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Register a new userMeasurement of the absolute branching fraction of inclusive semielectronic $D_s^+$ decays
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We measure the inclusive semielectronic decay branching fraction of the $D_s^+$ meson. A double-tag technique is applied to $e^+e^-$ annihilation data collected by the BESIII experiment at the BEPCII collider, operating in the center-of-mass energy range $4.178 - 4.230$ GeV. We select positrons from $D_s^+rightarrow Xe^{+} u_e$ with momenta greater than 200 MeV/$c$, and determine the laboratory momentum spectrum, accounting for the effects of detector efficiency and resolution. The total positron yield and semielectronic branching fraction are determined by extrapolating this spectrum below the momentum cutoff. We measure the $D_s^+$ semielectronic branching fraction to be $mathcal{B}left(D_s^+rightarrow Xe^{+} u_eright)=left(6.30pm0.13;(text{stat.})pm 0.10;(text{syst.})right)%$, showing no evidence for unobserved exclusive semielectronic modes. We combine this result with external data taken from literature to determine the ratio of the $D_s^+$ and $D^0$ semielectronic widths, $frac{Gamma(D_{s}^{+}rightarrow Xe^+ u_e)}{Gamma(D^0rightarrow Xe^+ u_e)}=0.790pm 0.016;(text{stat.})pm0.020;(text{syst.})$. Our results are consistent with and more precise than previous measurements.
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Using a sample of tagged D_s decays collected near the D^*_s D_s peak production energy in e+e- collisions with the CLEO-c detector, we study the leptonic decay D^+_s to tau^+ nu_tau via the decay channel tau^+ to e^+ nu_e bar{nu}_tau. We measure B(D^+_s to tau^+ nu_tau) = (6.17 +- 0.71 +- 0.34) %, where the first error is statistical and the second systematic. Combining this result with our measurements of D^+_s to mu^+ nu_mu and D^+_s to tau^+ nu_tau (via tau^+ to pi^+ bar{nu}_tau), we determine f_{D_s} = (274 +- 10 +- 5) MeV.
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 $f_{D^+_s}/f_{D^+} = 1.232pm0.035$.
Using a data sample corresponding to an integrated luminosity of 567 pb$^{-1}$ collected at a center-of-mass energy of $sqrt{s}=4.6$ GeV with the BESIII detector, we measure the absolute branching fraction of the inclusive semileptonic $Lambda_c^+$ decay with a double-tag method. We obtain $mathcal{B}(Lambda_c^+ rightarrow X e^+ u_e) = (3.95pm0.34pm0.09)%$, where the first uncertainty is statistical and the second systematic. Using the known $Lambda_c^+$ lifetime and the charge-averaged semileptonic decay width of nonstrange charmed measons ($D^0$ and $D^+$), we obtain the ratio of the inclusive semileptonic decay widths $Gamma(Lambda_c^+ rightarrow X e^+ u_e)/bar{Gamma}(Drightarrow X e^+ u_e)= 1.26pm0.12$.
We report the first measurement of the absolute branching fraction of the inclusive decay $Lambda_c^+ to K_S^0X$. The analysis is performed using an $e^+e^-$ collision data sample corresponding to an integrated luminosity of 567 pb$^{-1}$ taken at $sqrt{s}$ = 4.6 GeV with the BESIII detector. Using eleven Cabibbo-favored $bar{Lambda}_c^-$ decay modes and the double-tag technique, this absolute branching fraction is measured to be $mathcal{B}(Lambda_c^+ to K_S^0X)=(9.9pm0.6pm0.4)%$, where the first uncertainty is statistical and the second systematic. The relative deviation between the branching fractions for the inclusive decay and the observed exclusive decays is $(18.7pm8.3)%$, which indicates that there may be some unobserved decay modes with a neutron or excited baryons in the final state.
Based on an $e^+e^-$ collision data sample corresponding to an integrated luminosity of 567$,rm{pb}^{-1}$ taken at the center-of-mass energy of $sqrt{s} = 4.6$ GeV with the BESIII detector, we measure the absolute branching fraction of the inclusive decay $Lambda_{c}^{+} to Lambda + X$ to be $mathcal{B}(Lambda_{c}^{+} to Lambda + X)=(38.2^{+2.8}_{-2.2}pm0.8)%$ using the double-tag method, where $X$ refers to any possible final state particles. In addition, we search for direct CP violation in the charge asymmetry of this inclusive decay for the first time, and obtain $mathcal{A}_{CP} equiv frac{mathcal{B}(Lambda_{c}^{+} to Lambda + X)-mathcal{B}(bar{Lambda}_{c}^{-} to bar{Lambda} + X)}{mathcal{B}(Lambda_{c}^{+} to Lambda + X)+mathcal{B}(bar{Lambda}_{c}^{-} to bar{Lambda} + X)} = (2.1^{+7.0}_{-6.6}pm1.4)%$, a statistically limited result with no evidence of CP violation.
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