Using particle correlations to probe the medium produced at RHIC

Transcription

1 Using particle correlations to probe the medium produced at RHIC Helen Caines - Yale University Oxford/RAL November 2008

2 Relativistic Heavy-Ion Collider (RHIC) PHENIX PHOBOS STAR 1 km RHIC BRAHMS v = c AGS s NN =200 GeV TANDEMS Helen Caines - Yale - Nov Oxford/RAL 2

3 QGP expectation came from Lattice ε/t 4 ~ # degrees of freedom deconfined: many d.o.f. confined: few d.o.f. Helen Caines - Yale - Nov Oxford/RAL 3

4 QGP expectation came from Lattice ε/t 4 ~ # degrees of freedom deconfined: many d.o.f. confined: few d.o.f. T C 173 MeV K ε C 0.7 GeV/fm 3 (~6x normal nuclear densities) Helen Caines - Yale - Nov Oxford/RAL 3

5 RHIC has created a new state of matter The QGP is the: hottest (T= MeV ~ K) densest (ε = εnuclear matter) matter ever studied in the lab. It flows as a (nearly) perfect fluid with systematic patterns, consistent with quark degree of freedom and a viscosity to entropy density ratio lower than any other known fluid. Helen Caines - Yale - Nov Oxford/RAL 4

6 RHIC has created a new state of matter The QGP is the: hottest (T= MeV ~ K) densest (ε = εnuclear matter) matter ever studied in the lab. It flows as a (nearly) perfect fluid with systematic patterns, consistent with quark degree of freedom and a viscosity to entropy density ratio lower than any other known fluid. Want to learn more about the properties Helen Caines - Yale - Nov Oxford/RAL 4

7 Elliptic flow rapid thermalization Reaction Plane beam b Initial spatial anisotropy Interactions y (fm) !5!10 Au+Au at b=7 fm Final momentum anisotropy!!-" R " R!10! x (fm) A Fourier expansion used to describe the angular distribution of the particles dn dϕ 1+2v 2 cos[2(ϕ ψ R )] +... Helen Caines - Yale - Nov Oxford/RAL 5

8 Elliptic flow rapid thermalization Reaction Plane beam b Initial spatial anisotropy Interactions y (fm) !5!10 Au+Au at b=7 fm Final momentum anisotropy!!-" R " R!10! x (fm) A Fourier expansion used to describe the angular distribution of the particles dn dϕ 1+2v 2 cos[2(ϕ ψ R )] +... Driving spatial anisotropy vanishes self quenching Helen Caines - Yale - Nov Oxford/RAL 5

9 Elliptic flow rapid thermalization Reaction Plane beam b Initial spatial anisotropy Interactions y (fm) !5!10 Au+Au at b=7 fm Final momentum anisotropy!!-" R " R!10! x (fm) A Fourier expansion used to describe the angular distribution of the particles dn dϕ 1+2v 2 cos[2(ϕ ψ R )] +... Driving spatial anisotropy vanishes self quenching Sensitive to early interactions and pressure gradients Helen Caines - Yale - Nov Oxford/RAL 5

10 The flow is ~Perfect 2v2 Huge asymmetry found at RHIC massive effect in azimuthal distribution w.r.t reaction plane At higher pt: Factor 3:1 peak to valley from 25% v2 Helen Caines - Yale - Nov Oxford/RAL 6

11 The flow is ~Perfect 2v2 Huge asymmetry found at RHIC massive effect in azimuthal distribution w.r.t reaction plane At higher pt: Factor 3:1 peak to valley from 25% v2 fine structure v 2 (p T ) ordering with mass of particle good agreement with ideal hydrodynamics (zero viscosity, λ=0) perfect liquid Helen Caines - Yale - Nov Oxford/RAL 6

12 The constituents flow m T = p 2 T + m2 0 baryons mesons Helen Caines - Yale - Nov Oxford/RAL 7

13 The constituents flow baryons mesons Scaling flow parameters by quark content n q (baryons=3, mesons=2) resolves meson-baryon separation of final state hadrons Helen Caines - Yale - Nov Oxford/RAL 7

14 The constituents flow baryons mesons Scaling flow parameters by quark content n q (baryons=3, mesons=2) resolves meson-baryon separation of final state hadrons Constituents of liquid are partons Helen Caines - Yale - Nov Oxford/RAL 7

15 How perfect is Perfect? Viscous fluid supports a shear stress viscosity η: η momentum density mean free path n pλ = n p 1 nσ = p σ small η large σ strong couplings F x A = η v x y Helen Caines - Yale - Nov Oxford/RAL 8

16 How perfect is Perfect? Viscous fluid supports a shear stress viscosity η: η momentum density mean free path n pλ = n p 1 nσ = p σ small η large σ strong couplings F x A = η v x y Hydrodynamic calculations for RHIC assumed zero viscosity η = 0 perfect fluid But there is a (conjectured) quantum limit: derived first in (P. Kovtun, D.T. Son, A.O. Starinets, PRL.94:111601, 2005) motivated by AdS/CFT correspondence N.B.: water (at normal conditions) η/s ~ 380 ћ/4π Helen Caines - Yale - Nov Oxford/RAL 8

17 What is η/s at RHIC? conjectured quantum limit 4 H 2 O 3 He N 2!/s 2 1 Meson Gas Observables that are sensitive to shear Elliptic Flow 0 RHIC R. Lacey et al.: Phys. Rev. Lett. 98:092301, 2007 H.-J. Drescher et al.: Phys. Rev. C76:024905, 2007 pt Fluctuations S. Gavin and M. Abdel-Aziz: Phys. Rev. Lett. 97:162302, 2006 Heavy quark motion (drag, flow) A. Adare et al. : Phys. Rev. Lett. 98:092301, 2007 (T-T 0 )/T 0 QGP Helen Caines - Yale - Nov Oxford/RAL 9

18 Probing the medium - Jet production Early production in parton-parton scatterings with large Q 2. Direct interaction with partonic phases of the reaction From p+p Obtain jet rate Obtain fragmentation functions Schematic view of jet production hadrons leading particle q q leading particle hadrons Helen Caines - Yale - Nov Oxford/RAL 10

19 Probing the medium - Jet production Early production in parton-parton scatterings with large Q 2. Direct interaction with partonic phases of the reaction From p+p Obtain jet rate Obtain fragmentation functions jet production in quark matter In A+A look at attenuation or absorption of jets: jet quenching suppression of high p T hadrons modification of angular correlation changes of particle composition q hadrons leading particle q Helen Caines - Yale - Nov Oxford/RAL 10

20 Probing the medium - Jet production Early production in parton-parton scatterings with large Q 2. Direct interaction with partonic phases of the reaction From p+p Obtain jet rate Obtain fragmentation functions In A+A look at attenuation or absorption of jets: jet quenching suppression of high p T hadrons modification of angular correlation changes of particle composition jet production in quark matter q hadrons leading particle Differences due to medium q Helen Caines - Yale - Nov Oxford/RAL 10

21 Jets a calibrated probe? STAR : PRL 97 (2006) Jet production in p+p understood in pqcd framework Helen Caines - Yale - Nov Oxford/RAL 11

22 Jets a calibrated probe? PHENIX STAR : PRL 97 (2006) K.Reygers QM2008 STAR : PLB 637 (2006) 161 S. Albino et al, NPB 725 (2005) 181 Jet production in p+p understood in pqcd framework Particle production in p+p also well modeled. Seems we have a reasonably calibrated probe Helen Caines - Yale - Nov Oxford/RAL 11

23 Charged hadron ξ in p+p 200 GeV 20<E reco <30 GeV 30<E reco <40 GeV 40<E reco <50 GeV R<0.4 M. Heinz Hard Probes 2008 Reasonable agreement between Pythia and data Helen Caines - Yale - Nov Oxford/RAL 12

24 Charged hadron ξ in p+p 200 GeV 20<E reco <30 GeV 30<E reco <40 GeV 40<E reco <50 GeV R<0.4 M. Heinz Hard Probes 2008 Reasonable agreement between Pythia and data R<0.7 Are these differences onset of beyond LL effects? Helen Caines - Yale - Nov Oxford/RAL 12

25 ξ for strange hadrons 10<E reco <15 20<E reco <50 15<E reco <20 p T <0.5 R<0.4 R<0.5 R<0.7 M. Heinz Hard Probes 2008 Clear differences between particles Helen Caines - Yale - Nov Oxford/RAL 13

26 Back to probing the medium Compare Au+Au with p+p Collisions R AA Nuclear Modification Factor: Average number of NN collision in an AA collision No Effect : R < 1 at small momenta R = 1 at higher momenta where hard processes dominate Suppression: R < 1 Helen Caines - Yale - Nov Oxford/RAL 14

27 High-p T suppression Observations at RHIC: figure by D. 1. Photons are not suppressed Good! γ don t interact with medium N coll scaling works Helen Caines - Yale - Nov Oxford/RAL 15

28 High-p T suppression Observations at RHIC: figure by D. 1. Photons are not suppressed Good! γ don t interact with medium N coll scaling works 2. Hadrons are suppressed in central collisions Huge: factor 5 Helen Caines - Yale - Nov Oxford/RAL 15

29 High-p T suppression Observations at RHIC: figure by D. 1. Photons are not suppressed Good! γ don t interact with medium N coll scaling works 2. Hadrons are suppressed in central collisions Huge: factor 5 3. Hadrons are not suppressed in peripheral collisions Good! medium not dense Helen Caines - Yale - Nov Oxford/RAL 15

30 Interpretation Gluon radiation: Multiple finalstate gluon radiation off the produced hard parton induced by the traversed dense colored medium E Hard Production "q T ~µ! " Medium!=xE!=(1-x)E Helen Caines - Yale - Nov Oxford/RAL 16

31 Interpretation q (GeV 2 /fm) Gluon radiation: Multiple finalstate gluon radiation off the produced hard parton induced by the traversed dense colored medium Helen Caines - Yale - Nov Oxford/RAL QGP Hadronic Matter cold nuclear matter R. Baier, Nucl. Phys. A715, 209c ! (GeV/fm 3 ) sqgp E Hard Production "q T ~µ Mean parton energy loss medium properties: ΔE loss ~ ρ gluon (gluon density) Coherence among radiated gluons ΔE loss ~ ΔL 2! " (medium length) ~ ΔL with expansion Characterization of medium transport coefficient is kt 2 transferred per unit path length gluon density dn g /dy Medium!=xE ˆq = ˆq( r, τ)!=(1-x)e 16

32 The model landscape (not exhaustive) PQM (Parton Quench model) Implementation of BDMPS (calc. E loss via coherent gluon radiation - many soft scattering approx. Realistic geometry Static medium, q time average (i.e. depends on initial density, scheme evolution dependent ) No initial state multiple scatterings No modified PDFs GLV Implementation of GLV formalism (calc. E loss via gluon brehmsstralung -few hard scatterings.) Realistic geometry Bjorken expanding medium - Calc. a priori (w/o E loss) average path length - use to calc. partonic E loss WHDG Implementation of GLV formalism (calc. E loss via gluon brehmsstralung -few hard scatterings) + collisional energy loss. Realistic geometry - integral over all paths Expanding medium No initial state multiple scatterings ZOWW Modified fragmentation model (radiative gluon E loss incorporated into effective medium modified FF) Hard sphere geometry Expanding medium Helen Caines - Yale - Nov Oxford/RAL 17

33 ^ Constraining q Model Opacity Parameter PQM q = 13.2 ( ) GLV dng/dy = 1400 ( ) WHDG dng/dy = 1400 ( ) ZOWW ε0 = 1.9 ( ) PHENIX: ( q ~1) ( q ~7) PQM: A. Dainese, C. Loizides, G. Paic, Eur. Phys. J C38: 461 (2005). C. Loizides, Eur. Phys. J.C49, 339 (2007). GLV: I. Vitev, Phys. Lett. B639, 38 (2006). M. Gyulassy, P. Levai, I. Vitev, Nucl. Phys. B571, 197 (2000). WHDG: W.A. Horowitz, S. Wicks, M. Djordjevic, M. Gyulassy,in preparation; S. Wicks, W. Horowitz, M. Djordjevic, M. Gyulassy, Nucl. Phys. A 783, 493 (2007); S. Wicks, W. Horowitz, M. Djordjevic,M. Gyulassy, Nucl. Phys. A 784, 426 (2007). ZOWW: H. Zhang, J.F. Owens, E. Wang, X-N Wang, Phys Rev. Lett. 98: (2007). WHDG PQM GLV q only the natural unit in PQM Helen Caines - Yale - Nov Oxford/RAL ZOWW Need other observables to dis-entangle all the possible effects 18

34 Jet correlations in heavy-ion collisions Full jet reconstruction very challenging background from bulk similar to signal for jet p T <~30 GeV p+p collisions Au+Au collisions Helen Caines - Yale - Nov Oxford/RAL 19

35 Jet correlations in heavy-ion collisions Full jet reconstruction very challenging background from bulk similar to signal for jet p T <~30 GeV p+p collisions Au+Au collisions Back-to-back (away side) jet Use di-hadron correlations Δφ p T assoc p T trigger φ trigger Trigger (near side) jet Helen Caines - Yale - Nov Oxford/RAL 19

36 RHIC seminal di-hadron results The disappearance of the away-side jet d+au results similar to p+p final state interaction d+au can be used as the reference measurement instead of p+p 4 < p T trig < 6 GeV/c p T assoc >2 GeV/c Phys Rev Lett 90, Helen Caines - Yale - Nov Oxford/RAL 20

37 RHIC seminal di-hadron results The disappearance of the away-side jet d+au results similar to p+p final state interaction d+au can be used as the reference measurement instead of p+p 4 < p T trig < 6 GeV/c p T assoc >2 GeV/c Phys Rev Lett 90, High pt Punch-through Away side correlation reappears for high pt correlations yield reduced compared to d+au 1/N trig dn/d(δφ) 8 < p trig T < 15 GeV/c p assoc T >6 GeV/c d+au Au+Au 20-40% Au+Au 0-5% STAR PRL 97 (2006) Helen Caines - Yale - Nov Oxford/RAL 20

38 Away-side di-hadron fragmentation Study medium-induced modification of fragmentation function due to energy loss Without full jet reconstruction, parton energy not measurable z not measured (z=p hadron / p parton ) z T =p T,assoc /p T,trig Helen Caines - Yale - Nov Oxford/RAL 21

39 I AA Away-side di-hadron fragmentation H. Zhong et al., PRL 97 (2006) C. Loizides, Eur. Phys. J. C 49, (2007) 6< p T trig < 10 GeV Au-Au PQM q=4 Cu-Cu PQM q=3 Au-Au PQM q=7 Cu-Cu PQM q=5.5 Au-Au PQM q=14 Cu-Cu PQM q=9 Au-Au Cu-Cu Au-Au modified frag Cu-Cu modified frag Study medium-induced modification of fragmentation function due to energy loss Without full jet reconstruction, parton energy not measurable z not measured (z=p hadron / p parton ) z T =p T,assoc /p T,trig O. Catu QM2008 N part Inconsistent with Parton Quenching Model calculation Modified fragmentation model better Helen Caines - Yale - Nov Oxford/RAL 21

40 Away-side di-hadron fragmentation I AA 1 H. Zhong et al., PRL 97 (2006) C. Loizides, Eur. Phys. J. C 49, (2007) 6< p T trig < 10 GeV Helen Caines - Yale - Nov Oxford/RAL Au-Au Cu-Cu Au-Au modified frag Cu-Cu modified frag Au-Au PQM q=4 Cu-Cu PQM q=3 Au-Au PQM q=7 Cu-Cu PQM q=5.5 Au-Au PQM q=14 Cu-Cu PQM q= N O. Catu QM2008 part Inconsistent with Parton Quenching Model calculation Modified fragmentation model better ratio to d-au 1/N trig dn/dz T d-au Cu-Cu 0-10% Au-Au 30-40% Cu-Cu 40-60% Au-Au 60-80% Au-Au 0-12% STAR Preliminary N part = 100 N part = z T =p T assoc /p T trig p+p theory Cu+Cu 0-10% theory Cu+Cu 40-60% theory Denser medium in central Au+Au than central Cu+Cu Similar medium for similar N part Vacuum fragmentation after parton E loss in the medium 21

41 Two particles are better than one Compare fits to RAA and IAA H. Zhang, J.F. Owens, E. Wang, X.N. Wang Phys. Rev. Lett. 98: (2007) χ 2 (IAA) Minima of data in same place Sharper for di-hadrons q0τ0 ~ q=2.8 ^ ±0.3 GeV 2 /fm χ 2 (RAA) Helen Caines - Yale - Nov Oxford/RAL 22

42 Two particles are better than one Compare fits to RAA and IAA H. Zhang, J.F. Owens, E. Wang, X.N. Wang Phys. Rev. Lett. 98: (2007) χ 2 (IAA) Minima of data in same place Sharper for di-hadrons q0τ0 ~ q=2.8 ^ ±0.3 GeV 2 /fm χ 2 (RAA) Parton production points in transverse plane Single Hadrons Helen Caines - Yale - Nov Oxford/RAL di-hadrons Renk and Eskola, hep-ph/ Surface bias effectively leads to saturation of R AA with density minimize bias: di-hadron correlations full jets 22

43 Path length dependencies Non-central events have elliptic overlap geometries Measurements w.r.t reaction plane angle: Change path length Keep everything else same Isolate effects due to path length Helen Caines - Yale - Nov Oxford/RAL 23

44 Path length effect on di-hadron correlation in-plane φ t -Ψ RP =0 B. Cole QM2008 Near side peak unchanged out-of-plane φ t -Ψ RP =90 o Shoulder peaks emerge as φ t - Ψ increases but are at fixed Δφ Head peak (di-jet remnant) decreases as φ t - Ψ RP increases Helen Caines - Yale - Nov Oxford/RAL 24

45 Centrality and path length effects Au+Au 200 GeV STAR Preliminary v 2 sys. error 20-60% 0-5% v 2 {RP} v 2 {4} A. Feng QM2008 3< p T trig < 4 GeV/c, 1.0 < p T asso < 1.5 GeV/c In-plane: 20-60% ~ d+au RMS 0-5% > d+au Out-of-plane: 20-60% ~ 0-5% Au+Au > d+au Helen Caines - Yale - Nov Oxford/RAL 25

46 Centrality and path length effects Au+Au 200 GeV STAR Preliminary v 2 sys. error 20-60% 0-5% v 2 {RP} v 2 {4} A. Feng QM2008 3< p T trig < 4 GeV/c, 1.0 < p T asso < 1.5 GeV/c In-plane: 20-60% ~ d+au 0-5% > d+au Out-of-plane: 20-60% ~ 0-5% Au+Au > d+au RMS Away-side features reveal path length effects Helen Caines - Yale - Nov Oxford/RAL 25

47 Deflected jets or conical emission? near STAR Preliminary Medium Deflected jets away near Medium away Conical Emission Conical emission or deflected jets? Distinguish between models using 3-particle correlations Helen Caines - Yale - Nov Oxford/RAL 26

48 Deflected jets or conical emission? near STAR Preliminary Deflected jets Medium away Deflected jets near Conical emission or deflected jets? Conical Emission Medium away Conical Emission Distinguish between models using 3-particle correlations Helen Caines - Yale - Nov Oxford/RAL 26

49 Deflected jets or conical emission? near STAR Preliminary Deflected jets Medium away Deflected jets near d+au 3 < p Ttrig < 4 GeV/c, 1 < p Tassoc < 2 GeV/c Medium Conical Emission away Conical Emission Au+Au 0-12% Helen Caines - Yale - Nov Oxford/RAL 26

50 Deflected jets or conical emission? STAR Preliminary Deflected jets (Δφ 1 -Δφ 2 )/2 d+au Au+Au 0-12% d+au 3 < p Ttrig < 4 GeV/c, 1 < p Tassoc < 2 GeV/c Conical Emission (Δφ 1 -Δφ 2 )/2 Au+Au 0-12% Helen Caines - Yale - Nov Oxford/RAL 26

51 Deflected jets or conical emission? STAR Preliminary Au+Au data consistent with Conical emission Deflected jets (Δφ 1 -Δφ 2 )/2 d+au Au+Au 0-12% d+au 3 < p Ttrig < 4 GeV/c, 1 < p Tassoc < 2 GeV/c Conical Emission (Δφ 1 -Δφ 2 )/2 Au+Au 0-12% Helen Caines - Yale - Nov Oxford/RAL 26

52 Possible causes of conical emission Similar to jet creating sonic boom Mach Cone in air. Energy radiated from parton deposited in collective hydrodynamic modes. Mach angle depends on C s T dependent Angle independent of p T assoc Helen Caines - Yale - Nov Oxford/RAL 27

53 Possible causes of conical emission Similar to jet creating sonic boom Mach Cone in air. Energy radiated from parton deposited in collective hydrodynamic modes. Mach angle depends on C s T dependent Angle independent of p T assoc Čerenkov Gluon Radiation Gluons radiated by superluminal parton. c n = cos( θ c ) v parton = Angle dependent on p T assoc c n( p)v parton 1 n( p) Helen Caines - Yale - Nov Oxford/RAL 27

54 Mach cone or Čerenkov gluons? Angle predictions: Mach-cone: Angle independent of associated p T Čerenkov gluon radiation: Angle decreases with associated p T Au+Au 0-12% Cone angle (radians) STAR Preliminary (Δφ 1 -Δφ 2 )/2 J. Ulery QM2006 p T (GeV/c) Helen Caines - Yale - Nov Oxford/RAL 28

55 Mach cone or Čerenkov gluons? Angle predictions: Mach-cone: Angle independent of associated p T Čerenkov gluon radiation: Angle decreases with associated p T Au+Au 0-12% Cone angle (radians) STAR Preliminary PHENIX 1D analysis M. McCumber QM2008 (Δφ 1 -Δφ 2 )/2 J. Ulery QM2006 p T (GeV/c) Helen Caines - Yale - Nov Oxford/RAL 28

56 Mach cone or Čerenkov gluons? Angle predictions: Mach-cone: Angle independent of associated p T Čerenkov gluon radiation: Angle decreases with associated p T Au+Au 0-12% Cone angle (radians) STAR Preliminary PHENIX 1D analysis M. McCumber QM2008 (Δφ 1 -Δφ 2 )/2 J. Ulery QM2006 p T (GeV/c) Helen Caines - Yale - Nov Oxford/RAL 28

57 Parton interactions on near side Δ(φ) correlations Helen Caines - Yale - Nov Oxford/RAL 29

58 Parton interactions on near side Δ(φ) correlations Δ(η) Δ(φ) correlations Long range Δ(η) correlation the Ridge Helen Caines - Yale - Nov Oxford/RAL 29

59 Parton interactions on near side Δ(φ) correlations Δ(η) Δ(φ) correlations Long range Δ(η) correlation the Ridge Persists out to very large Δ(η) >2 Helen Caines - Yale - Nov Oxford/RAL 29

60 Energy loss of trigger - The ridge d+au, % Au+Au, 0-5% 3 < p T (trig) < 6 GeV 2 < p T (assoc) < p T (trig) Helen Caines - Yale - Nov Oxford/RAL 30

61 Energy loss of trigger - The ridge d+au, % Au+Au, 0-5% 3 < p T (trig) < 6 GeV 2 < p T (assoc) < p T (trig) C. Nattrass QM2008 Ridge: Increases with N part Independent of colliding system Helen Caines - Yale - Nov Oxford/RAL 30

62 Energy loss of trigger - The ridge d+au, % Au+Au, 0-5% 3 < p T (trig) < 6 GeV 2 < p T (assoc) < p T (trig) C. Nattrass QM2008 Ridge: Increases with N part Independent of colliding system Jet: Approx. flat with N part Independent of colliding system Helen Caines - Yale - Nov Oxford/RAL 30

63 Energy loss of trigger - The ridge d+au, % Au+Au, 0-5% 3 < p T (trig) < 6 GeV 2 < p T (assoc) < p T (trig) C. Nattrass QM2008 Ridge: Increases with N part Independent of colliding system Jet: Approx. flat with N part Independent of colliding system Parton interacts with medium (ridge), then vacuum fragments (jet)? Helen Caines - Yale - Nov Oxford/RAL 30

64 Spectra of ridge and shoulder particles Preliminary Ridge Jet J. Putschke QM2006 slope ridge > slope jet ~ slope inclusive Helen Caines - Yale - Nov Oxford/RAL 31

65 Spectra of ridge and shoulder particles Preliminary Ridge Jet J. Putschke QM2006 slope ridge > slope jet ~ slope inclusive slope shoulder M. McCumber QM2008 Helen Caines - Yale - Nov Oxford/RAL 31

66 Un-triggered pair correlations Method: measure pair densities ρ(η 1 -η 2,φ 1 -φ 2 ) for all possible pairs in same and mixed events. Define correlation measure as: M. Daugherty QM2008 Minijet: Same-side jet-like correlations with no trigger particle Helen Caines - Yale - Nov Oxford/RAL 32

67 Un-triggered pair correlations STAR Preliminary Helen M. Daugherty Caines - Yale QM Nov Oxford/RAL 33

68 Un-triggered pair correlations Small residual indicates goodness of fit Helen M. Daugherty Caines - Yale QM Nov Oxford/RAL 34

69 Evolution of mini-jet with centrality Same-side peak 83-94% 55-65% STAR Preliminary STAR Preliminary 46-55% STAR Preliminary 0-5% STAR Preliminary η Δ width Little shape change from peripheral to 55% centrality Large change within ~10% centrality Smaller change from transition to most central M. Daugherty QM2008 Helen Caines - Yale - Nov Oxford/RAL 35

70 Evolution of mini-jet with centrality Same-side peak 83-94% 55-65% STAR Preliminary STAR Preliminary 46-55% STAR Preliminary 0-5% STAR Preliminary η Δ width Little shape change from peripheral to 55% centrality peak amplitude peak η width STAR Preliminary 200 GeV 62 GeV STAR Preliminary Large change within ~10% centrality Smaller change from transition to most central binary scaling references M. Daugherty QM2008 ν path length ν Helen Caines - Yale - Nov Oxford/RAL 35

71 Evolution of mini-jet with centrality Same-side peak 83-94% 55-65% STAR Preliminary STAR Preliminary 46-55% STAR Preliminary 0-5% STAR Preliminary η Δ width Little shape change from peripheral to 55% centrality peak amplitude peak η width STAR Preliminary 200 GeV 62 GeV STAR Preliminary Large change within ~10% centrality Binary scaling reference followed until sharp transition at ρ ~ 2.5 ~30% of the hadrons in central Au+Au participate in the same-side correlation peak amplitude STAR Preliminary 200 GeV 62 GeV Smaller change from transition to most central peak η width STAR Preliminary binary scaling references M. Daugherty QM2008 ν path length ν Transverse particle density Helen Caines - Yale - Nov Oxford/RAL 35

72 RHIC in Au-Au collisions ~ 47 GeV pt per grid cell [GeV] STAR preliminary Clearly visible in central events on E-by-E basis η ϕ J. Putschke Hard Probes 2008 Helen Caines - Yale - Nov Oxford/RAL 36

73 RHIC in Au-Au collisions ~ 47 GeV pt per grid cell [GeV] STAR preliminary STAR preliminary Clearly visible in central events on E-by-E basis ~ 21 GeV η Energies as low as 20 GeV resolvable J. Putschke Hard Probes 2008 ϕ pt per grid cell [GeV] η ϕ Helen Caines - Yale - Nov Oxford/RAL 36

74 Jet-finding strategies in heavy-ion Jet energy fraction outside cone R=0.3 CDF preliminary Unmodified (p+p) jets: ~ 80% of energy within R~0.3 R = Δη 2 + Δφ 2 Need to suppress heavy-ion background: small jet cones areas R~ remove underlying event p t,track,et,tower >1-2 GeV J. Putschke Hard Probes 2008 Helen Caines - Yale - Nov Oxford/RAL 37

75 Jet-finding strategies in heavy-ion Jet energy fraction outside cone R=0.3 CDF preliminary R = Δη 2 + Δφ 2 Unmodified (p+p) jets: ~ 80% of energy within R~0.3 Need to suppress heavy-ion background: small jet cones areas R~ remove underlying event p t,track,et,tower >1-2 GeV Estimate background E-by-E by sampling Out-of-Cone area: pt per grid cell [GeV] STAR preliminary Out-of-Cone area: used to estimate mean background energy and mean background FF function Caveat: Precision depends on acceptance, event-byevent fluctuations and elliptic flow (small effect for central heavy-ion collisions) η ϕ reconstructed jets J. Putschke Hard Probes 2008 Helen Caines - Yale - Nov Oxford/RAL 37

76 Jet spectrum in Au+Au collisions STAR preliminary; stat. errors only HT not trigger bias corrected! LOCone Rc=0.4, pt Seed >4.6 GeV pt cut >1 GeV MB-Trig: Good agreement with Nbin scaled p+p collisions HT-Trig: Large trigger bias how far up does it persist? (in p+p at least to 30 GeV) Au+Au HT 0-10% Au+Au MB 0-10% p+p scaled by Nbin black points: p+p mid-cone corrected to particle level (scaled by Nbin) blue solid points: Au+Au minbias corrected for pt cut and eff. using Pythia red open points: Au+Au HT trigger not corrected for pt cut and eff. using Pythia Relative normalization systematic uncertainty: ~50%. Further statistics of MB is needed to assess the bias in HT Trigger. First reconstructed jets in central heavy ion collisions. S. Salur Hard Probes 2008 Helen Caines - Yale - Nov Oxford/RAL 38

77 Modification of fragmentation function MLLA: good description of vacuum fragmentation (basis of PYTHIA) Introduce medium effects at parton splitting Borghini and Wiedemann, hep-ph/ Jet quenching hump-back plateau p T hadron ~2 GeV ξ=ln(e Jet /p hadron ) Jet quenching fragmentation should be strongly modified at p T hadron ~1-5 GeV Can we measure this at RHIC? Helen Caines - Yale - Nov Oxford/RAL 39

78 RHIC Summary We create a strongly coupled medium sqgp not the asymptotically plasma of free quarks and gluons as expected - high pt partons interact very strongly with it It flows like a (nearly) perfect fluid with quark degrees of freedom and a viscosity to entropy density ratio lower than any other known fluid We are past the discovery stage towards the quantitative i.e. η/s, transport coefficients First full jet reconstruction in heavy-ion collisions - probing medium How medium varies as a function of collision energy/centrality/species New phenomena (e.g. ridge) challenge our understanding much remains to be done: EOS, initial conditions (ultimately needs EIC) Next steps Ongoing upgrades to STAR and PHENIX Vertex detectors, increased coverage and PID, improved triggering capabilities rare probes, heavy flavor, γ-jet,... Electron Beam Ion Source (EBIS) to extend ranges of species (U+U) RHIC-II: increase luminosity by factor 5 using stochastic cooling Helen Caines - Yale - Nov Oxford/RAL 40

79 The Next Energy Frontier: LHC A unique opportunity to investigate QGP at unparalleled high s Will this too create a strongly-coupled fluid? 16!SB/T4 RHIC 14 3 flavor!/t flavor 10 2 flavor 8 LHC SPS flavor T (MeV) Targeted Studies: ATLAS Helen Caines - Yale - Nov Oxford/RAL Targeted Studies: CMS Dedicated Experiment: ALICE 41

80 END Helen Caines - Yale - Nov Oxford/RAL 42

81 Some possible explanations of the ridge Recombination between thermal and shower partons at intermediate p T R.C. Hwa & C.B. Chiu Phys. Rev. C 72 (2005) QCD bremsstrahlung radiation boosted by transverse flow S.A. Voloshin, Phys. Lett. B 632 (2007) 490 E. Shuryak, hep-ph: In medium radiation and longitudinal flow push N. Armesto et.al Phys. Rev. Lett. 93 (2007) Broadening of quenched jets in turbulent color fields A. Majumder et.al Phys. Rev. Lett. 99 (2004) Momentum Kick Model C.Y. Wong hep-ph: All qualitatively consistent with the features of the ridge Helen Caines - Yale - Nov Oxford/RAL 43

82 pt systematics of di-hadron correlations Increase pt Trigger ! 1-2 GeV/c " 1.5 PHENIX: arxiv: Au+Au 0-20 % p+p 0 a ab Y jet_ind = (1/N )dn /d!" ! 1-2 GeV/c " ! 1-2 GeV/c ! 1-2 GeV/c 5-10! 2-3 GeV/c " ! 3-4 GeV/c " ! 4-5 GeV/c " ! 5-10 GeV/c " 14.0 Increase pt Assoc !" (rad) Helen Caines - Yale - Nov Oxford/RAL 44

83 pt systematics of di-hadron correlations Increase pt Trigger ! 1-2 GeV/c " 1.5 PHENIX: arxiv: Au+Au 0-20 % p+p a ab Y jet_ind = (1/N )dn /d!" ! 1-2 GeV/c " ! 1-2 GeV/c Away-side peak reemerges Shoulder emerges ! 1-2 GeV/c 5-10! 2-3 GeV/c " ! 3-4 GeV/c " ! 4-5 GeV/c " ! 5-10 GeV/c " 14.0 Increase pt Assoc !" (rad) Helen Caines - Yale - Nov Oxford/RAL 44

84 pt systematics of di-hadron correlations Increase pt Trigger ! 1-2 GeV/c " 1.5 PHENIX: arxiv: Au+Au 0-20 % p+p a ab Y jet_ind = (1/N )dn /d!" ! 1-2 GeV/c " ! 1-2 GeV/c Au+Au yield increases (why later ridge) ! 1-2 GeV/c 5-10! 2-3 GeV/c " ! 3-4 GeV/c " ! 4-5 GeV/c " ! 5-10 GeV/c " 14.0 Increase pt Assoc !" (rad) Helen Caines - Yale - Nov Oxford/RAL 44

85 pt systematics of di-hadron correlations Increase pt Trigger ! 1-2 GeV/c " 1.5 PHENIX: arxiv: Au+Au 0-20 % p+p a ab Y jet_ind = (1/N )dn /d!" ! 1-2 GeV/c " ! 1-2 GeV/c Shoulder structure remains but gets smaller and smaller ! 1-2 GeV/c 5-10! 2-3 GeV/c " ! 3-4 GeV/c " ! 4-5 GeV/c " ! 5-10 GeV/c " 14.0 Increase pt Assoc !" (rad) Helen Caines - Yale - Nov Oxford/RAL 44

86 High p T triggered away side RMS width A. Adare QM2008 RMS Width - centrality independent Helen Caines - Yale - Nov Oxford/RAL 45

87 High p T triggered away side RMS width p+p π 0 -h: p T trig = GeV/c p T assoc = GeV/c RMS = ± 0.03 PHENIX: Phys Rev D A. Adare QM2008 RMS Width - centrality independent Consistent with p+p data Helen Caines - Yale - Nov Oxford/RAL 45

88 High p T triggered away side RMS width p+p π 0 -h: p T trig = GeV/c p T assoc = GeV/c RMS = ± 0.03 PHENIX: Phys Rev D A. Adare QM2008 RMS Width - centrality independent Consistent with p+p data Vacuum fragmentation? Helen Caines - Yale - Nov Oxford/RAL 45

89 Composition of ridge and shoulders Ridge Inclusive C. Nattrass QM2008 STAR Preliminary STAR Preliminary Jet Cone Inclusive ridge ratio ~ inclusive ratio > jet ratio Helen Caines - Yale - Nov Oxford/RAL 46

90 Composition of ridge and shoulders Ridge Inclusive C. Nattrass QM2008 STAR Preliminary STAR Preliminary Jet Cone Inclusive ridge ratio ~ inclusive ratio > jet ratio shoulder ratio ~ inclusive ratio > jet ratio PHENIX M. McCumber QM2008 Helen Caines - Yale - Nov Oxford/RAL 46

91 Composition of ridge and shoulders Ridge Inclusive C. Nattrass QM2008 STAR Preliminary STAR Preliminary Jet Cone Inclusive ridge ratio ~ inclusive ratio > jet ratio shoulder ratio ~ inclusive ratio > jet ratio PHENIX M. McCumber QM2008 Ridge and Shoulder similar properties NOT vacuum fragmentation Energy lost by jet partons seems to be re-distributed into the medium and freezes out in similar fashion Helen Caines - Yale - Nov Oxford/RAL 46

92 trigger Medium Associated track C Δφ ( ) Y Δφ same( ) ( Δφ) Y Δφ mixed Y same Δφ C Δφ Y mixed ( ) b v 2 assoc ( )dφ ( )dφ [ v trig 2 cos( 2Δφ) ] + J Δφ ( )

93 Trigger Mach angle depends on speed of sound in medium T dependent Angle independent of associated p T. Mikherjee, Mustafa, Ray Phys. Rev. D75 (2007) Away-side PNJL Model

94 Trigger Mach angle depends on speed of sound in medium T dependent Angle independent of associated p T. Mikherjee, Mustafa, Ray Phys. Rev. D75 (2007) Away-side PNJL Model

95 Trigger Mach angle depends on speed of sound in medium T dependent Angle independent of associated p T. Mikherjee, Mustafa, Ray Phys. Rev. D75 (2007) Away-side PNJL Model

96 Trigger θ M Mach angle depends on speed of sound in medium T dependent Angle independent of associated p T. Mikherjee, Mustafa, Ray Phys. Rev. D75 (2007) Away-side PNJL Model

97 Trigger θ M Mach angle depends on speed of sound in medium T dependent Angle independent of associated p T. Mikherjee, Mustafa, Ray Phys. Rev. D75 (2007) Away-side PNJL Model

98 Čerenkov angle vs emitted particle momentum Koch, Majumder, Wang PRL (2006) p (GeV/c)

99 ξ for strange hadrons PYTHIA R<0.4 QCD predicts a <ξ> p mass ordering We observe an inversion of K 0 s and Λ Similar observation from BABAR for K and p <ξ> Pion Proton Kaon Helen Caines - Yale - Nov Oxford/RAL 50 s BABAR preliminary (Trento 2008 hep-ph/ )

100 Observation of di-jets: punch through

101 Observation of di-jets: punch through T1 A1 Di-jet trigger T2 Select di-jets events: Require T1 and T2 b-to-b T1: p T >5GeV/c T2: p T >4GeV/c A1: p T >1.5GeV/c

102 Observation of di-jets: punch through T1 A1 Di-jet trigger T2 Select di-jets events: Require T1 and T2 b-to-b T1: p T >5GeV/c T2: p T >4GeV/c A1: p T >1.5GeV/c What happens to away-side hump and near-side ridge if we trigger on di-jets?

103 Data analysis: di-jet selection Correlation between primary trigger (T1) and away-jetaxis trigger (T2). T1 Di-jet trigger T2 a.u T1T2 correlation Raw, uncorrected signal Require that the 2 highest p T particles are back-to-back in φ Δφ T1: p T >5 GeV/c T2: p T >4 GeV/c π ± 0.2 Helen Caines - Yale - Nov Oxford/RAL 52

104 Hope to shift distribution of hard scattering towards center of medium. Near-side parton travels through more medium Trigger Trigger Assoc h Trigger ssoc Assoc h Conditional charged hadron at high-pt Create path lengths comparable in dense medium. However not always from center could be tangential

105 3 1 _dn_ Ntrig d(δφ ) GeV Au+Au & d+au Au+Au d+au STAR Preliminary Δφ Di-jets are suppressed Once selected: No Away-side suppression Au+Au ~ d+au No Away-side shape modification 1 _dn_ Ntrig d(δφ ) T2A1_T1 12% Central 40-60% MB 60-80% MB STAR Preliminary Δφ

106 3 1 _dn_ Ntrig d(δφ ) GeV Au+Au & d+au Au+Au d+au STAR Preliminary Δφ Di-jets are suppressed Once selected: No Away-side suppression Au+Au ~ d+au No Away-side shape modification 1 _dn_ Ntrig d(δη ) 0 T2A1_T1 T1A1_T2 Au+Au 12% central Δφ <0.7 No Ridge STAR Preliminary Δη

107 1 _dn_ Ntrig d(δη ) _dn_ Ntrig d(δφ ) GeV Au+Au & d+au Au+Au d+au Δφ T2A1_T1 T1A1_T2 STAR Preliminary STAR Preliminary Au+Au 12% central Δφ < Δη Di-jets are suppressed Once selected: No Away-side suppression Au+Au ~ d+au No Away-side shape modification No Ridge Di-Jets don t interact with medium. Tangential jets or punch through without interaction?