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Register a new userA puzzle in $bar{B}_{(s)}^0 to D_{(s)}^{(*)+} lbrace pi^-, K^-rbrace$ decays and extraction of the $f_s/f_d$ fragmentation fraction
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We provide updated predictions for the hadronic decays $bar{B}_s^0to D_s^{(*)+} pi^-$ and $bar{B}^0to D^{(*)+} K^-$. They are based on $mathcal{O}(alpha_s^2)$ results for the QCD factorization amplitudes at leading power and on recent results for the $bar{B}_{(s)} to D_{(s)}^{(*)}$ form factors up to order ${cal O}(Lambda_{rm QCD}^2/m_c^2)$ in the heavy-quark expansion. We give quantitative estimates of the matrix elements entering the hadronic decay amplitudes at order ${cal O}(Lambda_{rm QCD}/m_b)$ for the first time. Our results are very precise, and uncover a substantial discrepancy between the theory predictions and the experimental measurements. We explore two possibilities for this discrepancy: non-factorizable contributions larger than predicted by the QCD factorization power counting, and contributions beyond the Standard Model. We determine the $f_s/f_d$ fragmentation fraction for the CDF, D0 and LHCb experiments for both scenarios.
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Recently, the standard model predictions for the $B$-meson hadronic decays, $bar{B}^0 to D^{(ast)+}K^-$ and $bar{B}^0_s to D^{(ast)+}_s pi^-$, have been updated based on the QCD factorization approach. This improvement sheds light on a novel puzzle in the $B$-meson hadronic decays: there are mild but universal tensions between data and the predicted branching ratios. Assuming the higher-order QCD corrections are not huge enough to solve the tension, we examine several new physics interpretations of this puzzle. We find that the tension can be partially explained by a left-handed $W^prime$ model, which can be compatible with other flavor observables and collider bounds.
We present a measurement of the $CP$-violating weak mixing phase $phi_s$ using the decay $bar{B}^{0}_{s}to D_{s}^{+}D_{s}^{-}$ in a data sample corresponding to $3.0$ fb$^{-1}$ of integrated luminosity collected with the LHCb detector in $pp$ collisions at centre-of-mass energies of 7 and 8 TeV. An analysis of the time evolution of the system, which does not constrain $|lambda|=1$ to allow for the presence of $CP$ violation in decay, yields $phi_s = 0.02 pm 0.17$ (stat) $pm 0.02$ (syst) rad, $|lambda| = 0.91^{+0.18}_{-0.15}$ (stat) $pm0.02$ (syst). This result is consistent with the Standard Model expectation.
The first observation of the decays $bar{B}^0_{s}to D_s^+K^-pi^+pi^-$ and $bar{B}^0to D_s^+K^-pi^+pi^-$ are reported using an integrated luminosity of 1.0 fb$^{-1}$ recorded by the LHCb experiment. The branching fractions, normalized with respect to $bar{B}^0_{s}to D_s^+pi^-pi^+pi^-$ and $bar{B}^0_{s}to D_s^+K^-pi^+pi^-$, respectively, are measured to be {br(bar{B}^0_{s}to D_s^+K^-pi^+pi^-)overbr(bar{B}^0_{s}to D_s^+pi^-pi^+pi^-)} &= (5.2pm0.5pm0.3)times10^{-2}, {br(bar{B}^0to D_s^+K^-pi^+pi^-)overbr(bar{B}^0_{s}to D_s^+K^-^pi^+pi^-)} &= 0.54pm0.07pm0.07, where the first uncertainty is statistical and the second is systematic. The $bar{B}^0_{s}to D_s^+K^-pi^+pi^-$ decay is of particular interest as it can be used to measure the weak phase $gamma$. First observation of the $bar{B}^0_sto D_{s1}(2536)^+pi^-, D_{s1}^+to D_s^+pi^-pi^+$ decay is also presented, and its branching fraction relative to $bar{B}^0_{s}to D_s^+pi^-pi^+pi^-$ is found to be {br(bar{B}^0_sto D_{s1}(2536)^+pi^-, D_{s1}^+to D_s^+pi^-pi^+)overbr(bar{B}^0_{s}to D_s^+pi^-pi^+pi^-)} &= (4.0pm1.0pm0.4)times10^{-3}.
Utilizing a data set corresponding to an integrated luminosity of 6.32~$rm fb^{-1}$, recorded by the BESIII detector at center-of-mass energies between 4.178 and 4.226~GeV, we perform an amplitude analysis of the decay $D_{s}^{+} to K_{S}^{0}pi^{+}pi^{0}$ and determine the relative fractions and phase differences of different intermediate processes, which include $K_{S}^{0}rho(770)^{+}$, $K_{S}^{0}rho(1450)^{+}$, $K^{*}(892)^{0}pi^{+}$, $K^{*}(892)^{+}pi^{0}$, and $K^{*}(1410)^{0}pi^{+}$. Using a double-tag technique, and making an efficiency correction that relies on our knowledge of the phase-space distribution of the decays coming from the amplitude analysis, the absolute branching fraction is measured to be $mathcal{B}(D_{s}^{+} to K_{S}^{0}pi^{+}pi^{0})=(5.43pm0.30_{text{stat}}pm 0.15_{text{syst}})times 10^{-3}$.
Measurements are presented of the branching fractions of the decays $B_{s}^{0} to D_{s}^{mp} K^{pm}$ and $B^{0} to D_{s}^{-} K^{+}$ relative to the decays $B_{s}^{0} to D_{s}^{-} pi^{+}$ and $B^{0} to D^{-} pi^{+}$, respectively. The data used correspond to an integrated luminosity of 3.0 fb$^{-1}$ of proton-proton collisions. The ratios of branching fractions are $dfrac{mathcal{B}(B_{s}^{0} to D_{s}^{mp} K^{pm})}{mathcal{B}(B_{s}^{0} to D_{s}^{-} pi^{+})} = 0.0752 pm 0.0015 pm 0.0019$ and $dfrac{mathcal{B}(B^{0} to D_{s}^{-} K^{+})}{mathcal{B}(B^{0} to D^{-} pi^{+})} = 0.0129 pm 0.0005 pm 0.0008,$ where the uncertainties are statistical and systematic, respectively.
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