12 research outputs found
Measurement of the B lifetime and production rate with D combinations in Z decays
The lifetime of the \bs meson is measured in approximately 3 million hadronic Z decays accumulated using the ALEPH detector at LEP from 1991 to 1994. Seven different \ds decay modes were reconstructed and combined with an opposite sign lepton as evidence of semileptonic \bs decays. Two hundred and eight \dsl candidates satisfy selection criteria designed to ensure precise proper time reconstruction and yield a measured \bs lifetime of \mbox{\result .} Using a larger, less constrained sample of events, the product branching ratio is measured to be \mbox{\pbrresult
Observation of the decay BÂŻÂŻÂŻ0sâÏ(2S)K+Ïâ
15 pages, 7 figures - See paper for full list of authorsInternational audienceThe decay BÂŻÂŻÂŻ0sâÏ(2S)K+Ïâ is observed using a data set corresponding to an integrated luminosity of 3.0fbâ1 collected by the LHCb experiment in pp collisions at centre-of-mass energies of 7 and 8 TeV. The branching fraction relative to the B0âÏ(2S)K+Ïâ decay mode is measured to beB(BÂŻÂŻÂŻ0sâÏ(2S)K+Ïâ)B(B0âÏ(2S)K+Ïâ)=5.38±0.36(stat)±0.22(syst)±0.31(fs/fd)%,where fs/fd indicates the uncertainty due to the ratio of probabilities for a b quark to hadronise into a B0s or B0 meson. Using an amplitude analysis, the fraction of decays proceeding via an intermediate Kâ(892)0 meson is measured to be 0.645±0.049(stat)±0.049(syst) and its longitudinal polarisation fraction is 0.524±0.056(stat)±0.029(syst). The relative branching fraction for this component is determined to beB(BÂŻÂŻÂŻ0sâÏ(2S)Kâ(892)0)B(B0âÏ(2S)Kâ(892)0)=5.58±0.57(stat)±0.40(syst)±0.32(fs/fd)%.In addition, the mass splitting between the B0s and B0 mesons is measured asM(B0s)âM(B0)=87.45±0.44(stat)±0.07(syst)MeV/c2
Observation of the B0âÏ0Ï0 decay from an amplitude analysis of B0â(Ï+Ïâ)(Ï+Ïâ) decays
See paper for full list of authorsInternational audienceProton-proton collision data recorded in 2011 and 2012 by the \lhcb experiment, co\-rres\-pon\-ding to an integrated luminosity of 3.0\invfb, are a\-na\-lysed to search for the charmless B0âÏ0Ï0 decay. More than 600 {\B^0 \to (\pi^+\pi^-)(\pi^+\pi^-)} signal decays are selected and used to perform an amplitude analysis from which the B0âÏ0Ï0 decay is observed for the first time with 7.1 standard deviations significance. The fraction of B0âÏ0Ï0 decays yielding a longitudinally polarised final state is measured to be \fL = 0.745^{+0.048}_{-0.058} ({\rm stat}) \pm 0.034 ({\rm syst}). The B0âÏ0Ï0 branching fraction, using the {\B^0 \to \phi K^*(892)^{0}} decay as reference, is also reported as {\BF(B^0 \to \rho^0 \rho^0) = (0.94 \pm 0.17 ({\rm stat}) \pm 0.09 ({\rm syst}) \pm 0.06 ({\rm BF})) \times 10^{-6}}
Quantum numbers of the state and orbital angular momentum in its decay
16 pages, 4 figures - See paper for full list of authorsInternational audienceAngular correlations in B+âX(3872)K+ decays, with X(3872)âÏ0J/Ï, Ï0âÏ+Ïâ and J/ÏâÎŒ+ÎŒâ, are used to measure orbital angular momentum contributions and to determine the JPC value of the X(3872) meson. The data correspond to an integrated luminosity of 3.0 fbâ1 of proton-proton collisions collected with the LHCb detector. This determination, for the first time performed without assuming a value for the orbital angular momentum, confirms the quantum numbers to be JPC=1++. The X(3872) is found to decay predominantly through S wave and an upper limit of 4% at 95% C.L. is set on the fraction of D wave
Measurement of -hadron branching fractions for two-body decays into charmless charged hadrons
15 pages, 5 figures, 7 tables - See paper for full list of authorsBased on data corresponding to an integrated luminosity of 0.37 fb^-1 collected by the LHCb experiment in 2011, the following ratios of branching fractions are measured: B(B0 -> pi+ pi-) / B(B0 -> K+pi-) = 0.262 +/- 0.009 +/- 0.017, (fs/fd) * B(Bs -> K+K-) / B(B^0 -> K+pi-) = 0.316 +/- 0.009 +/- 0.019, (fs/fd) * B(Bs ->pi+ K-) / B(B0 -> K+pi-) = 0.074 +/- 0.006 +/- 0.006, (fd/fs) * B(B0 -> K+K-) / B(Bs -> K+K-) = 0.018 {+ 0.008 - 0.007} +/- 0.009, (fs/fd) * B(Bs -> pi+pi-) / B(B0 -> pi+pi-) = 0.050 {+ 0.011 - 0.009} +/- 0.004, B(Lambda_b -> p pi-) / B(Lambda_b -> p K-) = 0.86 +/- 0.08 +/- 0.05, where the first uncertainties are statistical and the second systematic. Using the current world average of B(B0 -> K+pi-) and the ratio of the strange to light neutral B meson production fs/fd measured by LHCb, we obtain: B(B0 -> pi+pi-) = (5.08 +/- 0.17 +/- 0.37) x 10^-6, B(Bs -> K+K-) = (23.0 +/- 0.7 +/- 2.3) x 10^-6, B(Bs -> pi+K-) = (5.4 +/- 0.4 +/- 0.6) x 10^-6, B(B0 -> K+K-) = (0.11 {+ 0.05 - 0.04} +/- 0.06) x 10^-6, B(Bs -> pi+pi-) = (0.95 {+ 0.21 - 0.17} +/- 0.13) x 10^-6. The measurements of B(Bs -> K+K-), B(Bs -> pi+ K-) and B(B0 -> K+K-) are the most precise to date. The decay mode Bs -> pi+pi- is observed for the first time with a significance of more than 5 sigma
First observation of the decays and
17 pages, 7 figures - See paper for full list of authorsThe first observation of the decays and are reported using an integrated luminosity of 1.0 fb recorded by the LHCb experiment. The branching fractions, normalized with respect to and , respectively, are measured to be {\br(\bar{B}^0_{s}\to D_s^+K^-\pi^+\pi^-)\over\br(\bar{B}^0_{s}\to D_s^+\pi^-\pi^+\pi^-)} &= (5.2\pm0.5\pm0.3)\times10^{-2}, {\br(\bar{B}^0\to D_s^+K^-\pi^+\pi^-)\over\br(\bar{B}^0_{s}\to D_s^+K^-^\pi^+\pi^-)} &= 0.54\pm0.07\pm0.07, where the first uncertainty is statistical and the second is systematic. The decay is of particular interest as it can be used to measure the weak phase . First observation of the decay is also presented, and its branching fraction relative to is found to be {\br(\bar{B}^0_s\to D_{s1}(2536)^+\pi^-, D_{s1}^+\to D_s^+\pi^-\pi^+)\over\br(\bar{B}^0_{s}\to D_s^+\pi^-\pi^+\pi^-)} &= (4.0\pm1.0\pm0.4)\times10^{-3}
Precision measurement of the ratio of the to lifetimes
11 pages, 6 figures - See paper for full list of authorsThe LHCb measurement of the lifetime ratio of the to the meson is updated using data corresponding to an integrated luminosity of 3.0 fb collected using 7 and 8 TeV centre-of-mass energy collisions at the LHC. The decay modes used are and , where the mass is consistent with that of the meson. The lifetime ratio is determined with unprecedented precision to be , where the first uncertainty is statistical and the second systematic. This result is in agreement with original theoretical predictions based on the heavy quark expansion. Using the current world average of the lifetime, the lifetime is found to be ps
Study of beauty hadron decays into pairs of charm hadrons
See paper for full list of authorsFirst observations of the decays are reported using data corresponding to an integrated luminosity of collected at 7 and 8 TeV center-of-mass energy in proton-proton collisions with the LHCb detector. In addition, the most precise measurement of the branching fraction is made and a search is performed for the decays . The results obtained are \begin{eqnarray*} \mathcal{B}(\Lambda_b^0 \to \Lambda_c^+ D^-)/\mathcal{B}(\Lambda_b^0 \to \Lambda_c^+ D_{s}^-) &=& 0.042 \pm 0.003({\rm stat}) \pm 0.003({\rm syst}), \left[\frac{\mathcal{B}(\Lambda_b^0 \to \Lambda_c^+ D_{s}^-)}{\mathcal{B}({\kern 0.2em}\overline{\kern -0.2em B}_d^0 \to D^+D_s^-)}\right]\big/\left[\frac{\mathcal{B}(\Lambda_b^0 \to \Lambda_c^+\pi^-)}{\mathcal{B}({\kern 0.2em}\overline{\kern -0.2em B}_d^0 \to D^+\pi^-)}\right] &=& 0.96 \pm 0.02({\rm stat}) \pm 0.06({\rm syst}), \mathcal{B}(B_s^0 \to D^+D_s^-)/\mathcal{B}({\kern 0.2em}\overline{\kern -0.2em B}_d^0 \to D^+D_s^-) &=& 0.038\pm0.004({\rm stat})\pm0.003({\rm syst}), \mathcal{B}({\kern 0.2em}\overline{\kern -0.2em B}^0 \to \Lambda_c^+ \Lambda_c^-)/\mathcal{B}({\kern 0.2em}\overline{\kern -0.2em B}_d^0 \to D^+D_s^-) & < & 0.0022\; [95\% \; {\rm C.L.}], \mathcal{B}(B^0_{s} \to \Lambda_c^+ \Lambda_c^-)/\mathcal{B}(B_s^0 \to D^+D_s^-) & < & 0.30\; [95\% \; {\rm C.L.}]. \end{eqnarray*} Measurement of the mass of the baryon relative to the meson gives MeV. This result provides the most precise measurement of the mass of the baryon to date
Measurement of the resonant and CP components in decays
28 pages 14 figures - See paper for full list of authorsThe resonant structure of the reaction is studied using data from 3 fb of integrated luminosity collected by the LHCb experiment, one-third at 7 Tev center-of-mass energy and the remainder at 8 Tev. The invariant mass of the pair and three decay angular distributions are used to determine the fractions of the resonant and non-resonant components. Six interfering states: , , , , and are required to give a good description of invariant mass spectra and decay angular distributions. The positive and negative CP fractions of each of the resonant final states are determined. The meson is not seen and the upper limit on its presence, compared with the observed rate, is inconsistent with a model of tetraquark substructure for these scalar mesons at the eight standard deviation level. In the model, the absolute value of the mixing angle between the and the scalar mesons is limited to be less than at 90% confidence level