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Jet medium interactions

Jet medium interactions. Pawan Kumar Netrakanti (For the STAR Collaboration) Purdue University, USA. Motivation Parton energy loss Medium response to energetic partons Summary. Outline. Workshop on Hot & Dense Matter in the RHIC-LHC Era February 21-14, 2008 TIFR. Motivation.

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Jet medium interactions

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  1. Jet medium interactions Pawan Kumar Netrakanti (For the STAR Collaboration) Purdue University, USA • Motivation • Parton energy loss • Medium response to energetic partons • Summary Outline Workshop on Hot & Dense Matter in the RHIC-LHC Era February 21-14, 2008 TIFR

  2. Motivation Correlations play a significant role in understanding medium properties

  3. Leading/trigger particle Near side Associated particles Dj Absence of medium STAR Preliminary Away side New STAR high pT p+p results away near Basic approach Calibrated probe Look for modification Medium formed in heavy-ion collisions Jet and high pT particle production in pp understood in pQCD framework STAR : PRL 97 (2006) 252001 STAR : PLB 637 (2006) 161 Is there any modification in heavy ion collisions ?

  4. Di-hadron Single y (fm) y (fm) x (fm) x (fm) Less surface bias Limited sensitivity of RAA to P(E,E) T. Renk, PRC 74 (2006) 034906 T. Renk and Eskola,hep-ph/0610059 2IAA 2RAA Di-hadron correlations more robust probes of initial density ~ H. Zhong et al., PRL 97 (2006) 252001 Advantage of di-hadron correlations

  5. Enhanced correlated yield at large  on near side Away side shape modification 2.5 < pTtrig< 4 GeV/c 1< pTassoc < 2.5 GeV/c d+Au Au+Au Medium response STAR: PRL 95 (2005) 152301 J.G. Ulery, QM 2005 STAR : J. Putschke, QM2006 STAR : M. J. Horner, QM2006 pTtrig=3-6 GeV/c, 2 GeV/c <pTassoc< pTtrig Reappearance of di-jets STAR : PRL 97 (2006) 162301 Current observations in STAR High pT suppression Away side yield modification Parton Eloss pTlp : 4 - 6 GeV/c STAR : PLB 655 (2007) 104 STAR : PRL 97 (2006) 152301 STAR : PRL 91 (2003) 072304 pTasoc : 2 GeV/c - pTlp How can we understand these features ?

  6. Where does the energy from the absorbed jets go or how are they distributed in the medium? Shock waves in recoil direction Coupling of radiation to collective flow Do they give answers to … Mechanism of energy loss in medium - • Few hard interactions or multiple soft interactions ? • What is the Path length dependence of energy loss ? - L2 or L • What is the probability distribution of parton energy loss? • Do partons loose energy continuously or discretely?

  7. 6< pT trig < 10 GeV IAA STAR Preliminary Npart • Inconsistent with PQM calculations • Modified fragmentation model better C. Loizides, Eur. Phys. J. C 49, 339-345 (2007) H. Zhong et al., PRL 97 (2006) 252001 Di-hadron fragmentation function (Away side) zT=pTassoc/pTtrig 1/Ntrig dN/dzT STAR Preliminary STAR Preliminary IAA zT • Denser medium in central Au+Au collisions compared to central Cu+Cu • zT distributions similar for Au+Au and Cu+Cu for similar Npart

  8. trigger in-plane trigger out-of-plane Observations : • 20-60% : away-side : from single-peak (φS =0) to double-peak (φS =90o) • Top 5% : double peak show up at a smaller φS • At large φS, little difference between two centrality bins Di-hadron correlations w.r.t reaction plane in-plane fS=0 3< pTtrig < 4 GeV/c, pTassoc : 1.0- 1.5 GeV/c out-of-plane fS=90o 20-60% STAR Preliminary Au+Au 200 GeV top 5% STAR Preliminary d+Au

  9. i ( i - )2 yi RMS = i yi RMS Path Length Effects STAR Preliminary v2 sys. error v2{RP} In-plane: similar to dAu in 20-60%. broader than dAu in top 5%. Out-of-plane: not much difference between the two centrality bins. v2{4} Au+Au 200 GeV 3< pTtrig < 4 GeV/c 1.0 < pTasso < 1.5 GeV/c Away-side features reveal path length effects

  10. STAR Preliminary near near dAu STAR Preliminary Medium Medium away away Conical emission or deflected jets ? (1-2)/2 deflected jets (1-2)/2 Central Au+Au 0-12% Conical Emission Conical Emission Experimental evidence of Conical emission 3 <pT-trig < 4 GeV/c 1 < pT-assoc < 2 GeV/c • Two component approach • Correlated to trigger (jets..) • Uncorrelated to trigger • (except via anisotropic flow) • Bkg normalization 3-particle ZYAM

  11. C3  STAR Preliminary  Subtraction of v2v2v4 terms using on v2 = 0.06 Subtraction of v2v2v4 term using v2 = 0.12 Strength and shape of away side structures observed depends on assumed magnitude of flow coefficients In cumulant approach: no conclusive evidence for conical emission so far Claude Pruneau : STAR : QM2008(Poster), PRC 74 (2006) 064910 Mach Cone or Cerenkov Gluons Cone angle (radians) • Mach-cone: Angle independent of associated pT • Cerenkov gluon radiation: Decreasing angle with associated pT STAR Preliminary pT(GeV/c) Naively the observed cone angle ~ 1.36 radians leads to very small (time averaged) velocity of sound in the medium

  12. d+Au, 40-100% Au+Au d+Au Au+Au, 0-5% 3 < pT(trig) < 6 GeV2 < pT(assoc) < pT(trig) Ridge in Heavy Ion Collisions What does these features reveal about the medium ? Can we get an idea about the energy lost by partons in the medium?

  13. J. Putschke (QM06) Ridge persists up to high pT-trig TRidge ~ Tinclusive < Tjet STAR Preliminary Features of the Ridge (at QM2006) STAR Preliminary Yield at large  independent on  STAR : J. Putschke, QM2006 Indication of two contributions Jet contribution + contribution arising due to jet propagating in the medium

  14. Jet and Ridge : Observations • Near-side jet yield independent of colliding system, Npart and trigger particle type • High pT-trig leads to higher jet yields • Supports : Parton fragmentation after parton Eloss in the medium • Ridge yield increases with Npart

  15. STAR Preliminary STAR Preliminary Jet ridge Particle Ratios: Jet & Ridge Jet Cone vs. Inclusive Ridge vs. Inclusive Jet : /K0s ~ 0.5 < inclusive Ridge : /K0s ~ 1 ~ inclusive • Ratios in cone smaller than inclusive • Ratios in ridge similar to inclusive

  16. Theoretical model interpretations 1)In medium radiation + longitudinal flow push N.Armesto et.al Phys.Rev.Lett. 93(2004) 242301 2)Transverse flow boost S.A.Voloshin, Phys.Lett.B. 632(2006)490 E.Shuryak, hep-ph:0706.3531 4)Momentum Kick C.Y. Wong hep-ph:0712.3282 3)Turbulent color fields A.Majumder et.al Phys. Rev. Lett.99(2004)042301 5)Recombination between thermal and shower partons R.C. Hwa & C.B. Chiu Phys. Rev. C 72 (2005) 034903 Can we discriminate between these physics interpretations?  3-particle Correlation in 

  17. 2 1 2) In medium radiated gluons diffused in  Motivation for 3-particle correlation in T : Trigger particle A1: First Associated particle A2: Second Associated particle STAR TPC acceptance for 3-particle correlation in  (||<1 and full azimuth) Dh1 = A1-T Dh2 = A2-T 1) Jet fragmentation in vacuum • In medium radiated gluons still collimated • 4) Combination between jet fragmentation and diffused gluons

  18. STAR Preliminary Analysis techniques Au+Au and d+Au at sNN = 200 GeV Trigger : 3<pT<10 GeV/c, ||<1 Associated : 1< pT<3 GeV/c, ||<1 Select both associated particles Near Side: || <0.7 Away Side: |- |<0.7 Mixed events to obtain background : (a) Min-bias events with same centrality (b) (primary vertex z) < 1 cm (c) Same magnetic field configuration

  19. - - 3-particle correlation background correlated • Raw  Raw Raw signal • Raw  Bkg Hard-Soft • Bkg1  Bkg1 • Bkg1  Bkg2 Soft-Soft

  20. dAu dAu dAu dAu STAR Preliminary STAR Preliminary STAR Preliminary STAR Preliminary AuAu 40-80% AuAu 40-80% AuAu 40-80% 2-particle Correlation AuAu 40-80% 0.7<R<1.4 STAR Preliminary AuAu 0-12% AuAu 0-12% AuAu 0-12% AuAu 0-12% 3-particle correlation (||<0.7) 3<pTTrig<10 GeV/c 1<pTAsso<3 GeV/c Shaded : sys. error. Line : v2 uncer.

  21. STAR Preliminary 0.7<R<1.4 STAR Preliminary Comparison (Projections) 3<pTTrig<10 GeV/c 1<pTAsso<3 GeV/c || <0.7 AuAu 0-12% is higher than dAu and AuAu 40-80%

  22. dAu AuAu 40-80% AuAu 0-12% STAR Preliminary STAR Preliminary STAR Preliminary Ridge = + Jet Summarizing … 3-particle correlation in Dh-Dh 3<pTTrig<10 GeV/c, 1<pTAsso<3 GeV/c, ||<0.7 • The ridge is approximately uniform or broadly falling with . • No significant structures along diagonals or axes. Ridge is uniform event by event.

  23. Potential for away-side analysis STAR Preliminary 3<pTTrig<10 GeV/c 1<pTAsso<3 GeV/c |-| <0.7 Another tool to study Ridge 3<pTtrig<4GeV/c 1.0<pTasso<1.5GeV/c Study the ridge with the help of Di-hardon correlation w.r.t. reaction plane. STAR Preliminary

  24. STAR Preliminary Ridge vs. Bulk Jet Cone vs. Bulk STAR Preliminary STAR Preliminary Summary : Medium Response • Strong jet-medium interaction observed. • Signals of conical emission observed in central Au+Au collisions at 200 GeV in 2-component approach • Medium responds through ridge formation. • New observations should provide significant constrains on the mechanism of ridge formation • Particle ratios in ridge similar to inclusive measurements • Di-hadron correlations with respect to reaction plane • indicates - ridge is dominated in-plane, consistent with • medium density effect STAR Preliminary

  25. Summary: Meduim Response • Three-particle correlation in - can potentially identify the underlying physics of the ridge. • Correlation peak at =~0, characteristic of jet fragmentation, is observed in d+Au, Au+Au 40-80% and central Au+Au 0-12%. • The peak sits atop of pedestal in central Au+Au. This pedestal, composed of particle pairs in the ridge, is approximately uniform or broadly falling with  in the measured acceptance. No significant structures along diagonals or axes. • Significant step forward in experimental study. Quantitative theoretical calculations are needed for further understanding.

  26. Thanks Thanks to STAR Collaboration Argonne National Laboratory Moscow Engineering Physics Institute Institute of High Energy Physics - Beijing City College of New York University of Birmingham NIKHEF and Utrecht University Brookhaven National Laboratory University of California, Berkeley Ohio State University Panjab University University of California - Davis Pennsylvania State University University of California - Los Angeles Institute of High Energy Physics - Protvino Universidade Estadual de Campinas Purdue University Carnegie Mellon University University of Illinois at Chicago Pusan National University University of Rajasthan Creighton University Rice University Nuclear Physics Inst., Academy of Sciences Instituto de Fisica da Universidade de Sao Paulo Laboratory of High Energy Physics - Dubna University of Science and Technology of China Particle Physics Laboratory - Dubna Shanghai Institue of Applied Physics Institute of Physics. Bhubaneswar SUBATECH Indian Institute of Technology. Mumbai Texas A&M University Indiana University Cyclotron Facility University of Texas - Austin Institut Pluridisciplinaire Hubert Curien Tsinghua University University of Jammu Valparaiso University Variable Energy Cyclotron Centre. Kolkata Kent State University Wayne State University University of Kentucky Institute of Modern Physics, Lanzhou Warsaw University of Technology Lawrence Berkeley National Laboratory University of Washington Massachusetts Institute of Technology Institute of Particle Physics Yale University Max-Planck-Institut fuer Physics Michigan State University University of Zagreb

  27. Back up

  28. STAR Preliminary ||<0.7 ||<0.7 Ridge 2-particle correlation AuAu ZDC central (0-12%) triggered data, 3<pTTrig<10 GeV/c, 1<pTAsso<3 GeV/c Black : Raw signal Pink:Mixed-event background Blue : Scaled bkgd by ZYA1 Red : Raw signal – bkgd Dh acceptance corrected

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