers are no longer state of the art. And even six digits are not necessarily sufficient. While guessing and brute-forcing is difficult, as your smartphone should have a lock-out procedure only allowing a small number of tries before introducing timeouts or even wiping your phone completely(!), PINs can be easily spied on and replayed once your smartphone has been stolen*. Or do you shield your screen as you type your smartphone PIN as you do for your credit card at an ATM? Of course, a better choice is a long and complex password or even passphrase (unless you use one of the top 10 most-used passwords). Admittedly, typing such long and complex passwords can be tedious. Enter: biometrics.
Biometrics: Still our favourite – using your fingerprint sensor or a capture of your face to unlock your phone. Your smartphone (and laptop) manufacturers went to extreme lengths to ensure that your biometric signature cannot be tampered with by your fingerprint on a piece of tape, your face in a photo or your sleeping self. And they also ensured that your biometric information is properly and securely stored using a special-purpose hardware chip (TPM: “trusted platform module”). Still, fingerprint authentication in particular has been broken into in the past for Android and Windows devices, making face recognition our favourite choice to protect access to your smartphone and all the personal (and professional!) data you store and access with it.
*Actually, Apple’s latest security patch also fixed some issues with this.
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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.
anschaef Tue, 04/09/2024 - 14:03 Byline Computer Security team Publication Date Tue, 04/09/2024 - 14:01Large Hadron Collider reaches its first stable beams in 2024
On Friday 5 April, at 6.25 p.m., the LHC Engineer-in-Charge at the CERN Control Centre (CCC) announced that stable beams were back in the Large Hadron Collider, marking the official start of the 2024 physics data-taking season. The third year of LHC Run 3 promises six months of 13.6 TeV proton collisions at an even higher luminosity than before, meaning more collisions for the experiments to take data from. This will be followed by a period of lead ion collisions in October.
Before the LHC could restart, each accelerator in the CERN complex had to be prepared for another year of physics data taking. Beginning with Linac4, which welcomed its first beam two months ago, each accelerator has gone through a phase of beam commissioning in which it is gradually set up and optimised to be able to control all aspects of the beam, from its energy and intensity to its size and stability. During this phase researchers also test the accelerator’s performance and address any issues before it is used for physics. Following Linac4, which contains the source of protons for the beam, each accelerator was commissioned in turn: the Proton Synchrotron Booster, the Proton Synchrotron, the Super Proton Synchrotron, and finally the LHC from 8 March until 5 April. The whole complex is now ready for data taking.
Back to the CCC. While stable beams are the goal, the CCC engineers must first take several steps to achieve them. First, they must inject the beams into the LHC from the previous accelerators in the chain. Then begins the ramp-up process, which involves increasing the beam energy up to the nominal energy of 6.8 TeV. The next step – shown as “flat top” on LHC Page 1 – is where the energy in the beams is consistent, but they’re not quite ready yet. In order to achieve stable beams, the circulating beams must then be “squeezed” and adjusted using the LHC magnets. This involves making the beams narrower and more centred on their paths, and therefore more likely to produce a high number of collisions in the detectors. Only after the squeezing and adjustment has been completed can stable beams be declared and the experiments around the LHC begin their data taking.
Watch a video explaining the process from first injection to stable beams:
Delphine Jacquet and Georges Trad, both engineers in charge of the LHC, explain how the LHC beams work from the injections of protons to stable beams. (Video: CERN)Did you know?
Although the solar eclipse on 8 April will not affect the beams in the LHC, the gravitational pull of the moon, like the tides, changes the shape of the LHC because the machine is so big. Read more here.
ndinmore Fri, 04/05/2024 - 10:28 Byline Naomi Dinmore Publication Date Fri, 04/05/2024 - 18:30FASER measures high-energy neutrino interaction strength
Operating at CERN’s Large Hadron Collider (LHC) since 2022, the FASER experiment is designed to search for extremely weakly interacting particles. Such particles are predicted by many theories beyond the Standard Model that are attempting to solve outstanding problems in physics such as the nature of dark matter and the matter-antimatter imbalance in the Universe. Another goal of the experiment is to study interactions of high-energy neutrinos produced in the LHC collisions, particles that are nearly impossible to detect in the four big LHC experiments. Last week, at the annual Rencontres de Moriond conference, the FASER collaboration presented a measurement of the interaction strength, or “cross section”, of electron neutrinos (νe) and muon neutrinos (νμ). This is the first time such a measurement has been made at a particle collider. Measurements of this kind can provide important insights across different aspects of physics, from understanding the production of “forward” particles in the LHC collisions and improving our understanding of the structure of the proton to interpreting measurements of high-energy neutrinos from astrophysical sources performed by neutrino-telescope experiments.
FASER is located in a side tunnel of the LHC accelerator, 480 metres away from the ATLAS detector collision point. At that location, the LHC beam is already nearly 10 metres away, bending away on its circular 27-kilometre path. This is a unique location for studying weakly interacting particles produced in the LHC collisions. Charged particles produced in the collisions are deflected by the LHC magnets. Most neutral particles are stopped by the hundreds of metres of rock between FASER and ATLAS. Only very weakly interacting neutral particles like neutrinos are expected to continue straight on and reach the location where the detector is installed.
The probability of a neutrino interacting with matter is very small, but not zero. The type of interaction that FASER is sensitive to is where a neutrino interacts with a proton or a neutron inside the detector. In this interaction, the neutrino transforms into a charged “lepton” of the same family – an electron in the case of an νe, and a muon in the case of a νμ – which is visible in the detector. If the energy of the neutrino is high, several other particles are also produced in the collision.
The detector used to perform the measurement consists of 730 interleaved tungsten plates and photographic emulsion plates. The emulsion was exposed during the period from 26 July to 13 September 2022 and then chemically developed and analysed in search of charged particle tracks. Candidates for neutrino interactions were identified by looking for clusters of tracks that could be traced back to a single vertex. One of these tracks then had to be identified as a high-energy electron or muon.
Event displays identified by the FASER collaboration as candidates for an νe (left) and a νμ (right) interacting in the detector. Invisible here, the neutrinos arrive from the left and then interact to create multiple tracks spraying out to the right (coloured lines), one of which is identified as a charged lepton (labelled). (credit: FASER collaboration)In total, four candidates for an νe interaction and eight candidates for a νμ interaction have been found. The four νe candidates represent the first direct observation of electron neutrinos produced at a collider. The observations can be interpreted as measurements of neutrino interaction cross sections, yielding (1.2+0.9−0.8) ×10−38 cm2 GeV−1 in the case of the νe and (0.5 ± 0.2) × 10−38 cm2 GeV−1 in the case of the νμ. The energies of the neutrinos were found to be in a range between 500 and 1700 GeV. No measurement of the neutrino interaction cross section had previously been made at energies above 300 GeV in the case of the νe and between 400 GeV and 6 TeV in the case of the νμ.
The results obtained by FASER are consistent with expectations and demonstrate the ability of FASER to make neutrino cross-section measurements at the LHC. With the full LHC Run 3 data, 200 times more neutrino events will be detected, allowing much more precise measurements.
Read more in the FASER publication.
cmenard Thu, 04/04/2024 - 14:46 Byline Piotr Traczyk Publication Date Thu, 04/04/2024 - 14:45Giuseppe Fidecaro (1926 – 2024)
We are saddened to learn that experimental physicist Giuseppe Fidecaro, who joined CERN in 1956, died on 28 March. He was 97 years old. Giuseppe was a familiar face to the CERN community, often seen arms linked with his wife Maria as the pair made their way through the CERN corridors. He was also known to CERN visitors, featuring prominently in the Synchrocyclotron exhibition’s film. Maria Fidecaro passed away in September 2023.
Born in Messina, Italy in 1926, Giuseppe graduated in physics from the University of Rome in 1947 under the supervision of Edoardo Amaldi. He came to CERN with Maria in the summer of 1956 and was assigned to the Synchrocyclotron. There, he established a group and prepared equipment for experiments that in 1958 enabled a successful search for pions decaying into an electron and a neutrino – a process which gave experimental ground to the universal Fermi interaction.
In 1975, Giuseppe was appointed co-chair of a joint scientific committee set up under the terms of the collaboration agreement between CERN and the former USSR for the utilization of atomic energy, a responsibility he held until 1986. He was also tasked with coordinating cooperation with the Joint Institute for Nuclear Research in Dubna.
Giuseppe officially retired in 1991 but, together with Maria, he continued his work at CERN as an honorary member of the personnel until as recently as 2020.
A funeral service will be held at the Italian Catholic Mission of Geneva on Friday 5 April at 10:00 a.m.
A full obituary will appear in the CERN Courier.
abelchio Thu, 04/04/2024 - 08:36 Publication Date Thu, 04/04/2024 - 08:29The CMS experiment at CERN measures a key parameter of the Standard Model
Last week, at the annual Rencontres de Moriond conference, the CMS collaboration presented a measurement of the effective leptonic electroweak mixing angle. The result is the most precise measurement performed at a hadron collider to date and is in good agreement with the prediction from the Standard Model.
The Standard Model of Particle Physics is the most precise description to date of particles and their interactions. Precise measurements of its parameters, combined with precise theoretical calculations, yield spectacular predictive power that allows phenomena to be determined even before they are directly observed. In this way, the Model successfully constrained the masses of the W and Z bosons (discovered at CERN in 1983), of the top quark (discovered at Fermilab in 1995) and, most recently, of the Higgs boson (discovered at CERN in 2012). Once these particles had been discovered, these predictions became consistency checks for the Model, allowing physicists to explore the limits of the theory’s validity. At the same time, precision measurements of the properties of these particles are a powerful tool for searching for new phenomena beyond the Standard Model – so-called “new physics” - since new phenomena would manifest themselves as discrepancies between various measured and calculated quantities.
The electroweak mixing angle is a key element of these consistency checks. It is a fundamental parameter of the Standard Model, determining how the unified electroweak interaction gave rise to the electromagnetic and weak interactions through a process known as electroweak symmetry breaking. At the same time, it mathematically ties together the masses of the W and Z bosons that transmit the weak interaction. So, measurements of the W, the Z or the mixing angle provide a good experimental cross-check of the Model.
The two most precise measurements of the weak mixing angle were performed by experiments at the CERN LEP collider and by the SLD experiment at the Stanford Linear Accelerator Center (SLAC). The values disagree with each other, which had puzzled physicists for over a decade. The new result is in good agreement with the Standard Model prediction and is a step towards resolving the discrepancy between the latter and the LEP and SLD measurements.
“This result shows that precision physics can be carried out at hadron colliders,” says Patricia McBride, CMS spokesperson. “The analysis had to handle the challenging environment of LHC Run 2, with an average of 35 simultaneous proton-proton collisions. This paves the way for more precision physics at the High-Luminosity LHC, where five times more proton pairs will be colliding simultaneously.”
Precision tests of the Standard Model parameters are the legacy of electron-positron colliders, such as CERN’s LEP, which operated until the year 2000 in the tunnel that now houses the LHC. Electron-positron collisions provide a perfect clean environment for such high-precision measurements. Proton-proton collisions in the LHC are more challenging for this kind of studies, even though the ATLAS, CMS and LHCb experiments have already provided a plethora of new ultra-precise measurements. The challenge is mainly due to huge backgrounds from other physics processes than the one being studied and to the fact that protons, unlike electrons, are not elementary particles. For this new result, reaching a precision similar to that of an electron-positron collider seemed like an impossible task, but it has now been achieved.
The measurement presented by CMS uses a sample of proton-proton collisions collected from 2016 to 2018 at a centre-of-mass energy of 13 TeV and corresponding to a total integrated luminosity of 137 fb−1, meaning about 11.000 million million collisions!
The mixing angle is obtained through an analysis of angular distributions in collisions where pairs of electrons or muons are produced. This is the most precise measurement performed at a hadron collider to date, improving on previous measurements from ATLAS, CMS and LHCb.
Read more:
angerard Wed, 04/03/2024 - 11:01 Publication Date Wed, 04/03/2024 - 16:00CERN and the Swiss Arts Council announce the artists selected for the sixth edition of Connect
Connect is an art residency programme launched by Arts at CERN and Pro Helvetia in 2021. Dedicated to Swiss-based artists working at the intersection of science and artistic research, this research-led residency invites them to come to CERN to explore ideas and develop new work.
The selected duo is composed of Robin Meier Wiratunga and Vimala Pons. Meier Wiratunga is an artist and composer who seeks to understand how humans, insects and objects think. Collaborating closely with scientific researchers, Meier Wiratunga's work blends machine learning with insights from animal intelligence, creating constellation scores where musical patterns emerge as ‘thinking tools'. Vimala Pons is an actress who has worked in independent and auteur cinema.
Meier Wiratunga and Pons will dedicate their residency at CERN to developing their proposal titled Guided Meditations for the End of the Universe. This project aims to delve into cosmological theories about the end of the Universe to transform them into meditative and embodied experiences. Employing an anthropological approach to engage with science, the artists intend to employ spoken voice recordings, electronic music, light environments and sonified data from particle events.
Now in its sixth edition, Connect has become a pivotal platform for Swiss-based artists to expand their artistic practice in dialogue with the field of physics and science at CERN. This collaboration framework between Arts at CERN and Pro Helvetia will continue through the next year with an iteration in Chile and India, sustaining its mission to foster interactions and dialogue between artistic and scientific communities.
“We find ourselves in a challenging yet exciting time, as we witness the emergence of a strong and vibrant infrastructure devoted to the integration of artistic activity within the sciences,” says Mónica Bello, Curator and Head of Arts at CERN. “This is a transformational and promising development that presents unprecedented opportunities for cultural innovation. Connect is evidence of these dynamics, and I am proud to see that our partnership with Pro Helvetia is advancing further, bringing in new residents with different perspectives and backgrounds and strengthening the confluence of art and science in Switzerland.”
“This sixth edition of Connect continues to reaffirm the significance of the interface between art, science and technology. The quality and diversity of applications received illustrate the rich interdisciplinarity inherent in this dynamic field, and the extent to which it is part of current artistic practice. We are happy to foster dialogue and innovation at this remarkable intersection and are very pleased about the ongoing collaboration with Arts at CERN,” explains Philippe Bischof, Director of Pro Helvetia.
The jury of Connect was formed by Mónica Bello, Curator and Head of Arts at CERN; Giulia Bini, Head of Program and Curator of “Enter the Hyper-Scientific” at EPFL Lausanne; and Federica Martini, Head of the CCC - Critical Curatorial Cybermedia Master at HEAD Genève.
angerard Tue, 04/02/2024 - 16:09 Publication Date Wed, 04/03/2024 - 14:00CERN to change name for 70th Anniversary
Since its inception in 1954, CERN has grown from a small group of physicists from a handful of countries to a thriving international hub for science and technology. This is why, on the occasion of the Laboratory’s 70th Anniversary, the time has come for the name to be adapted to reflect its new role in society. The new name, the Network of Experiments for Research and Development in Society, will come into force on 1 October 2024, at the Laboratory’s 70th birthday party.
The acronym CERN was borne from an intergovernmental meeting of UNESCO in Paris in December 1951. This is when the first resolution concerning the establishment of a European Council for Nuclear Research (in French Conseil Européen pour la Recherche Nucléaire, or CERN) was adopted. Two months later, an agreement was signed establishing the provisional Council – and the name “CERN” stuck. However, today, our understanding of matter goes much deeper than the nucleus, and “CERN” is now widely viewed across the scientific community as an outdated and exclusionary name.
“The word “nuclear” doesn’t really reflect the full breadth of scientific research we do here,” says Noah Lott, Head of Rebranding at the Organization. “Network of Experiments for Research and Development in Society indicates the range of particle physics, computing, engineering and technology research that takes place at the Laboratory, as well as its impact on society.”
“We are also no longer just a European organisation, as we have grown to a global community encapsulating more than 80 countries,” adds Ivana Reed, spokesperson for international relations at the Laboratory. “We feel that everyone, no matter who they are, will feel accepted and proud to be associated with NERDS.”
A dedicated working group – the Decision for a Unified Moniker Board – was created in 2021 to assess potential options for the new name. “NERDS is so much more memorable and inclusive than CERN,” explains Wirall Geex, president of the working group. “Since we are a global network of varied experiments, we hope the new name will remove negative stereotypes about the type of people who work at the Organization,” he adds, pushing up his glasses.
NERDS was chosen by the working group out of a list of names put forward by the CERN community. Among the high contenders were A Large International Experimental Network (ALIEN), the High Energy Laboratory for Physics (HELP), and the initial frontrunner, the Global Organization for Discovery (GOD). However, following a spirited debate in the working group, GOD was discarded on account of unfortunate echoes of the “God particle” – the controversial name accidentally given to the Higgs boson in 1993.
NERDS looks forward to continuing to be at the forefront of scientific research for the next 70 years and beyond.
ndinmore Wed, 03/27/2024 - 19:02 Publication Date Mon, 04/01/2024 - 09:00Accelerator Report: Protons or Easter eggs? Let’s hope for both
Beam commissioning is progressing well across the entire accelerator complex, with initial completion achieved in the first machines of the chain. Last week, the first physics experiments started in the East Area, behind the PS, and others will follow suit shortly.
A Cell-Coupled-Drift-Tube-Linac (CCDTL) ready to be tested in SM18. (Image: CERN)However, despite the overall positive momentum of beam commissioning, challenges have arisen along the way, highlighting the complexities involved. Last week, some of the components of one of the Linac4 accelerating structures, specifically the Cell-Coupled-Drift-Tube-Linacs (CCDTLs) 3 and 4, presented some issues. Both CCDTLs rely on a single klystron*, a high-power microwave amplifier crucial for providing accelerating power to the structures, which, in turn, transfer the power to the protons, which are then accelerated.
The high-voltage and high-frequency amplifier chain, including the klystron, experienced frequent voltage breakdowns, resulting in a significant drop in accelerating voltage within the two CCDTLs. This disruption severely perturbed the beam, rendering it unusable for the PS Booster. Experts intervened multiple times, initially focusing on fine-tuning the parameters of the amplifier chain and later on cleaning and replacing various components suspected to be causing the breakdowns.
By 22 March, a set of parameters was established to allow the acceleration of beams with a low proton intensity, enabling commissioning activities to continue in the downstream machines, including the LHC. However, these parameters did not meet the requirements for generating the full-blown physics beams that will be required in the coming weeks. On 24 March, a collaborative effort with experts from various groups convened in the CERN Control Centre (CCC) to conduct a final assessment. This evaluation aimed to determine whether the klystron needed replacing.
After re-establishing the parameters suitable for high-intensity beam acceleration, the beam was switched back on. Unfortunately, within the first hour, at least two high-voltage breakdowns occurred – the team thus concluded that the klystron replacement was necessary.
To maintain commissioning activities in the downstream machines, parameters allowing low-intensity beam acceleration were reinstated. This allowed operations to continue until Monday morning, when the klystron replacement process started. Such an intervention typically requires two to three days before beam operations can be restored.
The new klystron is in place, ready to feed the CCDTLs 3 and 4. (Image: CERN)Meanwhile, commissioning activities in the downstream machines have been suspended and the start of physics at the n_TOF facility, behind the PS, has been postponed (it was originally scheduled to start on 25 March). Commissioning of the North Area's secondary beams began on 22 March instead of 25 March. Thanks to this head start, the incident in Linac4 does not impact the overall schedule for the North Area, where physics is still scheduled to start on 10 April.
In Linac4, the old klystron has been removed, and the new one had been installed and tested by 26 March. Beam was sent to the PS Booster at 5 p.m. that day and, at 9 p.m., the LHC beam commissioning activities resumed. Since then, they have been progressing well.
On 27 March, beams entered into “test” collisions at the target energy of 6.8 TeV in the LHC. These were not yet stable beams, which meant that the experiments did not take data. Collisions for physics at 6.8 TeV are expected to take place on 8 April.
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* A klystron is a high-power microwave amplifier used to generate high-power radiofrequency (RF) signals at a specific frequency. It operates on the principle of velocity modulation, where bunches of electrons are alternately accelerated and decelerated within a resonant cavity structure. This modulation process results in the amplification of the RF signal.
anschaef Wed, 03/27/2024 - 15:59 Byline Rende Steerenberg Publication Date Thu, 03/28/2024 - 10:49