Theoretical physicists find that the Higgs boson does not appear to contain any harbingers of new physics

The Higgs boson was discovered in the detectors of the Large Hadron Collider a dozen or so years ago. It has proved to be such a difficult particle to produce and observe that, despite the passage of time, its properties are still not known with satisfactory accuracy. Now we know a little more about its origin, thanks to the newly published achievement of an international group of theoretical physicists with the participation of the Institute of Nuclear Physics of the Polish Academy of Sciences.

The research is published in the journal Physical review papers.

The scientific world is unanimous in its opinion that the greatest discovery made with the Large Hadron Collider (LHC) is the famous Higgs boson. For twelve years, physicists have been trying to learn as precisely as possible about the properties of this very important elementary particle. The task is extremely difficult due to experimental challenges and numerous computational hurdles.

Fortunately, significant progress has just been made in theoretical research, thanks to a group of physicists from the Institute of Nuclear Physics of the Polish Academy of Sciences (IFJ PAN) in Krakow, the RWTH Aachen University (RWTH) in Aachen and the Max-Planck-Institut für Physik (MPI) in Garching near Munich.

The Standard Model is a complex theoretical framework built in the 1970s to coherently describe the elementary particles of matter (quarks, as well as electrons, muons, tau, and the related neutrinos) and electromagnetic forces (photons) and nuclear forces (gluons). in the case of strong interactions, W and Z bosons in the case of weak interactions).

The icing on the cake in the creation of the Standard Model was the discovery, thanks to the LHC, of ​​the Higgs boson, a particle that plays a key role in the mechanism responsible for giving mass to other elementary particles. The discovery of the Higgs was announced in mid-2012. Since then, scientists have been trying to get as much information as possible about this fundamentally important particle.

“To 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 about 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 in gluon-gluon collisions, which are responsible for the production of about 90% of the Higgs detected in the LHC accelerator, explains Dr. Rene Poncelet (IFJ PAN).

Prof. Michal Czakon (RWTH), co-author of the article, 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, some corrections that, due to their apparently small contribution, is usually neglected, because ignoring them greatly simplifies the calculations.

The importance of the role of higher-order corrections in understanding the properties of Higgs bosons can be seen from the fact that the secondary corrections calculated in the paper, apparently small, contribute almost one fifth to the value of the required active cross section. . This compares with third-order corrections of 3% (but which reduce computational uncertainties to only 1%).

A novelty of the work was taking into account the effect of the bottom quark masses, leading to a small but noticeable shift of about 1%. It is worth remembering here that the LHC collides with protons, ie particles composed of two up quarks and one down quark. The temporary presence of quarks with larger masses inside protons, such as the beauty quark, is a consequence of the quantum nature of the strong interactions that bind the quarks in the proton.

“The values ​​of the active cross section for the production of the Higgs boson found by our group and measured in previous beam collisions at the LHC are practically the same, of course taking into account the current computational and measurement inaccuracies. Therefore there appear to be no physics caveats new. visible within the mechanisms responsible for the formation of the Higgs bosons that we are investigating – at least for now,” summarizes Dr. Poncelet team work.

The widespread belief among scientists in the need for the existence of new physics stems from the fact that a number of fundamentally important questions cannot be answered by the Standard Model. Why do elementary particles have the mass they do? Why do they create families? What does dark matter consist of, traces of which are so clearly visible in the cosmos? What is the reason for the predominance of matter over antimatter in the universe? The Standard Model also needs to be extended because it does not take into account gravity at all, which is such a common interaction.

Importantly, the recent achievement of theoretical physicists from IFJ PAN, RWTH and MPI does not definitively exclude the presence of new physics in the phenomena accompanying the birth of the Higgs boson. A lot could change when data from the Large Hadron Collider’s fourth research cycle, which is gradually starting to be analyzed, begins to be analyzed.

Increasing the number of observations of new particle collisions may make it possible to narrow the measurement uncertainties so that the measured range of cross sections allowed for Higgs production no longer matches that determined by theory. Whether this will happen or not, physicists will find out in a few years.

Right now, the Standard Model can feel safer than ever – and that fact is slowly starting to become the most surprising discovery made with the LHC.