The Large Hadron Collider (LHC) begins delivering proton collisions to experiments today at an unprecedented energy of 13.6 TeV, marking the start of the accelerator's third run of data collection (Run 3)
5 July 2022
Today, Tuesday 5 July 2022, a new data collection period begins for experiments at the world's most powerful particle accelerator, CERN's Large Hadron Collider (LHC), after more than three years of upgrades, improvements and maintenance work. Beams have already been circulating around CERN's accelerator complex since April, with the LHC and its injectors set to operate with new beams of higher intensity and energy. Now, LHC operators are ready to announce "stable beams", a condition that allows the experiments to switch on all their subsystems and start taking data that will be used for analysis of the physics collected. The LHC will operate 24 hours a day for about four years at the record energy of 13.6 trillion electron volts (TeV).
"We will focus the proton beams at the interaction points down to a beam size of less than 10 micrometres to increase the collision rate. Compared to the first data collection period (Run 1), when the Higgs boson was discovered with 12 inverse femtobarns, in Run 3 we will work with 280 inverse femtobarns, a significant increase that opens the way to new discoveries," says accelerator director Mike Lamont.
Note: an inverse femtobarn is a measure of the number of collisions or amount of data collected. One inverse femtobarn corresponds to approximately 70 trillion proton-proton collisions.
The four large LHC experiments have carried out major upgrades to their data reading and selection systems, with new detection mechanisms and computing infrastructure. The ATLAS and CMS detectors expect to record more collisions during Run 3 than in the previous two physics cycles combined. The LHCb experiment has undergone a complete overhaul and expects to increase its data collection rate by a factor of 10, while ALICE aims for a 50-fold increase in the number of collisions recorded. Improvements to the detectors in each experiment will allow significantly larger and higher quality data samples to be collected than in previous operating periods.
By increasing the data sample and using higher collision energies, Run 3 aims to further expand the LHC's already diverse physics programme: scientific collaborations on the experiments will investigate the nature of the Higgs boson with unprecedented precision, will be able to observe previously inaccessible processes, and will have the ability to improve the accuracy of measurements taken on many known processes that address fundamental questions, such as the origin of matter-antimatter asymmetry in the Universe. In addition, it is expected that researchers will be able to study the properties of matter under extreme conditions of temperature and density. Scientists will also search for dark matter candidates and other new phenomena, either through direct or indirect searches, in the latter case by measuring more precisely the properties of known particles.
The LHC today. / CERN
"We are eagerly awaiting new data concerning the decay of the Higgs boson into second-generation particles, such as muons. This would be a completely new result in the Higgs boson saga, confirming for the first time that also second-generation particles gain mass through the Higgs mechanism," says CERN theorist Michelangelo Mangano.
"We will measure the strength of Higgs boson interactions with matter and force-bearing particles with unprecedented precision and deepen the search for Higgs boson decays in dark matter particles," Andreas Hoecker, ATLAS spokesperson
One topic that will be closely followed is the study of rare processes in which an asymmetry in lepton flavour (an unexpected difference between electrons and their cousin particles, muons) was observed in the data collected by the LHCb experiment during the previous periods of LHC operation. "The data acquired during this third cycle with our new detector will allow us to improve the precision by a factor of two and to confirm or exclude possible deviations in the universality of the lepton flavour," says Chris Parkes, LHCb spokesman. Many of the theories that explain the anomalies observed by LHCb also predict new phenomena in different physical processes already known. These will be studied in ATLAS and CMS as well. "This complementary approach is essential: if we are able to confirm new phenomena in this way, they can be important discoveries in particle physics," says Luca Malgeri, spokesperson for the CMS collaboration.
The ALICE programme, which focuses on the study of heavy-ion collisions, will make it possible to investigate, with unprecedented precision, the quark-gluon plasma (QGP), a state of matter that existed in the first 10 microseconds after the Big Bang. "We hope to move from a phase where we observe many interesting properties of the quark-gluon plasma to a phase where we precisely quantify these properties and relate them to the dynamics of its constituents," says Luciano Musa, spokesperson for the ALICE experiment. In addition to studies using lead, a short period with oxygen collisions will be included for the first time, with the aim of exploring the occurrence of QGP-like effects in other colliding systems.
The smaller LHC experiments, namely TOTEM, LHCf, MoEDAL with its new MAPP sub-detector, and the recently installed FASER and SND@LHC, are also prepared to explore phenomena inside and outside the Standard Model, from magnetic monopoles to neutrinos and cosmic rays.
IFCA on Run 3
The data extracted from the LHC will feed several of the projects in which IFCA is involved, as Celso Martínez, CMS representative in Spain and researcher at the institute, explains. "One for computation, by Francisco Matorras, another for upgrade, which is led by Gervasio Gómez and Iván Vila, and another for analysis in Run 3, mine together with Alicia Calderón, which will analyse all the data we receive in Higgs, top quark, SUSY (Supersymmetry) and dark matter".
"Our goal is to analyse the data, to see new physics, if possible, and this is going to take us several years from now. In addition, we will now have to go to CMS to analyse the data," says Alicia Calderón, researcher in the IFCA's Particle Physics Group and lecturer at the University of Cantabria.
The wide-ranging and promising scientific programme planned for this new physics season at the LHC has the Spanish community expectant and excited. "We have been preparing for this exciting new challenge for some time. Run 3 will provide greater sensitivity to as yet unexplored phenomena, allow us to investigate in more detail the still little-known Higgs field, and hopefully clarify the anomalies observed in some rare heavy quark decays," explains Antonio Pich, director of the Centro Nacional de Física de Partículas, Astropartículas y Nuclear (CPAN). And he concludes: "We are starting another exciting period of experimentation that may bring us great surprises.