Imprints of high-momentum nucleons in nuclei on hard photons from heavy-ion collisions around the Fermi Energy

TL;DR

This study investigates how high-momentum tails in nucleon momentum distributions, caused by short-range correlations, influence hard photon emissions in heavy-ion collisions near the Fermi energy, revealing observable effects in photon spectra.

Contribution

It introduces an isospin- and momentum-dependent transport model incorporating nucleon high-momentum tails to analyze photon emissions in heavy-ion collisions.

Findings

Energy spectra of hard photons are sensitive to the shape of the nucleon HMT.

Angular distributions of hard photons do not reflect HMT shape.

Transverse momentum spectra at mid-rapidity show strong imprints of HMT shape.

Abstract

The short-range correlation (SRC) induced by the tensor force in the isosinglet neutron-proton interaction channel leads to a high-momentum tail (HMT) in the single-nucleon momentum distributions n(k) in nuclei. Owing to the remaining uncertainties about the tensor force, the shape of the nucleon HMT may be significantly different from the dilute interacting Fermi gas model prediction $n(k) \sim1/k^4$ similar to the HMT in cold atoms near the unitary limit. Within an isospin- and momentum-dependent Boltzmann-Uehling-Uhlenbeck transport model incorporating approximately the nucleon HMT, we investigate hard photon emissions in $^{14}$N+$^{12}$C and $^{48}$Ca+$^{124}$Sn reactions at beam energies around the Fermi energy. Imprints of different shapes of the HMT on the energy spectrum, angular distribution and transverse momentum spectrum of hard photons are studied. While the angular distribution does not carry any information about the shape of the nucleon HMT, the energy spectra and especially the mid-rapidity transverse momentum spectra of hard photons are found to bare strong imprints of the shapes of nucleon HMTs in the two colliding nuclei.