Production of excited $Λ_c^+$ baryons through $Λ_b$ hadronic weak decays

TL;DR

The paper addresses the production of excited Λ_c baryons in Λ_b hadronic weak decays by employing a quark-based framework with a single W-emission mechanism. It computes decay amplitudes and partial widths for Λ_b→Λ_c^{(*)}h^- across a wide spectrum of Λ_c excitations, using harmonic-oscillator spatial wavefunctions and a detailed color-flavor-spin structure, with amplitudes decomposed into parity-conserving and parity-violating parts. The results reproduce established ground-state data and predict sizable production for many excited Λ_c states, with branching fractions up to $O(10^{-3})$ in π^- emitting channels and specific patterns across 1P, 1D, 2S, 3S, 2P, 1F, and 2D states that can guide future searches. These predictions offer concrete channels and ratios to test λ-mode assignments and to map missing excitations, thereby advancing hadron spectroscopy in the bottom sector and providing a benchmark for upcoming LHCb data.

Abstract

In this work, to establish a more abundant $Λ_c$ baryon spectrum, we discuss the production potentials of the excited $Λ_c$ baryons through $Λ_b$ hadronic weak decays within a constituent quark model. Based on our successful explanations of the existing experimental data for the $Λ_b \to Λ_c(π^-, K^{-}, D^{-}, D^{-}_s, D_s^{*-})$ processes, we further calculate the decay rates of the $Λ_b$ baryon into the $1P$-, $1D$-, $2S$-, $3S$-, $2P$-, $1F$-, and $2D$-wave $Λ_c$ excited states. It is found that these $Λ_c$ excitations have a large production rate in the $Λ_b$ hadronic weak decay process associated $π^-$ meson emitting, i.e., $Λ_b\to Λ_c^{*}π^-$, their branching fractions can reach up to $\mathcal{O}(10^{-3})$. To search for the higher $3S$-, $2P$-, $1F$-, and $2D$-wave $Λ_c$ states, the $Λ_b \to Λ_c (3S) π^-\to D^{*0}p π^-$, and $Λ_b\to Λ_c(2P,2D,1F) π^-\to D^{(*)0}pπ^-$ decays are worth observing in future experiments.

Figures (1)

• Figure 1: Feynman diagram for the nonleptonic weak decay processes of $\Lambda_b \rightarrow \Lambda_c^{(\ast)} h^-$ ($h^-=\pi^-$, $\rho^-$, $K^-$, $K^{\ast-}$, $D^-$, $D^{\ast-}$, $D_s^-$, $D_s^{\ast-}$).