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Axel Drees, University Stony Brook EINN, Milos Greece, Sep. 23 2005 Energy Loss in Dense Media “Jet Quenching” PHENIX PRL 88 (2002) 22301 One of the first.

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Presentation on theme: "Axel Drees, University Stony Brook EINN, Milos Greece, Sep. 23 2005 Energy Loss in Dense Media “Jet Quenching” PHENIX PRL 88 (2002) 22301 One of the first."— Presentation transcript:

1 Axel Drees, University Stony Brook EINN, Milos Greece, Sep. 23 2005 Energy Loss in Dense Media “Jet Quenching” PHENIX PRL 88 (2002) 22301 One of the first discoveries at RHIC!

2 Axel Drees Outline of My Talk l Introduction l Quark Gluon Plasma at RHIC l Jets and how they probe the QGP l Jet quenching in heavy ion collisions l pp baseline l High pt particle suppression in Au-Au l d-Au control experiment l Suppression of jet-jet correlations l New experimental results l Medium modification of jet-correlations l Medium modifications of charm spectra l Summary & Outlook

3 Axel Drees RHIC Relativistic Heavy Ion Collisions The Phase Diagram of Nuclear Matter Color super- conductor Color-flavor locking Critical point  baryon or nucleon density Temperature nuclei Quark-Gluon Plasma Hadron Gas “frozen Quarks” Early Universe Neutron Stars? l QGP in Astrophysics l early universe: time < 10 6 seconds l possibly in the interior of neutron stars l Quest of heavy ion collisions l create QGP as transient state in heavy ion collisions l verify existence of QGP l study properties of QGP 170 MeV 1Gev/fm 3 Overwhelming evidence for strongly interacting plasma produced at RHIC

4 Axel Drees I. Transverse Energy central 2% PHENIX 130 GeV Bjorken estimate:   ~ 0.3 fm Matter at RHIC has 15 GeV/fm 3  ~15 GeV/fm 3 III. Jet Quenching dN g /dy ~ 1100 Initial conditions:  therm ~ 0.6 -1.0 fm/c  ~15-25 GeV/fm 3 II. Hydrodynamics PHENIX Huovinen et al V2V2 Pt GeV/c

5 Axel Drees Ideal Experiment to Probe the QGP Rutherford experiment   atomdiscovery of nucleus SLAC electron scattering e  protondiscovery of quarks penetrating beam (jets or heavy particles) absorption or scattering pattern QGP Nature needs to provide penetrating beams and the QGP in Au-Au collisions l QGP created in Au-Au collisions as transient state for 10 fm l penetrating beams created by parton scattering before QGP is formed l high transverse momentum particles  jets l Heavy particles  charm and bottom

6 Axel Drees hadrons leading particle hadrons leading particle q q hadrons leading particle leading particle schematic view of jet production hadrons Jets: A Penetrating Probe for Dense Matter l In a gold gold collision l Scattered partons travel through dense matter l Expected to loose a lot of their energy l Energy loss observed as l suppression of high p T leading particles l suppression of angular correlation l Depending on path length, i.e. centrality and angle to reaction plane l What is a jet? l Incoming partons may carry large fraction x of beam momentum l These partons can scatter with large momentum transfer l Results in large p T of scattered partons l appears in laboratory as “jet” of particles l Jet production can be observed as l high p T leading particles l angular correlation reaction plane

7 Axel Drees l Jet production measured indirectly by transverse momentum (p T ) spectrum Identified particles (  0 ) Charged particles (h = , K, p,.. ) l At RHIC energies different mechanisms are responsible for different regions of particle production l Thermally produced “soft” particles l “hard” particles from jet production l Hard component can be calculated with QCD l Data agrees with QCD calculation l “calibrated” reference Particle Spectra from p-p Collisions  0 from p-p collisions soft hard QCD calculation

8 Axel Drees l Hard-scattering processes in p-p l quarks and gluons are point-like objects l small probability for scattering in p-p l p-p independent superposition of partons l Minimum bias A-A collision l assume small medium effects on parton density l superposition of independent p,n collisions l collision probability increases by A 2 l cross section scales by number of binary collisions l Impact parameter selected A-A collisions l superposition of p,n collisions among participants l calculable analytically by nuclear overlap integral l or by MC simulation of geometry “Glauber Model” Scaling from p-p to Heavy Ion Collisions Participants

9 Axel Drees Hard processes in Au-Au scale with N binary Binary Scaling in Au-Au tested with Direct Photons l pp collisions: l qg-Compton scattering Direct  production described by NLO pQCD q qg  l Au-Au collisions: Direct  rates scale with N binary l Similar scaling observed for charm quark production

10 Axel Drees Suppression of   in Central AuAu Collisions High p T suppressed by factor ~ 5 pp to central AuAu and peripheral to central Au-Au PHENIX preliminary Nuclear modification factor: PHENIX PRL 91 (2003) 72301

11 Axel Drees Control Experiment with d-Au Final state effect: no suppression Initial state effect: suppression gold-gold collision deuteron gold collision l Final state effect “jet quenching” l Medium created in d-Au has small volume l Jets easily penetrate short distance l No suppression of jet yield expected in d-Au l Initial state saturation effect l Gluon density saturated in incoming gold nucleus l Deuteron shows no or little saturation l Expect suppression of jet yield, but with reduced magnitude

12 Axel Drees Suppression at Parton Level l No suppression for direct photons l Hadron suppression persists up to >20 GeV jets Common suppression for  0 and  it is at partonic level Typical model calculation:  > 15 GeV/fm 3 ; dN g /dy > 1100 Hot opaque partonic medium:  > 15 GeV/fm 3

13 Axel Drees Centrality Dependence of Suppression Convolute jet absorption or energy loss with nuclear geometry (many publications) Centrality dependence characteristic for jet absorption in extremely opaque medium! Insensitive to details of energy loss mechanism l Hard region: p T > 7 GeV/c l Suppression depends on centrality but not on p T l Characteristic features of jet fragmentation independent of centrality pQCD spectral shape h/  0 constant x T scaling

14 Axel Drees Azimuthal Correlations from Jets pp  jet+jet STAR Trigger particle with high p T > p T cut 1  to all other particles with p T > p T cut-2 Au+Au  ??? 0  /2   0 yield/trigger p+p yield/trigger 0  /2   0 Au+Au random background elliptic flow  0  /2  0 yield/trigger Au-Au statistical background subtraction suppression? Jet correlations in Au-Au via statistical background subtraction

15 Axel Drees Disappearance of the “Away-Side” Jet pedestal and flow subtracted Near-side: p+p, d+Au, Au+Au similar Back-to-back: Au+Au strongly suppressed relative to p+p and d+Au Suppression of the away side jet in central Au+Au trigger 6 <pt< 8 GeV partner 2 < pt < 6 GeV Integrate yields in some  window on near and away side

16 Axel Drees Suppression of Back-to-Back Pairs Away side jets are suppressed consistent with jet absorption in opaque medium Jet correlation strength: Compared to jet absorption model (J.Jia et al.) Near side Away side “Mono jets” point outward

17 Axel Drees Remaining Jets from Matter Surface 8 < p T (trig) < 15 GeV/c STAR Preliminary p T (assoc)>6 GeV D. Magestro, QM2005 Surviving “Di jets” tangential Qualitatively consistent with surface emission Decreased surface/volume “Mono jets” point outward ~factor 5

18 Axel Drees Where Does the Energy Go? Trigger > 2.5 GeVpartner > 1 GeV

19 Axel Drees Modification of Jet Shape at Lower p T PHENIX preliminary Near side Away side Can jet shape be related to properties of matter?

20 Axel Drees Sound velocity? Dielectric Constant? Jet Tomography will be power tool to probe matter! l Energy loss of jet results in conical shock wave in strongly interacting plasma l Hydrodynamic mach cone? l Longitudinal modes ? l Cherenkov radiation ? l Momentum conservation “multiple scattering” with meduium l Medium evolution of radiated gluons Theoretical Speculation: Wake effect or “sonic boom” Shuryak et al.

21 Axel Drees How opaque is the medium? Check Charm Production! p+p l Default PYTHIA parameterization l PDF – CTEQ5L; m C = 1.25 GeV; m B = 4.1 GeV l = 1.5 GeV; K = 3.5 l Parameterization tuned to describe  s < 63 GeV p+N world data l Spectral shape is “harder” than PYTHIA expectation pp PHENIX preliminary background subtracted electron spectrum l Signal: l Background: D p e,  p X   e e

22 Axel Drees Open Charm in Au+Au at  s NN =200 GeV l Total yield scales with number of binary collisions No indication of strong medium modification of charm production

23 Axel Drees Heavy Quark Energy Loss: Nuclear Modification Factor l Strong modification of the spectral shape l Suppression by factor 2-5, similar to pion suppression l Large bottom contribution above 4 GeV? Production of charm scales like hard process Spectral shape modified while propagating in medium

24 Axel Drees Elliptic Flow: A Collective Effect Initial spatial anisotropy is converted into momentum anisotropy  x y z  dn/d  ~ 1 + 2 v2(pT) cos (2  ) +...

25 Axel Drees Greco,Ko,Rapp: PLB595(2004)202 Charm Quarks flow with light quarks Charm flows, strength ~ 60% of light quarks (   ) l Drop of the flow strength at high p T due to b-quark contribution? l The data favor the model that charm quark itself flows at low p T. High parton density and strong coupling in the matter

26 Axel Drees Strongly interacting QGP produced at RHIC State of unprecedented energy density ~ 15 GeV/fm 3 Opaque to colored “hard” probes, jets and heavy flavor Hard probes will be critical to study properties of QGP Discovery of jet quenching On tape; analysis ongoing Most data seen today 4x larger Au-Au data sample in 2006 Factor 10 luminosity increase with electron cooling after 2010 Summary & Outlook 2004 2002 2001

27 Axel Drees Backup Slides

28 Axel Drees Outlook into the “Away” Future Quark gluon Compton scattering:  -energy fixes jet energy  & Jet direction fix kinematics measure  E as function of: E, “L”, flavor q qg   -jet: the golden channel for jet tomography pQCD direct  + jet quenching PHENIX Preliminary AuAu 200 GeV 0-10% pQCD direct  70% of photons are prompt photons Promising measurement at RHIC: every low cross section; p T < 8-10 GeV on tape luminosity and detector upgrades: extend range to p T ~25 GeV and |y|<3

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