Title: Semi-inclusive hadron+jet measurement in Ru+Ru and Zr+Zr collisions at 200 GeV in STAR

PAs: Yang He, Maowu Nie, Rongrong Ma, Li Yi

Contact information: yanghe@rcf.rhic.bnl.gov

Target journal: Physical Review C

Talks in PWG meeting:

https://drupal.star.bnl.gov/STAR/system/files/pwgmeeting_20230316.pdf
https://drupal.star.bnl.gov/STAR/system/files/pwgmeeting_20230309.pdf
https://drupal.star.bnl.gov/STAR/system/files/pwgmeeting_Dec22.pdf
https://drupal.star.bnl.gov/STAR/system/files/HP2023_plan.pdf
https://drupal.star.bnl.gov/STAR/system/files/isobar_embeding_testrun_QA_March18.pdf
https://drupal.star.bnl.gov/STAR/system/files/Isobar_embedding_QA_ver2.pdf
https://drupal.star.bnl.gov/STAR/system/files/Isobar_Run18_Step2_QA_Oct14_0.pdf
https://drupal.star.bnl.gov/STAR/system/files/RecoilJetIsobarAug_YangHe.pdf

Talks in collaboration meeting:

https://drupal.star.bnl.gov/STAR/system/files/20241022_collaborationmeeting.pdf
https://drupal.star.bnl.gov/STAR/system/files/collaborationMeeting_202310.pdf
https://drupal.star.bnl.gov/STAR/system/files/collaborationmeeting_20230301_0.pdf
https://drupal.star.bnl.gov/STAR/system/files/CollaborationMeeting_Sep14.pdf
https://drupal.star.bnl.gov/STAR/system/files/collaborationMeeting_Feb16_0.pdf
https://drupal.star.bnl.gov/STAR/system/files/SignDca_Check_inIsobar_Sep16_0.pdf
https://drupal.star.bnl.gov/STAR/system/files/collaboration_meeting_March3.pdf
https://drupal.star.bnl.gov/STAR/system/files/Recoil_jet_in_Isobar_Sep15.pdf

Abstract:

Motivation:

Icp has been measured across various collision systems, with Icp<1 observed in large systems while Icp close to unity in small systems. In order to bridge the gap between large and small, we measured Icp in relatively smaller collision systems (Zr+Zr and Ru+Ru collisions). This study will help us understand the system size dependence of parton energy loss, and provide important input for theory to complete the correlation picture between q_hat and temperature, which will in turn help search for lower limit of medium size to signal jet quenching. On the other hand, STAR has done a system size dependence study on inclusive charged particles. The study finds it is the energy density that drives jet quenching not the collision geometry. Doing a similar study using jet will help to confirm the picture and better understand the effect of fragmentation process.

Figures:


Figure 1: Fully corrected pT distributions of h+jet for 0-10% and 60-80% centrality Zr+Zr and Ru+Ru collisions at 200 GeV, with jet R = 0.2, 0.5.

Figure 2: Fully. corrected pT distribution ratios of 0-10% to 60-80% centrality (Icp) in Zr+Zr and Ru+Ru collisions at 200 GeV, with jet R = 0.2, 0.3, 0.4, 0.5.

Figure 3: Fully. corrected pT distribution ratios of 0-10% to 60-80% centrality (Icp) in merged Zr+Zr and Ru+Ru collision system at 200 GeV, with jet R = 0.2, 0.3, 0.4, 0.5.

Figure 4: Fully corrected Icp ratio of R = 0.2 to 0.5 in merged Zr+Zr and Ru+Ru collision system at 200 GeV.

Summary:

1. Fully corrected jet pT spectra has been measured in Zr+Zr and Ru+Ru collisions separately with no large discrepancy observed

2. Merged Icp of Zr+Zr and Ru+Ru collisions are shown with jet R=0.2 to 0.5
    a). Icp < 1 in lower pT signals the jet quenching
    b). Model study find trigger energy loss enhance the ”true” baseline of no jet quenching. So Icp > 1 at high pT can still signal jet quenching

3. We calculate Icp ratio between R=0.2 and 0.5, and find the value smaller than unity in large pT indicating medium induced jet broadening