The LHC’s ATLAS collaboration publishes the first measurements of the Higgs boson at record energy

The ATLAS collaboration at the Large Hadron Collider (LHC) at CERN has made new measurements of the production rate of Higgs bosons at the energy of 13.6 TeV, a record value that the LHC accelerator has managed to achieve in its third period of operation known as Run 3. The results, published this week in the European Physical Journal C, have the direct participation of the IFIC researcher Salvador Martí García.

The results, presented for the first time at the LHCP conference held in May and published this week in the European Physical Journal C, have been obtained from the data sample collected during this new cycle of LHC operations, which began in July 2022. They represent the first measurements of the production of the Higgs boson at this new energy.

The new published study combines the analysis of two of the most distinctive ’traces’ that the Higgs boson produces when 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 probability that the Higgs boson will decay through these two processes is very small, the ATLAS detector was designed to identify and measure with great efficiency and precision the particles that emerge from these processes. This potential allows the physics research community to study the properties of the Higgs boson in great detail through the analysis of both processes.

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

When analysing these decay events, the Higgs boson ’signal’ is expected to appear in the graphs as an accumulation of events - a peak - on top of some background values. This peak is located around 125 GeV, the mass value of the Higgs boson.

The new results have made it possible to test the performance of the ATLAS detector under the new data acquisition conditions of Run 3 and make it possible to study the physics of the Higgs boson at an unprecedented energy of 13.6 TeV.

IFIC’s contribution

Salvador Martí García , science researcher at the Institute of Corpuscular Physics (IFIC, University of Valencia-CSIC), has contributed directly to this study as an expert in the alignment of the detector and the muon calibration of the ATLAS experiment.

"In order to observe a distinctive Higgs boson signal on the background, we need to measure the properties of the particles resulting from the Higgs decay with great precision. Therefore, our detector must be aligned with maximum accuracy, which means reaching the level of one micron for the most sensitive components of the detector", declares the researcher, adding: "We have achieved this thanks to meticulous work and the experience acquired over the years".

For her part, Carmen García García , CSIC research professor at IFIC and leader of the ATLAS group in Valencia, highlights: "Our group is very committed to the ATLAS experiment and participates in the analysis of the physics, the performance studies of the detector and its operation. It is a great satisfaction to see that all our efforts bear fruit".

Next steps

These results represent the first set of Higgs boson measurements recorded at the new energy of 13.6 TeV, the highest ever achieved in a particle physics collider. In turn, they pave the way for increasingly precise measurements.

"Now that we have observed this Higgs boson decay process, we can scrutinise in detail the properties of the final particles that appear as a product of the decay and check whether they behave as predicted by the Standard Model. We also plan to study another process that involves the Higgs and that produces a similar experimental signal, but that will allow us to analyse one of the rarest processes of decay of a Higgs boson", explains Martí-García.