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Register a new userFirst observation of B0->J/psi K+K- and search for B0->J/psiphi decays
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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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An analysis of the decay B0 -> J/psi K*(892)0 is presented using data, corresponding to an integrated luminosity of 1.0fb^-1, collected in pp collisions at a centre-of-mass energy of 7TeV with the LHCb detector. The polarisation amplitudes and the corresponding phases are measured to be |A_{parallel}|^2 = 0.227 +- 0.004 (stat.) +- 0.011 (syst.), |A_{perp}|^2 = 0.201 +- 0.004 (stat.) +- 0.008 (syst.), delta_{parallel} [rad] = -2.94 +- 0.02 (stat.) +- 0.03 (syst.), delta_{perp} [rad] = 2.94 +- 0.02 (stat.) +- 0.02 (syst.). Comparing B0 -> J/psi K*(892)0 and bar{B}0 -> J/psi bar{K}*(892)0 decays, no evidence for direct CP violation is found.
The first full amplitude analysis of $B^+to J/psi phi K^+$ with $J/psitomu^+mu^-$, $phito K^+K^-$ decays is performed with a data sample of 3 fb$^{-1}$ of $pp$ collision data collected at $sqrt{s}=7$ and $8$ TeV with the LHCb detector. The data cannot be described by a model that contains only excited kaon states decaying into $phi K^+$, and four $J/psiphi$ structures are observed, each with significance over $5$ standard deviations. The quantum numbers of these structures are determined with significance of at least $4$ standard deviations. The lightest has mass consistent with, but width much larger than, previous measurements of the claimed $X(4140)$ state.
The decay Bs -> J/psi K+ K- is investigated using 0.16/fb of data collected with the LHCb detector using 7 TeV pp collisions. Although the J/psi phi channel is well known, final states at higher K+K- masses have not previously been studied. In the K+K- mass spectrum we observe a significant signal in the f2(1525) region as well as a non-resonant component. After subtracting the non-resonant component, we find B(Bs->J/psi f_2(1525))/B(Bs->J/psi phi)=(26.4 +/- 2.7 +/- 2.4)%.
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.
The first observation of exotic states with a new quark content $c bar{c} u bar{s}$ decaying to the $J/psi K^+$ final state is reported with high significance from an amplitude analysis of the $B^+ to J/psi phi K^+$ decay. The analysis is carried out using proton-proton collision data corresponding to a total integrated luminosity of 9 fb$^{-1}$ collected by the LHCb experiment at centre-of-mass energies of 7, 8 and 13 TeV. The most significant state, $Z_{cs}(4000)^+$, has a mass of $4003pm6,^{+,phantom{0}4}_{-,14}$ MeV, a width of $131pm15pm26$ MeV, and spin-parity $J^P=1^+$, where the quoted uncertainties are statistical and systematic, respectively. A new $1^+$ $X(4685)$ state decaying to the $J/psi phi$ final state is also observed with high significance. In addition, the four previously reported $J/psi phi$ states are confirmed and two more exotic states, $Z_{cs}(4220)^+$ and $X(4630)$, are observed with significance exceeding five standard deviations.
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