The detectors at the Large Hadron Collider began recording high-energy collisions at the unprecedented energy of 13.6 TeV.
The Large Hadron Collider is once again delivering proton collisions for experiments, this time at an unprecedented energy of 13.6 TeV, marking the start of the accelerator’s third cycle of physics data collection.
A burst of applause erupted at the CERN Control Center on 5 July 2022 at 16.47 CEST as the Large Hadron Collider (LHC) detectors turned on all subsystems and began recording high-energy collisions at the unprecedented energy of 13.6 TeV, setting the beginning of a new physics season. This achievement was made possible by operators who have been working around the clock since the LHC restarted in April to ensure the smooth start of these higher-intensity, increased-energy beam collisions.
After more than three years of upgrades and maintenance, the LHC is now set to operate for nearly four years at its record energy of 13.6 trillion electron volts (TeV), providing increased precision and potential for discovery. Many factors point to a promising physics season that will further expand the LHC’s already very diverse physics program: increased collision rates, higher collision energy, improved data readout and selection systems, improved detector systems and computing infrastructure.
Celebrations at the CERN Control Center (CCC) to mark the start of LHC Run 3. Credit: CERN)
On Tuesday, July 5, a new period of data collection for experiments at the Large Hadron Collider (LHC), the world’s most powerful particle accelerator, began after more than three years of upgrades and maintenance. The beams have been circulating at CERN’s accelerator complex since April, with the LHC machine and its injectors restarted to run new beams of higher intensity and increased energy. Now, however, LHC operators have declared “stable beams,” the condition allowing the experiments to turn on all their subsystems and begin collecting the data that will be used for physical analysis. The LHC will operate around the clock for nearly four years at a record energy of 13.6 trillion electron volts (TeV), providing greater precision and potential for discovery than ever before.
“We will focus the proton beams at the interaction points down to a beam size below 10 microns to increase the collision speed. Compared to cycle 1 where the Higgs was discovered with 12 inverse femtobars, now in cycle 3 we will provide 280 inverse femtobars. This is a significant increase, paving the way for new discoveries,” says Director of Accelerators and Technologies Mike Lamont.
3D cross section of the Large Hadron Collider dipole. Credit: CERN)
The four major LHC experiments have undergone major upgrades to their data reading and selection systems, with new detector systems and computing infrastructure. The changes will allow them to collect significantly larger samples of data, with higher quality data than previous series. The ATLAS and CMS detectors expect to record more collisions during Series 3 than in the two previous series combined. The LHCb experiment has undergone a complete overhaul and is aiming to increase its data collection rate by a factor of ten, while ALICE is aiming for a staggering fifty-fold increase in the number of recorded collisions.
With the increased data samples and higher collision energy, Run 3 will further expand the LHC’s already very diverse physics program. Scientists in the experiments will probe the nature of the Higgs boson with unprecedented precision and in new channels. They can observe previously inaccessible processes and will be able to improve the precision of measurement of many known processes, addressing fundamental questions such as the origin of the matter-antimatter asymmetry in the universe. Scientists will study the properties of matter at extreme temperatures and densities, and will also look for candidates for dark matter and other new phenomena, either through direct searches or – indirectly – through precise measurements of the properties of known particles.
“We look forward to measurements of the decay of the Higgs boson to second-generation particles, such as muons. This would be an entirely new result in the saga of the Higgs boson, confirming for the first time that second-generation particles also gain mass through the Higgs mechanism,” says CERN theorist Michelangelo Mangano.
“We will measure the strength of the interactions of the Higgs boson with matter and force the particles to unprecedented precision and continue our searches for the decay of the Higgs boson to dark matter particles, as well as the search for additional Higgs bosons,” says Andreas Höcker, spokesman for the collaboration ATLAS. “It is not at all clear that the Higgs mechanism realized in nature is the minimal one involving only one Higgs particle.”
A closely watched topic will be studies of a class of rare processes where an unexpected difference (lepton flavor asymmetry) between electrons and their particle cousins, muons, has been probed by the LHCb experiment in data from previous LHC runs. “The data obtained during Run 3 with our brand new detector will allow us to improve the precision by a factor of two and confirm or rule out possible deviations from the universality of the lepton flavor,” says Chris Parkes, spokesperson for the LHCb collaboration. Theories explaining the anomalies observed by LHCb usually also predict new effects in various processes. They will be the target of specific studies carried out by ATLAS and CMS. “This additional approach is essential; if we can confirm new effects in this way, it will be a major discovery in particle physics,” says Luca Malgheri, spokesperson for the CMS collaboration.
The Heavy Ion Collider program will enable the study of quark-gluon plasma (QGP) – a state of matter that existed in the first 10 microseconds after the Big Bang – with unprecedented precision. “We expect to move from a phase where we observed very 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 collaboration. In addition to the main tests, a short period with oxygen collisions will be included for the first time, in order to study the occurrence of QGP-like effects in small collision systems.
The smallest experiments at the LHC – TOTEM, LHCf, MoEDAL, with its all-new MAPP subdetector and the recently installed FASER and [email protected] – are also ready to explore phenomena within and beyond the Standard Model, from magnetic monopoles to neutrinos and cosmic rays.
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