Natural interpretation on the data of Λc→Σπ

Hong-Wei Ke,Xue-Qian Li

doi:10.1103/physrevd.102.113013

Abstract

Even though the Standard Model (SM) has achieved great success, its application to the field of low energies still lacks solid foundation due to our limited knowledge on non-perturbative QCD. Practically, all theoretical calculations of the hadronic transition matrix elements are based various phenomenological models. There indeed exist some anomalies in the field which are waiting for interpretations. The goal of this work is trying to solve one of the anomalies: the discrepancy between the theoretical prediction on the sign of the up-down asymmetry parameter of $\Lambda_c\to\Sigma\pi$ and the experimental measurement. In the literatures several authors calculated the rate and determined the asymmetry parameter within various schemes, but there exist obvious loopholes in those adopted scenarios. To solve the discrepancy between theory and data, we suggest that not only the direct transition process contributes to the observed $\Lambda_c\to\Sigma\pi$, but also other portals such as $\Lambda_c\to \Lambda\rho$ also play a substantial role via an isospin-conserving re-scattering $\Lambda\rho\to\Sigma\pi$. Taking into account of the effects induced by the final state interaction, we re-evaluate the relevant quantities. Our numerical results indicate that the new theoretical prediction based on this scenario involving an interference between the direct transition of $\Lambda_c\to\Sigma\pi$ and the portal $\Lambda_c\to\Lambda\rho\to\Sigma\pi$ can make both the decay rate and sign of the asymmetry parameter to be consistent with data.

Highlights

Even though the Standard Model (SM) has achieved great success, its application to the field of low energy still lacks solid foundation due to our limited knowledge on nonperturbative QCD
All theoretical calculations of the hadronic transition matrix elements are based on various phenomenological models
Our theoretical prediction based on this scenario involving an interference between the direct transition of Λc → Σπ and the portal Λc → Λρ → Σπ can make both the decay rate and sign of the asymmetry parameter to be consistent with data

Summary

INTRODUCTION

Even though the Standard Model (SM) has achieved great success, its application to the field of low energy still lacks solid foundation due to our limited knowledge on nonperturbative QCD. One of the anomalies is the discrepancy between the theoretical prediction on the sign of the up-down asymmetry parameter of Λc → Σπ and the experimental measurement. Besides the meson case, for baryons that contain three ingredients, their complexity makes a thorough study on them more difficult than on mesons. From another aspect, the involved physics in the transitions between baryons is richer and by the research one can get better understanding of the governing mechanisms. Among the previous theoretical studies on the decay rate of Λc → Σπ and the corresponding up-down asymmetry parameter α, the pole model was adopted because of its advantage. A naïve conjecture would expect that the prediction obtained with this model should be

Published by the American Physical Society

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SUMMARY