Nuclear-Medium Modification of the Rho(1S)- and Rhoprim(2S)-Mesons in Coherent Photo- and Electroproduction: Coupled Channel Analysis

TL;DR

This paper investigates how nuclear environments modify the dilepton mass spectrum in coherent photo- and electroproduction of Rho(1S) and Rhoprim(2S) mesons, highlighting the importance of off-diagonal rescatterings and interference effects.

Contribution

It introduces a coupled channel analysis to quantify medium modifications of Rho and Rhoprim mesons, emphasizing the role of off-diagonal rescatterings and sequential mechanisms.

Findings

Off-diagonal rescatterings have a marginal effect on Rho(1S) but are crucial for Rhoprim(2S).

Sequential gamma* -> Rho -> Rhoprim mechanism dominates Rhoprim(2S) production in heavy nuclei.

Interference between Rho(1S) tail and Rhoprim affects the mass spectrum in the Rhoprim region.

Abstract

We study medium modifications of the dilepton mass spectrum in coherent photo- and electroproduction of the Rho(1S)- and Rhoprim(2S)-meson resonances on nuclear targets. The analysis is performed within the coupled Rho, Rhoprim... channel formalism in which nuclear modifications derive from the off-diagonal rescatterings. We find that the effect of off-diagonal rescatterings on the shape of the dilepton mass spectrum in the Rho(1S)-meson mass region is only marginal but is very important in the Rhoprim mass region. The main off-diagonal contribution in the Rhoprim mass region comes from the sequential mechanism gamma* -> Rho -> Rhoprim(2S), which dominates the Rhoprim(2S) production for heavy nuclei. Our results show also that in the Rhoprim(2S) mass region there is a considerable effect of the interference of the Breit-Wigner tail of Rho(1S)-meson with the Rhoprim-meson.