Abstract

A combination of measurements sensitive to the CP violation angle γ of the Cabibbo-Kobayashi-Maskawa unitarity triangle and to the charm mixing parameters that describe oscillations between D0 and overline{D} 0 mesons is performed. Results from the charm and beauty sectors, based on data collected with the LHCb detector at CERN’s Large Hadron Collider, are combined for the first time. This method provides an improvement on the precision of the charm mixing parameter y by a factor of two with respect to the current world average. The charm mixing parameters are determined to be x=left({0.400}_{-0.053}^{+0.052}right)% and y = left({0.630}_{-0.030}^{+0.033}right)% . The angle γ is found to be γ = left({65.4}_{-4.2}^{+3.8}right){}^{circ} and is the most precise determination from a single experiment.

Highlights

  • Collider, are combined for the first time. This method provides an improvement on the precision of the charm mixing parameter y by a factor of two with respect to the current world average

  • The CKM angle γ is measured in decays which are sensitive to interference between favoured b → c and suppressed b → u quark transition amplitudes that are proportional to Vcb and Vub, respectively

  • The pvalue distribution as a function of γ is shown in figure 2 for the total combination and for subsets in which the input observables are split by the species of the initial B meson

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Summary

Introduction

Collider, are combined for the first time. This method provides an improvement on the precision of the charm mixing parameter y by a factor of two with respect to the current world average. The CKM angle γ is measured in decays which are sensitive to interference between favoured b → c and suppressed b → u quark transition amplitudes that are proportional to Vcb and Vub, respectively.1 The ratio of these two amplitudes is given by Asup/Afav = rBeiδB±γ, where the + or − sign indicates whether the initial state contains a b- or b-quark, rB is the ratio of the amplitude magnitudes, and δB their CP -conserving strong-phase difference. Equation (1.1) has at least five unknown parameters, even more if the coherence factors are not set to unity, they cannot be determined using a single pair of B± decay rates This is overcome by combining the results from many different D-decay modes to overconstrain the parameters of the B-meson decay, provided that the corresponding rD, δD and κD parameters are constrained by other measurements. This improved precision on δDKπ can be used to improve knowledge of charm mixing as described below

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