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Register a new userObservation of $B_{c}^{+} to J/psi D^{(*)} K^{(*)}$ decays
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A search for the decays $B_c^+ to J/psi D^{(*)0} K^+$ and $B_c^+ to J/psi D^{(*)+} K^{*0}$ is performed with data collected at the LHCb experiment corresponding to an integrated luminosity of 3 fb$^{-1}$. The decays $B_c^+ to J/psi D^0 K^+$ and $B_c^+ to J/psi D^{*0} K^+$ are observed for the first time, while first evidence is reported for the $B_c^+ to J/psi D^{*+} K^{*0}$ and $B_c^+ to J/psi D^+ K^{*0}$ decays. The branching fractions of these decays are determined relative to the $B_c^+ to J/psi pi^+$ decay. The $B_c^+$ mass is measured, using the $J/psi D^0 K^+$ final state, to be $6274.28 pm 1.40 (stat) pm 0.32 (syst)$ MeV/$c^2$. This is the most precise single measurement of the $B_c^+$ mass to date.
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The decay $B_c^+to J/psi K^+$ is observed for the first time using a data sample, corresponding to an integrated luminosity of 1.0 ${,fb}^{-1}$, collected by the LHCb experiment in $pp$ collisions at a centre-of-mass energy of $7mathrm{,Tekern -0.1em V}$. A yield of $46pm12$ events is reported, with a significance of 5.0 standard deviations. The ratio of the branching fraction of $B_c^+to J/psi K^+$ to that of $B_c^+to J/psipi^+$ is measured to be $0.069pm0.019pm0.005$, where the first uncertainty is statistical and the second is systematic.
Using proton-proton collision data corresponding to an integrated luminosity of 3.0 fb$^{-1}$, recorded by the LHCb detector at centre-of-mass energies of 7 and 8 TeV, the $B_{c}^{+} rightarrow D^{0} K^{+}$ decay is observed with a statistical significance of 5.1 standard deviations. By normalising to $B^{+} rightarrow bar{D}^{0} pi^{+}$ decays, a measurement of the branching fraction multiplied by the production rates for $B_{c}^{+}$ relative to $B^{+}$ mesons in the LHCb acceptance is obtained, $$ R_{D^{0} K} = frac{f_{c}}{f_{u}}timesmathcal{B}(B_{c}^{+} rightarrow D^{0} K^{+}) = (9.3,^{+2.8}_{-2.5} pm 0.6) times 10^{-7},, $$ where the first uncertainty is statistical and the second is systematic. This decay is expected to proceed predominantly through weak annihilation and penguin amplitudes, and is the first $B_{c}^{+}$ decay of this nature to be observed.
The ratio of branching fractions $R_{K/pi} equiv mathcal{B}(B_{c}^{+} to J/psi K^{+})/mathcal{B}(B_{c}^{+} to J/psipi^{+})$ is measured with $pp$ collision data collected by the LHCb experiment at centre-of-mass energies of 7 TeV and 8 TeV, corresponding to an integrated luminosity of 3${mbox{fb}^{-1}}$. It is found to be $ R_{K/pi} = 0.079pm0.007pm0.003$, where the first uncertainty is statistical and the second is systematic. This measurement is consistent with the previous LHCb result, while the uncertainties are significantly reduced.
A search for the rare decays of $J/psi to D_s^-rho^+ + c.c.$ and $J/psi to overline{D}{}^0overline{K}{}^{ast0} + c.c.$ is performed with a data sample of 225.3 million $J/psi$ events collected with the BESIII detector. No evident signal is observed. Upper limits on the branching fractions are determined to be $mathcal{B}(J/psi to D_s^-rho^+ + c.c.) < 1.3 times 10^{-5}$ and $mathcal{B}(J/psi to overline{D}{}^0overline{K}{}^{ast0} + c.c.) < 2.5 times 10^{-6}$ at the $90%$ confidence level.
The first observation of the B0->J/psi K+K- decay is presented with a data sample corresponding to an integrated luminosity of 1.0/fb of pp collisions at a center-of-mass energy of 7 TeV collected with the LHCb detector. The branching fraction is measured to be B(B0->J/psi K+K-) = (2.53 +/- 0.31 +/- 0.19)x10^{-6}, where the first uncertainty is statistical and the second is systematic. An amplitude analysis of the final state in the B0->J/psi K+K- decay is performed to separate resonant and nonresonant contributions in the K+K- spectrum. Evidence of the a0(980) resonance is reported with statistical significance of 3.9 standard deviations. The corresponding product branching fraction is measured to be B(B0->J/psi a0(980), a0(980)->K+K-)=(4.70 +/- 3.31 +/- 0.72)x10^{-7}, yielding an upper limit of B(B0->J/psi a0(980), a0(980)->K+K-)<9.0x10^{-7} at 90% confidence level. No evidence of the resonant decay B0->J/psiphi; is found, and an upper limit on its branching fraction is set to be B(B0->J/psiphi)< 1.9x10^{-7} at 90% confidence level.
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