ICHEP 2022

Measurements of jet yield and acoplanarity using semi-inclusive γdir+jet and π0+jet distributions in p+p and central Au+Au collisions at sNN=200 GeV by STAR

8 Jul 2022, 15:20

15m

Room 3 (Verde)

Parallel Talk Heavy Ions Heavy Ions

Speaker

Derek Anderson (Texas A&M University)

Description

We report high-statistics measurements of semi-inclusive distributions of charged jets recoiling from high-$E_{\text{T}}$ direct photon (${\gamma }_{\text{dir}}$) and ${\pi }^0$ triggers in $p$+$p$ and central Au+Au collisions at $\sqrt{s_{NN}}=200$ GeV. In a semi-inclusive approach, event bias is induced solely by the choice of trigger; separately utilizing ${\gamma }_{\text{dir}}$ and ${\pi }^0$ triggers therefore provides direct comparison of effects due to jet quenching - the suppression of energetic partons due to the energy loss in the Quark-Gluon Plasma (QGP) - for jet populations with different quark/gluon fractions and different in-medium path length distributions. Jets are reconstructed from charged particles using the anti-${\text{k}}_{\text{T}}$ algorithm with jet resolution parameters $R_{\text{jet}}=0.2$ and 0.5. The large uncorrelated background in central Au+Au collisions is removed statistically using a mixed event technique. This enables a jet measurement with well-controlled systematic uncertainties extending to low jet transverse momentum ($p_{\text{T}}$) and large $R_{\text{jet}}$, which are of particular importance in searching for large-angle jet scattering. We report recoil jet yield and trigger-jet acoplanarity distributions for jets with $p_{\text{T}}>5$ GeV/$c$. The comparison of recoil yields in Au+Au and $p$+$p$ collisions at fixed $R_{\text{jet}}$ probes energy loss in heavy-ion collisions, while the comparison of recoil yields for different $R_{\text{jet}}$ in Au+Au and $p$+$p$ collisions probes intra-jet broadening due to jet quenching. The modification of trigger-jet acoplanarity distributions in central Au+Au collisions relative to $p$+$p$ collisions is sensitive to QGP transport parameters, and can be used to search for evidence of large-angle scattering of jets off of quasi-particles in the QGP. The measured recoil yields and acoplanarity distributions are compared to theoretical calculations.

Presentation materials

AndersonTalk_ICHEP2022.v5.pdf