Diffractive longitudinal structure function at the Electron Ion Collider

TL;DR

This paper explores how the future Electron Ion Collider can precisely measure the diffractive longitudinal structure function, enhancing understanding of diffraction and photon polarization effects in high-energy physics.

Contribution

It demonstrates the potential for high-precision measurements of the diffractive longitudinal structure function at the EIC across various energy scenarios, including novel extraction methods for related ratios.

Findings

Achieves 5-10% precision on $F_L^D$ in key regions.

Enables extraction of $F_L^D$ over a wide kinematic range.

Provides a method to measure the ratio $R^D$ of photon cross sections.

Abstract

Possibilities for the measurement of the longitudinal structure function in diffraction $F_\mathrm{L}^\mathrm{D}$ at the future US Electron Ion Collider are investigated. The sensitivity to $F_\mathrm{L}^\mathrm{D}$ arises from the variation of the reduced diffractive cross section with centre-of-mass energy. Simulations are performed with various sets of beam energy combinations and for different assumptions on the precision of the diffractive cross section measurements. Scenarios compatible with current EIC performance expectations lead to an unprecedented precision on $F_\mathrm{L}^\mathrm{D}$ at the 5-10 % level in the best measured regions. While scenarios with data at a larger number of centre-of-mass energies allow the extraction of $F_\mathrm{L}^\mathrm{D}$ in the widest kinematic domain and with the smallest uncertainties, even the more conservative assumptions lead to precise measurements. The ratio $R^\mathrm{D}$ of photoabsorption cross sections for longitudinally to transversely polarised photons can also be obtained with high precision using a separate extraction method.