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, ${\bar{B}}^0\to B_{-}$ and $B_{-}\to {\bar{B}}^0$, as a function of the time difference between the two B decays. Using 468 million $B\bar{B}$ pairs produced in ${\rm Y}(4S)$ 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 through the exchange of initial and final states in transitions that can only be connected by a T-symmetry transformation.

7 pages, 3 postscript figures, 1 table, appendix with 4 pages containing supplementary material. Accepted by Phys. Rev. Lett

References in corpus (3)

• An Improved Experimental Limit on the Electric Dipole Moment of the Neutron
• Time Reversal Violation from the entangled B0-antiB0 system
• Measurement of the charge asymmetry in semileptonic Bs decays

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