Abstract
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 $D_s^+\rightarrow Xe^{+}\nu_e$ 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 $\mathcal{B}\left(D_s^+\rightarrow Xe^{+}\nu_e\right)=\left(6.30\pm0.13\;(\text{stat.})\pm 0.10\;(\text{syst.})\right)\%$, 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, $\frac{\Gamma(D_{s}^{+}\rightarrow Xe^+\nu_e)}{\Gamma(D^0\rightarrow Xe^+\nu_e)}=0.790\pm 0.016\;(\text{stat.})\pm0.020\;(\text{syst.})$. Our results are consistent with and more precise than previous measurements.
Highlights
The Dþs meson is the ground state of charmed-strange mesons, and precise measurements of its semileptonic decays allow for crucial tests of Standard Model predictions of flavor-changing interactions
The difference of the “Combined” result from Table VI, BðDþs → XeþνeÞ 1⁄4 ð6.30 Æ 0.13ðstat:ÞÞ%, and the sum of the observed exclusive semielectronic branching fractions from Table I gives the unobserved Dþs semielectronic branching fraction as ð−0.04 Æ 0.21Þ%, where the stated uncertainty includes the total uncertainty from the exclusive measurements, but only the statistical uncertainty from the inclusive measurement presented in this article
Using data collected by the BESIII detector in the centerof-mass-energy range of Ecm 1⁄4 4.178–4.230 GeV, we measure the inclusive semielectronic branching fraction of the Dþs meson to be 1⁄4 ð6.30 Æ 0.13ðstat:Þ Æ 0.09ðsyst:Þ Æ 0.04ðext:ÞÞ%; where the external systematic uncertainty is from BðDþs → τþντÞ
Summary
The Dþs meson is the ground state of charmed-strange mesons, and precise measurements of its semileptonic decays allow for crucial tests of Standard Model predictions of flavor-changing interactions. (Here and throughout this article, charge conjugate modes are implied.) A previous measurement by the CLEO-c experiment reported the first results for these quantities, including the measurement of BðDþs → XeþνeÞ 1⁄4 ð6.52 Æ 0.39ðstat:Þ Æ 0.15ðsyst:ÞÞ% [1] Measuring this branching fraction with improved precision contributes to a comprehensive understanding of Dþs decays and is an important component of the overall experimental and theoretical heavy-flavor physics program. 0.052, is in agreement with predictions employing an effective quark model [18] and shows that nonspectator effects are present in semielectronic charmed-meson decays It has been demonstrated with CLEO-c data that the inclusive semielectronic momentum spectrum can be used to make sensitive tests for specific nonspectator processes, such as weak annihilation [19,20].
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