An international team of physicists working at the Large hadron Collider in the composition of the ATLAS and CMS collaborations (CERN), the first to observe Higgs decays to two d-quark (down-quark). This discovery reaffirms the Standard model describes the properties of elementary particles. Scientists also found no evidence of the possible existence of New physics that could explain possible shortcomings of the existing theory. About it reported in a press release on Phys.org.
In particle accelerators, the Higgs boson arises in a frontal collision of two protons occurs when the fusion of gluons — species bosons, responsible for interaction between quarks and their retention inside the proton. As a result of the gluons arises u-quark and u anti-quark from which in turn arises short-lived Higgs boson. After that, he almost immediately breaks up, with the possible formation of electron-positron pairs, photons, muons and anti.
According to the prediction of the Standard model in the decay d-quarks occurs in 60 percent of cases. Other types of decay of the Higgs boson are distinguishable against the background “noise”, while the emergence of d-quark and d-antiquark masked by other processes that lead to the emergence of bottom quarks. For example, the collision of protons creates a shower of subatomic particles, including the desired. Therefore, to determine the predicted events physicists needed to accumulate statistics for five standard deviations (equal to the probability of non-random result in 99.97 percent), analyzing hundreds of thousands of decays of particles in proton-proton collisions.
New data were obtained from two runs of charged particle beams in a 27-kilometre ring of the Large hadron Collider. Collisions of protons occurred at energies of 7, 8 and 13 teraelectronvolt. The researchers then analysed the information given by-products of the interaction of particles. It allowed to detect not only the Higgs decays into bottom quarks, but also confirm that its velocity corresponds to that predicted by the Standard model value.
The Higgs boson is involved in the mechanism (the Higgs mechanism) of the occurrence of masses of these fundamental particles, as carriers of the weak interaction (W and Z bosons), and determines the absence of the rest mass of the gluon and photon. Despite the fact that the discovery of this particle and study its properties confirms the Standard model, there are problems (for example, asymmetry of matter and antimatter in the Universe or incompatibility with the theory of relativity), which from its position can not be explained. At the same time in particle accelerators so far there has been no hint of the existence of New physics. Some scientists believe that the New physics does not exist (or it is in principle not observable), and at the moment of the Universe we know almost everything there is to know.
Video, photo All from Russia.