An improved measurement of the decay $B^0_S$ → $μ^+μ^-$ and searches for the decays $B^0$ → $μ^+μ^+$ and $B^0_S$ → $μ^+μ^-γ$ are performed at the LHCb experiment using data collected in proton-proton ...collisions at $\sqrt{s}$ = 7, 8 and 13 TeV. corresponding to integrated luminosities of 1, 2 and 6 fb-1, respectively. The $B^0_S$ → $μ^+μ^-$ branching fraction and effective lifetime are measured to be $\mathscr{B}$($B^0_S$ → $μ^+μ^-$) = (3.09$^{(+0.46+0.15)}_{(-0.43-0.11)}$) x 10-9 and $τ(B^0_s →μ^+μ^-)$ = (2.07 ± 0.29 ± 0.03) ps, respectively, where the uncertainties include both statistical and systematic contributions. No significant signal for $B^0$ → $μ^+μ^-$ and $B^0_S$ → $μ^+μ^-γ$ decays is found and the upper limits $\mathscr{B}$($B^0$ → $μ^+μ^-$) < 2.6 x 10-10 and $B^0_S$ → $μ^+μ^-γ$ < 2.0 x 10-9 at 95% confidence level are determined, where the latter is limited to the range $m_{μμ}$ > 4.9 GeV/c2. Additionally, the ratio between the $B^0$ → $μ^+μ^-$ and $B^0_S$ → $μ^+μ^-$ branching fractions is measured to be $\mathscr{R}_{μ+μ-}$ < 0.095 at 95% confidence level. The results are in agreement with the Standard Model predictions.
A study of the lineshape of the χc1 ( 3872 ) state is made using a data sample corresponding to an integrated luminosity of 3 fb−1 collected in p p collisions at center-of-mass energies of 7 and ...8 TeV with the LHCb detector. Candidate χc1 ( 3872 ) and ψ ( 2S ) mesons from b -hadron decays are selected in the J / ψ π+ π− decay mode. Describing the lineshape with a Breit-Wigner function, the mass splitting between the χc1 ( 3872 ) and ψ ( 2S ) states, Δm, and the width of the χc1 ( 3872 ) state, ΓBW, are determined to be ..., where the first uncertainty is statistical and the second systematic. Using a Flatté-inspired model, the mode and full width at half maximum of the lineshape are determined to be ... . An investigation of the analytic structure of the Flatté amplitude reveals a pole structure, which is compatible with a quasibound D0 D*0 state but a quasivirtual state is still allowed at the level of 2 standard deviations. (ProQuest: ... denotes formulae omited.).
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First evidence of a structure in the J/ψΛ invariant mass distribution is obtained from an amplitude analysis of Ξb-→J/ψΛK- decays. The observed structure is consistent with being due ...to a charmonium pentaquark with strangeness with a significance of 3.1σ including systematic uncertainties and look-elsewhere effect. Its mass and width are determined to be 4458.8±2.9-1.1+4.7MeV and 17.3±6.5-5.7+8.0MeV, respectively, where the quoted uncertainties are statistical and systematic. The structure is also consistent with being due to two resonances. In addition, the narrow excited Ξ- states, Ξ1690- and Ξ1820-, are seen for the first time in a Ξb- decay, and their masses and widths are measured with improved precision. The analysis is performed using pp collision data corresponding to a total integrated luminosity of 9 fb-1, collected with the LHCb experiment at centre-of-mass energies of 7, 8 and 13 TeV.
The first observation of exotic states with a new quark content ccus decaying to the J/Psi K+ final state is reported with high significance from an amplitude analysis of the B+-> 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 center-of-mass energies of 7, 8, and 13 TeV. The most significant state, Z(cs)(4000)+, has a mass of 4003 +/- 6 (-14) (+4) MeV, a width of 131 +/- 15 +/- 26 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 5 standard deviations.
Quantum chromodynamics, the theory of the strong force, describes interactions of coloured quarks and gluons and the formation of hadronic matter. Conventional hadronic matter consists of baryons and ...mesons made of three quarks and quark-antiquark pairs, respectively. Particles with an alternative quark content are known as exotic states. Here a study is reported of an exotic narrow state in the (DD0)-D-0 pi(+) mass spectrum just below the D*+D-0 mass threshold produced in proton-proton collisions collected with the LHCb detector at the Large Hadron Collider. The state is consistent with the ground isoscalar T-cc(+), tetraquark with a quark content of cc (u) over bar(d) over bar and spin-parity quantum numbers J(P) =1(+). Study of the DD mass spectra disfavours interpretation of the resonance as the isovector state. The decay structure via intermediate off-shell D*(+) mesons is consistent with the observed D-0 pi(+) mass distribution. To analyse the mass of the resonance and its coupling to the DID system, a dedicated model is developed under the assumption of an isoscalar axial-vector T-cc(+), state decaying to the D*D channel. Using this model, resonance parameters including the pole position, scattering length, effective range and compositeness are determined to reveal important information about the nature of the T-cc(+), state. In addition, an unexpected dependence of the production rate on track multiplicity is observed.
The production of χc1(3872) and ψ(2S) hadrons is studied as a function of charged particle multiplicity in p p collisions at a center-of-mass energy of 8 TeV, corresponding to an integrated ...luminosity of 2 fb−1. For both states, the fraction that is produced promptly at the collision vertex is found to decrease as charged particle multiplicity increases. The ratio of χc1(3872) to ψ(2S) cross sections for promptly produced particles is also found to decrease with multiplicity, while no significant dependence on multiplicity is observed for the equivalent ratio of particles produced away from the collision vertex in b-hadron decays. This behavior is consistent with a calculation that models the χc1(3872) structure as a compact tetraquark. Comparisons with model calculations and implications for the binding energy of the χc1(3872) state are discussed.
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