Search for Violations of Lorentz Invariance and CPT Symmetry in B0(s) Mixing

Violations of CPT symmetry and Lorentz invariance are searched for by studying interference effects in B0 mixing and in B0s mixing. Samples of B0 → J/ψ K0S and B0s → 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 CPT symmetry. Results are expressed in terms of the standard model extension parameter Δaμ with precisions of O(10^−15) and O(10^−14) GeV for the B0 and B0s systems, respectively. With no assumption on Lorentz (non)invariance, the CPT-violating parameter z in the B0s system is measured for the first time and found to be Re(z) = −0.022 ± 0.033 ± 0.005 and Im(z) = 0.004 ± 0.011 ± 0.002, where the first uncertainties are statistical and the second systematic.