Villa, Andrea
(2020)
Measurement of y_CP with D^0 mesons from semileptonic B-meson decays at LHCb.
[Laurea magistrale], Università di Bologna, Corso di Studio in
Fisica [LM-DM270]
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Abstract
This thesis reports a measurement of the charm-mixing observable yCP using D^0->K^+K^−, D^0->pi^+pi^−, and D^0->K^−pi^+ decays, where the D^0 meson originates from semileptonic B-meson decays. The analysis is performed on the full Run 2 dataset collected by LHCb with pp collisions at a centre-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 5.57 fb^−1 . The dataset is divided into 18 exclusive D^0 decay-time bins, in which an invariant mass fit is performed to extract the signal yield for each decay channel. The ratios of KK/Kpi and pipi/Kpi yields in each bin, corrected for the efficiency as function of the decay-time estimated from a Monte Carlo sample, are then fitted to extract the difference between the decay widths of KK (pipi) and Kpi channels, ∆Γ^{KK} (∆Γ^{pipi}). Finally, y_CP is computed as ∆Γt(D^0), where t(D^0) is the precisely known D^0 lifetime. The values obtained from the two decay channels with preliminary systematic uncertainties are y_CP^{KK} = (75.98 ± 0.07 (stat) ± 0.06 (syst))%, y_CP^{pipi} = (76.29 ± 0.14 (stat) ± 0.05 (syst))%, which are consistent with each other (the central values are blind), and when combined yield a result of y_CP = (76.08 ± 0.06 (stat) ± 0.04 (syst))%. The analysis aims at updating the previous LHCb measurement with a larger data sample size, and is expected to improve the precision by a factor two with respect to the current world average y_CP = (0.715 ± 0.111)%.
Abstract
This thesis reports a measurement of the charm-mixing observable yCP using D^0->K^+K^−, D^0->pi^+pi^−, and D^0->K^−pi^+ decays, where the D^0 meson originates from semileptonic B-meson decays. The analysis is performed on the full Run 2 dataset collected by LHCb with pp collisions at a centre-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 5.57 fb^−1 . The dataset is divided into 18 exclusive D^0 decay-time bins, in which an invariant mass fit is performed to extract the signal yield for each decay channel. The ratios of KK/Kpi and pipi/Kpi yields in each bin, corrected for the efficiency as function of the decay-time estimated from a Monte Carlo sample, are then fitted to extract the difference between the decay widths of KK (pipi) and Kpi channels, ∆Γ^{KK} (∆Γ^{pipi}). Finally, y_CP is computed as ∆Γt(D^0), where t(D^0) is the precisely known D^0 lifetime. The values obtained from the two decay channels with preliminary systematic uncertainties are y_CP^{KK} = (75.98 ± 0.07 (stat) ± 0.06 (syst))%, y_CP^{pipi} = (76.29 ± 0.14 (stat) ± 0.05 (syst))%, which are consistent with each other (the central values are blind), and when combined yield a result of y_CP = (76.08 ± 0.06 (stat) ± 0.04 (syst))%. The analysis aims at updating the previous LHCb measurement with a larger data sample size, and is expected to improve the precision by a factor two with respect to the current world average y_CP = (0.715 ± 0.111)%.
Tipologia del documento
Tesi di laurea
(Laurea magistrale)
Autore della tesi
Villa, Andrea
Relatore della tesi
Correlatore della tesi
Scuola
Corso di studio
Indirizzo
Curriculum B: Fisica nucleare e subnucleare
Ordinamento Cds
DM270
Parole chiave
LHCb,Charm,Quark mixing,CP violation
Data di discussione della Tesi
25 Settembre 2020
URI
Altri metadati
Tipologia del documento
Tesi di laurea
(NON SPECIFICATO)
Autore della tesi
Villa, Andrea
Relatore della tesi
Correlatore della tesi
Scuola
Corso di studio
Indirizzo
Curriculum B: Fisica nucleare e subnucleare
Ordinamento Cds
DM270
Parole chiave
LHCb,Charm,Quark mixing,CP violation
Data di discussione della Tesi
25 Settembre 2020
URI
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