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Register a new userMeasurement of the $D_s^+ to ell^+ u_ell$ branching fractions and the decay constant $f_{D_s^+}$
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Using 482~pb$^{-1}$ of $e^+e^-$ collision data collected at a center-of-mass energy of $sqrt{s} = 4.009$ GeV with the BESIII detector, we measure the branching fractions of the decays $D_s^+tomu^+ u_mu$ and $D_s^+totau^+ u_tau$. By constraining the ratio of decay rates of $D_s^+$ to $tau^+ u_tau$ and to $mu^+ u_mu$ to the Standard Model prediction, the branching fractions are determined to be $mathcal{B}(D_s^+ to mu^+ u_mu) = (0.495 pm 0.067 pm 0.026)%$ and $mathcal{B}(D_s^+ to tau^+ u_tau) = (4.83 pm 0.65 pm 0.26)%$. Using these branching fractions, we obtain a value for the decay constant $f_{D_s^+}$ of $(241.0 pm 16.3 pm 6.5)~text{MeV}$, where the first error is statistical and the second systematic.
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We have observed $23.2 pm 6.0_{-0.9}^{+1.0}$ purely-leptonic decays of $D_s^+ -> mu^+ u_mu$ from a sample of muonic one prong decay events detected in the emulsion target of Fermilab experiment E653. Using the $D_s^+ -> phi mu^+ u_mu$ yield measured previously in this experiment, we obtain $B(D_s^+ --> mu^+ u_mu) / B(D_s^+ --> phi mu^+ u_mu) =0.16 pm 0.06 pm 0.03$. In addition, we extract the decay constant $f_{D_s}=194 pm 35 pm 20 pm 14 MeV$.
Using a $3.19~mathrm{fb}^{-1}$ data sample collected at an $e^+e^-$ center-of-mass energy of $E_{rm cm}=4.178$ GeV with the BESIII detector, we measure the branching fraction of the leptonic decay $D_s^+tomu^+ u_mu$ to be $mathcal{B}_{D_s^+tomu^+ u_mu}=(5.49pm0.16_{rm stat.}pm0.15_{rm syst.})times10^{-3}$. Combining our branching fraction with the masses of the $D_s^+$ and $mu^+$ and the lifetime of the $D_s^+$, we determine $f_{D_s^+}|V_{cs}|=246.2pm3.6_{rm stat.}pm3.5_{rm syst.}~mathrm{MeV}$. Using the $cto s$ quark mixing matrix element $|V_{cs}|$ determined from a global standard model fit, we evaluate the $D_s^+$ decay constant $f_{D_s^+}=252.9pm3.7_{rm stat.}pm3.6_{rm syst.}$,MeV. Alternatively, using the value of $f_{D_s^+}$ calculated by lattice quantum chromodynamics, we find $|V_{cs}| = 0.985pm0.014_{rm stat.}pm0.014_{rm syst.}$. These values of $mathcal{B}_{D_s^+tomu^+ u_mu}$, $f_{D_s^+}|V_{cs}|$, $f_{D_s^+}$ and $|V_{cs}|$ are each the most precise results to date.
We measure the decay constant fDs using the Ds -> l+ nu channel, where the l+ designates either a mu+ or a tau+, when the tau+ -> pi+ nu. Using both measurements we find fDs = 274 +-13 +- 7 MeV. Combining with our previous determination of fD+, we compute the ratio fDs/fD+ = 1.23 +- 0.11 +- 0.04. We compare with theoretical estimates.
We report a measurement of the $B^0$ and $B^+$ meson decays to the $D_s^-K^0_S pi^+$ and $D_s^- K^+K^+$ final states, respectively, using $657 times 10^{6} Boverline{B}$ pairs collected at the $Upsilon(4S)$ resonance with the Belle detector at the KEKB asymmetric-energy $e^+e^-$ collider. Using the $D_s^-to phipi^-$, $K^{*}(892)^0 K^-$ and $K^0_S K^-$ decay modes for the $D_s$ reconstruction, we measure the following branching fractions: ${cal B}(B^0to D_s^{-}K^0_Spi^+)=[0.47 pm 0.06 (mathrm {stat}) pm 0.05 (mathrm {syst})]times 10^{-4}$ and ${cal B}(B^+to D_s^-K^+K^+)= [0.93 pm 0.22 (mathrm {stat})pm 0.10 (mathrm {syst})]times 10^{-5}$. We find the ratio of the branching fraction of $B^+to D_s^-K^+K^+$ to that of the analogous Cabibbo favored $B^+to D_s^-K^+pi^+$ decay to be ${cal R}_{cal B} = 0.054 pm 0.013 ({rm stat}) pm 0.006 ({rm syst})$, which is consistent with the na{i}ve factorization model. We also observe a deviation from the three-body phase-space model for both studied decays.
The branching fractions of D_s meson decays serve to normalize many measurements of processes involving charm quarks. Using 298 /pb of e+ e- collisions recorded at a center of mass energy of 4.17 GeV, we determine absolute branching fractions for eight D_s decays with a double tag technique. In particular we determine the branching fraction B(D_s -> K- K+ pi+) = (5.50 +- 0.23 +- 0.16)%, where the uncertainties are statistical and systematic respectively. We also provide partial branching fractions for kinematic subsets of the K- K+ pi+ decay mode.
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