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Register a new userFirst Measurement of the Absolute Branching Fraction of $Lambda to p mu^- bar{ u}_{mu}$
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M. Ablikim
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The absolute branching fraction of $Lambda to p mu^- bar{ u}_{mu}$ is reported for the first time based on an $e^+e^-$ annihilation sample of ten billion $J/psi$ events collected with the BESIII detector at $sqrt{s}=3.097$ GeV. The branching fraction is determined to be ${mathcal B}(Lambda to pmu^- bar{ u}_{mu}) = [1.48pm0.21(rm stat) pm 0.08(rm syst)]times 10^{-4}$, which is a significant improvement in precision over the previous indirect measurements. Combining this result with the world average of ${mathcal B}(Lambda to p e^- bar{ u}_{e})$, we obtain the ratio, $frac{Gamma(Lambda to p mu^- bar{ u}_{mu})}{Gamma(Lambda to p e^- bar{ u}_{e})}$, to be $0.178 pm 0.028$, which agrees with the standard model prediction assuming lepton flavor universality. The asymmetry of the branching fractions of $Lambda to p mu^- bar{ u}_{mu}$ and $bar{Lambda} to bar{p} mu^+ u_{mu}$ is also determined, and no evidence for $CP$ violation is found.
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We report the first measurement of the absolute branching fraction for $Lambda^+_{c}rightarrow Lambda mu^+ u_{mu}$. This measurement is based on a sample of $e^+e^-$ annihilation data at a center-of-mass energy of $sqrt{s}=4.6$ GeV collected with the BESIII detector at the BEPCII storage rings. The sample corresponds to an integrated luminosity of 567 pb$^{-1}$. The branching fraction is determined to be $mathcal B({Lambda^+_crightarrow Lambda mu^+ u_{mu}})=(3.49pm0.46({rm stat})pm0.27({rm syst}))%$. In addition, we calculate the ratio $mathcal{B}(Lambda^+_crightarrow Lambda mu^+ u_{mu})/mathcal{B}(Lambda^+_crightarrow Lambda e^+ u_{e})$ to be $0.96pm0.16({rm stat})pm0.04({rm syst})$.
By analyzing 2.93 fb$^{-1}$ of data collected at $sqrt s=3.773$ GeV with the BESIII detector, we measure the absolute branching fraction ${mathcal B}(D^{+}rightarrowbar K^0mu^{+} u_{mu})=(8.72 pm 0.07_{rm stat.} pm 0.18_{rm sys.})%$, which is consistent with previous measurements within uncertainties but with significantly improved precision. Combining the Particle Data Group values of ${mathcal B}(D^0to K^-mu^+ u_mu)$, ${mathcal B}(D^{+}rightarrowbar K^0 e^{+} u_{e})$, and the lifetimes of the $D^0$ and $D^+$ mesons with the value of ${mathcal B}(D^{+}rightarrowbar K^0 mu^{+} u_{mu})$ measured in this work, we determine the following ratios of partial widths: $Gamma(D^0to K^-mu^+ u_mu)/Gamma(D^{+}rightarrowbar K^0mu^{+} u_{mu})=0.963pm0.044$ and $Gamma(D^{+}rightarrowbar K^0 mu^{+} u_{mu})/Gamma(D^{+}rightarrowbar K^0 e^{+} u_{e})=0.988pm0.033$.
A search for the rare decays $B^0_s tomu^+mu^-$ and $B^0 tomu^+mu^-$ is performed at the LHCb experiment. The data analysed correspond to an integrated luminosity of 1 fb$^{-1}$ of $pp$ collisions at a centre-of-mass energy of 7 TeV and 2 fb$^{-1}$ at 8 TeV. An excess of $B^0_s tomu^+mu^-$ signal candidates with respect to the background expectation is seen with a significance of 4.0 standard deviations. A time-integrated branching fraction of ${cal B}(B^0_s tomu^+mu^-) = (2.9^{+1.1}_{-1.0})times 10^{-9}$ is obtained and an upper limit of ${cal B}(B^0 tomu^+mu^-) < 7.4times 10^{-10}$ at 95% confidence level is set. These results are consistent with the Standard Model expectations.
Based on a sample of 300 million $K_S$ mesons produced in $phi to K_L K_S$ decays recorded by the KLOE experiment at the DA$Phi$NE $e^+e^-$ collider we have measured the branching fraction for the decay $K_S to pi mu u$. The $K_S$ mesons are identified by the interaction of $K_L$ mesons in the detector. The $K_S to pi mu u$ decays are selected by a boosted decision tree built with kinematic variables and by a time-of-flight measurement. Signal efficiencies are evaluated with data control samples of $K_L to pi mu u$ decays. A fit to the reconstructed muon mass distribution finds $7223 pm 180$ signal events. Normalising to the $K_S to pi^+ pi^-$ decay events the result for the branching fraction is $mathcal{B}(K_S to pi mu u) = (4.56 pm 0.11_{rm stat} pm 0.17_{rm syst})times10^{-4}$.
From the 2002 data taking with a neutral kaon beam extracted from the CERN-SPS, the NA48/1 experiment observed 97 $Xi^{0}rightarrow Sigma^{+} mu^{-} bar{ u}_{mu}$ candidates with a background contamination of $30.8 pm 4.2$ events. From this sample, the BR($Xi^{0}rightarrow Sigma^{+} mu^{-} bar{ u}_{mu}$) is measured to be $(2.17 pm 0.32_{mathrm{stat}}pm 0.17_{mathrm{syst}})times10^{-6}$.
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