First measurements of the Higgs boson at record energy

Scientists from the ATLAS collaboration at the Large Hadron Collider (LHC) at the European Particle Physics Laboratory (CERN) have made new measurements of the production rate of Higgs bosons at an energy of 13.6 TeV, a record value achieved by the LHC accelerator. managed to reach the third period of work, known as Run 3.

The results, first presented at the LHCP conference in May and published this week in the European Physics Journal C, were obtained from a sample of data collected during the new cycle of LHC operations, which began in July 2022. first measurements of Higgs boson production at this new energy.

A newly published study combines analysis of two of the most characteristic traces left by the Higgs boson as it decays into other particles. In fact, these are the same decay modes that allowed ATLAS to discover the Higgs boson in 2012.

Although the likelihood of the Higgs boson decaying as a result of these two processes is very small, the ATLAS detector was designed to identify and measure with great efficiency and accuracy the particles resulting from these processes. This potential allows the scientific community of physicists to study the properties of the Higgs boson in great detail by analyzing both processes.

The first step in the study is to measure the rate of Higgs boson production within the ATLAS detector’s range. These measurements, in turn, provide insight into the performance of all detector components.

When analyzing these decay events, the Higgs boson signal is expected to appear in the graphs as a cluster of events – a peak – on top of the background values. This peak is located around 125 GeV, the mass of the Higgs boson.

The new results allowed the ATLAS detector to be tested under the new data collection conditions of the third run and to study the physics of the Higgs boson at an unprecedented energy of 13.6 TeV.

Spanish contribution to IFIC

Salvador Martí García, CSIC Research Fellow at the Institute of Corpuscular Physics (CSIC – University of Valencia), contributed directly to this research as an expert on detector alignment and muon calibration of the ATLAS experiment.

“To observe the characteristic signal of the Higgs boson against the background, we need to measure with great precision the properties of the particles formed as a result of Higgs decay. Therefore, our detector must be tuned with maximum precision, which means achieving a level of one micron. for the most sensitive components of the detector,” the researcher states. And he adds: “We achieved this through hard work and experience acquired over the years.”

For her part, Carmen García García, CSIC Research Professor at IFIC and leader of the ATLAS group in Valencia, emphasizes: “Our group is very dedicated to the ATLAS experiment and is involved in physics analysis, detector performance studies and We are very happy to see what all our efforts bring fruit.

Next steps

These results represent the first set of measurements of the Higgs boson recorded at a new energy of 13.6 TeV, the highest ever achieved at the Particle Physics Collider. In turn, they open the way to more precise measurements.

“Now that we have observed the decay of the Higgs boson, we can study in detail the properties of the final particles that emerge as the decay product and test whether they behave as predicted by the Standard Model. We also plan to study another process. this is related to the Higgs boson and gives a similar experimental signal, but it will allow us to analyze one of the rarest decay processes of the Higgs boson,” explains Martí-García.

Link:

ATLAS Collaboration., Aad G., Abbott B. et al. Measurement of cross sections and in TeV pp collisions with the ATLAS detector. European Journal of Physics 84, 78 (2024). https://doi.org/10.1140/epjc/s10052-023-12130-5