Interpretation of near-threshold peaks using the method of independent S-matrix poles

TL;DR

This paper introduces a model-independent method using independent S-matrix poles to analyze near-threshold signals, highlighting potential misinterpretations from limited parametrizations and applying it to pentaquark candidates.

Contribution

It develops a novel S-matrix pole analysis framework that avoids physical sheet poles and demonstrates its application to coupled-channel scattering, especially in pentaquark studies.

Findings

Misinterpretation risks with limited parametrizations.

Ambiguous pole pairs can exist without manifesting in single S-matrix elements.

Pentaquark interpretation of $P_ ext{ψ}^N(4312)^+$ remains plausible.

Abstract

We propose a model-independent analysis of near-threshold enhancements using independent S-matrix poles. In this formulation, we constructed a Jost function with controllable zeros to ensure that no poles are generated on the physical Riemann sheet. We show that there is a possibility of misinterpreting the observed near-threshold signals if one utilized a limited parametrization and restrict the analysis to only one element of the S-matrix. Specifically, there is a possibility of the emergence of ambiguous pair of poles which are singularities of the full S-matrix but may not manifest in one of its elements. For a more concrete discussion, we focused on an effective two-channel scattering where the full S-matrix is a $2\times2$ matrix. We apply our method to the coupled two-channel analysis of the $P_\psi^N(4312)^+$ and found that the compact pentaquark interpretation cannot be ruled out yet.