The B0s ; B0 mixing frequencies, Δms ; Δmd, are measured using a data sample corresponding to an integrated luminosity of 1.0 fb−1 collected by the LHCb experiment in pp collisions at a centre of mass energy of 7 TeV during 2011. Around 1.8 × 106 candidate events are selected of the type B0(s) → D−(s)μ+ (+ anything), where about half are from peaking ; combinatorial backgrounds. To determine the B decay times, a correction is required for the momentum carried by missing particles, which is performed using a simulation-based statistical method. Associated production of muons or mesons allows us to tag the initialstate flavour ; so to resolve oscillations due to mixing. We obtain Δms = (17.93 ± 0.22 (stat) ± 0.15 (syst)) ps−1, Δmd = (0.503 ± 0.011 (stat) ± 0.013(syst)) ps−1. The hypothesis of no oscillations is rejected by the equivalent of 5.8 standard deviations for B0s ; 13.0 standard deviations for B0. This is the first observation of B0s mixing to be made using only semileptonic decays. © 2013, CERN for the benefit of the LHCb collaboration.
Observation of B0s – B0s mixing ; measurement of mixing frequencies using semileptonic B decays
PALANO, Antimo;PAPPAGALLO, MARCO IGNAZIO;
2013-01-01
Abstract
The B0s ; B0 mixing frequencies, Δms ; Δmd, are measured using a data sample corresponding to an integrated luminosity of 1.0 fb−1 collected by the LHCb experiment in pp collisions at a centre of mass energy of 7 TeV during 2011. Around 1.8 × 106 candidate events are selected of the type B0(s) → D−(s)μ+ (+ anything), where about half are from peaking ; combinatorial backgrounds. To determine the B decay times, a correction is required for the momentum carried by missing particles, which is performed using a simulation-based statistical method. Associated production of muons or mesons allows us to tag the initialstate flavour ; so to resolve oscillations due to mixing. We obtain Δms = (17.93 ± 0.22 (stat) ± 0.15 (syst)) ps−1, Δmd = (0.503 ± 0.011 (stat) ± 0.013(syst)) ps−1. The hypothesis of no oscillations is rejected by the equivalent of 5.8 standard deviations for B0s ; 13.0 standard deviations for B0. This is the first observation of B0s mixing to be made using only semileptonic decays. © 2013, CERN for the benefit of the LHCb collaboration.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.