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Observation of Time-Reversal Violation in the B0 Meson System

J. P. Lees et al. (The BABAR Collaboration)
Phys. Rev. Lett. 109, 211801 – Published 19 November 2012
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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 (B0 or B¯0), and J/ψKL0 or cc¯KS0 final states (referred to as B+ or B), allow comparisons between the probabilities of four pairs of T-conjugated transitions, for example, B¯0B and BB¯0, as a function of the time difference between the two B decays. Using 468×106 BB¯ pairs produced in Υ(4S) decays collected by the BABAR detector at SLAC, we measure T-violating parameters in the time evolution of neutral B mesons, yielding ΔST+=1.37±0.14(stat)±0.06(syst) and ΔST=1.17±0.18(stat)±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.

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  • Received 24 July 2012

DOI:https://doi.org/10.1103/PhysRevLett.109.211801

© 2012 American Physical Society

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Particle Decays Point to an Arrow of Time

Published 19 November 2012

An experiment studying B meson decays makes a direct observation of time-reversal violation without relying on assumed relationships with other fundamental symmetries.

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Vol. 109, Iss. 21 — 21 November 2012

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