Mixing of B mesons and Decay Constants with the Non-Perturbatively Improved Action

TL;DR

This paper presents lattice QCD calculations of B meson decay constants and mixing parameters using a non-perturbatively improved action, providing key inputs for phenomenological studies and Standard Model extensions.

Contribution

First non-perturbative lattice computation of B and D meson mixing parameters using improved Clover action at a specific lattice spacing.

Findings

Calculated decay constants and mixing parameters for B and D mesons.

Predicted the B_s - B_d mass difference (Delta m_s).

Quantified systematic errors in lattice QCD calculations.

Abstract

Several quantities relevant to phenomenological studies of the mixing of neutral B mesons are computed on the lattice. Our main results are: f_{Bd} sqrt(B_{Bd})=206(28)(7) MeV, f_{Bs} sqrt(B_{Bs})/f_{Bd}sqrt(B_{Bd})=1.16(7). We also obtain the related quantities f_{Bs}sqrt(B{Bs})=237(18)(8) MeV, f_{Bd}= 174(22)(+7-0)(-4-0) MeV, f_{Bs}= 204(15)(+7-0)(+3-0) MeV, f_{Bs}/f_{Bd}=1.17(4)(+0-1), f_{Bd}/f_{Ds}=0.74(5). After combining our results with the experimental world average (Delta m_d), we predict (Delta m_s)=15.8(2.1)(3.3) ps^{-1}. We have also computed the relevant parameters for mixing of neutral D mesons which may be useful in some extensions of the Standard Model. All the quantities were obtained from a quenched simulation with a non-perturbatively improved Clover action at beta=6.2, corresponding to a lattice spacing 1/a=2.7(1) GeV, on a sample of 200 gauge-field configurations. A discussion of the main systematic errors is also presented.