Angular distributions for $Λ_b\to Λ^*_J (pK^-)J/ψ$ Decays

Abstract

We carry out an analysis of the multibody decay cascade Λ b → Λ * J J/ψ → pK − J/ψ with the Λ * J resonance including Λ * 1520 , Λ * 1600 , and Λ * 1800 , and J/ψ reconstructed by the lepton pair final state. Using the helicity amplitude technique, we derive a compact form for the angular distributions for the decay chain, from which one can extract various one-dimensional distributions. Using the Λ b → Λ * J form factors from Lattice QCD and quark model, we calculate the differential and integrated partial widths. Decay branching fractions are found as B(Λ b → pKµ + µ − ) = (1.41 ± 0.31) × 10 −5 , B(Λ b → pKe + e − ) = (1.41±0.32)×10 −5 . In addition, we also explore forward-backward asymmetry, and various polarizations. Results in this work will serve a calibration for the study of b → sμµ decays in Λ b decays in future and provide useful information towards the understanding of the properties of the Λ * J baryons.

Searching for tetraquark through weak decays of b-baryons

“…We carry out an analysis of 0 b → 0 Z 0 c (3900) in terms of the helicity amplitude technique. As we will see later the helicity amplitudes are particularly convenient for expressing various observable quantities in the 0 b decays [55][56][57][58]. The amplitude M( 0 b → 0 Z 0 c (3900)) is induced by the b → sc c transition whose effective Hamiltonian has been presented in Eq.…”

“…( 8) whose dimension is GeV −3 , it is used to characterize the nonperturbative effects caused by the quark and gluon propagators on which the momentum is of order QCD . This idea is analogous to the intermediate state propagator in 0 b → 0 * J/ψ [55] or the resonant propagator in the analysis of + c → π + π 0 [62]. As a rough estimation, we take the value of this factor at the order of 1.…”

“…These relations can be used as tests for pinning down the suitable model for Z c states. Very recently, the angular distributions for the decays 0 b → 0 * J/ψ, where the 0 * are 0 -type excited states, have been derived in terms of the helicity amplitude technique [55,56]. We will also use this technique to calculate the partial decay widths of 0 b → 0 Z 0 c (3900), − b → − Z 0 c (3900) and 0 b → 0 Z 0 c (3900).…”