Dilepton Spectra and Even Flow Harmonics in a Magnetized QGP: An Ideal Hydrodynamic Study

TL;DR

This study models dilepton production and flow harmonics in a magnetized quark-gluon plasma using an advanced hydrodynamic approach, revealing magnetic field effects on spectra and anisotropic flow in heavy-ion collisions.

Contribution

It introduces a realistic, time-dependent magnetic field profile into hydrodynamic simulations of dilepton production, advancing beyond static homogeneous field models.

Findings

Transverse momentum spectra increase with impact parameter.

Elliptic flow $v_2$ from decay channels is nonzero even in central collisions.

Higher harmonics like $v_4$ are significantly smaller than $v_2$.

Abstract

We present the first comprehensive study of dilepton production from a hot, magnetized quark-gluon plasma in heavy-ion collisions (HIC), incorporating realistic, time-dependent, and spatially inhomogeneous magnetic field profiles within an analytically solvable Gubser flow background. This framework provides a significant improvement over previous static calculations with homogeneous fields and moves toward the long-term goal of full $3+1$D magnetohydrodynamic simulations. We explore the effects of impact parameter, electrical conductivity, and invariant mass on the dilepton spectra and anisotropic even flow coefficients. It is found that transverse momentum spectra increase with impact parameter, dominated by annihilation processes, while decay contributions remain sub-leading. Strikingly, the elliptic flow $v_2$ from decay channels is nonzero even in nearly central collisions, exhibiting a characteristic shape--positive at low $p_T$ and negative at high $p_T$--that is largely independent of impact parameter and conductivity. In contrast, $v_2$ from annihilation processes is smaller in magnitude but dominates the total flow in magnitude due to its larger yield. Higher harmonics, such as $v_4$, are an order of magnitude smaller as compared to $v_2$ along with distinctive zero-crossing patterns. Conductivity enhances both spectra and flow but leaves no unambiguous signature for its extraction. Varying the invariant mass reveals the strongest enhancements at low mass, with harmonic coefficients suppressed at higher masses. Overall, our results suggest that central and semi-central collisions can carry imprints of the background magnetic field, and that characteristic correlations in even flow harmonics may provide a robust probe of electromagnetic effects in HICs.