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Register a new userFirst Observation of $D^+to etamu^+ u_mu$ and Measurement of its Decay Dynamics
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By analyzing a data sample corresponding to an integrated luminosity of $2.93~mathrm{fb}^{-1}$ collected at a center-of-mass energy of 3.773 GeV with the BESIII detector, we measure for the first time the absolute branching fraction of the $D^+to eta mu^+ u_mu$ decay to be ${mathcal B}_{D^+to eta mu^+ u_mu}=(10.4pm1.0_{rm stat}pm0.5_{rm syst})times 10^{-4}$. Using the world averaged value of ${mathcal B}_{D^+to eta e^+ u_e}$, the ratio of the two branching fractions is determined to be ${mathcal B}_{D^+to eta mu^+ u_mu}/{mathcal B}_{D^+to eta e^+ u_e}=0.91pm0.13$, which agrees with the theoretical expectation of lepton flavor universality within uncertainty. Here, the uncertainty is the sum in quadrature of the statistical and systematic uncertainties. By studying the differential decay rates in five four-momentum transfer intervals, we obtain the product of the hadronic form factor $f^{eta}_{+}(0)$ and the $cto d$ Cabibbo-Kobayashi-Maskawa matrix element $|V_{cd}|$ to be $f_{+}^eta (0)|V_{cd}|=0.087pm0.008_{rm stat}pm0.002_{rm syst}$. Taking the input of $|V_{cd}|$ from the global fit in the standard model, we determine $f_{+}^eta (0)=0.39pm0.04_{rm stat}pm0.01_{rm syst}$. On the other hand, using the value of $f_+^{eta}(0)$ calculated in theory, we find $|V_{cd}|=0.242pm0.022_{rm stat}pm0.006_{rm syst}pm0.033_{rm theory}$.
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We report the first observation of the semi-muonic decay $D^+to omega mu^+ u_mu$ using an $e^+e^-$ collision data sample corresponding to an integrated luminosity of $2.93~mathrm{fb}^{-1}$ collected with the BESIII detector at a center-of-mass energy of 3.773 GeV. The absolute branching fraction of the $D^+to omega mu^+ u_mu$ decay is measured to be ${mathcal B}_{D^+to omegamu^+ u_mu}=(17.7pm1.8_{rm stat}pm1.1_{rm syst})times 10^{-4}$. Its ratio with the world average value of the branching fraction of the $D^+to omega e^+ u_e$ decay probes lepton flavor universality and it is determined to be ${mathcal B}_{D^+to omega mu^+ u_mu}/{mathcal B}^{rm PDG}_{D^+to omega e^+ u_e}=1.05pm0.14$, in agreement with the standard model expectation within one standard deviation.
By analyzing an $e^+e^-$ annihilation data sample corresponding to an integrated luminosity of $2.93~mathrm{fb}^{-1}$ collected at a center-of-mass energy of 3.773 GeV with the BESIII detector, we measure the branching fraction of the $D^0to rho^- mu^+ u_mu$ decay for the first time. We obtain ${mathcal B}_{D^0to rho^- mu^+ u_mu}=(1.35pm0.09_{rm stat}pm0.09_{rm syst})times 10^{-3}$. Combining with theoretical predictions, we extract the CKM matrix element $|V_{cd}|=0.204pm0.007_{rm stat}pm0.007_{rm syst}pm0.014_{rm theory}$. Using the world average of ${mathcal B}_{D^0to rho^- e^+ u_e}$, we find a branching fraction ratio of ${mathcal B}_{D^0to rho^- mu^+ u_mu}/{mathcal B}_{D^0to rho^- e^+ u_e}=0.90pm0.11$, which agrees with the theoretical expectation of lepton flavor universality within the uncertainty. Combining the world average of ${mathcal B}_{D^+to rho^0 mu^+ u_mu}$ and the lifetimes of $D^{0(+)}$, we obtain a partial decay width ratio of ${Gamma}_{D^0to rho^- mu^+ u_{mu}}/(2{Gamma}_{D^+to rho^0 mu^+ u_{mu}}) = 0.71pm0.14$, which is consistent with the isospin symmetry expectation of one within $2.1sigma$. For the reported values of ${mathcal B}_{D^0to rho^- mu^+ u_mu}/{mathcal B}_{D^0to rho^- e^+ u_e}$ and ${Gamma}_{D^0to rho^- mu^+ u_{mu}}/2{Gamma}_{D^+to rho^0 mu^+ u_{mu}}$, the uncertainty is the quadratic sum of the statistical and systematic uncertainties.
The first observation of the suppressed semileptonic $B_s^0 to K^-mu^+ u_mu$ decay is reported. Using a data sample recorded in {it pp} collisions in 2012 with the LHCb detector, corresponding to an integrated luminosity of 2 $mathrm{fb}^{-1}$, the branching fraction mbox{$mathcal{B}(B_s^0 to K^-mu^+ u_mu)$} is measured to be $(1.06pm0.05~(mathrm{stat})pm0.08~(mathrm{syst}))times 10^{-4}$, where the first uncertainty is statistical and the second one represents the combined systematic uncertainties. The decay $B_s^0 to D_s^-mu^+ u_mu$, where $D_s^-$ is reconstructed in the final state $K^+K^-pi^-$, is used as a normalization channel to minimize the experimental systematic uncertainty. Theoretical calculations on the form factors of the $B_s^0 to K^-$ and $B_s^0 to D_s^-$ transitions are employed to determine the ratio of the CKM matrix elements ${|V_{ub}|}/{|V_{cb}|}$ at low and high $B_s^0 to K^-$ momentum transfer.
The $B^{+}to D^{+} K^{+} pi^{-}$ decay is observed in a data sample corresponding to $3.0,{rm fb}^{-1}$ of $pp$ collision data recorded by the LHCb experiment during 2011 and 2012. The signal significance is $8,sigma$ and the branching fraction is measured to be ${cal B}left(B^{+}to D^{+} K^{+} pi^{-}right) = (5.31 pm 0.90 pm 0.48 pm 0.35)times 10^{-6}$, where the uncertainties are statistical, systematic and due to the normalisation mode $B^{+}to D^{-} K^{+} pi^{+}$, respectively. The Dalitz plot appears to be dominated by broad structures. Angular distributions are exploited to search for quasi-two-body contributions from $B^{+}to D^{*}_{2}(2460)^{0}K^{+}$ and $B^{+}to D^{+} K^{*}(892)^{0}$ decays. No significant signals are observed and upper limits are set on their branching fractions.
The $B^{-}to D^{+}K^{-}pi^{-}$ decay is observed in a data sample corresponding to $3.0~rm{fb}^{-1}$ of $pp$ collision data recorded by the LHCb experiment during 2011 and 2012. Its branching fraction is measured to be ${cal B}(B^{-}to D^{+}K^{-}pi^{-}) = (7.31 pm 0.19 pm 0.22 pm 0.39) times 10^{-5}$ where the uncertainties are statistical, systematic and from the branching fraction of the normalisation channel $B^{-}to D^{+}pi^{-}pi^{-}$, respectively. An amplitude analysis of the resonant structure of the $B^{-}to D^{+}K^{-}pi^{-}$ decay is used to measure the contributions from quasi-two-body $B^{-}to D_{0}^{*}(2400)^{0}K^{-}$, $B^{-}to D_{2}^{*}(2460)^{0}K^{-}$, and $B^{-}to D_{J}^{*}(2760)^{0}K^{-}$ decays, as well as from nonresonant sources. The $D_{J}^{*}(2760)^{0}$ resonance is determined to have spin~1.
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