# Observation of Time-Reversal Violation in the B0 Meson System

Abstract : Although CP violation in the B meson system has been well established by the B factories, there has been no direct observation of time reversal violation. The decays of entangled neutral B mesons into definite flavor states ($B^0$ or $\bar{B}^0$), and $J/\psi K_S^0$ or $c\bar{c} K_S^0$ final states (referred to as $B_+$ or $B_-$), allow comparisons between the probabilities of four pairs of T-conjugated transitions, for example, $\bar{B}^0 \rightarrow B_-$ and $B_- \rightarrow \bar{B}^0$, as a function of the time difference between the two B decays. Using 468 million $B\bar{B}$ pairs produced in $\Upsilon(4S)$ decays collected by the BABAR detector at SLAC, we measure T-violating parameters in the time evolution of neutral B mesons, yielding $\Delta S_T^+ = -1.37 \pm 0.14 (stat.) \pm 0.06 (syst.)$ and $\Delta S_T^- = 1.17 \pm 0.18 (stat.) \pm 0.11 (syst.)$. These nonzero results represent the first direct observation of T violation in the B meson system, through the exchange of initial and final states in transitions that can only be connected by a T-symmetry transformation.
Document type :
Journal articles

http://hal.in2p3.fr/in2p3-00720925
Contributor : Sabine Starita <>
Submitted on : Thursday, July 26, 2012 - 10:57:08 AM
Last modification on : Sunday, March 31, 2019 - 1:34:18 AM

### Citation

J. P. Lees, V. Poireau, V. Tisserand, J. Garra Tico, E. Grauges, et al.. Observation of Time-Reversal Violation in the B0 Meson System. Physical Review Letters, American Physical Society, 2012, 109, pp.211801. ⟨10.1103/PhysRevLett.109.211801⟩. ⟨in2p3-00720925⟩

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