Recent RHIC Results with AA Mark D Baker

Recent RHIC Results with AA Mark D. Baker Brookhaven National Laboratory The Motivation What have we learned about AA? What have we learned about QCD? Conclusions Many thanks to: Peter Steinberg Mark D. Baker

The RHIC community • >1000 people from around the world – Brazil, Canada, China, Croatia, Denmark, France, Germany, India, Israel, Japan, Korea, Norway, Poland, Russia, Sweden, Taiwan, UK, US Mark D. Baker

Mark D. Baker

There’s a lot to summarize! 130 Ge. V 200 Ge. V Total STAR: PRL 86 (2001) 402 PRL 86 (2001) 4778 PRL 87 (2001) 082301 PRL 87 (2001) 112303 PRL 87 (2001) 182301 PRL 87 (2001) 262302 + 1 more submitted Published 16 1 17 PHOBOS: PRL 85 (2000) 3100 PRL 87 (2001) 102301 PRL 87 (2001) 102303 PRC 65 (2002) 031901 PRL 88 (2002) 022302 + 1 more submitted Submitted 4 2 6 PHENIX: PRL 86 (2001) 3500 PRL 87 (2001) 052301 PRL 88 (2002) 022301 + 3 more submitted http: //www. ******. bnl. gov/ Mark D. Baker BRAHMS: PRL 87 (2001) 112305 PLB 523 (2001) 227 + 1 more submitted

The QCD Phase Diagram (adapted from Axel Drees) early universe T RHIC & LHC Quark Matter TC~170 Me. V (2*1012 K) Hadron Resonance Gas Nuclear Matter 940 Me. V Mark D. Baker Color nductor Superco neutron stars 1200 -1700 Me. V m. B

Heat is also a window back in time Mark D. Baker

The plan of attack • Collide gold nuclei at high energy • Is it “strongly interacting bulk matter”? – Initial State – Collective motion – Temperature, density • Learn about the strong interaction – Just beginning – Confinement, Chiral Symmetry Mark D. Baker

Heavy-Ion Collisions VNI Simulations: Geiger, Longacre, Srivastava, nuclth/9806102 1 2 Colliding Nuclei Hard Collisions 3 Parton Cascade 4 Hadron Gas & Freeze-out • Entropy produced as system evolves – Where does most of it come from? – Initial, partonic or hadronic stage? Mark D. Baker

We have collisions Year 2000: Au-Au s = (56) & 130 Ge. V Year 2001: Au-Au s = 19. 6 & 200 Ge. V Mark D. Baker

RHIC results at 200 Ge. V Theory 1999 Theory 2000 PHOBOS 2001 PHOBOS 2000 PRL 85 (2000) 3100 PRL 88 (2002) 022302 Total Ncharged ~ 5000 particles Mark D. Baker

Energy Dependence PRL 88 (2002) 022302 Hard Soft • Data favors models with minimal entropy production Mark D. Baker

Heavy Ion Collisions have a centrality (impact parameter) Forward Spectator Energy Mark D. Baker Peripheral Central

Parton Saturation Does Work PHENIX, PRL 86 (2001), PHOBOS PRC 65 (2002) Kharzeev/Nardi PLB 507, 2001 UA 5 Mark D. Baker BUT: DESCRIPTION NOT UNIQUE. We need an independent look at the saturation scale Qs!

We like to think in “rapidity” -1 Fragmentation Region 0 Fragmentation Region 1 x. F~0. 1 ybeam-2. 3 -ybeam Mark D. Baker 0 ybeam

Parton Saturation may connect e. A to AA Kharzeev & Levin, nucl-th/0108006 • Saturated initial state gives predictions about final state. Nh = c x N g l~0. 25 from fits to HERA data: x. G(x)~x-l Fit PHOBOS data at 130 Ge. V to set c, Qs Mark D. Baker PRL 87 (2001)

Saturation Works at 200 Ge. V L. Mc. Lerran, DNP 2001 nucl-ex/0112001 • Saturation models describe the data – Initial state parton density might be high enough to reach saturation regime Mark D. Baker h

Implications: • The initial state is dominated by soft physics • Limited entropy production in late stages. 1 Colliding Nuclei Geometry/Saturation Mark D. Baker 2 3 4 Parton Cascade Hadron Gas & Freeze-out QGP? / Fragmentation Gentle Freeze-out Hard Collisions QCD

Elliptic Flow: A collective effect Beam’s eye view of a non-central collision: Asymmetric particle distribution: f Particles prefer to be “inplane” d. N/d(f -YR ) = N 0 (1 + 2 V 1 cos (f-YR) + 2 V 2 cos (2(f-YR)) +. . . ) Mark D. Baker Elliptic flow

Elliptic Flow Expectations Particle asymmetry V 2 midrapidity : |h| < 1. 0 Hydrodynamic model Hydrodynamic Preliminary “Flow” No collective motion Normalized Multiplicity Mark D. Baker

Elliptic Flow PRL 86 (2001) 402 Particle asymmetry V 2 midrapidity : |h| < 1. 0 Hydrodynamic model Preliminary Normalized Multiplicity Mark D. Baker Peripheral Central

Collective motion largest at RHIC STAR, PRL 86 (2001) 402 Mark D. Baker

It even makes sense in detail Particle asymmetry Huovinen, Kolb, Heinz Mark D. Baker

We see the conditions at freezeout (a lower limit to the maximum Temperature) Hottest period Freezeout Expansion cooling Mark D. Baker

Separating Temperature & Expansion Effective Temperature mass Compare produced particles with different masses! Mark D. Baker

RHIC shows rapid expansion & a high temperature Effective Temperature (Ge. V) ary in AR T elim Pr S 150 Me. V CERN NA 49 PHENIX: p’s and pbar’s outnumber p’s at pt of 3 Ge. V/c! Mark D. Baker

Another “Thermometer” STAR Preliminary 4 6 2 1, 5, 7 Mark D. Baker T ~ 170 -200 Me. V 3

The plan of attack - where are we? • Collide gold nuclei at high energy • Is it “strongly interacting bulk matter” – Initial State – Collective motion – Temperature, density • Learn about the strong interaction – Some good news – Some puzzles – Confinement, Chiral Symmetry Mark D. Baker

Energy Density Estimate (Bj) PRL 87 (2001) 052301 formation time: 0. 2 - 1 fm e. Bj ~ 25 Ge. V/fm 3 e. Bj ~ 5 Ge. V/fm 3 Lattice ec Mark D. Baker

If you just believe the lattice. . . Karsch et al. CERN SPS ( s = 17 Ge. V) ei ~ 3 -10 Ge. V/fm 3 Ti ~ 220 -290 Me. V BNL RHIC ( s = 200 Ge. V) ei ~ 5 -25 Ge. V/fm 3 Ti ~ 250 -350 Me. V Mark D. Baker

Putting it all together 400 LEP! • Universal curve! • RHIC: 350 Temperature (Me. V) RHIC 300 quark gluon plasma 250 200 – “bulk” matter – high energy density einitial ~ 5 -25 Ge. V/fm 3 (lattice Ti >250 Me. V) SPS 150 – freezeout near TC AGS 100 50 – early collective expansion vt ~ 0. 65 c SIS hadron gas 0. 2 0. 4 0. 6 0. 8 1 1. 2 1. 4 Baryonic chemical potential m. B (Ge. V) Mark D. Baker

What happens before freeze-out? • Energetic particles come from quark or gluon “jets”. • They interact with the dense medium, but can’t thermalize. • Jet energy loss (“quenching”) is predicted (~1 Ge. V/fm). • Jet quenching measures the density early in the collision. pion Mark D. Baker

Suppression of High p. T Hadrons • Au. Au data – central (0 -10%) and peripheral (60 -80%) • compared to N-N reference – peripheral collisions • described at high p. T – central collision • suppressed at high p. T Mark D. Baker PHENIX, PRL 88 (2002) 022301

Scaling failure: might be quenching PHENIX, PRL 88 (2002) 022301 But it could be parton saturation p 0 (h-+h+)/2 h- p 0 Mark D. Baker

Charm Does Scale (doesn’t quench) Favors quenching interpretation for pions. Gluon radiation suppressed for heavy quarks. Dokshitzer, Kharzeev hep-ph/0106202 Mark D. Baker

Jet quenching at RHIC? Number Neutral pions Central collisions (10%) Neutral pions Peripheral collisions (75 -92%) No quenching X. N. Wang et al. Quenching (0. 25 Ge. V/fm) Transverse Momentum (Ge. V/c) Mark D. Baker Transverse Momentum (Ge. V/c)

Summary • We’ve learned a lot about the AA system – It is dense, hot & rapidly expanding. – Initial state soft effects dominate • Parton saturation? • We are beginning to probe this state. – Universal freezeout/hadronization curve. • Including a clear “bulk” state for the first time – Possible first evidence of jet quenching! • Should lead to a measure of the density • Especially at higher p. T Mark D. Baker

STAR Preliminary Mark D. Baker ud u