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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(µþs 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*+³Ýμν̄)/µþ(µþ⁰ s→Xμν̄)=(3.3±1.0±0.4)%, and B(B⁰ s→D⁺ s1³Ýμν̄)/µþ(µþ⁰ 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.

Abstract:

The Ā/A and Ā/K0S production ratios are measured by the LHCb detector from 0.3 nb-1 of pp collisions delivered by the LHC at s√ = 0.9TeV and 1.8 nb-1 at s√ = 7TeV. Both ratios are presented as a function of transverse momentum, pT, and rapidity, y, in the ranges 0.15 < pT < 2.50GeV/c and 2.0 < y < 4.5. Results at the two energies are in good agreement as a function of rapidity loss, Δy = ybeam - y, and are consistent with previous measurements. The ratio Ā/A, measuring the transport of baryon number from the collision into the detector, is smaller in data than predicted in simulation, particularly at high rapidity. The ratio Ā/K0S , measuring the baryon-to-meson suppression in strange quark hadronisation, is significantly larger than expected.

Abstract:

The cross-section for inclusive Φ meson production in pp collisions at a centre-of-mass energy of s=7 TeV has been measured with the LHCb detector at the Large Hadron Collider. The differential cross-section is measured as a function of the Φ transverse momentum pT and rapidity y in the region 0.6