Abstract
We study time-reversal (T) asymmetries in the charmless two-body decays of antitriplet bottom baryons. We find that in Bb → BnP with Bb = ( {Xi}_b^{-} , {Xi}_b^0 , Λb) and Bn(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, βw, for the color-enhanced channels are expected to be around −40% and 25% in b → s and b → d transitions for the standard model, which can be measured by the experiments at LHCb, respectively. On the other hand, in Bb → BnV(γ) with V(γ) 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 Ξb decays based on the angular distributions.
Highlights
T-odd observablesThe naive T-odd observable is given by the asymmetry between λt = ±1/2, read as [64]
JHEP01(2022)128 spin [55,56,57,58,59,60,61,62]
We study time-reversal (T) asymmetries in the charmless two-body decays of antitriplet bottom baryons
Summary
The naive T-odd observable is given by the asymmetry between λt = ±1/2, read as [64]. In Bb → BnP , TV depends on the relative CP-odd phase between VubVu∗f and VtbVt∗f in the different helicity amplitudes (see eq (2.9) and figure 1), related to the interferences between O1f,2 and O5f,6. Since C1,6 are much larger compared to C2,5, respectively, one expects that large T-asymmetries can be induced in the color-enhanced decays. We evaluate the form factors of fs and ga in eq (2.21) from the modified bag model [48] with the numerical results given in table 1,1 where the first and second uncertainties in the branching ratios come from the bag radius of R = (4.8 ± 0.2 GeV)−1 [48] and CKM elements [29], respectively. The Ξ−b decays are free from the W-exchange diagrams, making the results reliable
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