We present a measurement of the time-dependent CP-violating asymmetry in B_s -> J/psi phi decays, using data collected with the LHCb detector at the LHC. The decay time distribution of B_s -> J/psi ...phi is characterized by the decay widths Gamma_H and Gamma_L of the heavy and light mass eigenstates of the B_s-B_s-bar system and by a CP-violating phase phi_s. In a sample of about 8500 B_s -> J/psi phi events isolated from 0.37 fb^-1 of pp collisions at sqrt(s)=7 TeV we measure phi_s = 0.15 +/- 0.18 (stat) +/- 0.06 (syst) rad. We also find an average B_s decay width Gamma_s == (Gamma_L + Gamma_H)/2 = 0.657 +/- 0.009 (stat) +/- 0.008 (syst) ps^-1 and a decay width difference Delta Gamma_s == Gamma_L - Gamma_H} = 0.123 +/- 0.029 (stat) +/- 0.011 (syst) ps^-1. Our measurement is insensitive to the transformation (phi_s,DeltaGamma_s --> pi - phi_s, - Delta Gamma_s.
A measurement of the effective $B_srightarrow K^+K^-$ lifetime is presented using approximately $37 pb^{-1}$ of data collected by LHCb during 2010. This quantity can be used to put constraints on ...contributions from processes beyond the Standard Model in the $B_s$ meson system and is determined by two complementary approaches as $tau_{B_sto K^+K^-} = 1.440 pm 0.096 (stat) pm 0.008 (syst) pm 0.003 (model) ps$.
A search for the decays Bs -> mu+ mu- and B0 -> mu+ mu- is performed with 0.37 fb^-1 of pp collisions at sqrt{s} = 7 TeV collected by the LHCb experiment in 2011. The upper limits on the branching ...fractions are BR (Bs -> mu+ mu-) < 1.6 x 10^-8 and BR(B0 -> mu+ mu-) < 3.6 x 10^-9 at 95% confidence level. A combination of these results with the LHCb limits obtained with the 2010 dataset leads to BR (Bs -> mu+ mu-) < 1.4 x 10^-8 and BR (B0 -> mu+ mu-) < 3.2 x 10^-9 at 95% confidence level.
The first observation of the decay Bs0 -> K*0 anti-K*0 is reported using 35 pb^{-1} of data collected by LHCb in proton-proton collisions at a centre-of-mass energy of 7 TeV. A total of 49.8 \pm 7.5 ...signal events are observed, with a significance of 10.9 sigma. The branching fraction and the CP-averaged K*0 longitudinal polarization fraction are measured to be BR(Bs0 -> K*0 anti-K*0) = (2.81 \pm 0.46 (stat.) \pm 0.45 (syst.) \pm 0.34 (f_s/f_d))x10^{-5} and f_L = 0.31 \pm 0.12 (stat.) \pm 0.04 (syst.).
The B^0_s-\bar{B}^0_s oscillation frequency Delta m_s is measured with 36 pb^{-1} of data collected in pp collisions at \sqrt{s} = 7 TeV by the LHCb experiment at the Large Hadron Collider. A total ...of 1381 B^0_s -> D_s^- \pi^+ and \B^0_s -> D_s^- pi^+ pi^- pi^+ signal decays are reconstructed, with average decay time resolutions of 44 fs and 36 fs, respectively. An oscillation signal with a statistical significance of 4.6 sigma is observed. The measured oscillation frequency is Delta m_s = 17.63 \pm 0.11 (stat) \pm 0.02 (syst) ps^{-1}.
Measurements of the differential branching fraction and angular moments of the decay B super(0) arrow right K super(+) pi super(-) mu super(+) mu super(-) in the K super(+) pi super(-) invariant mass ...range 1330 < m(K super(+) pi super(-)) < 1530 MeV/c super(2) are presented. Proton-proton collision data are used, corresponding to an integrated luminosity of 3 fb super(-1) collected by the LHCb experiment. Differential branching fraction measurements are reported in five bins of the invariant mass squared of the dimuon system, q super(2), between 0.1 and 8.0 GeV super(2) /c super(4). For the first time, an angular analysis sensitive to the S-, P- and D-wave contributions of this rare decay is performed. The set of 40 normalised angular moments describing the decay is presented for the q super(2) range 1.1-6.0 GeV super(2) /c super(4). Figure not available: see fulltext.
(ProQuest: ... denotes formulae and/or non-USASCII text omitted; see image).A measurement of the differential branching fraction of the decay B super(0) arrow right K super()(892) super(0) mu ...super(+) mu super(-) is presented together with a determination of the S-wave fraction of the K super(+) pi super(-) system in the decay B super(0) arrow right K super(+) pi super(-) mu super(+) mu super(-). The analysis is based on pp-collision data corresponding to an integrated luminosity of 3 fb super(-1) collected with the LHCb experiment. The measurements are made in bins of the invariant mass squared of the dimuon system, q super(2). Precise theoretical predictions for the differential branching fraction of B super(0) arrow right K super()(892) super(0) mu super(+) mu super(-) decays are available for the q super(2) region 1.1 < q super(2) < 6.0 GeV super(2) /c super(4). In this q super(2) region, for the K super(+) pi super(-) invariant mass range 796 < m sub(K pi ) < 996 MeV/c super(2), the S-wave fraction of the K super(+) pi super(-) system in B super(0) arrow right K super(+) pi super(-) mu super(+) mu super(-) decays is found to be ... ... and the differential branching fraction of B super(0) arrow right K super()(892) super(0) mu super(+) mu super(-) decays is determined to be ... ... The differential branching fraction measurements presented are the most precise to date and are found to be in agreement with Standard Model predictions. Figure not available: see fulltext.
(ProQuest: ... denotes formulae and/or non-USASCII text omitted; see image).A measurement of the cross-section for W arrow right e nu production in pp collisions is presented using data corresponding ...to an integrated luminosity of 2 fb super(-1) collected by the LHCb experiment at a centre-of-mass energy of ... TeV. The electrons are required to have more than 20 GeV of transverse momentum and to lie between 2.00 and 4.25 in pseudorapidity. The inclusive W production cross-sections, where the W decays to e nu , are measured to be ... ... ... ... where the first uncertainties are statistical, the second are systematic, the third are due to the knowledge of the LHC beam energy and the fourth are due to the luminosity determination. Differential cross-sections as a function of the electron pseudorapidity are measured. The W super(+) /W super(-) cross-section ratio and production charge asymmetry are also reported. Results are compared with theoretical predictions at next-to-next-to-leading order in perturbative quantum chromodynamics. Finally, in a precise test of lepton universality, the ratio of W boson branching fractions is determined to be ... ... where the first uncertainty is statistical and the second is systematic. Figure not available: see fulltext.
(ProQuest: ... denotes formulae and/or non-USASCII text omitted; see image).The ratio of branching fractions ... 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 fb super(-1). It is found to be R sub( )K pi = 0.079 plus or minus 0.007 plus or minus 0.003, 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. Figure not available: see fulltext.
(ProQuest: ... denotes formulae and/or non-USASCII text omitted; see image).A measurement of the production cross-section of Z bosons in pp collisions at ... TeV is presented using dimuon and ...dielectron final states in LHCb data. The cross-section is measured for leptons with pseudorapidities in the range 2.0 < eta < 4.5, transverse momenta p sub(T) > 20 GeV and dilepton invariant mass in the range 60 < m() < 120 GeV. The integrated cross-section from averaging the two final states is sigma sub( Z) super()=194.3 plus or minus 0.9 plus or minus 3.3 plus or minus 7.6 pb, where the first uncertainty is statistical, the second is due to systematic effects, and the third is due to the luminosity determination. In addition, differential cross-sections are measured as functions of the Z boson rapidity, transverse momentum and the angular variable sub( eta ) super(*). Figure not available: see fulltext.
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