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Fuqiang Wang

Jet correlation measurements from RHIC/STAR. Fuqiang Wang. p+p. Au+Au. hadrons. q. q. q. q. well cali brated: can be calculated by pQCD. leading particle. hadrons. q. q. hadrons. leading particle. The Idea. embed di-jet in AA interact with the medium

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Fuqiang Wang

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  1. Jet correlation measurements from RHIC/STAR Fuqiang Wang

  2. p+p Au+Au hadrons q q q q well calibrated: can be calculated by pQCD. leading particle hadrons q q hadrons leading particle The Idea • embed di-jet in AA • interact with the medium • probe medium properties • di-jet, back-to-back. • well calibrated – pQCD.

  3. AA over binary-scaled pp Single hadron suppressed High-pt mostly from jets. x5 Strong jet-quenching

  4. Di-hadron Single y (fm) y (fm) x (fm) x (fm) Less surface bias Dihadron better sensitivity dihadron T. Renk, PRC 74 (2006) 034906 T. Renk and Eskola,hep-ph/0610059 single hadron H. Zhang et al., PRL 97 (2006) 252001

  5. pTtrig>4 GeV/c, 2<pTassoc<4 GeV/c Dihadron suppressed

  6. Occasionally they do come out STAR, PRL 97 (2006) 162301.

  7. 1 _dN_ Ntrigd(Df ) STAR Preliminary Au+Au d+Au 3 2 1 T2A1_T1 T1A1_T2 1.0 1 _dN_ Ntrigd(Dh ) Au+Au 12% central |Df |<0.7 0 -2 -1 2 0 1 3 4 5 0.5 Df 0 STAR Preliminary -1 -1.5 0 0.5 -0.5 1.5 1 Dh Detour: if trigger on the di-jet… Trigger 1: pT>5 GeV/c, Trigger 2: pT>4 GeV/c, Assoc: pT>1.5 GeV/c STAR Preliminary no ridge No modification from d+Au to Au+Au No energy loss for triggered di-jets! Tangential di-jets (or punch-through without interactions).

  8. pTtrig=4-6 GeV/c, pTassoc=0.15-4 GeV/c PRL95 (2005) 152301 Energy is not lost STAR, PRL95 (2005) 152301 Low pT Broader, softer.

  9. near away mach cone Energy shows up in a strange way near near pTtrig=3-4 GeV/c, pTassoc=1-2.5 GeV/c deflected jets away away M. Horner, QM06. double peaked

  10. near away 3-particle correlation d+Au Au+Au 0-12% Evidence of Conical emission 1.38 ± 0.02 (stat.) ± 0.06 (syst.)

  11. length x 1016 time x 1022 3cSDt 2cSDt cSDt qM zone ofaction 2 1 0 v > cS zone of silence Why is it important? Casalderrey-Solana, Shuryak, Teaney, hep-ph/0411315 Mach cone angle qM speed of sound cS = sin(qM) equation of state

  12.   (z - ut) dE/dx model, pQCD, N=4 SYM Renk, Ruppert, PRC 76, 014908 (2007) Neufeld, Muller, Ruppert u = 0.99955 c Chesler & Yaffe arXiv:0712.0050 u = 0.75 c

  13. The near-side ridge STAR, PRL95 (2005) 152301. Au+Au ridge d+Au

  14. Extend to very forward rapidity Trigger: 3<pTtrig<4 GeV/c, 0.2<pTassoc< 2 GeV/c d+Au MB Au+Au central PHOBOS preliminary • Away-side very similar. • Ridge extends to very forward rapidity.

  15. What is the ridge? In medium radiation + Longitudinal flow push N.Armesto et.al PRL 93 (2004) 242301 Turbulent color fields A.Majumder et.al PRL 99 (2004) 042301

  16. dAu AuAu 40-80% AuAu 0-12% STAR Preliminary 3-particle correlation in Dh-Dh 3<pTTrig<10 GeV/c, 1<pTAsso<3 GeV/c, ||<0.7 • The ridge is uniform in every event. • No significant structures along diagonals or axes.

  17. in-plane fS=0 out-of-plane fS=90o jet ridge Near-side: jet + ridge Aoqi Feng, CCNU Au+Au 20-60% 3<pTtrig<4, 1.5<pTtrig<2.0 GeV/c Ridge |Dh|>0.7 Away-side STAR Preliminary Jet |Dh|<0.7 – |Dh|>0.7 Increasing away-side pathlength  increasing modification

  18. out-of-plane in-plane STAR Preliminary jet ridge 20-60% v2{4} Jet consistent with d+Au. Ridge drops with trigger angle from RP. v2{RP} Ridge dominant only in-plane Aoqi Feng, CCNU 3<pTtrig<4, 1.5<pTtrig<2.0 GeV/c STAR Preliminary Strong near-side jet-medium interaction in reaction plane  large ridge. Minimal near-side interaction perpendicular to reaction plane.

  19. Summary • Strong jet quenching. • Strong medium modification to jet correlation. • Evidence of conical emission – Mach-cone shock wave. • Ridge not well understood yet –new results to come.

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