arXiv:1202.4717·v4·High Energy Physics — Experiment
Determination of the sign of the decay width difference in the B_s system
LHCb Collaboration: R. Aaij · C. Abellan Beteta · B. Adeva · M. Adinolfi · C. Adrover · A. Affolder · Z. Ajaltouni · J. Albrecht · F. Alessio · M. Alexander · G. Alkhazov · P. Alvarez Cartelle
Abstract
The interference between the K+K- S-wave and P-wave amplitudes in B_s -> J/psi K+K- decays with the K+K- pairs in the region around the phi(1020) resonance is used to determine the variation of the difference of the strong phase between these amplitudes as a function of K+K- invariant mass. Combined with the results from our CP asymmetry measurements in B_s -> J/psi phi decays, we conclude that the B_s mass eigenstate that is almost CP =+1 is lighter and decays faster than the mass eigenstate that is almost CP =-1. This determines the sign of the decay width difference DeltaGamma_s == Gamma_L -Gamma_H to be positive. Our result also resolves the ambiguity in the past measurements of the CP violating phase phi_s to be close to zero rather than pi. These conclusions are in agreement with the Standard Model expectations.
Comments: 7 pages, 4 figures, published on Physical Review Letters