Time dependent angular analysis of the decay B-s(0) -> J/ψϕ and extraction of ΔΓ(s) and the CP-violating weak phase ϕ(s) by ATLAS

Abstract

A measurement of B0(s)→J/ψϕ decay parameters, including the CP -violating weak phase ϕ(s) and the decay width difference ΔΓ(s) is reported, using 4.9 fb⁻¹ of integrated luminosity collected in 2011 by the ATLAS detector from LHC pp collisions at a centre-of-mass energy √s=7 TeV. The mean decay width Γ(s) and the transversity amplitudes |A 0(0)|² and |A ∥(0)|² are also measured. The values reported for these parameters are: ϕ(s)=0.22±0.41 (stat.)±0.10 (syst.) rad, ΔΓ(s)=0.053±0.021 (stat.)±0.010 (syst.) ps⁻¹, Γ(s)=0.677±0.007 (stat.)±0.004 (syst.) ps⁻¹, |A0(0)|2=0.528±0.006 (stat.)±0.009 (syst.), |A∥(0)|2=0.220±0.008 (stat.)±0.007 (syst.) where the values quoted for ϕ(s) and ΔΓ(s) correspond to the solution compatible with the external measurements to which the strong phase δ(⊥) is constrained and where ΔΓ(s) is constrained to be positive. The fraction of S-wave KK or f₀ contamination through the decays B0(s)→J/ψK+K−(f₀) is measured as well and is found to be consistent with zero. Results for ϕ(s) and ΔΓ(s) are also presented as 68%, 90% and 95% likelihood contours, which show agreement with Standard Model expectations.