Lepton polarization asymmetries for FCNC decays of the Λb baryon

Abstract

Branching ratios, lepton forward-backward asymmetries, and lepton polarization asymmetries for the flavor-changing neutral current (FCNC) dileptonic decays of the Λ b baryon to the ground state and a number of excited state Λ baryons are calculated using form factors extracted using wave functions from a constituent quark model. The SM branching ratios for the transition to the ground state calculated using these quark model form factors are consistent with the recent measurement reported by the LHCb collaboration. It is shown that the lepton polarization asymmetries are largely insensitive to the transition form factors and, therefore, to the effects of QCD in the nonperturbative regime. These observables can therefore provide somewhat model independent ways of extracting various combinations of the Wilson coefficients.

Rare $Λ_b\toΛl^+l^-$ and $Λ_b\toΛγ$ decays in the relativistic quark model

“…The values obtained in our model and Refs. [20,27,28] agree well with data, while other results are significantly larger. From Table IV we also see that predictions for the rare Λ b → Λτ + τ − decay vary significantly.…”

“…In Table IV we compare different theoretical predictions [20,21,[26][27][28][29] for the total branching fractions of rare semileptonic Λ b decays with available experimental data [25].…”

“…Data from LHCb [6] are given by dots with solid error bars. The presented values include results of the relativistic and nonrelativistic quark model calculations [20,27,28] as well as evaluations based on various versions of the light-cone QCD sum rules [21,26,29]. At present, experimental data are available for Λ b → Λµ + µ − decay only.…”

Λb→Λℓ+ℓ−form factors,

“…Similarly to B → K * (→ K π) + − , this decay provides a wealth of angular observables that can be used to disentangle the contributions from individual operators in the b → s + − effective Hamiltonian [29,30] (see also Refs. [31][32][33][34][35][36][37][38][39][40][41][42][43][44]). The theoretical description of Λ b → Λ(→ p π) + − is cleaner than that of B → K * (→ K π) + − because the Λ is stable under the strong interactions.…”

Comparative analysis of theΛb→Λℓ+ℓ−Azizi1, Olgun2, Tavukoğlu3 2015Phys. Rev. D6020View full textAdd to dashboardCite

“…In the literature, there are a lot of studies on this decay channel via different approaches (for some recent studies see for instance Refs. [12][13][14][15][16][17]). …”