Time-reversal asymmetries and angular distributions in ${\Lambda }_b\to \Lambda V$

Abstract

We study the spin correlations to probe time-reversal~(T) asymmetries in the decays of ${\Lambda }_b\to \Lambda V(V=\varphi ,{\rho }^0,\omega ,K^{\ast 0})$. The eigenstates of the T-odd operators are obtained along with definite angular momenta. We obtain the T-odd spin correlations from the complex phases among the helicity amplitudes. We give the angular distributions of ${\Lambda }_b\to \Lambda (\to p{\pi }^{-})V(\to P{P}^{\prime })$ and show the corresponding spin correlations, where $P^{(\prime )}$ are the pseudoscalar mesons. Due to the helicity conservation of the $s$ quark in $\Lambda$, we deduce that the polarization asymmetries of $\Lambda$ are close to $-1$. Since the decay of ${\Lambda }_b\to \Lambda \varphi$ in the standard model~(SM) is dictated by the single weak phase from the product of CKM elements, $V_{tb}{V}_{ts}^{\ast }$, the true T and CP asymmetries are suppressed, providing a clean background to test the SM and search for new physics. In the factorization approach, as the helicity amplitudes in the SM share the same complex phase, T-violating effects are absent. Nonetheless, the experimental branching ratio of $Br({\Lambda }_b\to \Lambda \varphi )=(5.18\pm 1.29)\times 10^{-6}$ suggests that the nonfactorizable effects or some new physics play an important role. By parametrizing the nonfactorizable contributions with the effective color number, we calculate the branching ratios and direct CP asymmetries. We also explore the possible T-violating effects from new physics.

26 pages, 1 figure, revised version accepted by JHEP

References in corpus (13)

• Rare baryon decays Lambda_b -> Lambda l+ l- (l=e, mu, tau) and Lambda_b -> Lambda gamma : Differential and total rates, lepton- and hadron-side forward-backward asymmetries
• Asymmetries of anti-triplet charmed baryon decays
• Improved Estimates of The $B_{(s)}\to VV$ Decays in Perturbative QCD Approach
• Revisiting semileptonic decays of ${\Lambda }_{b(c)}$ supported by baryon spectroscopy
• Nonleptonic two-body weak decays of ${\Lambda }_b$ in modified MIT bag model
• Non-leptonic beauty baryon decays and $CP$-asymmetries based on $SU(3)$-Flavor analysis
• New CP phase of $B_s-{\bar{B}}_s$ mixing on $\mathrm{T}$ violation in $B_{d(s)}\to K^{\ast }(\varphi ){\ell }^{+}{\ell }^{-}$
• Direct CP and T Violation in Baryonic B Decays
• Non-leptonic two-body decays of ${\Lambda }_b^0$ in light-front quark model
• Testing CP and Time Reversal Symmetries with ${\Lambda }_b\to \Lambda V(1-)$ Decays
• Study of the weak annihilation contributions in charmless $B_s\to VV$ decays
• Beauty baryon non-leptonic decays into decuplet baryons and $CP$-asymmetries based on $SU(3)$-Flavor analysis
• Fits of Weak Annihilation and Hard Spectator Scattering Corrections in $B_{u,d}\to VV$ Decays

Cited by in corpus (11)

• Weak Radiative Decays of Anti-triplet Bottomed Baryons in Light-Front Quark Model
• Estimates of exchange topological contributions and $CP$-violating observables in ${\Lambda }_b\to \Lambda \varphi$ decay
• Time-reversal asymmetries in ${\Lambda }_b$ semileptonic decays
• Sizable Time-reversal violating effects in bottom baryon decays
• Final-state rescattering mechanism in bottom-baryon decays
• Study of charmless two-body baryonic $B$ decays
• Searching $B_c^{\ast }$ via conservation laws
• Center of mass motion in bag model
• CP Violation In Baryon Decays At LHCb
• Bottomed baryon decays with invisible Majorana fermions
• Topological amplitudes of bottom baryon decays in the $SU(3{)}_F$ limit