T-odd Triple-product Asymmetries Research Articles

Measurement of CP violation in the {B}_s^0to phi phi decay and search for the B0\u2192 \u03d5\u03d5 decay

A measurement of the time-dependent CP-violating asymmetry in {B}_s^0to phi phi decays is presented. Using a sample of proton-proton collision data corresponding to an integrated luminosity of 5.0 fb−1 collected by the LHCb experiment at centre-of-mass energies sqrt{s} = 7 TeV in 2011, 8 TeV in 2012 and 13 TeV in 2015 and 2016, a signal yield of around 9000 {B}_s^0to phi phi decays is obtained. The CP-violating phase {phi}_s^{soverline{s}s} is measured to be −0.073 ± 0.115(stat) ± 0.027(syst) rad, under the assumption it is independent of the helicity of the ϕϕ decay. In addition, the CP-violating phases of the transverse polarisations under the assumption of CP conservation of the longitudinal phase are measured. The helicity-independent direct CP-violation parameter is also measured, and is found to be |λ| = 0.99 ± 0.05(stat) ± 0.01(syst). In addition, T-odd triple-product asymmetries are measured. The results obtained are consistent with the hypothesis of CP conservation in overline{b}to overline{s}soverline{s}s transitions. Finally, a limit on the branching fraction of the B0 → ϕϕ decay is determined to be mathcal{B}left({B}^0to phi phi right)<2.7times {10}^{-8} at 90 % confidence level.

CPTviolation and triple-product correlations inBdecays

The T-odd triple product (TP) asymmetries in B decays to a pair of vector mesons are treated as a good probe of CP violation because of the CPT symmetry. If CPT is no longer a good symmetry, such correlations between T-odd and CP-odd observables do not exist, and one might get unexpected nonzero TP asymmetries as a signal for CPT violation. We give a general formalism of TP asymmetries in the presence of CPT violation, either in decay or in neutral meson mixing. We also discuss how the observables depending on the transversity amplitudes are modified, and compare our expressions with the LHCb results, showing that the study of TP asymmetries might turn out to be one of the best probes for CPT violation.