A guide through pT landscale of di-hadron correlation

1. A guide through pT landscale of di-hadron correlation and what can we learn about the partonic medium? Jiangyong Jia Stony Brook University EIC, 2007

2. Should I worry about non-flow in correlation? DΦ Away jet Near jet Dη PHENIX: event plane measured at 3<|h|<4, tracks in |h|<0.35 • Embed PYTHIA dijet into HIJING event to estimate the non-flow due to jets • HIJING event is weighed with measured v2(pt,h,b) • PYTHIA has 10 GeV dijet • Dijet->Biased Event plane->Fake v2 for trigger of the embedded jets. • Use away-side pp jet to approximate the ridge Y Ridge Hijing+flow

3. Should I worry about non-flow in correlation? 0.4<h<2.8 DΦ Away jet Near jet 3.0<h<4.0 Dη PHENIX: event plane measured at 3<|h|<4, tracks in |h|<0.35 • Embed PYTHIA dijet into HIJING event to estimate the non-flow due to jets • HIJING event is weighed with measured v2(pt,h,b) • PYTHIA has 10 GeV dijet • Dijet->Biased Event plane->Fake v2 for trigger of the embedded jets. • Use away-side pp jet to approximate the ridge Y Ridge Hijing+flow Fake v2 nucl-ex/0609009

4. What v2 to use in correlation? C(Df) = x(1+2<v2tv2a>cos2Df) + J(Df) • Non-flow due to jet is small with BBC Event plane • Other Non-flow and v2 fluctuations contribute to C(Df), so should be included in the two source model. • If minijets are important, then it should be much longer range in h, or many minijets emitted in a correlated way?

5. Sources of single particles 1 Flow+coalescense RAA Jet 3 5 pT 0.2 Production mechanisms: Jet (>5 GeV/c) and Flow+coalescense • How the energy of the 80% jet redistributed to low pT? • How to separate the Hard and Soft contribution down to low pT?

6. Sources of single particles 1 Flow+coalescense RAA Jet 3 5 pT 0.2 Production mechanisms: Jet (>5 GeV/c) and Flow+coalescense • How the energy of the 80% jet redistributed to low pT? • How to separate the Hard and Soft contribution down to low pT? • Jet correlation: Energy dissipation to low pT • partonic stage: Jet energy couple with hydro-flow • hadronization stage: Correlation affected by the coalescence process • Jet correlation provide constraints on the Geometrical bias

7. Sources of “jet” pairs Near jet p 0 Ridge Cone Away jet • Jet fragmentation contribution: • Near jet and away jet • Medium-induced contributions: • Near-side Ridge, away-side Cone. Energy at low pT • How they evolve/compete in pT1 vs pT2 landscape?

8. High pT : Geometrical bias STAR, Phys. Rev. Lett. 97 (2006) 162301 IAA T. Renk notation Transmission, Absorption shift IAA  RAA, Why?? 0.2

9. High pT : Geometrical bias STAR, Phys. Rev. Lett. 97 (2006) 162301 IAA T. Renk notation Transmission, Absorption shift RAA Absorption picture always predicts IAA<RAA. Need shift term! PRC.71:034909,2005 pT IAA  RAA, Why?? 0.2 Shift term is needed For fixed RAA, a larger eloss required for a flatter spectra

10. Energy shift n=4.8 in dn/dpt for 5-10 GeV/c trigger n= 8.1 in dn/ptdpt p0 spectra Per-trigger spectra Away spectra flatter than single spectra

11. Energy shift n=4.8 in dn/dpt for 5-10 GeV/c trigger n= 8.1 in dn/ptdpt p0 spectra Per-trigger spectra Away spectra flatter than single spectra nucl-ex/0410003 50% bigger • Bigger fractional eloss + flatter spectra --> Iaa ~ Raa • For g-jet, IAA>RAA! • constrains the geometry bias by combing Iaa and Raa

12. Correlation landscape in pTA, pTB arXiv:0705.3238 [nucl-ex] Dip grows Jet emerges • Suppression in HR, enhancement in SR • Peak location D independent of pT, jet reappearance not due to merging of side peaks?

13. Correlation landscape in pTA, pTB pTB • Many possible routes! • A single number summarizing the shape: RHS • Dip: RHS<1; Peak: RHS>1; flat: RHS=1 • Jet shape symmetry : • RHS (pTA, pTB) = RHS (pTB, pTA) pTA Head region: Suppression of jet Shoulder Region: Response of the medium

14. Awayside modification pattern vs pT • 1<pTA,B < 4 -> RHS<1 -> Shoulder region dominant! • pTA,B >5 -> RHS>1 -> Head region dominant! • pTA,B < 1 -> RHS~1 -> SR feed in + radiated gluons? Peak pt,1 pt,2>5 Flat 1<pt,1 pt,2<4 Cone Competition between “Head” and “shoulder”. Suppression and enhancement arXiv:0705.3238 [nucl-ex]

15. Jet spectra shape: Near and Shoulder region 2<pTA<3 3<pTA<4 4<pTA<5 Mean-pT at intermediate pT (1<pTB< 5) vs. Npart Near side • Near-side: flat with Npart (>100), increase with pTA. • Jet fragmentation • S region: flat with Npart (>100) , independent of pTA! • Universal slope, reflects property of the medium? arXiv:0705.3238 [nucl-ex]

16. Jet spectra shape: Near and Shoulder region 2<pTA<3 Away shoulder 3<pTA<4 4<pTA<5 Mean-pT at intermediate pT (1<pTB< 5) vs. Npart Near side • Near-side: flat with Npart (>100), increase with pTA. • Jet fragmentation • S region: flat with Npart (>100) , independent of pTA! • Universal slope, reflects property of the medium? arXiv:0705.3238 [nucl-ex]

17. Chemistry of Shoulder 0-20% 2.5-4x1.6-2 GeV/c • Similar shape for asso Baryon and Meson • Jet frag.<Bayron/meson< bulk medium. W. Holtzmann

18. Chemistry of the Shoulder? u u d d u u u d d u u d u u d Cooper-Fryer • Bulk medium are boosted by shock wave, which then coalesce into hadrons? => jet frag.<Bayron/meson<Bulk • Coalescence plays a big role here.

19. Parton-medium interaction Collective mode 1) Radiative energy loss -> High pT suppression 2) Lost energy converted into flow -> Intermediate pT enhancement 3) Remaining propagate -> Gluon feedback at low pT Deflected jet Propagation mode Punch-through jet Large angle radiation Coupling with medium: Mach flow / deflection. Deflection: Deflection angle decrease with increasing pT? No enhancement in multiplicity?

20. Radiation contribution • Polosa, C. Salgado, hep-ph/0607295, • sudokov splitting Can explain multiplicity Can be large angle => But for hard jets, radiation almost collinear I. Vitev, gluon feedback C. Salgado, U. Wiedemann, hep-ph/0310079

21. Near side: jet+ ridge 3 < pt,trigger < 4 GeV pt,assoc. > 2 GeV Au-Au 0-10% STAR preliminary Near side Components • jet peak • Elongated ridge

22. Near-side shape modification Trigger pT = 2.5-4 x 2-3 GeV/c unmodified at high pT Broaden at intermediate pT Df width broadening limited to intermediate pT

23. Near-side yield modification: IAA Dilution effects due to soft triggers Jet Ridge • Modifications decrease with increasing trigger pT (flattening) • Modification limited to pTA,B 4 GeV/c, similar to the away-side Shoulder. • STAR: This is due to the Ridge.

24. Intermediate pT : dilution effect • IAA reflects modification on Pairs √ and Triggers x per-jet yield  per-trig yield • Quantification via IAA is complicated when the trigger jet is modified. Dilutions effects Triggers have recombination contribution Boost from the radial flow? Trigger jet multiplicity is enhanced due to interaction with medium

25. Near side Iaa RAA We calculate the pair suppression factor, Jaa, from Iaa and Raa

26. Near side Jaa • At high pT, both hadrons comes from same jet! The JAA represent the suppression on the jet (>pt1+pt2). Since Jet suppression is constant at high pT, Jaa should approach the constant RAA level at high pT! • Real enhancement is factor of 4-5 at low pT? (no suppression of jet pairs!) Imply intermediate pT single enhancement not due to jets?! Jet pair suppression Leading hadron suppression =

27. Role of hadronization in correlation? • Bulk hadronization mechanisms can affect both the single (Thermal+Thermal Reco) and pairs (Thermal+Shower reco). Can it modify the correlation? • If so, how to isolate the pure partonic medium effect? Hadronization via Coalescence Parton-medium interaction X.N. Wang et.al : in medium fragmentation

28. Jet contribution at low pT? 1 Flow+coalescense RAA Jet 3 5 pT • Once we map out the jet properties in pT1, pT2, can we combine correlation results with single particle measurements and estimate the jet contribution or contribution initiated by jet, as function of pT. 0.2

29. Jet contribution at low pT? • We know the ratio of jet pair/combinatoric pair vs pT1, pT2. • How to translate this into single yield from jet? l

30. Ridge and cone : different mechanism? Near jet p 0 Ridge Cone Away jet • Both have similar property in pT and PID composition and softer than jet. • They are results of same matter, ridge and cone mechanism should play a role on both sides. • Reduced/no surface bias for intermediate pT correlation. Df Df

31. Summary • Jet correlation @ high pT provide constraints on the <eloss> and geometrical bias • Jet correlation @ intermediate pT shows complex evolution due to competition between Jet quenching and medium response on both near- and away-side. • Constrain the particle production mechanism by combing single and correlation landscape in pT. • Physics varying drastically with pT, good model should describe the full pT dependence.

32. Backup

33. Head region: jet punch-through • Low pTB range, decrease with Npart • Turn on of jet quenching, soft contribution dominates • High pTB range, flat with Npart • Punch through jet dominate and has same slope (soft contribution dies out) Fuqiang |Df-p|<0.4 STAR Preliminary dn/dh

34. Details of the suppression and enhancement arXiv:0705.3238 [nucl-ex] • HR exhibits early onset of suppression, relative to p+p, approach Raa at high pT: jet quenching! • H+S (entire away side) exhibits overall enhancement due to SR, up to pTA,B <4 GeV/c IAA depends on the integration window!

35. Integration range and pT matters! HR SR • One might reach misleading conclusion if only focus on limited pT. • No Modification seen in HR for this pTA x pTB bin but: • Would see enhancement for this pTA x pTB bin in the SR+HR, and • At high pT, would see a suppression even in SR+HR, and • At low pT, would see an enhancement even in HR. • Thus it is important to map out the full pTA, pTB and Df space!

37. pT evolution of jet function