John Harris (Yale) Hadron Collider Conference, East Lansing MI, 6/14/04 The Quenching of Jets at RHIC – Evidence for Hot Bulk QCD Matter Introduction Relativistic Heavy Ion Collider (RHIC) Creating Hot Bulk QCD Matter – Overview Using Hard Scattering to Probe the Medium Suppression of High Pt Particles Jet Quenching (Parton Energy Loss) Properties of the Medium Conclusions & Expectations

John Harris (Yale) Hadron Collider Conference, East Lansing MI, 6/14/04 Early Universe National Geographic (1994) & Michael Turner quark-hadron phase transition 2 x Kelvin

John Harris (Yale) Hadron Collider Conference, East Lansing MI, 6/14/04 Lattice QCD at Finite Temperature F. Karsch, et al. Nucl. Phys. B605 (2001) 579 Action density in 3 quark system in full QCD H. Ichie et al., hep-lat/ G. Schierholz et al., Confinement 2003 T C ~ 175  8 MeV   C ~ GeV/fm 3

John Harris (Yale) Hadron Collider Conference, East Lansing MI, 6/14/04 Phase Diagram of QCD Matter see: Alford, Rajagopal, Reddy, Wilczek Phys. Rev. D64 (2001)

John Harris (Yale) Hadron Collider Conference, East Lansing MI, 6/14/04 Hot Bulk QCD Matter (QGP) Standard Model  Lattice Gauge Calculations predict Deconfinement phase transition at high T in QCD Cosmology  Quark-hadron phase transition in early Universe Astrophysics  Cores of dense stars Establish bulk properties of QCD at high T and density Can we make it in the lab?

John Harris (Yale) Hadron Collider Conference, East Lansing MI, 6/14/04 Relativistic Heavy Ion Collider STAR PHENIX PHOBOS BRAHMS RHIC Design PerformanceAu + Aup + p Max  s nn 200 GeV500 GeV L [cm -2 s -1 ]2 x x Interaction rates1.4 x 10 3 s -1 3 x 10 5 s -1 Two Concentric Superconducting Rings Ions: A = 1 ~ 200, pp, pA, AA, AB

John Harris (Yale) Hadron Collider Conference, East Lansing MI, 6/14/04 Relativistic Heavy Ion Collider and Experiments STAR

John Harris (Yale) Hadron Collider Conference, East Lansing MI, 6/14/04 Space-time Evolution of RHIC Collisions e  space time jetjet Hard Scattering + Thermalization (< 1 fm/c) Au  Expansion  Hadronization p K   Freeze-out (~ 10 fm/c)   QGP (~ few fm/c)  e

John Harris (Yale) Hadron Collider Conference, East Lansing MI, 6/14/04 What Can We Learn from Collisions at RHIC? Early Stage of Collisions –Parton (fast quark and gluon) scattering and propagation –Pressure buildup from azimuthal asymmetries (elliptic flow) Thermodynamic Properties –Bjorken longitudinal expansion and energy density –Baryo-chemical potential from baryon density/particle ratios –Pressure from flow –Entropy from particle production –Temperature from chemical freezeout (particle ratios) –Temperature from thermal freezeout (particle spectra) Phase Transitions? –Deconfinement (s,  cc,,  bb?) –Chiral Restoration General - Collision Geometry, Space-time Evolution, Freezeout –number of participants vs centrality –stages of collisions (space-time diagram as function of geometry) –short-lived resonances –hadronization timescales Medium Effects? – on masses and widths of resonances – on parton propagation, other?

John Harris (Yale) Hadron Collider Conference, East Lansing MI, 6/14/04 Creating & Probing Hot Nuclear Matter at RHIC Create Hot Nuclear Matter –Equilibration? Thermodynamic properties? –Equation of State? –How to determine its properties? Probe Soft Physics  reflect bulk properties (p T < 2 GeV/c) Hard Scattering & Heavy Quarks  probe the medium

John Harris (Yale) Hadron Collider Conference, East Lansing MI, 6/14/04 Characteristics of Collisions at RHIC from Experiments global observations: Large produced particle multiplicities  dn ch /d  |  =0 = 670, N total ~ 7500  15,000 quarks in final state, > 92% are produced quarks Large energy densities  dn/d  dE T /d   GeV/fm 3  x nuclear density Large elliptic flow  Extreme early pressure gradients and gluon densities  quark-gluon equation of state!

John Harris (Yale) Hadron Collider Conference, East Lansing MI, 6/14/04 Early Pressure in System  Elliptic Flow? x z y Initial Ellipticity (coord. space) Reaction Plane (xz) Sufficient interactions early (~ 1 fm/c) in system  to respond to early pressure?  before self-quench (insufficient interactions)? System able to convert original spatial anisotropy into momentum anisotropy? Sensitive to early dynamics of initial system p p Azimuthal anisotropy (momentum space) ?

John Harris (Yale) Hadron Collider Conference, East Lansing MI, 6/14/04 Large Elliptic Flow Observed Azimuthal asymmetry of charged particles: dn/d  ~ v 2 (p T ) cos (2  ) +... x z y

John Harris (Yale) Hadron Collider Conference, East Lansing MI, 6/14/04 Characteristics of Collisions at RHIC from Experiments global observations: Large produced particle multiplicities  dn ch /d  |  =0 = 670, N total ~ 7500  92% of (>15,000) quarks of final state are produced quarks Large energy densities  dn/d  dE T /d   GeV/fm 3  –   x nuclear density Large elliptic flow  Large early pressure gradients and gluon densities  quark-gluon equation of state! “chemical” equilibration (particle yields & ratios): Do particles yields represent equilibrium values?

John Harris (Yale) Hadron Collider Conference, East Lansing MI, 6/14/04 Chemically and thermally equilibrated fireball at one temperature T and one ( baryon) chemical potential  : –One ratio (e.g.,  p / p ) determines  / T : –Second ratio (e.g., K /  ) provides T   Then all hadronic yields and ratios determined: Particle Ratios  Chemical Equilibrium  Temperature Ratios  equilibrium values

John Harris (Yale) Hadron Collider Conference, East Lansing MI, 6/14/04 QCD Phase Diagram At RHIC: T = 177 MeV T ~ T critical (QCD)

John Harris (Yale) Hadron Collider Conference, East Lansing MI, 6/14/04 Summary of Characteristics of Collisions at RHIC global observations: Large produced particle multiplicities  dn ch /d  |  =0 = 670, N total ~ 7500  92% of (>15,000) quarks of final state are produced quarks Large energy densities  dn/d  dE T /d   GeV/fm 3  –   x nuclear density Large elliptic flow  Large early pressure gradients and gluon densities  quark-gluon equation of state! “chemical” equilibration (particle yields & ratios): Small net baryon density  K + /K -,  B/B ratios)  B ~ MeV Quark coalescence / recombination Chemical Freezeout T  from global particle ratios)  T = 177 MeV,  B = 29 MeV  T ~ T critical (QCD) “thermal” equilibration (particle spectra) : Thermal freezeout + large transverse flow  T FO = MeV,  T  = 0.5 – 0.6c hard scattering probes: Suppression of high Pt particles Quenching of away-side jets (central Au + Au)  final state effect in Au + Au  dN g /dy ~ 1100  > 100  o

John Harris (Yale) Hadron Collider Conference, East Lansing MI, 6/14/04 Hard Scattering to Probe the Hot Bulk QCD Medium hadrons leading particle hadrons leading particle

John Harris (Yale) Hadron Collider Conference, East Lansing MI, 6/14/04 New for heavy ion physics  Hard Parton Scattering  s NN = 200 GeV at RHIC (vs 17 GeV at SPS) Using Hard Scattered Partons to Probe the Medium Jets and mini-jets  % of particle production  high p t leading particles (jets?)  azimuthal correlations vacuum mediummedium Scattered partons propagate through matter radiate energy (~ few GeV/fm) in colored medium suppression of high p t particles called “parton energy loss” or “jet quenching” alter di-jets and azimuthal correlations hadrons leading particle hadrons leading particle

John Harris (Yale) Hadron Collider Conference, East Lansing MI, 6/14/04 Inclusive Hadron p t -spectra:  s = 200 GeV AuAu power law:  pp = d 2 N/dp t 2 = A (p 0 +p t ) -n Preliminary STAR

John Harris (Yale) Hadron Collider Conference, East Lansing MI, 6/14/04 Hadron Spectra: Comparison of AA to NN Nuclear Modification Factor R AA : AA = Nucleus-Nucleus NN = Nucleon-Nucleon Nuclear overlap integral: # binary NN collisions / inelastic NN cross section NN cross section AA cross section AA (pQCD) Parton energy loss  R < 1 at large P t

John Harris (Yale) Hadron Collider Conference, East Lansing MI, 6/14/04 Brookhaven Science Associates U.S. Department of Energy Suppression of High Transverse Momentum Hadrons at RHIC Large transverse momentum hadrons are suppressed in central collisions at RHIC √s nn = 17.3 GeV √s nn = 31 GeV √s nn = 130 GeV

John Harris (Yale) Hadron Collider Conference, East Lansing MI, 6/14/04 Centrality Dependence of Suppression at RHIC Au+Au 130 GeV Phys. Rev. Lett. 89, (2002) STAR

John Harris (Yale) Hadron Collider Conference, East Lansing MI, 6/14/04 Brookhaven Science Associates U.S. Department of Energy Factor Suppression of High Transverse Momentum Hadrons at Top RHIC Energy Large transverse momentum hadrons are suppressed by factor ~ 4-5 in central collisions at RHIC

John Harris (Yale) Hadron Collider Conference, East Lansing MI, 6/14/04 Is Origin of Suppression Initial or Final State? Final state parton energy loss? A + A collisions in medium: gluon saturation? nuclear effects in initial state Initial state no parton energy loss nuclear effects in initial state gluon saturation? p,d + A collisions - no medium Distinguish effects - initial state final state

John Harris (Yale) Hadron Collider Conference, East Lansing MI, 6/14/04 Unique to Heavy Ion Collisions! Crucial control measurement using d-Au collisions

John Harris (Yale) Hadron Collider Conference, East Lansing MI, 6/14/04 Extreme Energy Densities! –Au-Au suppression (I. Vitev and M. Gyulassy, hep-ph/ ) –d-Au enhancement (I. Vitev, nucl-th/ ) understood in an approach that combines multiple scattering with absorption in a dense partonic medium  high p T probes require dN g /dy ~ 1100  > 100  0 Au-Au d-Au

John Harris (Yale) Hadron Collider Conference, East Lansing MI, 6/14/04 Hard Scattering (Jets) as a Probe of Dense Matter II Jet event in e  e   collision STAR p + p  jet event Can we see jets in high energy Au+Au? STAR Au+Au (jet?) event

John Harris (Yale) Hadron Collider Conference, East Lansing MI, 6/14/04 In QCD Medium Additional k T Significant energy loss?  high p T suppression Sensitive to color properties of medium Studying Jets and High Pt Particles in Detail at RHIC Hard probes  early times Calculable: pQCD Abundant at RHIC, LHC k T “radiative corrections” pre- and post-scattering di-jet:  Fragmentation: p(hadron) p (parton) z = Induced Gluon Radiation  ~collinear  gluons in cone  “Softened” fragmentation Gyulassy et al., nucl-th/

John Harris (Yale) Hadron Collider Conference, East Lansing MI, 6/14/04 Use Geometry to Vary Parameters of Collision x z y

John Harris (Yale) Hadron Collider Conference, East Lansing MI, 6/14/04 Using p+p to Study Au+Au Jet Correlations Assume: high p T triggered Au+Au event is a superposition: high p T triggered p+p event + elliptic flow of AuAu event –v 2 from reaction plane analysis –A from fit in non-jet region (0.75 < |  | < 2.24) Peripheral Au + Au Away-side jet Central Au + Au disappears STAR 200 GeV/c peripheral & central Au+Au p+p minimum bias 4<p T (trig)<6 GeV/c 2<p T (assoc.)<pT(trig)

John Harris (Yale) Hadron Collider Conference, East Lansing MI, 6/14/04 Path Length Dependence of Di-jet Topologies y x p T trigger =4-6 GeV/c, 2<p T associated <p T trigger, |  |<1 in-plane Out-of-plane Back-to-back suppression out-of-plane stronger than in-plane Effect of path length on suppression is experimentally accessible

John Harris (Yale) Hadron Collider Conference, East Lansing MI, 6/14/04 Hammering the Nail in the Coffin STAR azimuthal correlation function shows ~ complete absence of “away-side” jet  Surface emission only? “Partner” in hard scatter is absorbed in the dense medium  Pedestal&flow subtracted no jet quenching!

John Harris (Yale) Hadron Collider Conference, East Lansing MI, 6/14/04 Partonic vs. Hadronic Mechanisms Hottest Questions:  Fragment inside/outside of medium?  Partonic vs. hadronic model of Final State interaction? A Better Question:  To what degree do partonic and hadronic interactions contribute to quenching?  Discussion only recently started! Energy loss insufficient w.o. large partonic energy loss

John Harris (Yale) Hadron Collider Conference, East Lansing MI, 6/14/04 Hard Scattering Conclusion I The hard scattering data at RHIC from p-p, Au- Au and d-Au collisions establish existence of a new final-state effect - early (parton!) energy loss – from dense matter (new state of matter?) in central Au-Au collisions Au + Au Experimentd + Au Control Experiment Preliminary DataFinal Data

John Harris (Yale) Hadron Collider Conference, East Lansing MI, 6/14/04 Hard Scattering Conclusion II High Pt hadrons suppressed in central Au + Au enhanced in d + Au Back-to-back Jets Di-jets in p + p, d + Au (all centralities) Away-side jets quenched in central Au + Au  emission from surface x

John Harris (Yale) Hadron Collider Conference, East Lansing MI, 6/14/04 Suggest QGP-based picture of RHIC collision evolution Major Findings of RHIC to Date Quark coalesce./flow  constituent q d.o.f. Ideal hydro - Early thermalization + quark-gluon EOS pQCD parton E loss - large early gluon density- Opaque! Statistical model Rapid u, d, s equilibration near T crit Gluon saturation or Color Glass Condensate? large initial gluon density

John Harris (Yale) Hadron Collider Conference, East Lansing MI, 6/14/04 To do! Deconfined QGP?  cc,  bb suppression / melting sequence Strangeness enhancement? Thermalized? Open charm, beauty, multiply-strange baryon production & flow Establish properties of the QCD medium Probe parton E-loss with higher p T triggers, jets,  -jet Flavor dependence of suppression & propagation Light vector mesons (mass and width modifications) Direct Photon Radiation? New phenomena……. RHIC II! “the adventure continues!”

John Harris (Yale) Hadron Collider Conference, East Lansing MI, 6/14/04 Still the beginning

A Comprehensive New Detector for RHIC II Physics Exploratory Working Group on a Comprehensive New Detector for RHIC-II Physics L. Bland, P. Steinberg, T. Ullrich (BNL), M. Calderon (BNL/Indiana), S. Margetis (Kent State), B. Surrow (MIT), J. Rak (New Mexico), M. Lisa, D. Magestro (Ohio State), R. Lacey (Stony Brook), G. Paic (UNAM Mexico), T. Nayak (VECC Calcutta), R. Bellwied, C. Pruneau, A. Rose, S. Voloshin (Wayne State), H. Caines, A. Chikanian, E. Finch, J.W. Harris, C. Markert, J. Sandweiss, N. Smirnov (Yale) NSAC Review, BNL, June 3, 2004

The Physics Pillars of a New RHIC-II Detector What are the detailed properties of the sQGP and can we probe a weakly interacting plasma state ? How do particles acquire mass and is chiral symmetry restored in the dense medium ? Is there another phase (CGC) of matter at low x, what are its features (how does it melt into the QGP) ? What is the structure and dynamics inside the proton (parton spin, L) and is parity violation important ?

HCAL & muon detector. 15 planes, (5 cm Fe, streamer tubes, 0.3 x 4 cm resolution) (available) EMC; Crystals + Fe(Pb)/Sc (accordion type) or LAr variant, 6x6 mrad towers (available) Tracking: Si Vertex Detector (Si Pixel) Primary Tracker: multi-layer Si strip or miniTPC  Pattern Pad Detectors in Barrel and End Caps “Very Forward Direction” (see next slide) R = 2.8 m dZ = 3.0 m PID Detectors: Cherenkov threshold (aerogel), RICH, Photon Converters, ToF (STAR clone?) Detector Concept: central |  | < 3 SC Magnet Coil, 1.5 T (“available”) p T > 0.5 GeV/c

Summary The New Comprehensive Detector Presents Unique New Physics Programs at RHIC II:   - jet/leading particle physics program flavor dependent modification of fragmentation due to medium  Quarkonium physics program deconfinement, initial conditions, nuclear effects Unique Physics Contributions to:  Gluon saturation (CGC)  Chiral symmetry restoration  Structure and dynamics of the proton New (as yet) undetermined physics