A new constraint for matter-antimatter asymmetries at LHCb experiment

A few moments after the Big Bang, matter and antimatter coexisted and annihilated each other, but surprisingly, a tiny amount of matter survived. However, why did matter prevail?
This is one of the questions scientists have not yet found an answer to, and in fact, even the model describing all particles and their interactions, the Standard Model, does not justify this difference. The asymmetry between matter and antimatter is proportional to the area of a triangle, whose angles and sides are obtained from measurements that can be made in particle physics.
The LHCb collaboration, with the crucial contribution of the Padova group, has recently measured the angle 𝛄 of this triangle, using a sample of Bs→DsK decays collected during the LHC accelerator collisions between 2015 and 2018. This measurement is important firstly because it is performed using neutral B mesons, allowing a clear comparison with theoretical data. Additionally, it can be compared with measurements of 𝛄 that exploit decays that may occur through the contribution of yet undiscovered particles. For this measurement, the number of decays as a function of time was specifically studied, and the comparison with theoretical data allowed the extraction of the sought-after angle.
The obtained value, 𝛄 = (74 ± 11) degrees, is compatible with theoretical predictions and turns out to be the most precise value ever obtained using neutral mesons.
All the details on this measurement can be found in the latest issue of the CERN COURIER (Jan/Feb 23).