PT Journal AU ATLAS Collaboration (Aad, Gea Alvarez Piqueras, D Cabrera Urban, S Castillo Gimenez, V Costa, MJ Fernandez Martinez, P Ferrer, A Fiorini, L Fuster, J Garcia, C Garcia Navarro, JE Gonzalez de la Hoz, S Hernandez Jimenez, Y Higon-Rodriguez, E Irles Quiles, A Jimenez Pena, J Kaci, M King, M Lacasta, C Lacuesta, VR Marti-Garcia, S Mitsou, VA Oliver Garcia, E Pedraza Lopez, S Perez Garcia-Estañ, MT Romero Adam, E Ros, E Salt, J Sanchez Martinez, V Soldevila, U Sanchez, J Valero, A Valladolid Gallego, E Valls Ferrer, JA Vos, M TI Measurement of the branching ratio Gamma(Lambda(0)(b) -> Psi(2S)Lambda(0))/ Gamma(Lambda(0.)(b) -> J/Psi Lambda(0)) with the ATLAS detector SO Physics Letters B JI Phys. Lett. B PY 2015 BP 63 EP 80 VL 751 DI 10.1016/j.physletb.2015.10.009 LA English AB An observation of the Lambda(0)(b) -> Psi (2S) Lambda(0) decay and a comparison of its branching fraction with that of the Lambda(0)(b) -> Psi (2S) Lambda(0) decay has been made with the ATLAS detector in proton-proton collisions at root s = 8 TeVat the LHC using an integrated luminosity of 20.6fb(-1). The J/Psi and Psi(2S) mesons are reconstructed in their decays to a muon pair, while the Lambda(0) -> p pi(-) decay is exploited for the Lambda(0) 0baryon reconstruction. The Lambda(0)(b) baryons are reconstructed with transverse momentum p(T)> 10 GeVand pseudorapidity vertical bar eta vertical bar < 2.1. The measured branching ratio of the Lambda(0)(b) -> Psi (2S) Lambda(0) and Lambda(0)(b) -> Psi (2S) Lambda(0) decays is Gamma(Lambda(0)(b) -> Psi (2S) Lambda(0)) / Gamma(Lambda(0)(b) -> Psi (2S) Lambda(0)) = 0.501 +/- 0.033(stat) +/- 0.019(syst), lower than the expectation from the covariant quark model. ER