Measurement of the parity-violating asymmetry parameter alpha_b and the helicity amplitudes for the decay Lambda_b->J/psi+Lambda with the ATLAS detector
arXiv:1404.1071 · doi:10.1103/PhysRevD.89.092009
Abstract
A measurement of the parity-violating decay asymmetry parameter, alpha_b, and the helicity amplitudes for the decay Lambda_b->J/psi(mu mu)+Lambda(p pi) is reported. The analysis is based on 1400 Lambda_b and anti-Lambda_b baryons selected in 4.6/fb of proton-proton collision data with a center-of-mass energy of 7 TeV recorded by the ATLAS experiment at the LHC. By combining the Lambda_b and anti-Lambda_b samples under the assumption of CP conservation, the value of alpha_b is measured to be 0.30+/-0.16(stat)+/-0.06(syst). This measurement provides a test of theoretical models based on perturbative QCD or heavy-quark effective theory.
12 pages plus author list (25 pages total), 6 figures, 6 tables, submitted to Physical Review D, All figures including auxiliary figures are available at http://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/BPHY-2013-03/