Speaker
Description
The quark-gluon plasma formed in heavy-ion collisions has a large momentum anisotropy, especially during early stages of collisions. For jet partons this leads to momentum broadening which is not isotropic in the parton's transverse plane. In this talk we discuss such anisotropic momentum broadening of jets in detail and evaluate how it changes the radiation of hard gluons, and gives rise to a net polarization of jets. We first present a microscopic calculation of momentum broadening of a jet parton. This calculation assumes an anisotropic distribution of quarks and gluons in the medium and is done in the hard thermal loops formalism with careful treatment of plasma instabilities [1]. A main result is increased magnetic screening at lower transverse momenta which reduces momentum broadening substantially [2]. In the second half of this talk, we calculate in detail the rate for a jet parton to radiate a gluon when undergoing anisotropic momentum broadening. Using the harmonic oscillator approximation, we show that the radiated gluon is polarized and that after successive branching this leads to net polarization of jets in heavy-ion collisions. We present a similar analysis for the polarization of photons. Finally, we discuss briefly how the anisotropy of the quark-gluon plasma could be measured directly from jet and photon polarization.
[1] S. Hauksson, S. Jeon, C. Gale, Phys. Rev. C 103, 064904 (2021), arXiv:2012.03640
[2] S. Hauksson, S. Jeon, C. Gale, arXiv:2109.04575
