Highp T azimuthal dihadron correlations with identified associated

High-p. T azimuthal di-hadron correlations with identified associated hadrons Essam Elhalhuli for the STAR Collaboration Essam Elhalhuli Hot Quarks 2008

Talk Outline s Au + Au collisions, √s = 200 Ge. V at RHIC s Motivation - Jet modification, baryon enhancement at intermediate p. T s Hadron identification method using d. E/dx s Identifying hadrons from near and away side jet cones s Discuss hadron ratios extracted from the d. E/dx fits 5/22/2021 Essam Elhalhuli Hot Quarks 2008 2

Baryon Enhancement § Observed at intermediate p. T in both 0 /K s neutral and charged light hadrons. § Shown to increase with centrality. § Suggests jet fragmentation not dominant particle production mechanism at intermediate p. T. (nucl-ex/0601042) 5/22/2021 Phys. Rev. Lett. 97 (2006) 152301 Essam Elhalhuli Hot Quarks 2008 3

Jet Modification Leading hadron fragmenting in vacuum Leading hadron now fragmenting in strongly interacting medium Proton - Proton Collision Au - Au Collision 5/22/2021 Essam Elhalhuli Hot Quarks 2008 4

Jet Hadron Composition CERN-PH-TH/2007 -111 Sapeta & Wiedermann Possible Exchanged Information Colour, baryon number, flavour, momentum. Additionally, possible jet/medium mixing (recoil) and recombination with thermal quarks J. Fries, B. Muller, C. Nonaka and S. A. Bass, Phys. Rev. Lett. 90 (2003) 202303. 5/22/2021 Essam Elhalhuli Hot Quarks 2008 5

The Star Experiment 5/22/2021 Essam Elhalhuli Hot Quarks 2008 6

Identifying Charged Hadrons at intermediate p. T § d. E/dx information from STAR TPC used to identify charged hadrons π± § Charged pions distinguished from (anti)protons after p. T ≈3 Ge. V/c K± 5/22/2021 p± Essam Elhalhuli Hot Quarks 2008 § Kaons cannot be distinguished from protons, yields estimated statistically. 7

d. E/dx Fitting Method § ± tracks are separated to allow for qualitative checks, § § π+/π- ≈ 1, p+/p- > 1, K+/K- > 1 Fit using 8 Gaussians for e±, K±, p±, π± Fixed parameters are the p± peak, π± peak - using + daughter d. E/dx and free fit respectively. 9 Free parameters are the peaks’ width, K± peak position (within constraints) and peak areas. Fits were performed in intervals of 0. 5 Ge. V/c from 3 -6 Ge. V/c for 0 -10% and 40 -80% centrality 5/22/2021 Essam Elhalhuli Hot Quarks 2008 8

De/dx fits & +/- charged hadron ratios §Hadron ratios agree with expectation 0 -10% STARPreliminary §π+/π- ≈ unity §p+/p- > unity §Evidence that fit is performing accurately §Large systematic uncertainty associated with kaon yields 40 -80% STAR Preliminary §Only statistical error 5/22/2021 Essam Elhalhuli Hot Quarks 2008 9

Projection & Near and Away side Jet Identification BEMC TPC The near and away side jets are 2 identified as xis a peaks above the am e 0 B uncorrelated 180° background 5/22/2021 p. T 4 -4. 5 Ge. V/C Barrel STAR EMCPreliminary towers registering >6 Ge. V of No v 2 subtraction energy from neutral sources (i. e π0) are correlated with TPC tracks in the azimuthally oriented plane. Essam Elhalhuli Hot Quarks 2008 10

Extracting Hadron Yields J 1 B 1 J 2 B 3 B 2 Where h is the designated hadron, y is Jn+Bn yield and TD is the Tracks radian-1. 5/22/2021 Essam Elhalhuli Hot Quarks 2008 11

Jet Track Density Statistical error only STAR Preliminary 5/22/2021 Essam Elhalhuli Hot Quarks 2008 § The near and away side fragmentation processes. § Background steeper - softer production mechanism. § Away side suppressed in central events quenching effect. 12

Extracted hadron yields Statistical error only STAR Preliminary 5/22/2021 Essam Elhalhuli Hot Quarks 2008 The π± jet yield Similarly so ± jet yields K is easily ± jet the p are more obtainable yield is also difficult after theto difficult to to obtain due background obtain. a π±high contribution background Leads to is subtracted in contribution large errors all p. T intervals in oncentral the events hadron/π± ratio 13

Corrected Hadron Ratios Statistical errors only STAR Preliminary Systematic errors under study No p±/π± enhancement seen for hadrons associated with high p. T π0 in central events. No p±/π± enhancement seen on away side. STAR Preliminary 5/22/2021 Essam Elhalhuli Hot Quarks 2008 14

Summary and conclusions • Work In Progress! • d. E/dx is a promising tool for identifying high p. T tracks. • Statistically sensitive, Systematic effects not estimated. • No evidence of baryon enhancement in hadrons associated with p. T > 6 Ge. V/c π0. • No clear indication of strangeness enhancement. • Jet p±/π± ratio consistent with p+p, background consistent with inclusive study. • Indicates baryon enhancement not associated with jet cone. Likely due to soft processes e. g. coalescence. 5/22/2021 Essam Elhalhuli Hot Quarks 2008 15

Back up slides 5/22/2021 Essam Elhalhuli Hot Quarks 2008 16