Hard bremsstrahlung in the pp -> pp gamma reaction

TL;DR

This study measures the hard bremsstrahlung in the proton-proton to proton-proton gamma reaction at 310 MeV, revealing angular distribution patterns and multipole contributions with high precision.

Contribution

The paper provides the first detailed angular distribution analysis of the pp -> pp gamma reaction at this energy, highlighting the dominance of E1 and M2 multipoles and minimal E2 influence.

Findings

Angular distribution follows cos^2(theta_gamma) pattern.

E1 and M2 multipoles are similarly significant.

E2 multipole contribution is negligible at this energy.

Abstract

The pp -> pp gamma reaction has been measured at a beam energy of 310 MeV by detecting both final protons in the PROMICE-WASA facility and identifying a missing-mass peak. For those events where the pp excitation is less than 3 MeV, the final diproton is almost purely in the 1S0 state and, under these conditions, there is complete coverage in the photon c.m. angle theta_gamma. The linear behaviour observed in cos^2(theta_gamma) shows that there is almost no influence of an E2 multipole at this energy, though the E1 and M2 must be rather similar in size.