Light-like mesons and deep inelastic scattering in finite-temperature AdS/CFT with flavor

TL;DR

This paper investigates meson excitations and deep inelastic scattering in a finite-temperature holographic gauge theory, revealing how high-energy flavor currents produce mesons and generate DIS structure functions similar to high-temperature phases.

Contribution

It provides analytic results for the meson spectrum at finite temperature, especially near the light-cone, and clarifies the mechanism of meson production and DIS in the low-temperature phase.

Findings

High-energy flavor currents produce highly excited mesons resonantly.

Meson levels are very finely spaced near the light-cone.

The DIS structure functions match those in the high-temperature phase.

Abstract

We use the holographic dual of a finite-temperature, strongly-coupled, gauge theory with a small number of flavors of massive fundamental quarks to study meson excitations and deep inelastic scattering (DIS) in the low-temperature phase, where the mesons are stable. We show that a high-energy flavor current with nearly light-like kinematics disappears into the plasma by resonantly producing mesons in highly excited states. This mechanism generates the same DIS structure functions as in the high temperature phase, where mesons are unstable and the current disappears through medium-induced parton branching. To establish this picture, we derive analytic results for the meson spectrum, which are exact in the case of light-like mesons and which corroborate and complete previous, mostly numerical, studies in the literature. We find that the meson levels are very finely spaced near the light-cone, so that the current can always decay, without a fine-tuning of its kinematics.