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Di-hadron and three-particle correlations at RHIC

Di-hadron and three-particle correlations at RHIC. Pawan Kumar Netrakanti Nuclear Physics Division B.A.R.C., Mumbai. The “Ridge” & “Cone” Theoretical model expectations 2- and 3-particle correlation results Reaction plane dependence Ridge and Cone Summary. Outline. WPCF-2011

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Di-hadron and three-particle correlations at RHIC

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  1. Di-hadron and three-particle correlations at RHIC Pawan Kumar Netrakanti Nuclear Physics Division B.A.R.C., Mumbai The “Ridge” & “Cone” Theoretical model expectations 2- and 3-particle correlation results Reaction plane dependence Ridge and Cone Summary Outline WPCF-2011 September 20th -24th, Tokyo

  2. “Ridge” : Near-side correlations Au+Au 0-12% d+Au pTTrig > 4 GeV/c 2<pTAssoc<pTTrig GeV/c Phys. Rev. C 80 (2009) 064912. Near-side “ridge” in central Au+Au collisions. Properties similar to bulk Extends even upto higher rapidities. Long range correlations. Ridge persists to very high pT trigger particle QM09

  3. “Ridge” : Theoretical model expectations 2)Turbulent color fields A.Majumder et.al Phys. Rev. Lett.99(2004)042301 1)In medium radiation + longitudinal flow push N.Armesto et.al Phys.Rev.Lett. 93(2004) 242301 4)Momentum Kick C.Y. Wong hep-ph:0712.3282 3) Recombination between thermal and shower partons R.C. Hwa & C.B. Chiu Phys. Rev. C 72 (2005) 034903 ?? Jet ?? ?? Ridge ?? Trigger 6) Glasma Flux tube A. Dumitru et. al Nucl. Phys. A 810, 91 (2008) K. Dusling et. al Nucl. Phys. A 828, 161 (2009) 5) Transverse flowboost S.A.Voloshin, Phys.Lett.B. 632(2006)490 E.Shuryak, hep-ph:0706.3531 Assoc. STAR 3-particle Acceptance Can we distinguish between these physics interpretations?  3-particle correlation in 

  4. “Cone” : Away-side correlations Au+Au • Away-side structure in 2-particle • correlations in central collisions. • Conical emission is a possible • explanation for shape: • Mach-cone shock waves • Čerenkov gluon radiation • Other explanations suggested: • Large angle gluon radiation • Deflected jets • deflected by radial flow • path-length dependent energy loss • Odd harmonics (v3 ,v5 …….) STAR PRL 95 152301 PHENIX PRL 97 052301  0 /2  Study di-hadron triggered correlations as a function of event plane angle () s = |t - | ~0o : In-plane s = |t -  | ~90o: Out-of-plane Path length dependence of energy loss 3-particle correlations in azimuthal angle

  5. in-plane fS~0 out-of-plane fS~90o Di-hadron correlations w.r.t EP Au+Au d+Au ||<1 STAR Preliminary Background : Mixed events (v2) ||>0.7 STAR Preliminary ||<0.7 arXiv : 1010.0690

  6. Estimate of triangular flow ZYAM background normalization Using FTPC v2 (2.5 < || < 4.0) arXiv : 1010.0690 V32 / v22=0.1 STAR Preliminary Using Fourier v2{2,|Dh|>0.7} D • The above results represent the v2{2} and v4{y2}=1.15v22 subtracted signal. • Blue/green curves represent estimated/measured v3{2}. • Remainder v4{y2-uncorr}:

  7. vn subtracted di-hadron correlations Au+Au 20-60%, pTtrig=3-4 GeV/c, pTassoc=1-2 GeV/c, large |Dh|>0.7, ZYAM background. 1/NtrigdN/dΔφ v3 flow background v4{uncorr} background STAR Preliminary STAR Preliminary Df Df Df • Black: v2{2} and v4{y2}=1.15v22 subtracted signal. • Red : v3{2} and v4{y2-uncorr} subtracted signal. • Results qualitatively consistent; near-side ridge slightly reduced due to vn.

  8. vn subtr. dihadron correl. w.r.t. y2 and y3 Au+Au 20-60%, pTtrig=3-4 GeV/c, pTassoc=1-1.5 GeV/c, large |Dh|>0.7 Simple background normalization: <signal> = 0. y3 in-plane y2 in-plane 1/NtrigdN/dΔφ STAR Preliminary STAR Preliminary y2 out-plane y3 out-plane Df Df Dihadron correlation broadens from in- to out-of-plane in y2 while narrows in y3

  9. Three-particle - correlations Phys. Rev. Lett. 102 (2009) 52302 3<pTTrig<4 GeV/c 1<pTAssoc<2GeV/c d+Au pp Au+Au 80-50% Au+Au 50-30% Au+Au 0-12% Au+Au 30-10% Have to estimate the vn effects….and working on it

  10. Projections and angle 3<pTTrig<4 GeV/c 1<pTAssoc<2GeV/c d+Au 0-12% Au+Au shows significant peaks in off-diagonal projections at: 1.370.02(stat.) +0.06 (sys.) radians. Black: reaction plane frame 3-particle cummulant. Au+Au 0-12% -0.07 Phys. Rev. Lett. 102 (2009) 52302 • No significant pT dependence of observed emission angle. • Consistent with Mach-cone • Inconsistent with simple Čerenkov radiation

  11. Three-particle - correlations 3<pTtrig<10GeV/c 1<pTassoc<3 GeV/c ||<0.7 Phys. Rev. Lett. 105, 022301 (2010) Same-sign triplets (AAT) Ridge : 4* AAT  (AAT ) Same-sign associated pair and opposite sign trigger particle Jet-like: Total - Ridge Like-sign triplets : Dominated by ridge

  12. Average pair densities 3<pTtrig<10GeV/c 1<pTassoc<3 GeV/c ||<0.7 Au+Au 0-12% Jet-like Ridge <Pjr> <Prr> <Pjj> <Pjr> <Pjr> <Pjr> <Prr> <Pjj> : 0.077  0.026 <Prr> : 0.114  0.039 Jet-ridge cross pairs <Pjr> : -0.004  0.025 Ridge production appears to be uncorrelated with the presence of jet. Phys. Rev. Lett. 105, 022301 (2010)

  13. Radial and angular dependence Phys. Rev. Lett. 105, 022301 (2010) +/2 R -/2 Ridge is broad. No prominent substructures in ridge.

  14. Data and models Model : Diagonal excess Data: Uniform 2)Turbulent color fields 1)In medium radiation + longitudinal flow push Model: uniform ridge, jet-ridge cross pairs. Data:Broad Ridge, no jet-ridge cross pairs 4) Momentum Kick 3) Recombination Model ?? Model : Jet-ridge cross pairs Data <Pjr> ~ 0 Model: jet-ridge cross pairs. Data : <Pjr> ~ 0 ?? ?? ?? 6) Glasma Flux tube 5) Transverse flowboost Model: Uniform, Jet-ridge cross pairs Model: Uniform. Jet-ridge cross pairs ???? Data: Uniform. No jet-ridge cross pairs Data: Uniform. No jet-ridge cross term

  15. Summary Study of correlation of particles has improved the understanding of the heavy-ion collisions. “Ridge” • Jet and Ridge are “separated” by using the charge dependence. • Ridge broad and uniform, jet narrow in . • Ridge production appears to be uncorrelated to the presence of • the jet. • Ridge may have the path length dependence. “Cone” • Evolution of double peak structure from in-plane to out-of-plane • Dihadron correlations w.r.t. y2 and y3 may indicate • path-length/geometry effects • Physics mechanism still under debate. Thank you

  16. Back up

  17. Triangular flow Odd harmonics may not be neglected. Alver, Roland, PRC 81, 054905 (2010) ALICE, PRL 107, 032301 (2011) dN/d = 1 + 2v22cos(2Df) + 2v32cos(3Df) + 2v42cos(4Df)….

  18. near near near Medium Medium M M Medium away away away di-jets deflected jets Conical Emission “Cone” : Theoretical model expectations Cerenkov gluon radiation : 3-particle correlation 2-particle correlation • Gluons radiated by superluminal partons. • Angle is dependent on emitted momentum. Čerenkov angle vs emitted particle momentum • I.M. Dremin (Nucl. Phys. A750: 233, 2006) • V. Koch et. al. (Phys. ReV. Lett. 96, 172302, 2006)  Mach Cone : PNJL Model Trigger • Mach angle depends on speed of sound in medium • T dependent • Angle independent of associated pT. Can we distinguish between these physics interpretations?  3-particle correlation in  Away-side 

  19. vn subtracted dihadron Correlations(pTtrig=3-4 GeV/c, pTassoc=1-2 GeV/c, large |Dh|>1) Simple background normalization: average signal = 0. Au+Au 80-50% 50-20% ZDC 12% STAR Preliminary STAR Preliminary STAR Preliminary Df Df Df Remark: Associated pT range ~ pTref. Case of data-data=0: jet-correl nonflow is subtracted; what’s left are similar between centralities, and resemble a v1 component. ALICE, PRL 107 (2011) pTref=0.2-5 GeV/c

  20. vn subtracted dihadron correlations(pTtrig=3-6 GeV/c, pTassoc=2-3 GeV/c, |Dh|>1) • Bkgdsubtracted using two-particle vn{2} (flow+fluctuation). • vn{4} may not be very relevant: fluctuation effect is negative; v3{4}~0. • Near-side ridge in central collisions seems still visible. Ridge may be not entirely due to vn. • Away-side is suppressed at high-pT in central collisions. Shape modification at intermediate-low pT. • Residual non-flow should be present in the measured vn. Important next step is to separate non-flow contribution. Simple background normalization: <signal> = 0. 50-20% ZDC 12% 80-50% STAR Preliminary STAR Preliminary STAR Preliminary Df Df Df

  21. STAR: Aihong Tang, Proc.24th Winter Workshop on Nuclear Dynamics Hydro, Boltzmann calculations: J. –Y. Ollitrault

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