Meson Branching Fractions Research Articles

Bs→Dsℓν form factors and the fragmentation fraction ratio fs/fd

We present a lattice quantum chromodynamics determination of the scalar and vector form factors for the $B_s \rightarrow D_s \ell \nu$ decay over the full physical range of momentum transfer. In conjunction with future experimental data, our results will provide a new method to extract $|V_{cb}|$, which may elucidate the current tension between exclusive and inclusive determinations of this parameter. Combining the form factor results at non-zero recoil with recent HPQCD results for the $B \rightarrow D \ell \nu$ form factors, we determine the ratios $f^{B_s \rightarrow D_s}_0(M_\pi^2) / f^{B \rightarrow D}_0(M_K^2) = 1.000(62)$ and $f^{B_s \rightarrow D_s}_0(M_\pi^2) / f^{B \rightarrow D}_0(M_\pi^2) = 1.006(62)$. These results give the fragmentation fraction ratios $f_s/f_d = 0.310(30)_{\mathrm{stat.}}(21)_{\mathrm{syst.}}(6)_{\mathrm{theor.}}(38)_{\mathrm{latt.}} $ and $f_s/f_d = 0.307(16)_{\mathrm{stat.}}(21)_{\mathrm{syst.}}(23)_{\mathrm{theor.}}(44)_{\mathrm{latt.}}$, respectively. The fragmentation fraction ratio is an important ingredient in experimental determinations of $B_s$ meson branching fractions at hadron colliders, in particular for the rare decay ${\cal B}(B_s \rightarrow \mu^+ \mu^-)$. In addition to the form factor results, we make the first prediction of the branching fraction ratio $R(D_s) = {\cal B}(B_s\to D_s\tau\nu)/{\cal B}(B_s\to D_s\ell\nu) = 0.301(6)$, where $\ell$ is an electron or muon. Current experimental measurements of the corresponding ratio for the semileptonic decays of $B$ mesons disagree with Standard Model expectations at the level of nearly four standard deviations. Future experimental measurements of $R(D_s)$ may help understand this discrepancy.

Charm decays at BaBar

In this talk I go over recent results involving charm decays obtained with the data collected by the BaBar experiment. I cover here results on leptonic and semileptonic charm decays, D meson branching fractions, Dalitz analyses and charm baryons.

Simultaneous least-squares treatment of statistical and systematic uncertainties

We present a least-squares method for estimating parameters from measurements of event yields in the presence of background and crossfeed. We adopt a unified approach to incorporating the statistical and systematic uncertainties on the experimental measurements input to the fit. We demonstrate this method with a fit for absolute hadronic D meson branching fractions, measured in e + e - → ψ ( 3770 ) → D D ¯ transitions.

Lifetimes and branching fractions of mesons with heavy-quark constituents

The authors calculate lifetimes and inclusive branching fractions based on (i) heavy-quark decays with gluon corrections and (ii) weak-current mixing angles from analysis of K0-K0 mixing and CP violation. The authors' predictions are 3.6*10-13< tau (mD)<6.6*10-13, 0.9*10-14< tau (mB=5 GeV)<1.2*10-13, 1.6*10-19< tau (mT=9-30 GeV)<4*10-16, and Gamma (D to eX)/ Gamma /D to all)=0.11. Bounds on quark coupling ratios and inclusive widths are also given.