Phase-shift analysis of low-energy pi+ p data

TL;DR

This paper revises low-energy pi+ p scattering data analysis using updated electromagnetic corrections, providing phase-shift values that differ from recent global fits but agree with older results, with implications for hadronic interaction models.

Contribution

It introduces a revised analysis method for low-energy pi+ p scattering data incorporating recent electromagnetic corrections and extended threshold expansions, resulting in updated phase-shift values.

Findings

Discrepancies with recent VPI global-fit solutions.

Agreement with older electromagnetic correction results.

Provision of tabulated phase-shift data with uncertainties.

Abstract

This work presents the results of a revised analysis of the low-energy (pion laboratory kinetic energy T(sub pi) < 100 MeV) pi+ p data using recently obtained electromagnetic corrections. The measurements are analyzed assuming extended threshold expansions for the hadronic K-matrix elements. With a few exceptions, the description of the experimental data is satisfactory. Several minimization functions have been used, yielding consistent results. The phase-shift values, obtained in the s and p(3/2) partial waves, disagree with those of the most recent VPI global-fit solution (SP98); the largest part of this disagreement is removed if we compare our numbers to their single-energy solutions. The s-wave scattering length a(sub 0+), the p-wave scattering volumes a(sub 1+) and a(sub 1-), as well as the hadronic phase shifts themselves, obtained herein, are in agreement with recent work using older electromagnetic corrections; the output of the present work (including meaningful uncertainties) is tabulated in order to enable straightforward use in other applications.