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Register a new userMeasurement of Branching Fractions for $Bto eta_c K^{(*)}$ Decays
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We report measurements of branching fractions for charged and neutral $Bto eta_c K$ decays where the $eta_c$ meson is reconstructed in the $K_S^0 K^{pm}pi^{mp}, K^+ K^- pi^0, K^{*0} K^-pi^+$ and $p bar{p}$ decay channels. The neutral $B^0$ channel is a CP eigenstate and can be used to measure the CP violation parameter $sin 2phi_1$. We also report the first observation of the $B^0to eta_c K^{*0}$ mode. The results are based on an analysis of 29.1 fb$^{-1}$ of data collected by the Belle detector at KEKB.
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The decays Upsilon(4S) -> BB, followed by B -> D* pi and D* -> D pi, permit reconstruction of all kinematic quantities that describe the sequence without reconstruction of the D, with reasonably low backgrounds. Using an integrated e+e- luminosity of 3.1 fb^{-1} accumulated at the Upsilon(4S) by the CLEO-II detector, we report measurements of BR(B0 -> D*+ pi-) = (2.81 +/- 0.11 +/- 0.21 +/- 0.05) x 10^{-3} and BR(B- -> D*0 pi-) = (4.34 +/- 0.33 +/- 0.34 +/- 0.18) x 10^{-3}.
We report new measurements of the branching fraction $cal B(D_s^+to ell^+ u)$, where $ell^+$ is either $mu^+$ or $tau^+(topi^+bar{ u}_tau)$, based on $6.32$ fb$^{-1}$ of electron-positron annihilation data collected by the BESIII experiment at six center-of-mass energy points between $4.178$ GeV and $4.226$ GeV. Simultaneously floating the $D_s^+tomu^+ u_mu$ and $D_s^+totau^+ u_tau$ components yields $cal B(D_s^+to tau^+ u_tau) = (5.21pm0.25pm0.17)times10^{-2}$, $cal B(D_s^+to mu^+ u_mu) = (5.35pm0.13pm0.16)times10^{-3}$, and the ratio of decay widths $R=frac{Gamma(D_s^+to tau^+ u_tau)}{Gamma(D_s^+to mu^+ u_mu)} = 9.73^{+0.61}_{-0.58}pm 0.36$, where the first uncertainties are statistical and the second systematic. No evidence of $CP$ asymmetry is observed in the decay rates $D_s^pmtomu^pm u_mu$ and $D_s^pmtotau^pm u_tau$: $A_{CP}(mu^pm u) = (-1.2pm2.7)%$ and $A_{CP}(tau^pm u) = (+2.9pm4.9)%$. Constraining our measurement to the Standard Model expectation of lepton universality ($R=9.75$), we find the more precise results $cal B(D_s^+to tau^+ u_tau) = (5.22pm0.10pm 0.14)times10^{-2}$ and $A_{CP}(tau^pm u_tau) = (-0.1pm2.1)%$. Combining our results with inputs external to our analysis, we determine the $cto s$ quark mixing matrix element, $D_s^+$ decay constant, and ratio of the decay constants: $|V_{cs}| = 0.973pm0.009pm0.014$, $f_{D^+_s} = 249.9pm2.4pm3.5~text{MeV}$, and $f_{D^+_s}/f_{D^+} = 1.232pm0.035$.
The first observation of the decay Bs -> D0bar K- {pi}+ is reported. The analysis is based on a data sample, corresponding to an integrated luminosity of 1.0 fb-1 of pp collisions, collected with the LHCb detector. The branching fraction relative to that of the topologically similar decay B0 -> D0bar {pi}+ {pi}- is measured to be BR(Bs -> D0bar K- {pi}+)/BR(B0 -> D0bar {pi}+ {pi}-) = 1.18 +- 0.05 (stat.) +- 0.12 (syst.). In addition, the relative branching fraction of the decay B0 -> D0bar K+ {pi}- is measured to be BR(B0 -> D0bar K+ {pi}-)/BR(B0 -> D0bar {pi}+ {pi}-) = 0.106 +- 0.007 (stat.) +- 0.008 (syst.).
This note describes the rediscovery of $Btoeta K$ decays in Belle II data, both in the charged and neutral final state: $B_0toeta K_S$ and $B^pmtoeta K^pm$. The $eta$ is searched for in two decay modes: $etatoetapi^+pi^-$ with $etatogammagamma$, and $etatorhogamma$. The analysis uses data collected in 2019 and 2020 at the SuperKEKB asymmetric $e^+e^-$ collider, with an integrated luminosity of $62.8~fb^{-1}$, corresponding to $68.2$ million of $Bbar{B}$ pairs produced. The signal yield is obtained via an unbinned maximum likelihood fit to signal sensitive variables, obtaining branching ratios: $$mathcal{B}left(B^pmtoetaK^pmright) = left(63.4~^{+3.4}_{-3.3},(stat),pm3.2,(syst),right) times10^{-6} $$ $$mathcal{B}left(B_0toetaK_Sright) = left(59.9~^{+5.8}_{-5.5},(stat),pm2.9,(syst),right) times10^{-6} $$ which are consistent with world average.
Based on a sample of $(1310.6 pm 7.0) times 10^6~J/psi$ events collected with the BESIII detector, we present measurements of $J/psi$ and $eta^prime$ absolute branching fractions using the process $J/psirightarrowgammaeta^prime$. By analyzing events where the radiative photon converts into an $e^+e^-$ pair, the branching fraction for $J/psi rightarrow gamma eta^prime$ is measured to be $(5.27pm0.03pm0.05)times 10^{-3}$. The absolute branching fractions of the five dominant decay channels of the $eta^prime$ are then measured independently for the first time and are determined to be $mathcal{B}(eta^prime rightarrow gamma pi^{+} pi^{-})$ = (29.90$pm$0.03$pm$0.55)%, $mathcal{B}(eta^prime rightarrow eta pi^{+} pi^{-})$ = (41.24$pm$0.08$pm$1.24)%, $mathcal{B}(eta^prime rightarrow eta pi^{0} pi^{0})$ = (21.36$pm$0.10$pm$0.92)%, $mathcal{B}(eta^prime rightarrow gamma omega)$ = (2.489$pm$0.018$pm$0.074)%, and $mathcal{B}(eta^prime rightarrow gamma gamma)$ = (2.331$pm$0.012$pm$0.035)%, where the first uncertainties are statistical and the second systematic.
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