Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userMeasurement of the Decay Constant $f_D{_S^+}$ using $D_S^+ --> ell^+ nu
99
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
We measure the decay constant fDs using the Ds -> l+ nu channel, where the l+ designates either a mu+ or a tau+, when the tau+ -> pi+ nu. Using both measurements we find fDs = 274 +-13 +- 7 MeV. Combining with our previous determination of fD+, we compute the ratio fDs/fD+ = 1.23 +- 0.11 +- 0.04. We compare with theoretical estimates.
rate research
Read More
Using 482~pb$^{-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.
The first measurement of the effective lifetime of the $bar{B}_s^0$ meson in the decay $bar{B}_s^0to D_s^-D_s^+$ is reported using a proton-proton collision dataset, corresponding to an integrated luminosity of 3 fb$^{-1}$, collected by the LHCb experiment. The measured value of the $bar{B}_s^0to D_s^-D_s^+$ effective lifetime is $1.379pm0.026pm0.017$ ps, where the uncertainties are statistical and systematic, respectively. This lifetime translates into a measurement of the decay width of the light $bar{B}_s^0$ mass eigenstate of Gamma_L$=0.725pm0.014pm0.009$ ps$^{-1}$. The $bar{B}_s^0$ lifetime is also measured using the flavor-specific $bar{B}_s^0to D^-D_s^+$ decay to be $1.52pm0.15pm0.01 {rm ps}$.
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 report on determinations of |Vub| resulting from studies of the branching fraction and q^2 distributions in exclusive semileptonic B decays that proceed via the b->u transition. Our data set consists of the 9.7x10^6 BBbar meson pairs collected at the Y(4S) resonance with the CLEO II detector. We measure B(B0 -> pi- l+ nu) = (1.33 +- 0.18 +- 0.11 +- 0.01 +- 0.07)x10^{-4} and B(B0 -> rho- l+ nu) = (2.17 +- 0.34 +0.47/-0.54 +- 0.41 +- 0.01)x10^{-4}, where the errors are statistical, experimental systematic, systematic due to residual form-factor uncertainties in the signal, and systematic due to residual form-factor uncertainties in the cross-feed modes, respectively. We also find B(B+ -> eta l+ nu) = (0.84 +- 0.31 +- 0.16 +- 0.09)x10^{-4}, consistent with what is expected from the B -> pi l nu mode and quark model symmetries. We extract |Vub| using Light-Cone Sum Rules (LCSR) for 0<= q^2<16 GeV^2 and Lattice QCD (LQCD) for 16 GeV^2 <= q^2 < q^2_max. Combining both intervals yields |Vub| = (3.24 +- 0.22 +- 0.13 +0.55/-0.39 +- 0.09)x10^{-3}$ for pi l nu, and |Vub| = (3.00 +- 0.21 +0.29/-0.35 +0.49/-0.38 +-0.28)x10^{-3} for rho l nu, where the errors are statistical, experimental systematic, theoretical, and signal form-factor shape, respectively. Our combined value from both decay modes is |Vub| = (3.17 +- 0.17 +0.16/-0.17 +0.53/-0.39 +-0.03)x10^{-3}.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
