Probing Vector Mesons in Deuteron Break-up Reactions

TL;DR

This paper investigates high-momentum transfer vector meson photoproduction from deuterons, revealing how final state interactions can be used to probe meson-nucleon interactions and demonstrating new phenomena in sub-threshold and high-energy regimes.

Contribution

It introduces a novel method using spectator nucleon angular distributions to extract vector meson-nucleon interaction amplitudes in high-energy photoproduction reactions.

Findings

Identification of two peaks in spectator nucleon angular distribution corresponding to rescattering processes.

Potential to extract $\

V$-$N$ interaction amplitudes from experimental data.

Abstract

We study vector meson photoproduction from the deuteron at high momentum transfer, accompanied by break-up of the deuteron into a proton and neutron. The large $-t$ involved allows one of the nucleons to be identified as struck, and the other as a spectator to the $\gamma N\rightarrow VN$ subprocess. Corrections to the plane wave impulse approximation involve final state interactions (FSIs) between the struck nucleon or the vector meson, either of which is energetic, with the slow spectator nucleon. In this regime, the eikonal approximation is valid, so is employed to calculate the cross-section for the reaction. Due to the high-energy nature of the FSIs, the maxima of the rescatterings are located at nearly transverse directions of the fast hadrons. This results in two peaks in the angular distribution of the spectator nucleon, each corresponding to either the $V$-$N$ or the $p$-$n$ rescattering. The $V$-$N$ peak provides a new means of probing the $V$-$N$ interaction. This is checked for near-threshold $\phi$ and $J/\Psi$ photoproduction reactions which demonstrate that the $V$-$N$ peak can be used to extract the largely unknown amplitudes of $\phi$-$N$ and $J/\Psi$-$N$ interactions. Two additional phenomena are observed when extending the calculation of $J/\Psi$ photoproduction to the sub-threshold and high-energy domains. In the first case we observe overall suppression of FSI effects due to a restricted phase space for sub-threshold production in the rescattering amplitude. In the second, we observe cancellation of the $V$-$N$ rescattering amplitudes for vector mesons produced off of different nucleons in the deuteron.