Search for $C\!P$ violation in $\Lambda_b\to pK^-\mu^+\mu^-$ decays

In this thesis the first search for $C\!P$-violation on rare heavy beauty baryon $\Lambda_b\to pK^-\mu^+\mu^-$ decays is described. This analysis is carried out on the whole dataset recorded by the LHCb experiment during 2011 and 2012. The $C\!P$ symmetry violation study is one of the most promising method for searching physics beyond the standard model, as the measured amount of $C\!P$-violation in high-energy physics experiments, even though compatible with standard model expectations, is not sufficient for explaining the observed matter-antimatter asymmetry of our universe. The $\Lambda_b\to pK^-\mu^+\mu^-$ decays occur via electroweak loop diagrams which allow possible new physics fields to give this process a sensible contribution. For the $\Lambda_b\to pK^-\mu^+\mu^-$ decay a limited quantity of $C\!P$-violation is expected in the standard model, making this transition suited to look for beyond standard model physics. In this thesis, $C\!P$-violation is searched exploiting direct $C\!P$ asymmetries and triple-products asymmetries, two complementary measurements sensitive to different new physics contributions. Experimentally, the study of $\Lambda_b\to pK^-\mu^+\mu^-$ transition is very clean thanks to the high performance of the muon detection and particle identification systems of LHCb experiment.