The Higgs boson is recognized as the most significant discovery of the LHC. For twelve years, physicists have strived to precisely determine its properties, a challenging task due to experimental and computational difficulties. A group of physicists from IFJ PAN in Cracow, RWTH Aachen University, and the Max Planck Institute for Physics in Garching has made notable progress in theoretical research.
The Standard Model, developed in the 1970s, describes elementary particles and forces, including quarks, electrons, muons, tau particles, neutrinos, photons, gluons, W, and Z bosons. The discovery of the Higgs boson in 2012 was a crucial milestone, explaining how particles acquire mass. Since then, scientists have worked to understand this essential particle.
"For a physicist, one of the most important parameters associated with any elementary or nuclear particle is the cross section for a specific collision. This is because it gives us information on how often we can expect the particle to appear in collisions of a certain type. We have focused on the theoretical determination of the Higgs boson cross section in gluon-gluon collisions. They are responsible for the production of about 90% of the Higgs, traces of whose presence have been registered in the detectors of the LHC accelerator," explains Dr. Rene Poncelet (IFJ PAN).
Prof. Michal Czakon (RWTH), co-author of the article in the prestigious physics journal Physical Review Letters, where the scientists presented their calculations, adds: "The essence of our work was the desire to take into account, when determining the active cross section for the production of Higgs bosons, certain corrections that, due to their apparently small contribution, are usually neglected, because ignoring them significantly simplifies the calculations. It's the first time we have succeeded in overcoming the mathematical difficulties and determining these corrections."
The study highlights the significant role of higher-order corrections in understanding Higgs boson properties. These corrections, though seemingly minor, contribute substantially to the active cross section value, with third-order corrections reducing computational uncertainties to just one percent.
A novel aspect of the research was considering bottom-quark masses, leading to a small but measurable shift in the results. The LHC collides protons, which contain up and down quarks. The temporary presence of heavier quarks like beauty quarks is due to the quantum nature of strong interactions.
"The values of the active cross section for Higgs boson production found by our group and measured in previous beam collisions at the LHC are practically the same, naturally taking into account current computational and measurement inaccuracies. It therefore appears that no harbingers of new physics are visible within the mechanisms responsible for the formation of Higgs bosons that we are investigating - at least for the time being," Dr. Poncelet summarises the team's work.
While the Standard Model answers many questions about particle physics, it leaves others unresolved, such as the nature of dark matter, the reason for matter-antimatter asymmetry, and the masses of elementary particles. These questions suggest the need for new physics beyond the Standard Model.
The latest findings from IFJ PAN, RWTH, and MPI do not rule out the possibility of new physics in Higgs boson phenomena. As the LHC begins its fourth research cycle, more data could narrow measurement uncertainties and potentially reveal discrepancies between theoretical and observed cross sections. Until then, the Standard Model remains robust.
Research Report:Top-Bottom Interference Contribution to Fully Inclusive Higgs Production
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