Constraints on the threshold K- nuclear potential from FINUDA (stopped K-, pi-) hypernuclear spectra

TL;DR

This paper compares experimental hypernuclear formation rates from FINUDA with theoretical models, suggesting a preference for a deep K- nuclear potential of 150-200 MeV based on the observed data and energy-dependent reaction branching ratios.

Contribution

It provides new constraints on the K- nuclear potential depth by analyzing hypernuclear spectra and comparing them with chiral model calculations, highlighting the importance of energy and density dependence.

Findings

Calculated formation rates are about 15% of experimental rates.

Data favors a deep K- potential of 150-200 MeV over a shallow one.

Energy and density dependence of the in-medium branching ratio is significant.

Abstract

1s(Lambda) hypernuclear formation rates in stopped K- reactions on several p-shell targets are derived from hypernuclear formation spectra measured recently by the FINUDA Collaboration and are compared with calculated 1s(Lambda) formation rates based on a KbarN coupled channels chiral model. The calculated rates are about 15% of the derived rates, depending weakly on the depth of the threshold K- nuclear potential. The A dependence of the calculated rates is in fair agreement with that of the derived rates, showing a slight preference for a deep density dependent K- nuclear potential of depth (150-200) MeV at nuclear matter density over a shallow potential of depth about 50 MeV. These new features originate from a substantial energy and density dependence found for the in-medium subthreshold (K- n --> pi- Lambda) branching ratio that serves as input to the K- capture at rest calculations.