Energy dependence of hard bremsstrahlung production in proton-proton collisions in the Delta(1232) region

TL;DR

This study measures the energy dependence of hard bremsstrahlung in proton-proton collisions near the Delta(1232) resonance, revealing a broad peak around 650 MeV linked to intermediate states.

Contribution

It provides new differential cross section data for proton-proton bremsstrahlung in the 353-800 MeV range, highlighting the role of Delta(1232)N states.

Findings

Broad peak at 650 MeV in cross section

Cross section up to two orders smaller than deuteron photodisintegration

Influence of Delta(1232)N intermediate states

Abstract

Hard bremsstrahlung production in proton-proton collisions has been studied with the ANKE spectrometer at COSY-Juelich in the energy range of 353-800 MeV by detecting the final proton pair {pp}_s from the pp -> {pp}_s reaction with very low excitation energy. Differential cross sections were measured at small diproton c.m. angles from 0 to 20 degrees and the average over this angular interval reveals a broad peak at a beam energy around 650 MeV with a FWHM of about 220 MeV, suggesting the influence of Delta(1232)N intermediate states. Comparison with deuteron photodisintegration shows that the cross section for diproton production is up to two orders of magnitude smaller, due largely to differences in the selection rules.