Rate and ellipticity of dilepton production in a magnetized quark-gluon plasma

TL;DR

This paper derives an explicit formula for dilepton production in a magnetized quark-gluon plasma, revealing how magnetic fields enhance production at small invariant masses and induce ellipticity, with implications for heavy-ion collision experiments.

Contribution

The paper provides a new explicit expression for dilepton production rate in a magnetic field using Landau levels, highlighting magnetic effects on rate enhancement and ellipticity.

Findings

Magnetic field significantly increases dilepton rate at small invariant masses.

Dilepton emission exhibits sizable ellipticity in a magnetic field.

At large invariant masses, the magnetic field effect diminishes, approaching the zero-field rate.

Abstract

Using the Landau-level representation for the imaginary part of the photon polarization tensor, we derive an explicit expression for the dilepton production rate from a hot quark-gluon plasma in a quantizing background magnetic field. We study in detail the dependence of the production rate on the dilepton invariant mass and the transverse momentum at mid-rapidity. We also investigate the angular dependence and ellipticity of dilepton emission. By comparing the result with the zero-field Born approximation, we find that the magnetic field leads to a strong enhancement of the dilepton rate at small values of the invariant mass ($M\lesssim\sqrt{|eB|}$). In the same kinematic region, the dilepton production is characterized by a sizable ellipticity. At large values of the dilepton invariant mass ($M\gtrsim\sqrt{|eB|}$), the role of the magnetic field decreases and the result approaches the isotropic zero-field Born rate. By investigating the dependence of ellipticity on the transverse momentum, we argue that the future measurements of dilepton rate in the region of small invariant masses can constrain the magnetic field produced in heavy-ion collisions.