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Abstract
This thesis presents a measurement of charm mixing and CP-violation parameters using D0 -> K0S pi+ pi- decays. These mixing parameters include the mass and decay-width differences of the mass eigenstates of the D0-D0bar system. A search for Charge-Parity violation is performed through measurements of D0-D0b mixing and of the interference between mixing and decay amplitudes. The dataset consists of events reconstructed in proton-proton collisions collected by the LHCb experiment during the
operation of the Large Hadron Collider (LHC) from 2016 to 2018. This sample corresponds to an integrated luminosity of 5.4 fb^-1. The D0 decays are selected in semileptonically decays of b hadrons. The results are expressed in terms of the CP-averaged mixing parameters and CP-violating differences as
x_cp= (+4.29 +/- 1.48 (stat) +/- 0.26 (syst)) x 10^{-3}
y_cp= (+12.61 +/- 3.12 (stat) +/- 0.83 (syst)) x 10^{-3}
delta x= (-0.77 +/- 0.93 (stat) +/- 0.28 (syst)) x 10^{-3}
delta y= (+3.01 +/- 1.92 (stat) +/- 0.26 (syst)) x 10^{-3}
where the first uncertainty is statistical and the second is systematic. They correspond to the mixing and CP-violation parameters
x = 0.46^{+0.15}_{-0.16} x 10^{-2}
y = 1.24^{+0.32}_{-0.33} x 10^{-2}
|q/p| = 1.21^{+0.21}_{-0.15}
\phi = -0.132^{+0.088}_{-0.120} rad.
The value of x deviates from zero with a significance of almost 3 sigma.
These results are complementary to and consistent with previous measurements and with the current world-average values.
They represent an independent and complementary knowledge of the charm-mixing parameters.
A combination with the recent LHCb analysis of Dstar -> D0 (->K0S pi+ pi-) pi decays is also reported.