Sizable Time-reversal violating effects in bottom baryon decays

Abstract

We study time-reversal~(T) asymmetries in the charmless two-body decays of antitriplet bottom baryons. We find that in ${\mathbf{B}}_b\to {\mathbf{B}}_{n}P$ with ${\mathbf{B}}_b=({\Xi }_b^{-},{\Xi }_b^0,{\Lambda }_b)$ and ${\mathbf{B}}_n(P)$ a octet baryon (pseudoscalar meson), the positive and negative helicity amplitudes are both sizable, resulting in the large T-violating effects. Particularly, the T-odd parameters, ${\beta }_w$, for the color-enhanced channels are expected to be around $40\%$ and $-25\%$ in $b\to s$ and $b\to d$ transitions for the standard model, which can be measured by the experiments at LHCb, respectively. On the other hand, in ${\mathbf{B}}_b\to {\mathbf{B}}_{n}V(\gamma )$ with $V(\gamma )$ a vector meson~(photon), the decays are predominated by a single helicity amplitude, and the T violating effects by the correlations among spins are suppressed. We also explore the T violating observables for the ${\Xi }_b$ decays based on the angular distributions.

Comments: 15 pages, 2 figures, revised version accepted by JHEP