Search for Violations of Lorentz Invariance and CPT Symmetry in B^0_(s) Mixing

Violations of C P T symmetry and Lorentz invariance are searched for by studying interference effects in B 0 mixing and in B 0 s mixing. Samples of B 0 → J / ψ K 0 S and B 0 s → J / ψ K + K − decays are recorded by the LHCb detector in proton-proton collisions at center-of-mass energies of 7 and 8 TeV, corresponding to an integrated luminosity of 3

fb − 1 . No periodic variations of the particle-antiparticle mass differences are found, consistent with Lorentz invariance and C P T symmetry. Results are expressed in terms of the standard model extension parameter Δ a μ with precisions of O ( 10 − 15 ) and O ( 10 − 14 )

GeV for the B 0 and B 0 s systems, respectively. With no assumption on Lorentz (non)invariance, the C P T -violating parameter z in the B 0 s system is measured for the first time and found to be R e ( z ) = − 0.022 ± 0.033 ± 0.005 and I m ( z ) = 0.004 ± 0.011 ± 0.002 , where the first uncertainties are statistical and the second systematic.