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Identifying the underlying physics of the ridge via 3-particle - correlations in STAR

This presentation discusses the ridge phenomenon and various theoretical models for its interpretation. It explores the motivation for studying 3-particle correlations in η and presents analysis techniques and results. The potential to discriminate between different physics interpretations is also discussed.

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Identifying the underlying physics of the ridge via 3-particle - correlations in STAR

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  1. Identifying the underlying physics of the ridge via 3-particle - correlations in STAR Pawan Kumar Netrakanti (For STAR Collaboration) Purdue University

  2. Outline • Ridge phenomenon and theoretical models • Motivation for 3-particle correlation in  • Analysis techniques • Results • Summary

  3. STAR Preliminary J. Putschke (QM06) C. Suarez (poster QM08) ridge jet Ridge Phenomena STAR, PRL 95 (2005) 152301 AuAu dAu

  4. 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 

  5. 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

  6. 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

  7. 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

  8. - - 3-particle correlation background correlated • Raw  Raw Raw signal • Raw  Bkg Hard-Soft • Bkg1  Bkg1 • Bkg1  Bkg2 Soft-Soft

  9. 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.

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

  11. Comparison (in pT) || <0.7 STAR Preliminary Run 4: 3<pTTrig<10 GeV/c 1<pTAsso<3 GeV/c STAR Preliminary Run 7: ETTrig>5.5 GeV 3<pTAsso<5.5 GeV/c

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

  13. 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. Aoqi Feng (Parallel Talk QM08) STAR Preliminary

  14. Summary • 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. Thank you

  15. Back Up

  16. A2 A1 Motivation for 3-particle correlation in  STAR TPC acceptance for 3-particle correlation in  (||<1 and full azimuth) T : Trigger particle A1: First Associated particle A2: Second Associated particle In medium radiation + Longitudinal flow Jet fragmentation in vacuum N.Armesto et.al Phys.Rev.Lett. 93(2004) 242301 Transverse flow boost Turbulent color field. Momentum Kick C.Y. Wong hep-ph:0712.3282 S.A.Voloshin, Phys.Lett.B. 632(2006)490 E.Shuryak, hep-ph:0706.3531 A.Majumder et.al Phys. Rev. Lett.99(2004)042301

  17. Comparison with pTTrig 1<pTAssoc<3 GeV/c || < 0.7 STAR Preliminary 3<pTTrig<4 GeV/c STAR Preliminary 4<pTTrig<10 GeV/c

  18. Comparison with pTAssoc 3<pTTrig<10 GeV/c ||<0.7 1<pTAsso<2 GeV/c STAR Preliminary 2<pTAsso<3 GeV/c STAR Preliminary

  19. Soft-Soft and Hard-Soft terms 3<pTTrig<10 GeV/c 1<pTAsso<3 GeV/c ||<0.7, 0-12% Au+Au Soft-Soft Term: STAR Preliminary STAR Preliminary STAR Preliminary Hard-Soft Term: STAR Preliminary STAR Preliminary STAR Preliminary

  20. 3-particle correlation 3<pTTrig<10 GeV/c 1<pTAsso<3 GeV/c STAR Preliminary dAu 0-100% Au+Au 40-80% Au+Au 0-12% STAR Preliminary

  21. 3<pTTrig<10 GeV/c 1<pTAsso<3 GeV/c Projections : For all regions STAR Preliminary dAu 0-100% Au+Au 40-80% STAR Preliminary Au+Au 0-12%

  22. 2-particle Correlation 3<pTTrig<10 GeV/c 1<pTAsso<3 GeV/c R1 : ||<0.7 STAR Preliminary STAR Preliminary

  23. 3-particle Signal and Background 3<pTTrig<10 GeV/c 1<pTAsso<3 GeV/c R1 : ||<0.7 RawRaw JetJet SoftSoft Hard-Soft STAR Preliminary STAR Preliminary STAR Preliminary Background Raw Signal Final Signal 

  24. dAu dAu dAu dAu STAR Preliminary STAR Preliminary STAR Preliminary AuAu 40-80% AuAu 40-80% STAR Preliminary 2-particle Correlation AuAu 40-80% AuAu 40-80% 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.

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