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Register a new userStudy of the $D^0to K^-mu^+ u_mu$ dynamics and test of lepton flavor universality with $D^0to K^-ell^+ u_ell$ decays
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Using $e^+e^-$ annihilation data of $2.93~mathrm{fb}^{-1}$ collected at center-of-mass energy $sqrt{s}=3.773$ GeV with the BESIII detector, we measure the absolute branching fraction of $D^{0}to K^{-}mu^{+} u_{mu}$ with significantly improved precision: ${mathcal B}_{D^{0}to K^{-}mu^{+} u_{mu}}=(3.413pm0.019_{rm stat.}pm0.035_{rm syst.})%$. Combining with our previous measurement of ${mathcal B}_{D^0to K^-e^+ u_e}$, the ratio of the two branching fractions is determined to be ${mathcal B}_{D^0to K^-mu^+ u_mu}/{mathcal B}_{D^0to K^-e^+ u_e}=0.974pm0.007_{rm stat.}pm0.012_{rm syst.}$, which agrees with the theoretical expectation of lepton flavor universality within the uncertainty. A study of the ratio of the two branching fractions in different four-momentum transfer regions is also performed, and no evidence for lepton flavor universality violation is found with current statistics. Taking inputs from global fit in the standard model and lattice quantum chromodynamics separately, we determine $f_{+}^{K}(0)=0.7327pm0.0039_{rm stat.}pm0.0030_{rm syst.}$ and $|V_{cs}| = 0.955pm0.005_{rm stat.}pm0.004_{rm syst.}pm0.024_{rm LQCD}$.
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The first measurements of the forward-backward asymmetry of the dimuon pair ($A_{FB}$), the triple-product asymmetry ($A_{2phi}$), and the charge-parity-conjugation asymmetry ($A_{CP}$), in $D^0topi^+pi^-mu^+mu^-$ and $D^0to K^+K^-mu^+mu^-$ decays are reported. They are performed using data from proton-proton collisions collected with the LHCb experiment from 2011 to 2016, corresponding to a total integrated luminosity of 5 fb$^{-1}$. The asymmetries are measured to be begin{align*} A_{FB}(D^0topi^+pi^-mu^+mu^-) &= (phantom{-}3.3pm3.7pm0.6)%, A_{2phi}(D^0topi^+pi^-mu^+mu^-)&= (-0.6pm3.7pm0.6)%, A_{CP}(D^0topi^+pi^-mu^+mu^-) &= (phantom{-}4.9pm3.8pm0.7)%, A_{FB}(D^0to K^+K^-mu^+mu^-) &= (0pm11pm2)%, A_{2phi}(D^0to K^+K^-mu^+mu^-)&= (9pm11pm1)%, A_{CP}(D^0to K^+K^-mu^+mu^-) &= (0pm11pm2)%, end{align*} where the first uncertainty is statistical and the second systematic. The asymmetries are also measured as a function of the dimuon invariant mass. The results are consistent with the Standard Model predictions.
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.
We report a measurement of the indirect CP-violating asymmetries ($A_{Gamma}$) between effective lifetimes of anticharm and charm mesons reconstructed in $D^0to K^+ K^-$ and $D^0to pi^+pi^-$ decays. We use the full data set of proton-antiproton collisions collected by the Collider Detector at Fermilab experiment and corresponding to $9.7$~fb$^{-1}$ of integrated luminosity. The strong-interaction decay $D^{*+}to D^0pi^+$ is used to identify the meson at production as $D^0$ or $overline{D}^0$. We statistically subtract $D^0$ and $overline{D}^0$ mesons originating from $b$-hadron decays and measure the yield asymmetry between anticharm and charm decays as a function of decay time. We measure $A_Gamma (K^+K^-) = (-0.19 pm 0.15 (stat) pm 0.04 (syst))%$ and $A_Gamma (pi^+pi^-)= (-0.01 pm 0.18 (stat) pm 0.03 (syst))%$. The results are consistent with the hypothesis of CP symmetry and their combination yields $A_Gamma = (-0.12 pm 0.12)%$.
A study of indirect CP violation in $D^0$ mesons through the determination of the parameter $A_Gamma$ is presented using a data sample of $pp$ collisions, corresponding to an integrated luminosity of 1.0 fb$^{-1}$, collected with the LHCb detector and recorded at the centre-of-mass energy of 7 TeV at the LHC. The parameter $A_Gamma$ is the asymmetry of the effective lifetimes measured in decays of $D^0$ and $bar{D}^0$ mesons to the CP eigenstates $K^-K^+$ and $pi^-pi^+$. Fits to the data sample yield $A_Gamma(KK)=(-0.35pm0.62pm0.12)times 10^{-3}$ and $A_Gamma(pipi)=(0.33pm1.06pm0.14)times 10^{-3}$, where the first uncertainties are statistical and the second systematic. The results represent the worlds best measurements of these quantities. They show no difference in $A_Gamma$ between the two final states and no indication of CP violation.
We present a measurement of $R_{K^{ast}}$, the branching fraction ratio ${{cal B}(Bto K^ast mu^+ mu^-)}$/ ${{cal B}(Bto K^ast e^+ e^-)}$, for both charged and neutral $B$ mesons. The ratio for the charged case, $R_{K{^{ast +}}}$, is the first measurement ever performed. In addition, we report absolute branching fractions for the individual modes in bins of the squared dilepton invariant mass, $q^2$. The analysis is based on a data sample of $711~mathrm{fb}^{-1}$, containing $772times 10^{6}$ $Bbar B$ events, recorded at the $Upsilon(4S)$ resonance with the Belle detector at the KEKB asymmetric-energy $e^+e^-$ collider. The obtained results are consistent with Standard Model expectations.
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