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What is the ridge? And why you should care Christine Nattrass University of Tennessee at Knoxville.

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Presentation on theme: "What is the ridge? And why you should care Christine Nattrass University of Tennessee at Knoxville."— Presentation transcript:

1 What is the ridge? And why you should care Christine Nattrass University of Tennessee at Knoxville

2 Christine Nattrass (UTK), UTK Particle Physics seminar, 27 April 2011 2 Di-hadron correlations Parton Parton Hadrons Hadrons Λ  Λ  K 0 S, Ξ +, Ξ -...

3 Christine Nattrass (UTK), UTK Particle Physics seminar, 27 April 2011 3 Di-hadron correlations

4 Christine Nattrass (UTK), UTK Particle Physics seminar, 27 April 2011 4 Di-hadron correlations Trigger Associated = -ln(tan(/2))‏ = -ln(tan(/2))‏

5 Christine Nattrass (UTK), UTK Particle Physics seminar, 27 April 2011 5 trigger Phys Rev Lett 90, 082302 Jets – azimuthal correlations p+p  dijet At RHIC energies, jets are dominantly produced as di-jets Assume that a high-p T trigger particle comes from a jet Look at distribution of high-p T associated particles relative to trigger TriggerNear-sideAway-side Near-sideAway-side 200 GeV

6 Christine Nattrass (UTK), UTK Particle Physics seminar, 27 April 2011 6 d+Au d+Au Phys.Rev.C80:064912,2009 Near-side Away-side Near-side Away-side Away-side Jets/mini-jets Multi-parton interactions Combinatorial background Normalization different in different measurements, may have different offset

7 Christine Nattrass (UTK), UTK Particle Physics seminar, 27 April 2011 7 4<p T trig <6 2>p T assoc Jets – azimuthal correlations p+p  dijet The away-side jet is quenched in Au+Au collisions Phys Rev Lett 90, 082302 200 GeV

8 Christine Nattrass (UTK), UTK Particle Physics seminar, 27 April 2011 8 In two dimensions in Au+Au nucl-ex/0701074

9 Christine Nattrass (UTK), UTK Particle Physics seminar, 27 April 2011 9 CMS results: p+p collisions at √s=7 TeV Minimum Bias no cut on multiplicity High multiplicity data set and N>110 New “ridge-like” structure extending to large  at  ~ 0 J. High Energy Phys.09 (2010) 091

10 Christine Nattrass (UTK), UTK Particle Physics seminar, 27 April 2011 10 Relativistic Heavy Ion Collider STAR PHENIX PHOBOSBRAHMS

11 Christine Nattrass (UTK), UTK Particle Physics seminar, 27 April 2011 11 PHOBOS Coverage: With tracking: 2x (0<<0.2); 0<<1.5 Without tracking: 0<<2 ; -3<<3 PHENIX Coverage: 2x(0<</2);-0.35<<0.35 STAR Coverage: 0<<2 ; -1<<1

12 Christine Nattrass (UTK), UTK Particle Physics seminar, 27 April 2011 12 At higher p T... 8<p T trig <15 2>p T assoc The away-side jet punches through the medium Phys.Rev.Lett.97:162301,200 6

13 Christine Nattrass (UTK), UTK Particle Physics seminar, 27 April 2011 13 STAR PRL 95 (2005) 152301 0.15<p T associated <4 GeV/c But at lower p T... Near-side, away-side: excess yield in Au+Au relative to p+p p T trig >4 GeV/c

14 Christine Nattrass (UTK), UTK Particle Physics seminar, 27 April 2011 14 p T assoc (GeV/c) 0 1.0 2.0 4.0 3.0 Near-sideAway-side Ridge Mach Cone PunchThrough Quenching Minimally modified fragmentation

15 Christine Nattrass (UTK), UTK Particle Physics seminar, 27 April 2011 15 Simple picture Jet-like correlation: Dominantly produced by fragmentation Ridge:  Part of the signal: created by hard parton interaction with the medium  Part of the background: some extra correlation we didn't realize was there Phys.Rev.C80:064912,2009

16 Christine Nattrass (UTK), UTK Particle Physics seminar, 27 April 2011 16 The Jet 3<p t,trigger <4 GeV p t,assoc. >2 GeV Au+Au 0-10% STAR preliminary Ridge Jet

17 Christine Nattrass (UTK), UTK Particle Physics seminar, 27 April 2011 17 Jet-like yield: p T trigger dependence Yield increases with p T trigger No collision system dependence PYTHIA 6.4.10 Tune A– Monte Carlo p+p event generator tuned to data and incorporating many features of pQCD 1.5 GeV/c < p T associated < p T trigger Eur.Phys.J.C62:265-269,2009 STAR Preliminary

18 Christine Nattrass (UTK), UTK Particle Physics seminar, 27 April 2011 18 The Ridge 3<p t,trigger <4 GeV p t,assoc. >2 GeV Au+Au 0-10% STAR preliminary Jet Ridge

19 Christine Nattrass (UTK), UTK Particle Physics seminar, 27 April 2011 19 Ridge vs N part No system dependence at given N part arXiv:0806.2261/nucl-ex arXiv:0804.4683/nucl-ex Eur.Phys.J.C62:265-269,2009 3.0 GeV/c < p T trigger 6.0 GeV/c 1.5 GeV/c < p T associated < p T trigger STAR preliminary

20 Christine Nattrass (UTK), UTK Particle Physics seminar, 27 April 2011 20 Baryon/meson ratios in jet-like correlation in Cu+Cu and Au+Au similar to p+p for both strange and non-strange particles Baryon/meson ratios in ridge similar to bulk for both strange and non- strange particles Suarez, QM08 M. Lamont (STAR), J.Phys.G32:S105-S114,2006 J. Bielcikova (STAR), v:0707.3100 [nucl-ex] C. Nattrass (STAR), arXiv:0804.4683/nucl-ex Jet-like correlation composition

21 Christine Nattrass (UTK), UTK Particle Physics seminar, 27 April 2011 21 Spectra of particles associated with ridge similar to inclusive Spectra of particles associated with jet-like correlation harder Jet-like correlation is like p+p, ridge is like bulk Phys.Rev.C80:064912,2009

22 Christine Nattrass (UTK), UTK Particle Physics seminar, 27 April 2011 22 Extent of ridge in Phys. Rev. Lett. 104, 062301 (2010) 2.5 GeV/c > p T trigger 0.035 GeV/c > p T associated Near-side Away-side

23 Christine Nattrass (UTK), UTK Particle Physics seminar, 27 April 2011 23 Hydrodynamical flow When nuclei collide, the overlap region is roughly elliptical If we have a fluid when we collide nuclei, there will be pressure gradients, pushing particles out We have measured this – and the liquid is made of quarks and gluons Au+Au  s NN = 200 GeV b=7 fm arXiv:nucl-th/0305084 Particles pushed out Equipotential lines

24 Christine Nattrass (UTK), UTK Particle Physics seminar, 27 April 2011 24 Phys.Rev.C78:014901,200 8 PHENIX ZYAM and the two-component model Two component model: Di-hadron correlations are composed of  Correlations arising from jet fragmentation  Correlations arising from elliptic flow (v 2 ) Assume jets are not correlated with background The background is then B(1+2 v 2 trig v 2 assoc cos(2 ΔΦ ))‏ Phys.Rev. C69 (2004) 021901 Zero-Yield-At-Minimum (ZYAM)  Assumes there is a region where there is no signal  Fix B in this region assuming two component model  Use v 2 from independent measurements

25 Christine Nattrass (UTK), UTK Particle Physics seminar, 27 April 2011 25 Models Radiated gluons broadened in pseudorapidity Longitudinal flow, Armesto et al, PRL 93 (2004) QCD magnetic fields, Majumder et al,Phys.Rev.Lett.99:042301,2007 Anisotropic plasma, P. Romatschke, PRC,75014901 (2007) So far unable to make enough ridge Interaction of jet+medium Momentum kick from jet, C.-Y. Wong, Phys.Rev.C76:054908,2007 Medium heating + recombination, Chiu & Hwa, PRC72, 034903 Agrees with data but lots of fits to the data Hydrodynamical flow Radial flow+trigger bias S. Voloshin, nucl-th/0312065, Nucl. Phys. A749, 287 C.. Pruneau, S. Gavin, S. Voloshin, arXiv:0711.1991v2 E. Shuryak, Phys.Rev.C76:047901,2007 Triangular flow (v 3 ) B.Alver, G.Roland, Phys.Rev.C81:054905,2010 P. Sorensen, arXiv:1002.4878v1 As an added bonus, these describe the away-side Armesto et al, PRL 93 (2004) arXiv:0805.2795v2 C.Y. Wong Phys.Rev.C78:064905,2008 N part arXiv:0711.1991 v2arXiv:0711.1991 v2Pruneau et al Phys.Rev.C81:054905,2010

26 Christine Nattrass (UTK), UTK Particle Physics seminar, 27 April 2011 26 Conclusions Most models for the ridge imply QGP formation or a relativistic hydrodynamic fluid Since the CMS result, some models have appeared to form a ridge without a QGP  Flux tubes in a Color Glass Condensate Stay tuned...

27 Christine Nattrass (UTK), UTK Particle Physics seminar, 27 April 2011 27 Ridge vs N part No system dependence at given N part Ridge/jet-like yield independent of energy* *Comparing these two energies in this kinematic region arXiv:0806.2261/nucl-ex arXiv:0804.4683/nucl-ex Eur.Phys.J.C62:265-269,2009 3.0 GeV/c < p T trigger 6.0 GeV/c 1.5 GeV/c < p T associated < p T trigger

28 Christine Nattrass (UTK), UTK Particle Physics seminar, 27 April 2011 28 Identified trigger: Near-side Yield vs N part Au+Au √ s NN =200 GeV from nucl-ex/0701047 Cu+Cu √ s NN =200 GeV from SQM2007 Data points at same N part offset for visibility Ridge yield - No trigger type dependence 3.0 GeV/c < p T trigger 6.0 GeV/c; 1.5 GeV/c < p T associated < p T trigger arXiv:0804.4683/nucl-ex

29 Christine Nattrass (UTK), UTK Particle Physics seminar, 27 April 2011 29 Identified trigger: Near-side Yield vs N part Au+Au √ s NN =200 GeV from nucl-ex/0701047 Cu+Cu √ s NN =200 GeV from SQM2007 Data points at same N part offset for visibility Ridge yield - No trigger type dependence 3.0 GeV/c < p T trigger 6.0 GeV/c; 1.5 GeV/c < p T associated < p T trigger arXiv:0804.4683/nucl-ex

30 Christine Nattrass (UTK), UTK Particle Physics seminar, 27 April 2011 30 Identified trigger: Near-side Yield vs N part Au+Au √ s NN =200 GeV from nucl-ex/0701047 Cu+Cu √ s NN =200 GeV from SQM2007 Data points at same N part offset for visibility Ridge yield - No trigger type dependence 3.0 GeV/c < p T trigger 6.0 GeV/c; 1.5 GeV/c < p T associated < p T trigger arXiv:0804.4683/nucl-ex

31 Christine Nattrass (UTK), UTK Particle Physics seminar, 27 April 2011 31 Baryon/meson ratios Clear evidence of different behavior for baryons and mesons For this kinematic region, baryon/meson ratio in bulk changing rapidly Phys.Rev.Lett.10 1:082301,2008 PHENIX Phys.Rev.Lett.10 1:082301,2008 PHENIX

32 Christine Nattrass (UTK), UTK Particle Physics seminar, 27 April 2011 32 The soft ridge Untriggered di-hadron correlations – no p T cuts Similar structure on the near-side - “Soft Ridge” Are soft and hard ridge the same? ηΔηΔ φΔφΔ J of Phys: Conf 27 (2005) 98 p+p 200 GeV Au+Au 200 GeV J.Phys.G35:104090,2008

33 Christine Nattrass (UTK), UTK Particle Physics seminar, 27 April 2011 33 The soft ridge Soft ridge → hard ridge with increasing p T Most likely two structures are the same Increasing p T cut Cu+Cu 200 GeV arXiv:0910.5938v1 Increasing p T cut arXiv:0910.5938v1 *Note the different normalizations for the hard and soft ridge

34 Christine Nattrass (UTK), UTK Particle Physics seminar, 27 April 2011 34 Conclusions Lots of data  Jet-like correlation dominated by fragmentation  Ridge is bulk-like. From the bulk?  Hard and soft ridge most likely the same phenomenon

35 Christine Nattrass (UTK), UTK Particle Physics seminar, 27 April 2011 35 Conclusions Lots of data  Jet-like correlation dominated by fragmentation  Ridge is bulk-like. From the bulk?  Hard and soft ridge most likely the same phenomenon Theories  Causal: Have some difficulty reproducing the data  Non-causal/Hydrodynamical models: Good candidates

36 Christine Nattrass (UTK), UTK Particle Physics seminar, 27 April 2011 36 Outlook My prediction: There will be a ridge at the LHC Hydro is mass dependent → need better mass dependent measurements Need to understand the ridge to understand fully reconstructed jets  Is it background? Is it signal? If the ridge isn't from jets, can we use it to learn something else?

37 Christine Nattrass (UTK), UTK Particle Physics seminar, 27 April 2011 37 Phase diagram of nuclear matter Here be dragons

38 Christine Nattrass (UTK), UTK Particle Physics seminar, 27 April 2011 38 How to make a Quark Gluon Plasma

39 Christine Nattrass (UTK), UTK Particle Physics seminar, 27 April 2011 39 The phase transition in the laboratory

40 Christine Nattrass (UTK), UTK Particle Physics seminar, 27 April 2011 40 ALICE CMS ATLAS LHCf LHCb 2.2 km 8.6 km

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