# Search for violations of Lorentz invariance and $CPT$ symmetry in $B^0_{(s)}$ mixing

LHCb Collaboration; Bernet, R; Müller, K; Steinkampf, O; Straumann, U; Vollhardt, A; et al (2016). Search for violations of Lorentz invariance and $CPT$ symmetry in $B^0_{(s)}$ mixing. Physical Review Letters, 116:241601.

## Abstract

Violations of $CPT$ symmetry and Lorentz invariance are searched for by studying interference effects in $B^0$ mixing and in $B^0_s$ mixing. Samples of $B^0\to J/\psi K^0_{\mathrm{S}}$ and $B^0_s\to J/\psi K^+ K^-$ decays are recorded by the LHCb detector in proton--proton collisions at centre-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 $\Delta a_{\mu}$ with precisions of $\mathcal{O}(10^{-15})$ and $\mathcal{O}(10^{-14})$ GeV for the $B^0$ and $B^0_s$ systems, respectively. With no assumption on Lorentz (non-)invariance, the $CPT$-violating parameter $z$ in the $B^0_s$ system is measured for the first time and found to be $\mathcal{R}e(z) = -0.022 \pm 0.033 \pm 0.005$ and $\mathcal{I}m(z) = 0.004 \pm 0.011\pm 0.002$, where the first uncertainties are statistical and the second systematic.

## Abstract

Violations of $CPT$ symmetry and Lorentz invariance are searched for by studying interference effects in $B^0$ mixing and in $B^0_s$ mixing. Samples of $B^0\to J/\psi K^0_{\mathrm{S}}$ and $B^0_s\to J/\psi K^+ K^-$ decays are recorded by the LHCb detector in proton--proton collisions at centre-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 $\Delta a_{\mu}$ with precisions of $\mathcal{O}(10^{-15})$ and $\mathcal{O}(10^{-14})$ GeV for the $B^0$ and $B^0_s$ systems, respectively. With no assumption on Lorentz (non-)invariance, the $CPT$-violating parameter $z$ in the $B^0_s$ system is measured for the first time and found to be $\mathcal{R}e(z) = -0.022 \pm 0.033 \pm 0.005$ and $\mathcal{I}m(z) = 0.004 \pm 0.011\pm 0.002$, where the first uncertainties are statistical and the second systematic.

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