1 Olga Barannikova University of Illinois at Chicago LHC09, Prague Multi-hadron correlations at RHIC and LHC Olga Barannikova

2 University of Illinois at Chicago LHC09, Prague Outline Jet quenching in heavy ion collisions Evolution of jet-type correlation analyses Theoretical interpretation of data Multi-hadron correlations at RHIC Jets studies via correlations at LHC Outlook

3 Olga Barannikova University of Illinois at Chicago LHC09, Prague Motivation: early results Signature two-particle correlation result: Disappearance of the away side jet in central Au+Au collisions Effect vanishes in peripheral/d+Au collisions 4<p T trig <6 GeV/c 2<p T assoc <p T trig PRL 91 (2003) PRL 91 (2003) High p T hadron suppression: Final state effect in Au+Au collisions Observation extends to all accessible p T range

4 Olga Barannikova University of Illinois at Chicago LHC09, Prague Motivation: higher p T ? 4<p T trig <6 GeV/c 2<p T assoc <p T trig Recovering the away side: Away-side yield suppression Little modification of the Near-side yields No broadening on Near- or Away-sides d+Au 1/N trig dN /d(  ) Au+Au 20-40%Au+Au 0-5% 8 6 GeV/c PRL 97 (2006)

5 Olga Barannikova University of Illinois at Chicago LHC09, Prague High-p T – vacuum fragmentation? Near> PRL 97 (2006) Near-side: No dependence on z T in the measured range – no modification Away side: Suppression ~ level of R AA No dependence on z T in the measured range – no modification

6 Olga Barannikova University of Illinois at Chicago LHC09, Prague Jet modifications: p T  One high-p T, one low-p T trigger Reappearance of the away-side jet Double-hump structure hints at additional physics phenomena 3<p T trig <4 GeV/c 1.3<p T assoc <1.8GeV/c M. v Leeuwen, Hangzhou ‘06 PHENIX PRL 97, (2006). 1.0 GeV/c < p T assoc

7 Olga Barannikova University of Illinois at Chicago LHC09, Prague Au+Au 0-10% STAR preliminary Intermediate p T : the ridge d+Au min. bias STAR preliminary 3 < p T,trigger < 4 GeV/c Near-side correlation structure: Central Au+Au: cone-like + ridge-like Strong dependence of cone yield on trigger p T Week dependence if ridge yield on trigger p T J. Putschke QM ‘06

8 Olga Barannikova University of Illinois at Chicago LHC09, Prague Energy Loss in QCD Medium Double-hump Away-side Long-range Ridge on Same-side  Mach Cone Possible “splash back”  Parton mult. scattering, recombination Chiu, Hwa PRC72:034903,2005 – Radial flow + jet-quenching S.A.Voloshin, Phys.Lett.B. 632(2006)490 E.Shuryak, hep-ph:  Parton + longitudinal flow coupling Armesto et.al PRL93(2004)  … Quantitative measures energy loss…  Mach Cone Stoecker, Nucl. Phys. A750(2005)121 Casalderrey-Solana, Shuryak, Teaney, J. Phys. 27(2005)22 Ruppert, B. Muller, PLB 618 (2005)123 Renk, Ruppert, PRC 76 (2007)  Parton mult. scattering, recombination Chiu, Hwa, PRC 74(2006)  Radial flow boost + jet quenching Armesto, Salgado, Wiedemann, PRL 93 (2004)  Parton + longitudinal flow coupling  …

9 Olga Barannikova University of Illinois at Chicago LHC09, Prague d+Au Au+Au central Away side:  -  correlation nucl-exp: Experimental observation of conical emission   = 1.37 ± 0.02 (stat.)± 0.06 (syst.) Constrains the speed of sound c S ~ 0.2

10 Olga Barannikova University of Illinois at Chicago LHC09, Prague Near-side:  -  correlations No acceptance No apparent substructure – no gluon fragments/flow coupling? No cross-like term – ridge and cone decoupled? P. Netrakanti QM’08 3<p T Trig <10 GeV/c 1<p T Asso <3 GeV/c

11 Olga Barannikova University of Illinois at Chicago LHC09, Prague Use di-jets to study jet-medium effects “pin” the jet axis selecting back-to- back triggers study correlation w.r.t. this axis 2+1 Correlation Technique Courtesy of R.Hollis “jet-axis” trigger (T2) primary trigger (T1) associates Raw, uncorrected signal  a.u T1: p T >5GeV/c T2: p T >4GeV/c   ± 0.2 O.B., QM’08

12 Olga Barannikova University of Illinois at Chicago LHC09, Prague Olga Barannikova University of Illinois at Chicago   2+1 Signal Construction: Raw Correlation Background Signal % % 20-30% % Flow T1: p T >5GeV/c T2: p T >4GeV/c A: p T >1.5GeV/c   STAR Preliminary Away-side! Phys. Rev. C72 (2005) O.B., QM’08

13 Olga Barannikova University of Illinois at Chicago LHC09, Prague Correlated Background: Signal + Background Background Signal a.u. T1T2  Accounting for correlated background on T1 and T2 side Correlated background approximated by di-hadron correlations T2A1, T1A1 2+1 Correlation  _dN_ N trig d  ) STAR Preliminary  _dN_ N trig d  ) -2 4 STAR Preliminary

14 Olga Barannikova University of Illinois at Chicago LHC09, Prague Di-jets in d+Au 200 GeV Minimum bias data Slight narrowing of the same-side, big effect for away-side Difference in yields Di-triggers sample higher energy jets Di-jets in d+Au Collisions T2A1_T1 T2A1  _dN_ N trig d  ) 2 STAR Preliminary Single trigger vs. Di-jet trigger O.B., QM’08

15 LHC09, Prague Olga Barannikova University of Illinois at Chicago Di-Jets in Au+Au Collisions Au+Au d+Au  _dN_ N trig d  ) STAR Preliminary GeV Au+Au & d+Au Central Au+Au ~ d+Au. No away-side suppression! Shapes of near- and away-sides are similar  projection: no significant shape/yield modifications  projection: no apparent ridge O.B., QM’08 Au+Au 12% central |  |<0.7 T2A1_T1 T1A1_T2  _dN_ N trig d  ) STAR Preliminary GeV Au+Au

16 Olga Barannikova University of Illinois at Chicago LHC09, Prague Model Predictions deposition for back-to-back jets The energy deposition  : T1 , T2  Tune the sensitivity of 2+1 correlations to any medium recoil T. Rank PRC75 (2007)

17 Olga Barannikova University of Illinois at Chicago LHC09, Prague Monte Carlo studies for LHC Generator level study “Generic” HI detector: Charge hadron tracker full azimuthal coverage within |  |<2.5 p T assoc > 2GeV/c RHIC-based efficiency/v 2 assumptions 10% central Pb+Pb 5.5TeV   HYDJET Lokhtin et al, hep-ph:

18 Olga Barannikova University of Illinois at Chicago LHC09, Prague 15<p T Trig <20 GeV/c Mixed Event Background (ZYAM normalization) Correlation studies with Hydjet Can compare UNQUENCHED and QUENCHED mode Raw Signal a. u.  HYDJET Lokhtin et al, hep-ph: 

19 Olga Barannikova University of Illinois at Chicago LHC09, Prague Unquenched Hydjet Jet yields and energy measurements Jet-energy measurements via associated hadrons  p T in the correlation peak Jet-multiplicity measurements Sensitivity to quenching? Lower p T ? V. Chetluru QM’08

20 Olga Barannikova University of Illinois at Chicago LHC09, Prague Summary &Outlook: Medium-induced jet modifications Double-hump away side Ridge Differential studies are afforded by multi-particle correlation techniques 3particle  -   consistent with mach cone 3 particle  -   no substructure in ridge Change fragmentation/surface bias with di-jet triggers 2+1 correlations – unmodified di-jet observation Au+Au ~d+Au Potent tool for the LHC 4-7 February 2009

21 Olga Barannikova University of Illinois at Chicago LHC09, Prague Back-Up

22 Olga Barannikova University of Illinois at Chicago LHC09, Prague One high-p T trigger (only) Away-side modification Mono-jets? Energy loss for away-side jet? Di-jet trigger No modification on away-side Surface dominated? No energy loss for di-jets? Preliminary Results: T1: p T >5GeV/c T2: p T >4GeV/c A: p T >1.5GeV/c T2A1 T2A1_T1  _dN_ N trig d  ) -2 4 STAR Preliminary

23 Olga Barannikova University of Illinois at Chicago LHC09, Prague 4-7 February 2009 STAR Preliminary ** Surface Effects 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 N part 0 N trig __ N evt N part 2/3 0.4 d+Au x STAR Preliminary ** #T1T2 pairs / #Single triggers #Di-Jets / #Single triggers N part

24 Olga Barannikova University of Illinois at Chicago LHC09, Prague 24 October 6-10, particle correlation in   A1  A2 T : Trigger particle A1: First Associated particle A2: Second Associated particle Jet fragmentation in vacuum In medium radiation + Longitudinal flow Transverse flow boost N.Armesto et.al Phys.Rev.Lett. 93(2004) S.A.Voloshin, Phys.Lett.B. 632(2006)490 E.Shuryak, hep-ph: STAR TPC acceptance for 3-particle correlation in  (|  |<1 and full azimuth) Turbulent color field. Momentum Kick C.Y. Wong hep-ph: A.Majumder et.al Phys. Rev. Lett.99(2004)042301