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Fireball (officially “HRMT-62”), a new experiment at the SPS HiRadMat facility, will receive its first beam this week. It is designed to study the micro-instabilities of a high-intensity electron-positron beam interacting with low-density plasma. The electron-positron beam is produced when a 440 GeV/c proton beam from the SPS impinges on a special target. The resulting beam propagates through the plasma and creates a highly unstable system: fluctuations of the magnetic field in the plasma cause charge separation in the beam, and this separation consequently causes further magnetic fluctuations in the plasma. This gives rise to non-linear phenomena and plasma emissions that have never been studied in this way before.
Members of the experimental team are working on the plasma cell during the 2022-2023 year-end-technical stop (YETS) in the HiRadMat surface laboratory. (Image: CERN)This study should give new insights into extreme astrophysical phenomena, in particular blazar jets and gamma-ray bursts (GRBs). GRBs are among the most energetic phenomena in the Universe and, even though they have been observed in distant galaxies, the enormous amount of energy they release can disrupt radio communications on Earth – some theories even suggest that they affected the evolution of life on Earth. However, the fundamental physical processes involved in GRBs are still not understood.
“Without the unique HiRadMat facility, it would not have been possible to implement Fireball; it will be the first accelerator-driven experiment of this kind”, says Gianluca Gregori, the experiment’s spokesperson from the University of Oxford. “Fireball will help lift the veil on the microphysics processes that are not observable with satellites or ground-based telescopes and are impossible to simulate numerically.”
Installation of Fireball in HiRadMat’s irradiation area. (Image: CERN)The experiment includes various instruments designed to study the formation of plasma instabilities and magnetic fields, in particular a custom-made magnetic spectrometer with a dipole magnet. “In order to power the magnetic spectrometer in a flexible and cost-effective way, along with SY/ABT and SY/EPC groups we disconnected one of the quadrupoles of the HiRadMat beamline and the optics were recalculated”, explains Nikos Charitonidis, HiRadMat facility coordinator. “The collaboration within CERN has once again been key to implementing all the necessary modifications in terms of beam and infrastructure. I’d really like to thank all the CERN groups involved for their collaborative effort in running this unique facility.”
Since its commissioning in 2011, HiRadMat has taken part in several European Transnational Access programmes, which have made the facility accessible to users from all over the world.
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For more information on the HiRadMat facility, read the article published for its 10th anniversary.
anschaef Wed, 05/24/2023 - 11:03 Publication Date Wed, 05/24/2023 - 11:01Although neutrinos are produced abundantly in collisions at the Large Hadron Collider (LHC), until now no neutrinos produced in such a way had been detected. Within just nine months of the start of LHC Run 3 and the beginning of its measurement campaign, the FASER collaboration changed this picture by announcing its first observation of collider neutrinos at this year’s electroweak session of the Rencontres de Moriond. In particular, FASER observed muon neutrinos and candidate events of electron neutrinos. “Our statistical significance is roughly 16 sigma, far exceeding 5 sigma, the threshold for a discovery in particle physics,” explains FASER’s co-spokesperson Jamie Boyd.
In addition to its observation of neutrinos at a particle collider, FASER presented results on searches for dark photons. With a null result, the collaboration was able to set limits on previously unexplored parameter space and began to exclude regions motivated by dark matter. FASER aims to collect up to ten times more data over the coming years, allowing more searches and neutrino measurements.
FASER is one of two new experiments situated at either side of the ATLAS cavern to detect neutrinos produced in proton collisions in ATLAS. The complementary experiment, SND@LHC, also reported its first results at Moriond, showing eight muon neutrino candidate events. “We are still working on the assessment of the systematic uncertainties to the background. As a very preliminary result, our observation can be claimed at the level of 5 sigma,” adds SND@LHC spokesperson Giovanni De Lellis. The SND@LHC detector was installed in the LHC tunnel just in time for the start of LHC Run 3.
Until now, neutrino experiments have only studied neutrinos coming from space, Earth, nuclear reactors or fixed-target experiments. While astrophysical neutrinos are highly energetic, such as those that can be detected by the IceCube experiment at the South Pole, solar and reactor neutrinos generally have lower energies. Neutrinos at fixed-target experiments, such as those from the CERN North and former West Areas, are in the energy region of up to a few hundred gigaelectronvolts (GeV). FASER and SND@LHC will narrow the gap between fixed-target neutrinos and astrophysical neutrinos, covering a much higher energy range – between a few hundred GeV and several TeV.
One of the unexplored physics topics to which they will contribute is the study of high-energy neutrinos from astrophysical sources. Indeed, the production mechanism of the neutrinos at the LHC, as well as their centre-of-mass energy, is the same as for the very-high-energy neutrinos produced in cosmic-ray collisions with the atmosphere. Those “atmospheric” neutrinos constitute a background for the observation of astrophysical neutrinos: the measurements by FASER and SND@LHC can be used to precisely estimate that background, thus paving the way for the observation of astrophysical neutrinos.
Another application of these searches is measuring the production rate of all three types of neutrinos. The experiments will test the universality of their interaction mechanism by measuring the ratio of different neutrino species produced by the same type of parent particle. This will be an important test of the Standard Model in the neutrino sector.
ckrishna Wed, 03/22/2023 - 10:42 Byline Kristiane Bernhard-Novotny Chetna Krishna Publication Date Wed, 03/22/2023 - 10:25The ATLAS collaboration is a global effort involving almost 6000 physicists, engineers, technicians and other experts. Made up of 182 institutions spread over every populated continent, its multinational efforts require a high level of coordination. Together, a new ATLAS management team will oversee all aspects of the collaboration throughout most of LHC Run 3.
ATLAS spokesperson Andreas Hoecker will work with several familiar faces in the management team. Manuella Vincter (Carleton University) continues as deputy spokesperson. She is joined by deputy spokesperson Stéphane Willocq (University of Massachusetts Amherst), who previously served as ATLAS physics coordinator. Technical coordinator Ludovico Pontecorvo (CERN) will continue in his role for another year, before handing the baton to Martin Aleksa (CERN) in March 2024. David Francis (CERN) continues as resources coordinator and Benedetto Gorini (CERN), who joined the team in October 2022, continues as upgrade coordinator. Stepping down from their roles are deputy spokesperson Marumi Kado (new Director of the Max Planck Institute for Physics, Munich) and, since October 2022, upgrade coordinator Francesco Lanni (new leader of the CERN Neutrino Platform). Both provided invaluable contributions to ATLAS during their terms.
“This is an exciting time for the ATLAS collaboration, as we are undertaking several key objectives simultaneously,” says Andreas. “In addition to collecting and analysing data from the current record-energy operation of the LHC, benefitting from recently installed detector improvements, our broad programme of physics analysis and experiment upgrade will continue apace. Meeting this wide range of goals will require our full commitment and focus of effort.”
In its 30 years of history, the ATLAS collaboration has proven to be a leading source of scientific excellence – a legacy the ATLAS management team plans to build on. “I am confident that ATLAS members will rise to the occasion to meet these challenges,” concludes Andreas. “Our members are a great source of inspiration to me; their ideas and contributions are the driving force behind our experiment’s excellent results. As spokesperson, I will continue to cultivate our longstanding culture of open and inclusive engagement.”
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Read the full text on the ATLAS collaboration’s website: https://atlas.cern/Updates/News/New-Management-Team
anschaef Thu, 03/09/2023 - 10:27 Byline ATLAS collaboration Publication Date Thu, 03/09/2023 - 10:20Current technology does not allow all Large Hadron Collider (LHC) proton–proton collision data to be stored and analysed. It is therefore necessary to filter out the data according to the scientific goals of each experiment. Physicists call this selection process the “trigger”. Thus, data taking and analysis at the LHC has traditionally been performed in two steps. In the first, which physicists call “online”, the detector records the data, which is then read out by fast electronics and computers, and a selected fraction of the events is stored on disks and magnetic tapes. Later, the stored events are analysed “offline”. In offline analysis, important data taken from the online process is used to determine the parameters with which to adjust and calibrate LHCb’s subdetectors. This whole process takes a long time and uses a large amount of human and computing resources.
In order to speed up and simplify this process, the LHCb collaboration has made a revolutionary improvement to data taking and analysis. With a new technique named real-time analysis, the process of adjusting the subdetectors takes place online automatically and the stored data is immediately available offline for physics analysis.
In LHC Run 2, LHCb’s trigger was a combination of fast electronics (“hardware trigger”) and computer algorithms (“software trigger”) and consisted of multiple stages. From the 30 million proton collisions per second (30 MHz) happening in the LHCb detector, the trigger system selected the more interesting collision events, eventually reducing the amount of data to around 150 kHz. Then, a variety of automatic processes used this data to calculate new parameters to adjust and calibrate the detector.
For Run 3 and beyond, the whole trigger system has changed radically: the hardware trigger has been removed and the whole detector is read out at the full LHC bunch-crossing rate of 40 MHz. This allows LHCb to use real-time analysis for the full selection of data, making it much more precise and flexible.
The real-time reconstruction allows LHCb to not only cherry-pick interesting events but also compress the raw detector data in real time. This means there is tremendous flexibility to select both the most interesting events and the most interesting pieces of each event, thus making the best use of LHCb’s computing resources. In the end, around 10 gigabytes of data are permanently recorded each second and made available to physics analysts.
The event display images shown were taken during the first Run 3 proton–proton collisions on 5 July (left) and the first lead–argon collisions on 18 November (right). The event display program used real-time analysis.The success of real-time analysis was only possible thanks to the extraordinary work of the online and subdetector teams during the construction and commissioning of this brand new version of the LHCb detector. More information about LHCb’s new trigger system and the team behind it can be found on the collaboration’s website.
ndinmore Wed, 03/01/2023 - 14:54 Byline LHCb collaboration Publication Date Wed, 03/01/2023 - 14:26
The Hellenic Society for the Study of High Energy Physics (HeSSHEP) promotes the scientific work of the Greek scientists, informs the general public and the Greek state on matters concerning the subject of High Energy Physics, organizes an workshop and conferences.
