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

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

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

Target journal: Physics Letters B

Paper Draft:
Current Version: Link

Analysis Note:
Current Version: Link

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:

We want to do semi-inclusive hadron jet measurements in intermediate-size collision systems: Zr+Zr and Ru+Ru collisions. Semi-inclusive hadron jets refer to the jets recoiling from high-pT triggers.
By requiring trigger particles, we can select on hard scatterings and largely suppress the background jet contribution.  
Combined with the mixed-event technique, we can explore jet energy loss over a broad jet pT range and study modification to jet fragment.

Figure 1: pT distributions for 0-10% Zr+Zr (top panels) and Ru+Ru (bottom panels) collisions at \sqrt{s_NN} = 200 GeV, with jet R = 0.2 (left panels), 0.5(right panels).
Upper sub-panels: red points for SE, grey shaded region for ME, blue shaded region for normalization range. Lower sub-panels: ratio of SE and normalized ME distributions.
Insert: ratio in the normalization range.

Figure 2: Fully corrected pT distribution of h+jet for 0-10% to 60-80% centrality in Zr+Zr and Ru+Ru collisions at 200 GeV, with jet R = 0.2, 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 at low pT signals the jet quenching
    b). Model study find trigger energy loss enhance the ”true” baseline of 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