Observation of Z production in proton-lead collisions at LHCb

The first observation of Z boson production in proton-lead collisions at a centre-of-mass energy per proton-nucleon pair of root(s) N N = 5TeV is presented. The data sample corresponds to an integrated luminosity of 1.6 nb(-1) collected with the LHCb detector. The Z candidates are reconstructed from pairs of oppositely charged muons with pseudorapidities between 2.0 and 4.5 and transverse momenta above 20 GeV/c. The invariant dimuon mass is restricted to the range 60-120 GeV/c. The Z production cross-section is measured to be sigma(Z ->mu+mu-) (fwd) = 13.5(-4.0)(+5.4)(stat.) +/- 1.2(syst.) nb in the direction of the proton beam and sigma(Z ->mu+mu-) (bwd) = 10.7(-5.1)(+8.4)(stat.) +/- 1.0(syst.) nb in the direction of the lead beam, where the first uncertainty is statistical and the second systematic

Precision Measurement of CP Violation in B-S(0) -> J/Psi K+K- Decays

The time-dependent CP asymmetry in Bs0\u2192J/\u3c8K+K- decays is measured using pp collision data, corresponding to an integrated luminosity of 3.0fb-1, collected with the LHCb detector at center-of-mass energies of 7 and 8 TeV. In a sample of 96000 Bs0\u2192J/\u3c8K+K- decays, the CP-violating phase \u3c6s is measured, as well as the decay widths \u393L and \u393H of the light and heavy mass eigenstates of the Bs0-B\uafs0 system. The values obtained are \u3c6s=-0.058\ub10.049\ub10.006rad, \u393s 61(\u393L+\u393H)/2=0.6603\ub10.0027\ub10.0015ps-1, and \u394\u393s 61\u393L-\u393H=0.0805\ub10.0091\ub10.0032ps-1, where the first uncertainty is statistical and the second, systematic. These are the most precise single measurements of those quantities to date. A combined analysis with Bs0\u2192J/\u3c8\u3c0+\u3c0- decays gives \u3c6s=-0.010\ub10.039rad. All measurements are in agreement with the standard model predictions. For the first time, the phase \u3c6s is measured independently for each polarization state of the K+K- system and shows no evidence for polarization dependence

Observation of Two New Xi(-)(b) Baryon Resonances

Two structures are observed close to the kinematic threshold in the \u39eb0\u3c0- mass spectrum in a sample of proton-proton collision data, corresponding to an integrated luminosity of 3.0fb-1, recorded by the LHCb experiment. In the quark model, two baryonic resonances with quark content bds are expected in this mass region: the spin-parity JP=(1/2)+ and JP=(3/2)+ states, denoted \u39eb\u2032- and \u39eb 17-. Interpreting the structures as these resonances, we measure the mass differences and the width of the heavier state to be m(\u39eb\u2032-)-m(\u39eb0)-m(\u3c0-)=3.653\ub10.018\ub10.006MeV/c2, m(\u39eb 17-)-m(\u39eb0)-m(\u3c0-)=23.96\ub10.12\ub10.06MeV/c2, \u393(\u39eb 17-)=1.65\ub10.31\ub10.10MeV, where the first and second uncertainties are statistical and systematic, respectively. The width of the lighter state is consistent with zero, and we place an upper limit of \u393(\u39eb\u2032-)<0.08MeV at 95% confidence level. Relative production rates of these states are also reported

Measurement of relative branching fractions of B decays to psi(2S) and J/psi mesons

The relative rates of B-meson decays into J/psi and psi(2S) mesons are measured for the three decay modes in pp collisions recorded with the LHCb detector. The ratios of branching fractions (B) are measured to be B(B+ -> psi(2S)K+)/B(B+ -> J/psi K+) = 0.594 +/- 0.006(stat) +/- 0.016(syst) +/- 0.015(R-psi), B(B-0 -> psi(2S)K*(0))/B(B-0 -> J/psi K*(0)) = 0.476 +/- 0.014(stat) +/- 0.010(syst) +/- 0.012(R-psi), B(B-s(0) -> psi(2S)phi)/B(B-s(0) -> J/psi phi) = 0.489 +/- 0.026(stat) +/- 0.021(syst) +/- 0.012(R-psi), where the third uncertainty is from the ratio of the psi(2S) and J/psi branching fractions to mu(+)mu(-). RI Galli, Domenico/A-1606-2012; Sarti, Alessio/I-2833-2012; Petrolini, Alessandro/H-3782-2011; Carbone, Angelo/C-8289-2012; de Paula, Leandro/I-9278-2012; manca, giulia/I-9264-2012; Patrignani, Claudia/C-5223-2009; Marconi, Umberto/J-2263-2012; de Simone, Patrizia/J-3549-2012; Cardini, Alessandro/J-5736-2012; Teodorescu, Eliza/K-3044-201

Framework TDR for the LHCb Upgrade

This document is a Framework Technical Design Report for the upgrade of the LHCb experiment. It adds to the information in the Letter of Intent, in particular concerning the foreseen schedule, cost and participating institutes. Updates are given for the physics performance, based on the experience gained with the first full year of data taking, on the detector requirements and the progress of the sub-system R&D. Within the framework presented here, it is expected that the individual sub-system TDRs will follow on completion of the R&D phase in the next year

Precision measurement of the ratio of the Lambda(0)(b) to (B)over-bar(0) lifetimes

The LHCb measurement of the lifetime ratio of the Lambda(0)(b) baryon to the (B) over bar (0) meson is updated using data corresponding to an integrated luminosity of 3.0 fb(-1) collected using 7 and 8 TeV centre-of-mass energy pp collisions at the LHC. The decay modes used are Lambda(0)(b) -> J/psi pK(-) and (B) over bar (0) -> J/psi pi K-+(-), where the pi K-+(-) mass is consistent with that of the (K) over bar*(0)(892) meson. The lifetime ratio is determined with unprecedented precision to be 0.974 +/- 0.006 +/- 0.004, 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 (B) over bar (0) lifetime, the Lambda(0)(b) lifetime is found to be 1.479 +/- 0.009 +/- 0.010 ps

Observation of Excited Lambda(0)(b) Baryons

Using pp collision data corresponding to 1.0 fb-1 integrated luminosity collected by the LHCb detector, two narrow states are observed in the Lambda0b pi+ pi- spectrum with masses 5911.97+-0.12(stat)+-0.02(syst)+- 0.66(Lambda0b mass) MeV/c2 and 5919.77+-0.08(stat)+-0.02(syst)+-0.66(Lambda0b mass) MeV/c2. The significances of the observations are 5.2 and 10.2 standard deviations, respectively. These states are interpreted as the orbitally excited Lambda0b baryons, Lambda*0b(5912) and Lambda*0b(5920)