Cone is medium response, Ridge is medium itself. Fuqiang Wang Purdue University For the STAR Collaboration

Plan of talk Away-side cone: medium response to hard probes Near-side ridge: medium response or itself? Bridger ridge, Montana 2Flow and Dissipation Workshop, Trento, Sept. 2009Fuqiang Wang

The away-side structure 3 p+p Au+Au Flow and Dissipation Workshop, Trento, Sept. 2009Fuqiang Wang PHENIX  High p T trigger particle associated particles Away- side trigger jet 0  1 

Possible physics scenarios p T trig =3-4 GeV/c, p T assoc =1-2.5 GeV/c Away-side trigger jet 0  1  trigger jet Mach cone away trigger jet deflected jets away event 1 event 2 Surface bias 4Flow and Dissipation Workshop, Trento, Sept. 2009Fuqiang Wang

 1 =  1  trig  2   0 0 =  2  trig 3-particle azimuthal correlation  1  2  0 0  away trigger jet deflected jets away event 1 event 2 trigger jet Mach cone away signature of conical emission 5Flow and Dissipation Workshop, Trento, Sept. 2009Fuqiang Wang

Evidence of conical emission d+AuAu+Au central  1  2  0 0  Away-side STAR, PRL 102, (2009) trigger 6Flow and Dissipation Workshop, Trento, Sept. 2009Fuqiang Wang

Conical emission angle  = 1.37 ± 0.02 (stat.) ± 0.06 (syst.) STAR, PRL 102, (2009) Away-side trigger  Constant cone angle vs p T suggests Mach Cone shock waves may be the underlying mechanism. 7Flow and Dissipation Workshop, Trento, Sept. 2009Fuqiang Wang

Higher trigger p T 4 < p T trig < 6 GeV/c 1 < p T assoc < 2.5 GeV/c 6 < p T trig < 10 GeV/c 1 < p T assoc < 2.5 GeV/c 1 < p T assoc < 2 GeV/c 8Flow and Dissipation Workshop, Trento, Sept. 2009Fuqiang Wang

Theory calculations Parton energy loss: Renk et al. PRC 76, (2007) pQCD + hydro: Neufeld et al. arXiv: quark v =  (z - ut)   9Flow and Dissipation Workshop, Trento, Sept. 2009Fuqiang Wang

AdS/CFT Correspondence N N = 4 Super-Yang-Mills theory in 4d with SU(N C ) Maldacena (1997), Gubser, Klebanov,Polyakov; Witten (1998) YM observables at infinite N C and infinite coupling can be computed using classical gravity. A string theory in 5d AdS Measure heavy quark Mach-cone shock waves:  Experimental consequence of string theory? Chesler & Yaffe arXiv: Heavy quark u = 0.75c 10Flow and Dissipation Workshop, Trento, Sept. 2009Fuqiang Wang

 M = 1.37 p  HG c S = 0.45 QGP c S = √1/3 = 0.58 Mixed phase c S = 0 Speed of sound? c S far smaller than HG or QGP. Must have mixed phase (phase transition). EOS: p(  ) speed of sound c S ~ 0.2 However, model calculations indicate that Mach Cone angle can be altered by medium flow. 11Flow and Dissipation Workshop, Trento, Sept. 2009Fuqiang Wang

Investigating flow effect on cone angle

Fit to large  azimuthal correlations 2 Gaus: Ridge at 0 and ridge at , same shape, diff. magnitudes 2 Gaus: identical conical emission peaks symmetric about . STAR Preliminary 13Flow and Dissipation Workshop, Trento, Sept. 2009Fuqiang Wang Au+Au 20-60%, 3<p T trig <4, 1<p T trig <2 GeV/c

Cone angle takes off after trigger  s =45 o. Split in p T after  s =45 o. Cone angle ~constant over p T at  s <45 o. STAR Preliminary 14Flow and Dissipation Workshop, Trento, Sept. 2009Fuqiang Wang

Is there a back-to-back RIDGE? RP Trig. Ridge Away 2 Away 1 Near Jet Away-Side Ridge 15Flow and Dissipation Workshop, Trento, Sept. 2009Fuqiang Wang

Connection between near- and away-side Away-side 0  1  STAR Preliminary 16Flow and Dissipation Workshop, Trento, Sept. 2009Fuqiang Wang

∆φ Separate 1 st and 2 nd quadrants trigger particles Azimuthal correlation for large |  |>0.7 Near-side ridge Gauss repeated at “+π” Subtract back-to-back symmetric ridge peaks ∆φ STAR Preliminary 17Flow and Dissipation Workshop, Trento, Sept. 2009Fuqiang Wang

Away-side asymmetric cone positions Evidence of flow effect on conical emission. Important to disentangle flow effect and conical emission angle. 1 st cone peak 2 nd Cone peak φsφs ∆φ STAR Preliminary RP trigger 2 nd Cone 1 st cone 18Flow and Dissipation Workshop, Trento, Sept. 2009Fuqiang Wang

 trigger particle p T > 3 GeV/c assoc. particle p T =1-2 GeV/c d+Au Au+Au ridge   The longitudinal ridge  ~ 1  ~ 0 High-p T trigger particle  associated particle |  |< 0.7 Bridger ridge, Montana 19Flow and Dissipation Workshop, Trento, Sept. 2009Fuqiang Wang

What’s already known about ridge M. Daugherity (STAR), QM’08, J.Phys.G35:104090,2008 STAR, arXiv: Ridge present in untriggered correlation. Ridge increases with centrality. Ridge pt spectrum is a bit harder than bulk. Ridge particle composition similar to bulk.

Ridge extended to very large  PHOBOS, arXiv: STAR Preliminary 2.7<|  |<3.9 p T assoc > 1.0 GeV/c STAR, arXiv:nucl-ex/ Flow and Dissipation Workshop, Trento, Sept. 2009Fuqiang Wang

New insights from RP-dependent dihadron correlations

jet ridge  cut to “separate” jet and ridge  |∆η|>0.7 = ridge + away-side Jet = (|∆η| 0.7) assuming ridge is uniform in ∆η.  Feng, QM’06. STAR Preliminary Au+Au 20-60%, 3<p T trig <4, 1.5<p T trig <2.0 GeV/c d+Au 23Flow and Dissipation Workshop, Trento, Sept. 2009Fuqiang Wang

Ridge decreases with RP Ridge drops when trigger particle moves away from RP. in-planeout-of-plane trigger |  s  STAR Preliminary 24Flow and Dissipation Workshop, Trento, Sept. 2009Fuqiang Wang

A model prediction motivated by data in-plane jet flow aligned more ridge out-of-plane jet flow misaligned less ridge Chiu,Hwa, arXiv: Correlated Emission Model (CEM) Alignment of jet propagation and medium flow produces the ridge. If correct, would produce measureable asymmetry in near-side ridge correlation peak. Correlated Emission Model (CEM) 25Flow and Dissipation Workshop, Trento, Sept. 2009Fuqiang Wang

Remove away-side from large  correlation Ridge Jet Konzer, QM’09. STAR Preliminary |∆η|>0.7 ∆  =  assoc –  trig Trig. pt=3-4 GeV/c, assoc pt=1-1.5 GeV/c φ s = 0 to to to to to to π Au-Au 20-60% ZYAM Jet remains constant Ridge Decreases Jet symmetric Ridge asymmetric 26Flow and Dissipation Workshop, Trento, Sept. 2009Fuqiang Wang

Correlation Asymmetry in-plane trigger pt=3-4 GeV/c Jet Ridge  s |=  trig – ψ RP out-of- plane CEM model Ridge: assoc pt=1-1.5 GeV/c Ridge: assoc pt=1.5-2 GeV/c Jet: assoc pt=1.5-2 GeV/c STAR Preliminary Away-side is Asymmetric (not shown in plot). Jet is symmetric. Ridge is Asymmetric! Ridge may be due to jet-flow alignment. v 2 syst. 27Flow and Dissipation Workshop, Trento, Sept. 2009Fuqiang Wang

New insights from 3-particle  -  correlation

How does long  come about? Many models on the market. |  |<0.7 3<p T trig <10 GeV/c, 1<p T assoc <3 GeV/c d+AuCentral Au+Au Netrakanti, QM’09. arXiv: STAR Preliminary 3-particle  -  correlations N. Armesto et al., Phys. Rev. Lett. 93 (2004) Fuqiang WangNucleus-Nucleus 2009, August

3<p T trig <10 GeV/c 1<p T assoc <3 GeV/c |  |<0.7 3-particle  -  correlations Charge independent (All) AA Like = (AA Like T Like + AA Like T Unlike ) AA Unlike = All - AA Like dAu AuAu 12% STAR Preliminary Netrakanti, QM’09. STAR Preliminary

Separate jet and ridge Jet has charge ordering ridge does not ridge Same-sign triplets: Only ridge, no jet. jet Netrakanti, QM’09. arXiv: STAR Preliminary

Ridge is structureless No prominent subtructures in ridge.  (jet) = 0.25  0.09  (ridge) = 1.53  0.41 Radial Projection Angular Projection STAR Preliminary Netrakanti, QM’09. arXiv: STAR Preliminary R  32Flow and Dissipation Workshop, Trento, Sept. 2009Fuqiang Wang

Ridge-jet cross pairs 33 Ridge and jet appear to be anti-correlated. Netrakanti, QM’09. arXiv: STAR Preliminary Fuqiang Wang

Experimental facts 1)Ridge increases with centrality. 2)Ridge spectrum a bit harder than bulk. 3)Ridge particle composition similar to bulk. 4)Ridge present in untriggered correlation. 5)Ridge is mainly in-plane. 6)Ridge is asymmetric in . 7)Ridge is very wide. 8)Ridge is random. 9)No jet-ridge cross-talk. 10)Ridge may be back-to-back. 11)Ridge seems unrelated to jet. Now let’s go to models… 34Flow and Dissipation Workshop, Trento, Sept. 2009Fuqiang Wang

In-medium rad. + long. Flow push Ridge increases with centrality. Ridge spectrum a bit harder than bulk. Ridge particle composition similar to bulk. Ridge present in untriggered correlation. Ridge is mainly in-plane. Ridge is asymmetric in . Ridge is very wide. Ridge is random. No jet-ridge cross-talk. Ridge may be back-to-back. Ridge seems unrelated to jet. N. Armesto et al., Phys. Rev. Lett. 93 (2004) x x x x 35Fuqiang Wang

Turbulent color field Ridge increases with centrality. Ridge spectrum a bit harder than bulk. Ridge particle composition similar to bulk. Ridge present in untriggered correlation. Ridge is mainly in-plane. Ridge is asymmetric in . Ridge is very wide. Ridge is random. No jet-ridge cross-talk. Ridge may be back-to-back. Ridge seems unrelated to jet. A. Majumder et al., Phys. Rev. Lett. 99 (2004) x x 36Fuqiang Wang

Recombination of thermal+shower partons 37 Ridge increases with centrality. Ridge spectrum a bit harder than bulk. Ridge particle composition similar to bulk. Ridge present in untriggered correlation. Ridge is mainly in-plane. Ridge is asymmetric in . Ridge is very wide. Ridge is random. No jet-ridge cross-talk. Ridge may be back-to-back. Ridge seems unrelated to jet. R.C. Hwa, C.B. Chiu, Phys. Rev. C 72 (2005) x x x Fuqiang Wang

Momentum kick model 38 Ridge increases with centrality. Ridge spectrum a bit harder than bulk. Ridge particle composition similar to bulk. Ridge present in untriggered correlation. Ridge is mainly in-plane. Ridge is asymmetric in . Ridge is very wide. Ridge is random. No jet-ridge cross-talk. Ridge may be back-to-back. Ridge seems unrelated to jet. C.Y. Wong hep-ph: x x x x Fuqiang Wang

Transverse flow boost 39 Ridge increases with centrality. Ridge spectrum a bit harder than bulk. Ridge particle composition similar to bulk. Ridge present in untriggered correlation. Ridge is mainly in-plane. Ridge is asymmetric in . Ridge is very wide. Ridge is random. No jet-ridge cross-talk. Ridge may be back-to-back. Ridge seems unrelated to jet. S.A. Voloshin, Phys. Lett. B 632 (2006) 490; E. Shuryak, Phys. Rev. C 76 (2007) x Fuqiang Wang

Glasma flux tube fluctuation + radial flow 40 Ridge increases with centrality. Ridge spectrum a bit harder than bulk. Ridge particle composition similar to bulk. Ridge present in untriggered correlation. Ridge is mainly in-plane. Ridge is asymmetric in . Ridge is very wide. Ridge is random. No jet-ridge cross-talk. Ridge may be back-to-back. Ridge seems unrelated to jet. R. Venugopalan et al., arXiv: ridge Fluctuation of color flux tubes  excess ridge particles (larger in-plane due to flow?) x Fuqiang Wang

Summary and open questions Conical emission of correlated particles. Medium response to hard probes. Suggests Mach cone shock waves. – What distortion to Mach angle by medium? – How to extract speed of sound? EOS? Ridge is uniform in pseudo-rapidity. Likely medium itself at early time. – Is it due to color flux tubes? – What additional work to falsify this and other models, or learn something from them? 41Flow and Dissipation Workshop, Trento, Sept. 2009Fuqiang Wang

Backups

v2 systematic uncertainties 43Flow and Dissipation Workshop, Trento, Sept. 2009Fuqiang Wang

On-diag projection Off-diag projection On-diag projection Off-diag projection Jet-like 3-p correlation RP-frame cumulant Lab-frame cumulant 44Flow and Dissipation Workshop, Trento, Sept. 2009Fuqiang Wang

45Flow and Dissipation Workshop, Trento, Sept. 2009Fuqiang Wang

 trigger particle p T > 3 GeV/c assoc. particle p T =1-2 GeV/c Large combinatorics N jet particles ~ 1, N bkgd particles ~ 20 p T trig =3-4 GeV/c, p T assoc =1-2 GeV/c Extremely difficult analysis. Careful subtraction of bkgd. Extensive assessment of systematics. Combinatorial pair bkgd is huge! 46Flow and Dissipation Workshop, Trento, Sept. 2009Fuqiang Wang

What’s left on the away-side? first peak second peak φsφs φsφs φsφs Differential pathlength sensitivity  / Peak position Peak area Peak  Peak distance 47Flow and Dissipation Workshop, Trento, Sept. 2009Fuqiang Wang

Jet  constant with  s. Ridge  decreases with  s. Cone  increases with  s. Jet  decreases with p T. Ridge  constant with p T. Cone  decreases with p T. STAR Preliminary 48Flow and Dissipation Workshop, Trento, Sept. 2009Fuqiang Wang

Black : Raw signal Pink : Mixed-event background Blue : Scaled bkgd by ZYA1 Red : Raw signal – bkgd 2-particle correlation AuAu ZDC central (0-12%) triggered data, 3<p T Trig <10 GeV/c, 1<p T Asso <3 GeV/c  acceptance corrected STAR Preliminary |  |<0. 7 Ridge 49Flow and Dissipation Workshop, Trento, Sept. 2009Fuqiang Wang

3-particle correlation background  Raw  Raw  Raw signal  Raw  Bkg  Hard-Soft  Bkg1  Bkg1  Bkg1  Bkg2 correlated Soft-Soft Flow and Dissipation Workshop, Trento, Sept. 2009Fuqiang Wang

Jet and Ridge contributions AA like T like : No Jet Only Ridge Ridge (T- A+) A+) = Ridge (T+ A+) A+) Ridge (T+ A- ) A-) = Ridge (T- A- ) A-) Ridge (T+ A-) A+) = Ridge (T+ A+) A+) Ridge (T- A+ ) A-) = Ridge (T- A- ) A-) Netrakanti, QM’09. STAR Preliminary 51Flow and Dissipation Workshop, Trento, Sept. 2009Fuqiang Wang