4. LHCb Collaboration Steps Forth Studying Beauty Quark

LHCb Collaboration Steps Forth Studying Beauty Quark

03.08.2015
According to CERN press office, the LHCb collaboration, which includes researchers from NSU, has published a paper in Nature Physics on the first |Vub| measurement, which describes the transition of a b quark to a u quark, to use a baryonic decay.

 

Quarks, being the fundamental constituents of ordinary protons and neutrons, are bound, have fractional electrical charges and can exist in six different forms referred to as flavors. Each variation of quark has a different name. They are: strange, charm, top, bottom (or beauty), up and down. The paper deals with two of the quarks, namely u and b quarks

The paper states that in the Standard Model (SM) of particle physics the decay of one quark to another by the emission of a virtual W boson is described by the Cabibbo–Kobayashi–Maskawa matrix. The determination of the parameter |Vub| reported was made by studying a particular decay of the Λb0 baryon, Λb0→pμνμ. The Λb0 transforms into a proton with a W boson emitted in this process and decaying in turn into a muon μ and a neutrino νμ. The probability of the Λb0→pμνμ decay depending on the SM parameter |Vub|, accurate measurement of these parameters allows checking the SM.

“Researchers have been studying the b quark for a long time,” says Alexander Bondar, the Dean of the Physics Department at NSU, “but there is a tricky issue. The probability of a b quark turning into a W boson and a u quark when applying exclusive and inclusive methods returns two sets of inconsistent results, depending on which method was used to determine the parameter. We might not know something, which could give rise to a new physics beyond that of the SM, or the methods used were defective. That is why any new measurement is of paramount importance for understanding the method. The result reported is based on sufficient statistics proving the exclusive method in mesons and baryons to provide the same result. We still do not know how the inclusive method works in Λb0 decay, though. Nevertheless, we stepped forth.”

The paper published is based on run 1 data from the previous LHC session. Further intensive research, both at the experimental and theoretical level, will continue to try to understand the disagreement of the methods. The results are to be checked during run 2 and with higher energies.