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STAR Back-to-Back Di-Jet Triggered Multi-Hadron Correlations as Medium Probes in STAR Back-to-Back Di-Jet Triggered Multi-Hadron Correlations as Medium.

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Presentation on theme: "STAR Back-to-Back Di-Jet Triggered Multi-Hadron Correlations as Medium Probes in STAR Back-to-Back Di-Jet Triggered Multi-Hadron Correlations as Medium."— Presentation transcript:

1 STAR Back-to-Back Di-Jet Triggered Multi-Hadron Correlations as Medium Probes in STAR Back-to-Back Di-Jet Triggered Multi-Hadron Correlations as Medium Probes in STAR Olga Barannikova University of Illinois at Chicago for the STAR Collaboration Physics motivations Data analysis: Results: Summary  di-jet events  background subtraction  correlations in d+Au and Au+Au  interpretations

2 STAR Quark Matter 2008, Jaipur Olga Barannikova, University of Illinois at Chicago 2 / 19 di-hadron high pt suppression effect vanishes in peripheral/d+Au collisions energy loss, jet quenching 4<p T trig <6 GeV/c, 2<p T assoc <p T trig STAR PRL 91 (2003) 072304 Current state of experiment di-hadron low-p T enhancement Reappearance of away-side correlation Double-hump structure hints at additional physics phenomena 3<p T trig <4 GeV/c, 1.3<p T assoc <1.8 M.v. Leeuwen, Hangzhou ‘06

3 STAR Quark Matter 2008, Jaipur Olga Barannikova, University of Illinois at Chicago 3 / 19 Partonic energy loss, jet-quenching in the hot and dense QCD medium Energy loss mechanisms Mach cone (Stoecker, Casalderrey-Solana, Shuryak, Teaney, Ruppert, Muller, Renk) Cherenkov gluon radiation (Dremin, Koch, Majumder, Wang) Large angle gluon radiation (Vitev, Salgado) Flow-induced deflection (Armesto, Salgado, Wiedemann) Parton multiple scattering (Chiu, Hwa) …. Current understanding of theory Important to know the away-jet-axis: use di-jets. Mach-Cone Double-hump structure on away-side. “near-side” “away-side” Jet Quenching Dissipation jet energy propagating through the medium

4 STAR Quark Matter 2008, Jaipur Olga Barannikova, University of Illinois at Chicago 4 / 19 Knowing away-jet-axis should improve the sensitivity to this and other effects. Use di-jets. *by M. Andrews (UIC) Unmodified Jet*   Simulation   Modified Jet* Simulation Benefit of knowing away-jet-axis: Mach-cone simulation unmodified jet Mach-cone away-side direction

5 STAR Quark Matter 2008, Jaipur Olga Barannikova, University of Illinois at Chicago 5 / 19 PRL 97 (2006) 162301 8<p T (trig)<15 GeV/c First di-jet observation Two high-p T triggers: di-jet observation New analysis exploits this observation: back-to-back hadrons pin down away-jet-axis in  and .

6 STAR Quark Matter 2008, Jaipur Olga Barannikova, University of Illinois at Chicago 6 / 19 8 < p T (trig) < 15 GeV/c Moreover… Away-side widths similar for d+Au and Au+Au. lose some energy, and then fragment?  = 0.12 ± 0.08: cannot rule out ~1 GeV large angle (90 o ) single gluon or softer multi-gluon radiation. 1 2 2 finite prob. of not interacting: fragmentation as in vacuum? 1 Look for a third, softer particle around away-side high p T hadron.

7 STAR Quark Matter 2008, Jaipur Olga Barannikova, University of Illinois at Chicago 7 / 19 Aim of this analysis is to “pin” the jet axis. Only select events with high-p T particles back-to-back in . Correlate all particles with this away-axis. associates primary trigger (T1) “jet-axis” trigger (T2) Signal sit atop of a largely uncorrelated background Data analysis: techniques

8 STAR Quark Matter 2008, Jaipur Olga Barannikova, University of Illinois at Chicago 8 / 19 Raw, uncorrected signal  -2 01 2 345 a.u. 0.6 0.4 0.2 T1: p T >5 GeV/c T2: p T >4 GeV/c T1T2 correlation Correlation between primary trigger (T1) and “away-jet-axis trigger” (T2). Require that the 2 highest p T particles are back-to-back in . Assume this defines the jet- axis, look in 2D-space about the second trigger. Data analysis: di-jet selection   ± 0.2 Di-jet trigger T2 T1

9 STAR Quark Matter 2008, Jaipur Olga Barannikova, University of Illinois at Chicago 9 / 19 Flow background T1: p T >5GeV/c T2: p T >4GeV/c A: p T >1.5GeV/c  Raw correlation STAR Preliminary Mixed-event background Flow background for T2A1_T1  0 - 10% 10-20% 20-30% 30-40% Phys. Rev. C72 (2005) 014904 T2A1_T1: where a=0.2

10 STAR Quark Matter 2008, Jaipur Olga Barannikova, University of Illinois at Chicago 10 / 19 Background Normalization T1: p T >5 GeV/c, T2: p T >4 GeV/c, A: p T >1.5 GeV/c  -2 01 2 345 a.u. 85 80 75  -2 01 2 345  1.0 0.5 1.0 0 STAR Preliminary T2A1: Mixed-event bkgd ZDC central Au+Au Raw T2A1_T1: – Flow background T2A1: T2 direction (away-side)

11 STAR Quark Matter 2008, Jaipur Olga Barannikova, University of Illinois at Chicago 11 / 19 Correlated Background Signal + Background Background Signal a.u. T1T2 Accounting for correlated background on T1 and T2 side Correlated background give by di-hadron correlations T1: p T >5GeV/c, T2: p T >4GeV/c, A: p T >1.5GeV/c  -2 01 2 345 2 1 0 1 _dN_ N trig d  ) STAR Preliminary T2A1_T1 flow subt. T2A1 T1A1 0 2 4   -2 01 2 345 2 0 1 _dN_ N trig d  ) -2 4 STAR Preliminary Final T2A1_T1 correlation ZDC central Au+Au 12% N dijet

12 STAR Quark Matter 2008, Jaipur Olga Barannikova, University of Illinois at Chicago 12 / 19 Di-jets in d+Au 200 GeV Minimum bias data Preliminary result: min-bias d+Au Di-jet trigger T2 A1 T1 Single trigger A1 T2 T1: p T >5 GeV/c, T2: p T >4 GeV/c, A: p T >1.5 GeV/c T2A1_T1 T2A1  -2 01 2 345 1 0 1 _dN_ N trig d  ) 2 STAR Preliminary Difference in associated yield Di-triggers sample higher energy jets

13 STAR Quark Matter 2008, Jaipur Olga Barannikova, University of Illinois at Chicago 13 / 19 One high-p T trigger only: Away-side modification. Di-jet trigger: jet peaks on both near and away side! Preliminary result: central Au+Au T1: p T >5 GeV/c, T2: p T >4 GeV/c, A: p T >1.5 GeV/c Di-jet trigger T2 A1 T1 Single trigger A1 T2 T2A1_T1 T2A1  -2 01 2 345 2 0 1 _dN_ N trig d  ) -2 4 STAR Preliminary 200 GeV ZDC central 12%

14 STAR Quark Matter 2008, Jaipur Olga Barannikova, University of Illinois at Chicago 14 / 19 Au+Au vs d+Au comparison T1A1_T2 T2A1_T1  -2 01 2 345 2 0 1 _dN_ N trig d  ) STAR Preliminary 200 GeV Au+Au, 12% central Di-jets are suppressed. Once select di-jets, away-side associated particles NOT suppressed. Shapes of near- and away-sides similar. Central Au+Au ~ d+Au. No energy loss for triggered di-jets! Tangential di-jets (or punch-through without interactions). T1: p T >5 GeV/c, T2: p T >4 GeV/c, A: p T >1.5 GeV/c Au+Au d+Au  -2 01 2 345 1 0 1 _dN_ N trig d  ) STAR Preliminary 2 3 200 GeV Au+Au & d+Au

15 STAR Quark Matter 2008, Jaipur Olga Barannikova, University of Illinois at Chicago 15 / 19 Au+Au centrality comparison  projection: no ridge J. Putschke, QM2006 12% Central 40-60% MB 60-80% MB  -2 01 2 345 1 _dN_ N trig d  ) 2 STAR Preliminary 0 T1: p T >5 GeV/c, T2: p T >4 GeV/c, A: p T >1.5 GeV/c  projection: no significant centrality dependence T2A1_T1 Au+Au 12% central |  |<0.7 T2A1_T1 T1A1_T2  -1.5 0 1 -0.5 0.5 1.5 1 _dN_ N trig d  ) STAR Preliminary 0 ZYAM normalization in  0.5 1.0 T: 3-4 GeV/c A: 1.5-3 GeV/c

16 STAR Quark Matter 2008, Jaipur Olga Barannikova, University of Illinois at Chicago 16 / 19 Surface effect T1: p T >5GeV/c T2: p T >4GeV/c If the triggers have tangential bias: expect a term related to the surface: ~ R 2 ~ N part 2/3 STAR Preliminary T1= 5 GeV/c 100 0 200 300 N part 0 N trig __ N evt N part 2/3 0.4 d+Au x 10 -3 STAR Preliminary #T1T2 pairs / #Single triggers #Di-Jets / #Single triggers 100 0 200 300 0.015 0.05 0.01 N part

17 STAR Quark Matter 2008, Jaipur Olga Barannikova, University of Illinois at Chicago 17 / 19 Model calculation Renk, Phys. Rev. C 75, 054910 (2007) deposition for back-to-back jets Thorsten Renk, private comm. 2 density models T1  & T2   energy deposition by T2  T1 T2

18 STAR Quark Matter 2008, Jaipur Olga Barannikova, University of Illinois at Chicago 18 / 19 Increase T1-T2 asymmetry EMC-triggered data  access to higher p T triggers T1: p T > 7 GeV/c T2: p T > 4 GeV/c A1: p T > 1.5 GeV/c ~10% Centrality  -2 01 2 345 a. u. STAR Preliminary T2A1_T1: T1T2 High-p T triggers ~ no combinatoric background Di-jet triggered correlations: near-side ~ away-side no significant modifications? no associated particle suppression? ~10% Centrality  -2 01 2 345 1 _dN_ N trig d  ) 2 STAR Preliminary 0 4 T2A1

19 STAR Quark Matter 2008, Jaipur Olga Barannikova, University of Illinois at Chicago 19 / 19 Summary: New analysis of 2+1 correlations: Events triggered with 2 high-p T particles (T1: p T >5 GeV/c, T2: p T >4 GeV/c) and look at a third, associated particle (A1: p T >1,5 GeV/c). Preliminary results show a di-jet structure, with no modification of associated particles  tangential jets, or punch-through without interactions. New technique allows further exploration of the “surface bias”, and will probe the medium in a more controlled way.

20 STAR Quark Matter 2008, Jaipur Olga Barannikova, University of Illinois at Chicago 20 / 19 Au+Au vs d+Au comparison T1A1_T2 T2A1_T1  -2 01 2 345 2 0 1 _dN_ N trig d  ) STAR Preliminary 200 GeV Au+Au, 12% central same away same away Au+Au d+Au  -2 01 2 345 1 0 1 _dN_ N trig d  ) STAR Preliminary 2 3 200 GeV Au+Au & d+Au Di-jets are suppressed. Once select di-jets, away-side associated particles NOT suppressed. Shapes of near- and away-sides similar. Central Au+Au ~ d+Au. No energy loss for triggered di-jets! Tangential di-jets (or punch-through without interactions). T1: p T >5 GeV/c, T2: p T >4 GeV/c, A: p T >1.5 GeV/c

21 STAR Quark Matter 2008, Jaipur Olga Barannikova, University of Illinois at Chicago 21 / 19 STAR Preliminary ** Surface effect T1: p T >5GeV/c T2: p T >4GeV/c A: p T >1.5GeV/c If the triggers have tangential bias: expect a term related to the surface Surface ~ R 2 ~ N part 2/3 ** Shown are statistical errors only Number of triggers per event (per number of binary collisions) Single triggers and (all qualified) pairs behave similar to inclusives STAR Preliminary ** T1= 5 GeV/c 100 0 200 300 N part 0 N trig __ N evt N part 2/3 0.4 d+Au x 10 -3 STAR Preliminary ** #T1T2 pairs / #Single triggers #Di-Jets / #Single triggers 100 0 200 300 0.015 0.05 0.01 N part

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