Physics Revealed at Intermediate p T Rudolph C. Hwa University of Oregon Quark Matter 2008 Jaipur, India February 6, 2008

2 pTpT 26 lowintermediatehigh pQCDhydrono rigorous theoretical framework But that is where the action is, albeit experimental. What can we learn from the abundant data?

3 Overview Single particle distribution pTpT  Two particle correlation data Near sideAway side RidgeJetDouble bump Three particle correlation (1 or 2 triggers) Auto-correlation (no trigger) decrease with  Huge p/  at  =3.2 B/M ~ 1 (dAu) universal quark number scaling & breaking

4 Overview Single particle distribution pTpT  decrease with  Huge p/  at  =3.2 Two particle correlation data Near sideAway side RidgeJetDouble bump Three particle correlation (1 or 2 triggers) Auto-correlation (no trigger) B/M ~ 1 (dAu) universal quark number scaling & breaking

5 pTpT   R J S Recombination at Intermediate p T partonshadrons Reco What partons?Medium effects u, d, s g converted to q c,b,t primordial

6 pTpT  /K STAR in recombination/coalescence model (Reco) Baryon/Meson ratios “Baryon anomaly” On the contrary, high B/M ratio is a signature of Reco. Baryons need less quark momenta than mesons. implies that fragmentation is normal.

7  Elliptic flow M: TT + TS + SSB: TTT + TTS + TSS + SSS If M: B: then Molnar & Voloshin, PRL91,(2003) quark number scaling (QNS) a property of naïve recombination

8 RH&CBY, STAR, PRC75,054906(07) minbias However, at larger KE T M: TT + TS + SSB: TTT + TTS + TSS + SSS QNS is broken, but hadronization is still by recombination  p  K

9 BRAHMS, nucl-ex/ Au+Au at 62.4 GeV  Forward production TT TS TTT x F = 0.9 x F = 0.8 x F = 1.0 Shower partons are suppressed at the kinematical boundary Few antiquarks at large  mainly p produced

10 BRAHMS (preliminary) Comments at the end, if asked.

11 Ridgeology Putschke, QM06     J+RJ+R R J Correlation on the near side STAR ridge R Jet J Properties of Ridge Yield Dependences on N part, p T,trig, p T,assoc, trigger  B/M ratio in the ridge

12 Jet+Ridge (  ) Jet (  ) Jet  ) Putschke, QM06 R 1.Dependence on N part on p T,trig 2. p t,assoc. > 2 GeV STAR preliminary Ridge is correlated to jet production. Surface bias of jet  ridge is due to medium effect near the surface Medium effect near surface Ridges observed at any p T,trig Ridge yield0 as N part 0  depends on medium

13 3.Dependence on trigger  STAR (preliminary)A. Feng 20-60%, 3-4:1.5-2 |   1 RP ss TT Ridge develops by radial flow near the jet axis Mismatch of  T and the direction of radial expansion. has more ridge yield than Ridge yield decreases with increasing  s Comments at the end, if asked.

14 Ridge Putschke, QM06 4. Dependence on p T,assoc Yet Ridge is correlated to jet production; thermal does not mean no correlation. Ridge is from thermal source enhanced by energy loss by semi-hard partons traversing the medium. Ridge is exponential in p T,assoc slope independent of p T,trig Exponential behavior implies thermal source. STAR

15 5.B/M ratio in the ridge Ridge hadrons are formed by recombination Large B/M Bielcikova, WWND07 K ++ p t,assoc. > 2 GeV Au+Au 0-10% Putschke, QM06 p   2-4 STAR

16 Medium effect near surface coordinated with radial flow SS trigger TT ridge (R)   associated particles These wings are useful to identify the Ridge But of interest below is mainly the  distribution. Ridge is from enhanced thermal source caused by semi-hard scattering. Recombination of partons in the ridge STST peak (J)

17 What are the consequences of Ridgeology? 1.Jet correlation at low and intermediate pT 2.Effect on single particle spectra 3.Effect on elliptic flow

18 PHENIX 2.5<pT,trig<4 GeV/c 1.8<pT,assoc<2.5 PHENIX, PLB 649,359(07) Peak is referred to as jet 1. Jet correlation at intermediate pT Not seeing the ridge does not mean that it is not there. J R Correlation in J is different from correlation in R Does not see the ridge |  |<0.35

19 STAR preliminary Jet STAR preliminary Jet + Ridge PHENIX, PLB 649,359(07) SSTS TT Not un-correlated. Ridge would not be there without semi-hard scattering. How can intermediate-pt Jet yield be independent of centrality?  0.35

20 PHENIX data cannot be properly understood without taking Ridge into account 2.5<p T,trig <4.0 GeV/c PHENIX J R   2 p t,assoc. > 2 GeV Au+Au 0-10% Putschke, QM06 p  STAR

21 2. Effect of Ridge on single-particle spectra Semi-hard scattering at k T ~2-3 GeV/c is pervasive. Ridges are present with or without triggers. STAR, PRC 73, (2006) Auto-correlation without triggers. 0.15<pt<2.0 GeV/c, |  |<1.3, at 130 GeV

22 Bulk+ Ridge TT Semi-hard partons generating ridge TS Fragments from hard partons SS (fragmentation) T includes enhanced thermal partons --- Ridge

23 sss How can we see better the TT component? Remove the TS and SS components, if possible.  production:Au+Au   + anything (sss) s quark suppressed in shower pt dN/ptdpt (log scale) TTS TTT uud Exposes the long exponential behavior in  production

24  spectrum is exponential (thermal) Chiu & Hwa, PRC76, (2007) How can it have correlated partners? --- the  puzzle. STAR Resolution: Both  and its associated hadrons are in the Ridge. Prediction: there is no peak (J) in the  distribution --- only R R only

25  = cos -1 (b/2R) If the semi-hard jets are soft enough, there are many of them, all restricted to |  | < . A semi-hard scattering near the surface gives rise to a jet, whose direction, on average, is normal to the surface.   Initial configuration There is a layer of ridges at the surface without triggers. 3. Effect of Ridge on elliptic flow

26 In momentum space B B+R Relate ridgeology to v 2 Hwa, Use data on B(p T ) and R(p T ) bow tie region

27 Elliptic flow at low p T v 2 driven by Ridge Made no assumption about rapid thermalization.

28 Elliptic flow at intermediate p T v 2 dominated by TS recombination Hwa & CB Yang,

29 Away-side correlation PHENIX &.3060 Double-bump first observed by STAR STAR, PRL 95, (05) has been studied extensively --- experimentally and theoretically. Mach cone gluon radiation Cherenkov radiation deflected jets … Is there any connection between the double bumps and ridge w/o peak(J)? 2D mild dependence of D on pt,assoc favors

30 Possible relationship between ridge and bump (Renk, Jia) Near sideAway side RidgeBump Generated by semi-hard scattering Mach cone, deflected jet,--- due to recoil of semi-hard parton Due to recombination of enhanced thermal partons What is partonic structure of the Mach-shock-wave? Exponential pt,assocDistribution in pt,assoc ? Large B/M ratioB/M ratio is also large.

31 Papers submitted to the session on: “Response of Medium to Jets” Experimental Netrakanti (STAR) Wenger(PHOBOS) McCumber(PHENIX) Suarez(STAR) Feng(STAR) Adare(PHENIX) Barannikova(STAR) Catu(STAR) Daugherity(STAR) Pei(PHENIX) Haag(STAR) Szuba(NA49) G. Ma(STAR) Wang(STAR) Noferini(ALICE) Chetluru(UIC) Theoretical Majumder C.Y.Wong Gavin Mizukawa, Hirano, Isse, Nara, Ohnishi Pantuev Lokhtin, Petrushanko, Snigirev, Sarycheva Levai, Barnafoldi, Fai Betz, Gyulassy, Rischke, Stoecker, Torrieri Molnar Asakawa, Mueller, Neufeld, Nonaka, Puppert Schenke, Dumitru, Nara, Strickland Bauchle Plenary session X Ulery Jia

32 On to LHC Many predictions made (see arXiv: ) Those with existing codes can make extrapolations. Eskola et al (EKRT model) Is there new physics that cannot be obtained by extrapolation? SS hard parton hadron energy loss p/  >>1 Density of semi-hard partons is high at LHC. S S semi-hard partons SS or SSS recombination to form  or p.

33 What is the bulk background at LHC? Since SS and SSS recombination of semi-hard partons are uncorrelated, they occur in mixed events. Thus they belong to the background. But those partons are not thermal,  not in hydro. Can Ridge be identified in association with a high p T trigger --- p T,trig > 20 GeV/c? The ridge may not stand out among the background that consists of TT, TS, SS, TTT, TTS, TSS, SSS hadrons. Physics at intermediate p T at LHC may be very different from that at RHIC cannot be obtained by extrapolation. So there is a mismatch between bg and hydro.

34 Summary pTpT   R J S Physics revealed by phenomena observed at intermediate p T soft & semi-hard partons

35 TS Large B/M ratio QN scaling and breaking Exponential pT at large  v2 Ridge Jet Double bump Reco at LHC

36 Backup slides

37 At large x F, proton can be formed by leading quarks from different nucleons. p x can exceed 1 Antiquarks at low x i are affected by the regeneration of that depends on .  Pions are suppressed due to the lack of antiquarks at large x i. BRAHMS (preliminary)  should be larger less degradation more protons less increase of pions larger p/  ratio  ~0.75 Hwa & CBYang, PRC76,104901(2007) momenta degraded  survival probability “baryon stopping” Forward production

38 STAR (preliminary)A. Feng 20-60%, 3-4:1.5-2 |   1 3.Dependence on trigger  RP ss TT Ridge develops by radial flow near the jet axis Ridge yield decreases with increasing  s Mismatch of  T and the direction of radial expansion. has more ridge yield than