Speaker
Description
Jet partons can trigger high momentum-exchange $2 \rightarrow 2$ elastic scatterings (aka Molière scatterings) with quark- and gluon-like quasiparticles in QGP, making jets valuable probes with which to study the microscopic structure of QGP. We describe how we have implemented such Molière scatterings in the Hybrid Model of jet quenching. We then describe how measurements of the Soft Drop angle $R_g$ of jets are especially sensitive to the effects of Molière scatterings, which impart rare but sizable transverse kicks to jet constituents, broadening the angular separation of the hardest resolved splitting in the jet. The narrowing of $R_g$ in PbPb collisions because jets which lose the least energy are preferentially selected is a confounding effect. We show that this selection bias can be partially mitigated by selecting gamma-jet events based on the photon energy, with $R_g$ of gamma-jets in PbPb collisions broadening due to Molière scatterings as long as jets which are sufficiently softer than the photon are included.
We then show that OO collisions are a much better arena in which to study Molière scatterings and the microscopic structure of QGP, because although jets do lose energy they lose less energy, resulting in less selection bias. We show that agreement with CMS data of charged-hadron $R_{AA}$ in OO collisions is obtained only when both energy loss and Molière scatterings are included in the Hybrid Model. We then show that because the confounding effects of selection bias are minimal, a genuine broadening of $R_g$ stands out in OO collisions even for inclusive jets: we see more anti-$k_t$ $R = 0.4$ jets with $R_g>0.2$ in OO collisions compared to pp collisions. We find complementary and consistent results via energy–energy correlator (EEC) measurements in OO collisions, showing that they exhibit enhanced large-angle correlations driven by elastic scatterings with minimal confounding effects from selection bias.
| Is this an experimental talk? | No |
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| Is this on behalf of a collaboration? | No |
| Are you willing to present as a poster if it is not selected for oral presentation? | Yes |