Absorption of 1$P$-wave heavy charmonium $\chi_{c1}(1P)$ in nuclei

TL;DR

This paper investigates the production and absorption of the $ ext{chi}_{c1}(1P)$ charmonium state in nuclei near threshold energies, aiming to inform quark-gluon plasma research.

Contribution

It introduces a collision model incorporating nuclear effects to analyze $ ext{chi}_{c1}(1P)$ photoproduction and absorption, providing predictions for future experimental comparison.

Findings

Sensitivity of observables to absorption cross section scenarios.

Predictions for excitation functions and transparency ratios at near-threshold energies.

Potential to determine absorption cross section from experimental data.

Abstract

We study the inclusive heavy charmonium $\chi_{c1}(1P)$ photoproduction from nuclei near the kinematic threshold within the collision model, based on the nuclear spectral function, for incoherent direct photon--nucleon charmonium creation processes. The model accounts for the final $\chi_{c1}(1P)$ absorption in nuclear medium, target nucleon binding and Fermi motion. We calculate the absolute and relative excitation functions on $^{12}$C and $^{184}$W target nuclei at near-threshold photon beam energies of 8.25--16.0 GeV, the absolute momentum differential cross sections and ratios of them for its production off these target nuclei at laboratory polar angles of 0$^{\circ}$--10$^{\circ}$ and for photon energy of 13 GeV as well as the A-dependences of the transparency ratios for the $\chi_{c1}(1P)$ at photon energy of 13 GeV within the different scenarios for its absorption cross section in nuclei. We demonstrate that the absolute and relative observables considered reveal distinct sensitivity to these scenarios. Therefore, they might be useful for the determination of this cross section from the comparison of them with the experimental data from the future experiments at the upgraded up to 22 GeV CEBAF facility, which is of crucial importance in understanding of charmonium production and suppression in high-energy heavy--ion collisions in a search for the quark-gluon plasma.