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

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


Early Universe

National Geographic(1994)

&Michael Turner

quark-hadronphase transition2 x 1012 Kelvin


Lattice QCD at Finite Temperature

F. Karsch, et al.Nucl. Phys. B605 (2001) 579

Action density in 3 quark system in full QCDH. Ichie et al., hep-lat/0212036

G. Schierholz et al., Confinement 2003

TC ~ 175 8 MeV C ~ 0.3 - 1 GeV/fm3


Phase Diagram of QCD Mattersee: Alford, Rajagopal, Reddy, Wilczek Phys. Rev. D64 (2001) 074017


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?


Relativistic Heavy Ion Collider

STAR

PHENIX

PHOBOS BRAHMS

RHIC

Design Performance Au + Au p + p

Max snn 200 GeV 500 GeV

L [cm-2 s -1 ] 2 x 1026 1.4 x 1031

Interaction rates 1.4 x 103 s -1 3 x 105 s -1

Two Concentric Superconducting Rings

Ions: A = 1 ~ 200, pp, pA, AA, AB


Relativistic Heavy Ion Collider and Experiments

STARSTAR


Space-time Evolution of RHIC Collisions

e

space

time jet

Hard Scattering + Thermalization (< 1 fm/c)

AuAu

Exp

ansi

on

Hadronization

p K

Freeze-out(~ 10 fm/c)

QGP (~ few fm/c)

e


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?


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(pT < 2 GeV/c)

Hard Scattering & Heavy Quarks probe the medium


Characteristics of Collisions at RHIC from Experiments

global observations:

Large produced particle multiplicities dnch/d |=0 = 670, Ntotal ~ 7500

15,000 quarks in final state, > 92% are produced quarksLarge energy densities dn/ddET/d GeV/fm3

x nuclear densityLarge elliptic flow Extreme early pressure gradients and gluon densities

quark-gluon equation of state!


Early Pressure in System Elliptic Flow?

x

z

y

Initial Ellipticity(coord. space)

ReactionPlane (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)

?

)

FlowElliptic

2cos2

FlowDirected

cos2 Isotropic

1 ( 2

121

2

3

3

RPRPtt

vvdydpp

d

pd

dE

x

y

p

patan


Large Elliptic Flow Observed

• Azimuthal asymmetry of charged particles: dn/d ~ 1 + 2 v2(pT) cos (2) + ...

x

z

y


Characteristics of Collisions at RHIC from Experiments

global observations:

Large produced particle multiplicities dnch/d |=0 = 670, Ntotal ~ 7500

92% of (>15,000) quarks of final state are produced quarksLarge energy densities dn/ddET/d GeV/fm3 –

x nuclear densityLarge 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?


• 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

pdedn E 3/)(~ Tμ

TμTμ

Tμ/2

/)(

/)(

ee

e

p

pE

E

Ratios equilibrium values


QCD Phase Diagram

At RHIC:

T = 177 MeV

T ~ Tcritical (QCD)


Hard Scattering to Probe the Hot Bulk QCD Medium

hadrons

leading particle

hadrons

leading particle


• New for heavy ion physics Hard Parton Scattering sNN = 200 GeV at RHIC (vs 17 GeV at SPS)

Using Hard Scattered Partons to Probe the Medium

• Jets and mini-jets

30 - 50 % of particle production

high pt leading particles (jets?)

azimuthal correlations

vacuum

medium

• Scattered partons propagate through matter

radiate energy (~ few GeV/fm) in colored medium

• suppression of high pt particles

called “parton energy loss” or “jet quenching”• alter di-jets and azimuthal correlations

hadrons

leading particle

hadrons

leading particle


Inclusive Hadron pt-spectra: s = 200 GeV AuAu

power law:

pp = d2N/dpt2 = A (p0+pt)-n

Preliminary

STAR


Hadron Spectra: Comparison of AA to NN

Nuclear Modification Factor RAA:AA = Nucleus-NucleusNN = Nucleon-Nucleon

ddpdT

ddpNdpR

TNN

AA

TAA

TAA /

/)(

2

2

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 Pt


Brookhaven Science AssociatesU.S. Department of Energy

Suppression of High Transverse Momentum Hadrons at RHIC

• Large transverse momentum hadrons are suppressed in central collisions at RHIC

√snn = 17.3 GeV

√snn = 31 GeV

√snn = 130 GeV


Centrality Dependence of Suppression at RHIC

Au+Au130 GeV

Phys. Rev. Lett. 89, 202301 (2002)STAR


Brookhaven Science AssociatesU.S. Department of Energy

Factor 4 - 5 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


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 partonenergy loss

nuclear effects in initial state

gluon saturation?p,d + A collisions -

no medium

Distinguish effects -initial statefinal state


Unique to Heavy Ion Collisions!• Crucial control measurement using d-Au collisions


Extreme Energy Densities! – Au-Au suppression

(I. Vitev and M. Gyulassy, hep-ph/0208108)– d-Au enhancement (I. Vitev, nucl-th/0302002 )

understood in an approach that combines multiple scattering with absorption in a dense partonic medium

high pT probesrequire

dNg/dy ~ 1100

> 100 0Au-Au

d-Au


Hard Scattering (Jets) as a Probe of Dense Matter II

Jet event in eecollision STAR p + p jet event

Can we see jets in high energy Au+Au?

STAR Au+Au (jet?) event


In QCD Medium

Additional kT

Significant energy loss? high pT suppression

Sensitive to color Sensitive to color properties of mediumproperties of medium

coneR

Studying Jets and High Pt Particles in Detail at RHIC

Hard probes early times

Calculable: pQCD

Abundant at RHIC, LHC

kT“radiative corrections”

pre- and post-scattering

di-jet:

Fragmentation:

z hadron

parton

p

p

Fragmentation:

p(hadron)p (parton)

z =Induced Gluon Radiation

~collinear gluons in cone “Softened” fragmentation

in je

i j t

t

n e

: increases

z : decreases

chn

Gyulassy et al., nucl-th/0302077


Use Geometry to Vary Parameters of Collision

x

z

y


Using p+p to Study Au+Au Jet Correlations

Assume:high pT triggered Au+Au event

is a superposition:high pT triggered p+p event +

elliptic flow of AuAu event

C2(Au Au)C2(p p) A *(1 2v22 cos(2))

– v2 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/cperipheral & central Au+Au

p+p minimum bias4<pT(trig)<6 GeV/c

2<pT(assoc.)<pT(trig)


Path Length Dependence of Di-jet Topologies

y

x

pTtrigger=4-6 GeV/c, 2<pT

associated<pTtrigger, ||<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


Hammering the Nail in the Coffin

C2(Au Au)C2(p p) A * (1 2v22 cos(2))

• 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!


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 Experiment d + Au Control Experiment

Preliminary DataFinal Data


Hard Scattering Conclusion II

High Pt hadrons suppressed in central Au + Au enhanced in d + AuBack-to-back Jets Di-jets in p + p, d + Au

(all centralities) Away-side jets quenched

in central Au + Au emission from surface

x


Suggest QGP-based picture of RHIC collision evolution

Major Findings of RHIC to DateMajor 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 Tcrit

Gluon saturation or Color Glass Condensate? large initial gluon density


To do!

RAA d 2N AA dydpT

d 2N pp dydpT NcollAA

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 pT 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!”


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 ForwardDirection”(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 || < 3SC Magnet Coil, 1.5 T (“available”) pT > 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

Documents

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