A study of the Z production cross-section in pp collisions at s√=7 TeV using tau final states

A measurement of the inclusive Z → ττ cross-section in pp collisions at s√=7TeV is presented based on a dataset of 1.0 fb−1 collected by the LHCb detector. Candidates for Z → τ τ decays are identified through reconstructed final states with two muons, a muon and an electron, a muon and a hadron, or an electron and a hadron. The production cross-section for Z bosons, with invariant mass between 60 and 120 GeV/c 2, which decay to τ leptons with transverse momenta greater than 20 GeV/c and pseudorapidities between 2.0 and 4.5, is measured to be σ pp→Z→ττ = 71.4 ± 3.5 ± 2.8 ± 2.5 pb; the first uncertainty is statistical, the second is systematic, and the third is due to the uncertainty on the integrated luminosity. The ratio of the cross-sections for Z → τ τ to Z → μμ is determined to be 0.93 ± 0.09, where the uncertainty is the combination of statistical, systematic, and luminosity uncertainties of the two measurements

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

The relative rates of B-meson decays into J/ψ and ψ(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 where the third uncertainty is from the ratio of the ψ(2S) and J/ψ branching fractions to μ + μ −

Measurement of ψ(2S) meson production in pp collisions at s√=7 TeV

The differential cross-section for the inclusive production of ψ(2S) mesons in pp collisions at √s = 7 TeV has been measured with the LHCb detector. The data sample corresponds to an integrated luminosity of 36 pb−1. The ψ(2S) mesons are reconstructed in the decay channels ψ(2S) → μ+μ− and ψ(2S) → J/ψπ+π−, with the J/ψ meson decaying into two muons. Results are presented both for promptly produced ψ(2S) mesons and for those originating from b-hadron decays. In the kinematic range pT(ψ(2S)) ≤ 16 GeV/c and 2 < y(ψ(2S)) ≤ 4.5 we measure σprompt ψ(2S) = 1.44 ± 0.01 (stat) ± 0.12 (syst) +0.20 −0.40 (pol) µb, σb ψ(2S) = 0.25 ± 0.01 (stat) ± 0.02 (syst) µb, where the last uncertainty on the prompt cross-section is due to the unknown ψ(2S) polarization. Recent QCD calculations are found to be in good agreement with our measurements. Combining the present result with the LHCb J/ψ measurements we determine the inclusive branching fraction B b → ψ(2S)X = 2.73 ± 0.06 (stat) ± 0.16 (syst) ± 0.24 (BF) × 10−3, where the last uncertainty is due to the B(b → J/ψX), B(J/ψ → μ+μ−) and B(ψ(2S) → e+e−) branching fraction uncertainties

Evidence for the decay B0 → J/ψω and measurementof the relative branching fractions of B0s meson decays to J/ψη and J/ψη′

First evidence of the B0→J/ψω decay is found and the B0s→J/ψη and B0s→J/ψη′ decays are studied using a dataset corresponding to an integrated luminosity of 1.0 fb−1 collected by the LHCb experimentin proton–proton collisions at a centre-of-mass energy of√s=7 TeV. The branching fractions of these decays are measured relative to that of the B0→J/ψρ0 decay: B(B0→J/ψω)B(B0→J/ψρ0)=0.89±0.19(stat)+0.07−0.13(syst),B(B0s→J/ψη)B(B0→J/ψρ0)=14.0±1.2(stat)+1.1−1.5(syst)+1.1−1.0(fdfs),B(B0s→J/ψη′)B(B0→J/ψρ0)=12.7±1.1(stat)+0.5−1.3(syst)+1.0−0.9(fdfs),where the last uncertainty is due to the knowledge of fd/fs, the ratio of b-quark hadronization factors thataccounts for the different production rate of B0 and B0s mesons. The ratio of the branching fractions of B0s→J/ψη′ and B0s→J/ψη decays is measured to be B(B0s→J/ψη′)B(B0s→J/ψη)=0.90±0.09(stat)+0.06−0.02(syst)

Prompt charm production inppcollisions at √s=7 TeV

Charm production at the LHC in pp collisions at √s=7 TeV is studied with the LHCb detector. The decays D0→K−π+,D+→K−π+π+,D∗+→D0(K−π+)π+,D+s→φ(K−K+)π+,Λ+c→pK−π+, and their charge conjugates are analysed in a data set corresponding to an integrated luminosity of 15 nb−1. Differential cross-sections dσ/dpT are measured for prompt production of the fivecharmed hadron species in bins of transverse momentum and rapidity in the region 0<pT<8GeV/c and 2.0<y<4.5. Theoretical predictions are compared to the measured differential cross-sections. The integrated cross-sections of the charm hadrons are computed in the above pT-y range, and their ratios arereported. A combination of the five integrated cross-section measurements gives σ(cc)pT<8GeV/c,2.0<y<4.5=1419±12(stat)±116(syst)±65(frag)μb,where the uncertainties are statistical, systematic, and due to the fragmentation functions

Measurements of the branching fractions of B+ → ppK¯ + decays

The branching fractions of the decay B+ → ppK¯ + for different intermediate states are measured using data, corresponding to an integrated luminosity of 1.0 fb−1, collected by the LHCb experiment. The total branching fraction, its charmless component (Mpp¯ < 2.85 GeV/c2) and the branching fractions via the resonant cc¯ states ηc(1S) and ψ(2S) relative to the decay via a J/ψ intermediate state are B(B+ → ppK¯ +)total B(B+ → J/ψK+ → ppK¯ +) = 4.91 ± 0.19 (stat) ± 0.14 (syst), B(B+ → ppK¯ +)Mpp¯<2.85 GeV/c2 B(B+ → J/ψK+ → ppK¯ +) = 2.02 ± 0.10 (stat) ± 0.08 (syst), B(B+ → ηc(1S)K+ → ppK¯ +) B(B+ → J/ψK+ → ppK¯ +) = 0.578 ± 0.035 (stat) ± 0.027 (syst), B(B+ → ψ(2S)K+ → ppK¯ +) B(B+ → J/ψK+ → ppK¯ +) = 0.080 ± 0.012 (stat) ± 0.009 (syst). Upper limits on the B+ branching fractions into the ηc(2S) meson and into the charmonium-like states X(3872) and X(3915) are also obtained

Measurement of the forward energy flow in pp collisions at √s = 7 TeV

The energy flow created in pp collisions at √s = 7 TeV is studied within the pseudorapidity range 1.9 <η< 4.9 with data collected by the LHCb experiment. The measurements are performed for inclusive minimum-bias interactions, hard scattering processes and events with an enhanced or suppressed diffractive contribution. The results are compared to predictions given by PYTHIA-based and cosmic-ray event generators, which provide different models of soft hadronic interactions

Exclusive J/ψ and ψ(2S) production in pp collisions at √s= 7 TeV

Exclusive J/ψ and ψ(2S) vector meson production has been observed in the dimuon channel using the LHCb detector. The cross-section times branching fractions to two muons with pseudorapidities between 2.0 and 4.5 are measured to be σpp→J/ψ(→μ+μ−)(2.0 < ημ± < 4.5) = 307 ± 21 ± 36 pb, σpp→ψ(2S)(→μ+μ−)(2.0 < ημ± < 4.5) = 7.8 ± 1.3 ± 1.0 pb, where the first uncertainties are statistical and the second are systematic. The measurements are found to be in good agreement with results from previous experiments and theoretical predictions. The J/ψ photoproduction cross-section has been measured as a function of the photon-proton centre-ofmass energy. The results are consistent with measurements obtained at HERA and confirm a similar power law behaviour for the photoproduction crosssection

Framework TDR for the LHCb Upgrade: Technical Design Report

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 yea

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

The relative rates of B-meson decays into J/ψ and ψ(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+ → ψ(2S)K+) B(B+ → J/ψK+) = 0.594 ± 0.006(stat) ± 0.016(syst) ± 0.015(Rψ ), B(B0 → ψ(2S)K∗0) B(B0 → J/ψK∗0) = 0.476 ± 0.014(stat) ± 0.010(syst) ± 0.012(Rψ ), B(B0 s → ψ(2S)φ) B(B0 s → J/ψφ) = 0.489 ± 0.026(stat) ± 0.021(syst) ± 0.012(Rψ ), where the third uncertainty is from the ratio of the ψ(2S) and J/ψ branching fractions to μ+μ−