A measurement of mixing and CP violation in neutral charm mesons is performed using data reconstructed in proton-proton collisions collected by the LHCb experiment from 2016 to 2018, corresponding to an integrated luminosity of 5.4 fb-1. A total of 30.6 million D0→KS0π+π- decays are analyzed using a method optimized for the measurement of the mass difference between neutral charm-meson eigenstates. Allowing for CP violation in mixing and in the interference between mixing and decay, the mass and decay-width differences are measured to be xCP=[3.97±0.46(stat)±0.29(syst)]×10-3 and yCP=[4.59±1.20(stat)±0.85(syst)]×10-3, respectively. The CP-violating parameters are measured as Δx=[-0.27±0.18(stat)±0.01(syst)]×10-3 and Δy=[0.20±0.36(stat)±0.13(syst)]×10-3. This is the first observation of a nonzero mass difference in the D0 meson system, with a significance exceeding seven standard deviations. The data are consistent with CP symmetry and improve existing constraints on the associated parameters. © 2021 CERN, for the LHCb Collaboration.

Observation of the Mass Difference between Neutral Charm-Meson Eigenstates

De Serio, M.;Pappagallo, M.;Simone, S.;
2021-01-01

Abstract

A measurement of mixing and CP violation in neutral charm mesons is performed using data reconstructed in proton-proton collisions collected by the LHCb experiment from 2016 to 2018, corresponding to an integrated luminosity of 5.4 fb-1. A total of 30.6 million D0→KS0π+π- decays are analyzed using a method optimized for the measurement of the mass difference between neutral charm-meson eigenstates. Allowing for CP violation in mixing and in the interference between mixing and decay, the mass and decay-width differences are measured to be xCP=[3.97±0.46(stat)±0.29(syst)]×10-3 and yCP=[4.59±1.20(stat)±0.85(syst)]×10-3, respectively. The CP-violating parameters are measured as Δx=[-0.27±0.18(stat)±0.01(syst)]×10-3 and Δy=[0.20±0.36(stat)±0.13(syst)]×10-3. This is the first observation of a nonzero mass difference in the D0 meson system, with a significance exceeding seven standard deviations. The data are consistent with CP symmetry and improve existing constraints on the associated parameters. © 2021 CERN, for the LHCb Collaboration.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11586/379263
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