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Abstract:

Measurements of the total and differential cross sections dσ/dpTB and dσ/dyB for B⁺ mesons produced in pp collisions at √s=7TeV are presented. The data correspond to an integrated luminosity of 5.8pb^-1 collected by the CMS experiment operating at the LHC. The exclusive decay B⁺→J/ψ��⁺, with J/ψ→μ⁺μ^-, is used to detect B⁺ mesons and to measure the production cross section as a function of pTB and yB. The total cross section for pTB>5GeV and |yB|<2.4 is measured to be 28.1±2.4±2.0±3.1μb, where the first uncertainty is statistical, the second is systematic, and the last is from the luminosity measurement. © 2011 American Physical Society.

Abstract:

The collection of a large number of B-hadron decays to hadronic final states at the CDF II Detector is possible due to the presence of a trigger that selects events based on track impact parameters. However, the nature of the selection requirements of the trigger introduces a large bias in the observed proper-decay-time distribution. A lifetime measurement must correct for this bias, and the conventional approach has been to use a Monte Carlo simulation. The leading sources of systematic uncertainty in the conventional approach are due to differences between the data and the Monte Carlo simulation. In this paper, we present an analytic method for bias correction without using simulation, thereby removing any uncertainty due to the differences between data and simulation. This method is presented in the form of a measurement of the lifetime of the B^- using the mode B^-→D0π ^-. The B^- lifetime is measured as τB ^-=1.663±0.023±0.015ps, where the first uncertainty is statistical and the second systematic. This new method results in a smaller systematic uncertainty in comparison to methods that use simulation to correct for the trigger bias. © 2011 American Physical Society.

Abstract:

Using data collected with the LHCb detector in proton-proton collisions at a centre-of-mass energy of 7 TeV, the hadronic decay Bs ⁰→J/Ψf0(980) is observed. This CP eigenstate mode could be used to measure mixing-induced CP violation in the Bs ⁰ system. Using a fit to the Π⁺Π^- mass spectrum with interfering resonances gives Rf0/Φ≡Γ(Bs0→J/Ψf0,f0→Π⁺Π ^-)Γ(��s ⁰→J/Ψφ,φ →K⁺K^-)=0.252-0.032-0.033⁺ 0.046+0.027. In the interval ±90 MeV around 980 MeV, corresponding to approximately two full f0 widths we also find R' ≡ Γ(Bs0→J/Ψf0,f0→Π⁺Π^-)-980 Mev < 90 Mev)/Γ(Bs ⁰→J/Ψφ,φ→K ⁺K^-)=0.162±0.022±0.016, where in both cases the uncertainties are statistical and systematic, respectively. © 2011 CERN.

Abstract:

Using data collected with the LHCb detector in proton-proton collisions at a centre-of-mass energy of 7 TeV, the semileptonic decays B⁰ s→D⁺ s+Xμν̄ and B⁰ s→D⁰K⁺Xμν̄ are detected. Two structures are observed in the D0K+ mass spectrum at masses consistent with the known Ds1(2536)⁺ and Ds2*(2573)⁺ mesons. The measured branching fractions relative to the total B-s0 semileptonic rate are B(B⁰ s→Ds2*+��μν̄)/��(��⁰ s→Xμν̄)=(3.3±1.0±0.4)%, and B(B⁰ s→D⁺ s1��μν̄)/��(��⁰ s→Xμν̄)=(5.4±1.2±0.5)%, where the first uncertainty is statistical and the second is systematic. This is the first observation of the D*⁺ s2 state in B⁰ s decays; we also measure its mass and width. © 2011 CERN.

Abstract:

The LHCb experiment at the CERN Large Hadron Collider (LHC) will measure the CKM parameters of the Unitarity Triangle with high precision, and is designed to discover physics beyond the Standard Model in rare heavy-flavour decays. The experiment is configured in the forward direction and covers a unique rapidity range at the LHC, 1.9 < & < 4.9. This paper describes the detector components of LHCb and the operating performances, focusing on the vertex locator, particle identification, calorimetry and muon system. In 2010, LHCb recorded a total of 37.7 pb-1 of data at √s = 7 TeV with a data-taking efficiency ofbetterthan90%. A selection of LHCb physics results will be shown, and the prospects for data taking in 2011 will be discussed. © Copyright owned by the author(s) under the terms of the Creative Commons Attribution-Non Commercial-Share Alike Licence.