Probing high-momentum component in nucleon momentum distribution by neutron-proton bremsstrahlung {\gamma}-rays in heavy ion reactions

TL;DR

This study investigates the high-momentum tail of nucleons in heavy ion reactions by analyzing high-energy gamma rays emitted during neutron-proton bremsstrahlung, revealing a significant high-momentum component linked to short-range correlations.

Contribution

It provides experimental evidence for the high-momentum tail in nucleon distributions using gamma-ray measurements and confirms the role of short-range correlations in heavy ion collisions.

Findings

High-momentum tail ratio of about 15% is supported by data.

The energy spectrum above 30 MeV matches IBUU model predictions.

The capture channel np → dγ influences gamma-ray production.

Abstract

The high momentum tail (HMT) of nucleons, as a signature of the short-range correlations in nuclei, has been investigated by the high-energy bremsstrahlung $\gamma$ rays produced in $^{86}$Kr + $^{124}$Sn at 25 MeV/u. The energetic photons are measured by a CsI(Tl) hodoscope mounted on the spectrometer CSHINE. The energy spectrum above 30 MeV can be reproduced by the IBUU model calculations incorporating the photon production channel from $np$ process in which the HMTs of nucleons is considered. A non-zero HMT ratio of about $15\%$ is favored by the data. The effect of the capture channel $np \to d\gamma$ is demonstrated.