No Arabic abstract
Using data collected near the Ds*+ Ds- peak production energy Ecm = 4170 MeV by the CLEO-c detector, we study the decays of Ds+ mesons to two pseudoscalar mesons. We report on searches for the singly-Cabibbo-suppressed Ds+ decay modes K+ eta, K+ eta, pi+ K0S, K+ pi0, and the isospin-forbidden decay mode Ds+ to pi+ pi0. We normalize with respect to the Cabibbo-favored Ds+ modes pi+ eta, pi+ eta, and K+ K0S, and obtain ratios of branching fractions: Ds+ to K+ eta / Ds+ to pi+ eta = (8.9 +- 1.5 +- 0.4)%, Ds+ to K+ eta / Ds+ to pi+ eta = (4.2 +- 1.3 +- 0.3)%, Ds+ to pi+ K0S / Ds+ to K+ K0S = (8.2 +- 0.9 +- 0.2)%, Ds+ to K+ pi0 / Ds+ to K+ K0S = (5.0 +- 1.2 +- 0.6)%, and Ds+ to pi+ pi0 / Ds+ to K+ K0S < 4.1% at 90% CL, where the uncertainties are statistical and systematic, respectively.
We measure the branching fractions for seven $D_{s}^{+}$ two-body decays to pseudo-scalar mesons, by analyzing data collected at $sqrt{s}=4.178sim4.226$ GeV with the BESIII detector at the BEPCII collider. The branching fractions are determined to be $mathcal{B}(D_s^+to K^+eta^{prime})=(2.68pm0.17pm0.17pm0.08)times10^{-3}$, $mathcal{B}(D_s^+toeta^{prime}pi^+)=(37.8pm0.4pm2.1pm1.2)times10^{-3}$, $mathcal{B}(D_s^+to K^+eta)=(1.62pm0.10pm0.03pm0.05)times10^{-3}$, $mathcal{B}(D_s^+toetapi^+)=(17.41pm0.18pm0.27pm0.54)times10^{-3}$, $mathcal{B}(D_s^+to K^+K_S^0)=(15.02pm0.10pm0.27pm0.47)times10^{-3}$, $mathcal{B}(D_s^+to K_S^0pi^+)=(1.109pm0.034pm0.023pm0.035)times10^{-3}$, $mathcal{B}(D_s^+to K^+pi^0)=(0.748pm0.049pm0.018pm0.023)times10^{-3}$, where the first uncertainties are statistical, the second are systematic, and the third are from external input branching fraction of the normalization mode $D_s^+to K^+K^-pi^+$. Precision of our measurements is significantly improved compared with that of the current world average values.
Using a data sample of $e^+e^-$ collision data with an integrated luminosity of 2.93 fb$^{-1}$ taken at the center-of-mass energy $sqrt s= 3.773$~GeV with the BESIII detector operating at the BEPCII storage rings, we measure the absolute branching fractions of the two-body hadronic decays $D^+to pi^+pi^0$, $K^+ pi^0$, $pi^+ eta$, $K^+eta$, $pi^+eta^prime$, $K^+eta^prime$, $K_S^0 pi^+$, $K_S^0 K^+$, and $D^0to pi^+ pi^-$, $K^+ K^-$, $K^mp pi^pm$, $K_S^0 pi^0$, $K_S^0 eta$, $K_S^0 eta^prime$. Our results are consistent with previous measurements within uncertainties. Among them, the branching fractions for $D^+topi^+pi^0$, $K^+pi^0$, $pi^+eta$, $pi^+eta^prime$, $K_S^0 pi^+$, $K_S^0 K^+$ and $D^0 to K_S^0 pi^0$, $K_S^0 eta$, $K_S^0 eta^prime$ are determined with improved precision compared to the world average values.
Using a sample of $4.48times10^{8}$ $psi(3686)$ events collected with the BESIII detector at the BEPCII collider, we study the two-photon decays of the pseudoscalar mesons $pi^0$, $eta$, $eta^prime$, $eta(1405)$, $eta(1475)$, $eta(1760)$, and $X(1835)$ in $J/psi$ radiative decays using $psi(3686)topi^{+}pi^{-}J/psi$ events. The $pi^0$, $eta$ and $eta^prime$ mesons are clearly observed in the two-photon mass spectra, and the branching fractions are determined to be $B(J/psitogammapi^{0}to3gamma)=(3.57pm0.12pm0.16)times10^{-5}$, $B(J/psitogammaetato3gamma)=(4.42pm0.04pm0.18)times10^{-4}$, and $B(J/psitogammaetato3gamma)=(1.26pm0.02pm0.05)times10^{-4}$, where the first errors are statistical and the second systematic. No clear signal for $eta(1405)$, $eta(1475)$, $eta(1760)$ or $X(1835)$ is observed in the two-photon mass spectra, and upper limits at the $90%$ confidence level on the product branching fractions are obtained.
A search for decays of $B_c^+$ mesons to two charm mesons is performed for the first time using data corresponding to an integrated luminosity of 3.0 fb$^{-1}$, collected by the LHCb experiment in $pp$ collisions at centre-of-mass energies of 7 and 8 TeV. The decays considered are $B_c^+to D^{(*)+}_{(s)} overline{D}^{(*)0}$ and $B_c^+to D^{(*)+}_{(s)} D^{(*)0}$, which are normalised to high-yield $B^+to D^+_{(s)} overline{D}^0$ decays. No evidence for a signal is found and limits are set on twelve $B_c^+$ decay modes.
A data set corresponding to an integrated luminosity of $9 text{fb}^{-1}$ of proton-proton collisions collected by the LHCb experiment has been analysed to search for $B_c^+ to D^{(*)+}_{(s)} overset{scriptstyle (-)}{D}{}^{(*)0}$ decays. The decays are fully or partially reconstructed, where one or two missing neutral pions or photons from the decay of an excited charm meson are allowed. Upper limits for the branching fractions, normalised to $B^+$ decays to final states with similar topologies, are obtained for fourteen $B_c^+$ decay modes. For the decay $B_c^+ to D_s^+ {overline{D}}^0$, an excess with a significance of 3.4 standard deviations is found.