New paper searching for Moliere scattering with jet substructure

I’m pleased to announce the release of our paper measuring jet substructure to search for evidence of quasi-particle scattering in the quark-gluon plasma!

In this paper from the ALICE collaboration, we measure the largest relative transverse momentum splitting \(k_{\text{T,g}}\), using proton-proton (pp) and lead-lead (Pb–Pb) collision data collected during Run 2 data. As partons propagate thorough and interact with the medium, they may rarely interact with quasi-particle excitations in the medium. If such interactions occur, they are predicted to enhance the number of large-\(k_{\text{T,g}}\) splittings in Pb–Pb as compared to pp collisions.

Experimentally, we identify this high relative transverse momentum splitting using grooming algorithms, which preferentially identify hard splittings. We used Soft Drop and Dynamical Grooming, with the latter employed for the first time in heavy-ion collisions.

The measurements shows a suppression at large-\(k_{\text{T,g}}\), consistent with the medium-induced narrowing that is observed in other angular-dependent substructure observables, in contrast to the expectation of yield enhancement due to quasi-particle scattering. Although the data can be described by model calculations, those which describe the data differ in the necessity of including quasi-particle scattering effects in order to do so. These new data therefore provide new constraints on theoretical modeling of the microscopic structure and dynamics of the quark–gluon plasma.

The paper is available on the arXiv and will be submitted to Physical Review Letters.