210 research outputs found
Measurement of the time-dependent CP asymmetry in B0 -> J/ψ KS0 decays
No full textThis Letter reports a measurement of the CP violation observables SJ/ψK0S and CJ/ψK0S in the decay channel B0→J/ψK0S performed with 1.0 fb−1 of pp collisions at s√=7 TeV collected by the LHCb experiment. The fit to the data yields SJ/ψK0S=0.73±0.07(stat)±0.04(syst) and CJ/ψK0S=0.03±0.09(stat)±0.01(syst). Both values are consistent with the current world averages and within
expectations from the Standard Model
Search for direct CP violation in D0→h−h+ modes using semileptonic B decays
No full textA search for direct CP violation in D0 → h-h+ (where h = K or π) is presented using data corresponding to an integrated luminosity of 1.0 fb-1 collected in 2011 by LHCb in pp collisions at a centre-of-mass energy of 7 TeV. The analysis uses D0 mesons produced in inclusive semileptonic b-hadron decays to the D0μX final state, where the charge of the accompanying muon is used to tag the flavour of the D0 meson. The difference in the CP-violating asymmetries between the two decay channels is measured to be ΔACP = ACP(K-K+) - ACP(π-π+) = (0.49± 0.30 (stat) ± 0.14 (syst))%
Measurement of the B-s(o) -> Ds-Ds+ and B-s(o) -> Ds-Ds+ Effective Lifetimes
No full textThe first measurement of the effective lifetime of the B̄s0 meson in the decay B̄s0→Ds-Ds+ is reported using a proton-proton collision data set, corresponding to an integrated luminosity of 3 fb-1, collected by the LHCb experiment. The measured value of the B̄s0→Ds-Ds+ effective lifetime is 1.379±0.026±0.017 ps, where the uncertainties are statistical and systematic, respectively. This lifetime translates into a measurement of the decay width of the light B̄s0 mass eigenstate of ΓL=0.725±0. 014±0.009 ps-1. The B̄s0 lifetime is also measured using the flavor-specific B̄s0→D-Ds+ decay to be 1.52±0.15±0.01 ps. © 2014 CERN, for the LHCb Collaboration
Combined QCD and electroweak analysis of HERA data
No full textA simultaneous fit of parton distribution functions (PDFs) and electroweak parameters to HERA data on deep inelastic scattering is presented. The input data are the neutral current and charged current inclusive cross sections which were previously used in the QCD analysis leading to the HERAPDF2.0 PDFs. In addition, the polarisation of the electron beam was taken into account for the ZEUS data recorded between 2004 and 2007. Results on the vector and axial-vector couplings of the Z boson to u- and d-type quarks, on the value of the electroweak mixing angle and the mass of the W boson are presented. The values obtained for the electroweak parameters are in agreement with Standard Model predictions.A simultaneous fit of parton distribution functions (PDFs) and electroweak parameters to HERA data on deep inelastic scattering is presented. The input data are the neutral current and charged current inclusive cross sections which were previously used in the QCD analysis leading to the HERAPDF2.0 PDFs. In addition, the polarization of the electron beam was taken into account for the ZEUS data recorded between 2004 and 2007. Results on the vector and axial-vector couplings of the Z boson to u- and d-type quarks, on the value of the electroweak mixing angle and the mass of the W boson are presented. The values obtained for the electroweak parameters are in agreement with Standard Model predictions.A simultaneous fit of parton distribution functions (PDFs) and electroweak parameters to HERA data on deep inelastic scattering is presented. The input data are the neutral current and charged current inclusive cross sections which were previously used in the QCD analysis leading to the HERAPDF2.0 PDFs. In addition, the polarisation of the electron beam was taken into account for the ZEUS data recorded between 2004 and 2007. Results on the vector and axial-vector couplings of the Z boson to u- and d-type quarks, on the value of the electroweak mixing angle and the mass of the W boson are presented. The values obtained for the electroweak parameters are in agreement with Standard Model predictions
Photoproduction of isolated photons, inclusively and with a jet, at HERA
No full textThe photoproduction of isolated photons, both inclusive and together with a jet, has been measured with the ZEUS detector at HERA using an integrated luminosity of 374 pb−1. Differential cross sections are presented in the isolated-photon transverse-energy and pseudorapidity ranges and −0.7<ηγ<0.9, and for jet transverse-energy and pseudorapidity ranges and −1.5<ηjet<1.8, for exchanged-photon virtualities Q2<1 GeV2. Differential cross sections are also presented for inclusive isolated-photon production as functions of the transverse energy and pseudorapidity of the photon. Higher-order theoretical calculations are compared to the results
Measurement of the cross-section ratio σψ(2S)/σJ/ψ(1S) in deep inelastic exclusive ep scattering at HERA
No full textThe exclusive deep inelastic electroproduction of ψ(2S) and J/ψ(1S) at an ep centre-of-mass energy of 317 GeV has been studied with the ZEUS detector at HERA in the kinematic range 2<Q2<80 GeV2, 30<W<210 GeV and |t|<1 GeV2, where Q2 is the photon virtuality, W is the photon–proton centre-of-mass energy and t is the squared four-momentum transfer at the proton vertex. The data for 2<Q2<5 GeV2 were taken in the HERA I running period and correspond to an integrated luminosity of 114 pb−1. The data for 5<Q2<80 GeV2 are from both HERA I and HERA II periods and correspond to an integrated luminosity of 468 pb−1. The decay modes analysed were μ+μ− and J/ψ(1S)π+π− for the ψ(2S) and μ+μ− for the J/ψ(1S). The cross-section ratio σψ(2S)/σJ/ψ(1S) has been measured as a function of Q2,W and t. The results are compared to predictions of QCD-inspired models of exclusive vector-meson production
Production of exclusive dijets in diffractive deep inelastic scattering at HERA
No full textProduction of exclusive dijets in diffractive deep inelastic e±p scattering has been measured with the ZEUS detector at HERA using an integrated luminosity of 372 pb-1. The measurement was performed for γ∗–p centre-of-mass energies in the range 9025GeV2. Energy flows around the jet axis are presented. The cross section is presented as a function of β and ϕ, where β=x/xIP, x is the Bjorken variable and xIP is the proton fractional longitudinal momentum loss. The angle ϕ is defined by the γ∗–dijet plane and the γ∗–e± plane in the rest frame of the diffractive final state. The ϕ cross section is measured in bins of β. The results are compared to predictions from models based on different assumptions about the nature of the diffractive exchange
Deep inelastic cross-section measurements at largeywith the ZEUS detector at HERA
No full textThe reduced cross sections for e+p deep inelastic scattering have been measured with the ZEUS detector at HERA at three different center-of-mass energies, 318, 251 and 225 GeV. The cross sections, measured double differentially in Bjorken x and the virtuality, Q2, were obtained in the region 0.13≤y≤0.75, where y denotes the inelasticity and 5≤Q2≤110 GeV2. The proton structure functions F2 and FL were extracted from the measured cross sections
- …
