LHCb presents latest study of beauty oscillations

LHCb has a new result on the probability that beauty mesons oscillate into their antimatter counterparts and vice versa

Today at the International Workshop on the CKM Unitarity Triangle, CKM2014, in Vienna, Austria, the LHCb collaboration has presented the results of a measurement of the "semileptonic asymmetry", adsl.

This parameter is related to a difference in the probability of a beauty meson, B0, oscillating into its antiparticle, B0, and the probability of the reverse process. Any difference would be a manifestation of the matter-antimatter difference known as CP-violation.

The label "d" indicates decays of B0 mesons composed of b antiquarks and d quarks, while "sl" (semileptonic) indicates that leptons, in this case muons, are present among the decay products. When a B0 meson decays in this manner, the charge of the lepton determines whether it is a decay of a B0 or its antiparticle, B0. The presence of a “wrong-sign” lepton in a decay of a B0 meson indicates that a transition to a B0 meson took place before decay.

LHCb used these "wrong-sign" B0 and B0 decays in this analysis to measure adsl. The measurement is interesting because its value is predicted to be very small by the Standard Model; any significant deviation from zero could indicate a contribution of as-yet-undiscovered particles in B0 - B0 oscillations.

Today the LHCb collaboration presented the new preliminary value of adsl = (-0.02 ± 0.19 ± 0.30)% using the full 3 fb-1 2011 and 2012 data sample from the LHC. The collaboration recently published the corresponding value for the strange beauty meson B0s, composed of b antiquarks and s quarks. Using 1 fb-1 of data taken in 2011, they found assl = (-0.06 ± 0.50 ± 0.36)%. Both results indicate no CP-violation to be present within the sensitivity of the measurements and are hence are consistent with the very small values predicted by the Standard Model.

Read more: "Measurement of the semileptonic asymmetry, adsl" – LHCb