“It is better to begin in the evening than not at all” Present and future measurements on hadronization in strongly interacting partonic matter at RHIC and RHIC-II. “It is better to begin in the evening than not at all” Old English Proverb

Particle production in RHI collision SPS, RHIC-I LHC, RHIC-II Hydro pQCD Parton recombination and coalescence Medium modified fragmentation (jet quenching) Fragmentation Soft ~ 2 GeV/c ~ 6 GeV/c ~ 30 GeV/c ? pT

Reaching the fragmentation regime QM’05 Same RCP for pT>~5 GeV RAA flat for pT > 5 GeV Dominance of fragmentation pT > 5 GeV/c - medium modified

Calculated fragmentation functions C. Bourrely and J. Soffer, PRD 68 (2003) 014003 z Parton fragmentation functions to p and  vary as function of z If energy loss in medium different for light and heavy quarks will see differences in p-p and A-A Au-Au not enough - Need measurements in p-p

First “direct” look at medium modification QM’ 05 pT(assoc) > 2 GeV/c 1/Ntrig dN/d(Df) Au+Au, 0-5% STAR Preliminary 8 < pT(trig) < 15 GeV/c Emergence of the away side peak with increased trigger pT Away-side D(zT) suppressed, shape unchanged No striking flavor dependence of modification - need PID

PID jet correlations Need more stats and measure of z Au+Au 0-5% 1.0<pTAssociated<2.0 50% p/pbar Λ Λbar 95% п K0s Near Side Nch/NTrigger pTTrigger Near side – more likely to findp Away side – find p orp Meson/baryon difference? Need more stats and measure of z

Large acceptance in h and f essential Can we do that? Large acceptance in h and f essential pq,g > 10 GeV/c all h 106 particles in AA Need triggering g tagged jets Multiply pp events by factor of ~ 8 x 1015 for AuAu events in 30 nb-1 RHIC year RHIC-II luminosities essential

Comprehensive new detector at RHIC (R2D) HCal and m-detectors Superconducting coil (B = 1.3T) Vertex tracking RICH Aerogel EM Calorimeter ToF Tracking: Si, mini-TPC(?), m-pad chambers PID: Forward tracking: 2-stage Si disks Forward magnet (B = 1.5T) Forward spectrometer: (h = 3.5 - 4.8) EMCal (CLEO) HCal (HERA) m-absorber |h|  1.2 h = 1.2 – 3.5 Central detector (|h|  3.4) SLD magnet 6m

Detector coverage PID (p, K, p) Hadronic and EM Calorimetry: η = +/- 3.4 Tracking: η = (-3.5 – +4.5) PID:  = +/- 1.2 (2.8) RICH : C5F12 - n = 1.00175 1. 2. 3. 4. 5. 6. 7. 8. 9. 10 12. 14. 16 18. p (GeV/c) A1+ToF A1+A2+RICH RICH dE/dx, ToF PID (p, K, p)

Summary The New Comprehensive Detector designed for the new era of UNIQUE physics at RHIC-II : High rates Large acceptance High pT tracking PID out to high pT Good momentum resolution Understand medium produced via jets/leading particle New (as yet) undetermined physics Large program of measurements for RHIC-II era

Requirements for an Ideal Detector High rate detectors, DAQ Required for high luminosity A+A, p+A and p+p collisions at RHIC II Uniform high magnetic field over “large volume” Good quality tracking/momentum measurements Precision Vertex tracking 4 EM and Hadronic Calorimeters Missing energy measurements and  identification e/h discrimination At low pT as well as at high pT /K/p identification Momentum up to ~ 25 GeV/c Forward capabilities High-rapidity measurement/identification possibility

Geometrical Dependence of RAA RAA scales smoothly See poster, van Leeuwen (91)

Can’t rely too heavily on NLO calculations p+p->p0 + X Work for light mesons don’t work for heavy baryons