1. John Harris (Yale) HEP Workshop, Valparaiso, Chile, 11 - 15 Dec. 2006 In QCD Medium Additional k T Significant energy loss?  high p T suppression Sensitive to color properties of medium High p T Physics in ALICE 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/0302077

2. John Harris (Yale) HEP Workshop, Valparaiso, Chile, 11 - 15 Dec. 2006 Highlights of High p T Physics Results from RHIC Suppression at High p T of Light Quark Hadrons ( , K, p, , …) Non-photonic e’s from Heavy Quarks (D+B) Quenching of Away-side Jet Disappearance of the Away-side Jet in Most Central Collisions Appearance of Away-side Jet Energy in Low p T Particles Re-emergence of the Away-side Jet at Much Larger Trigger Jet p T Appearance of a “Ridge” on the Near-side Large parton E-loss Large gluon density Strongly-coupled QGP Medium response and properties

3. John Harris (Yale) HEP Workshop, Valparaiso, Chile, 11 - 15 Dec. 2006 The Start of Detailed “Tomography” of the QGP F QGP (  g QGP ) = f initial (√s, A 1 +A 2, b, x 1, x 2, Q 2 )  f QGP (p T ,y ,  ,p T jet,y jet,  jet, flavor jet,  flow ) “jet flow plane  /parton parton near-side Renk, hep-ph/0602045 Di-hadrons penetrate core! Renk, hep-ph/0602045 near-side Triggered jets come from near-side surface

4. John Harris (Yale) HEP Workshop, Valparaiso, Chile, 11 - 15 Dec. 2006 Di-Hadron Correlations at RHIC “jet Data: STAR, nucl-ex/0510002; pQCD E-loss Model + expansion: Renk, hep-ph/0602045 No near-side sensitivity to medium Slight away-side sensitivity to medium More extensive di-hadron measurements from PHENIX (hep-ex/0605039) and STAR (nucl-ex/0510002): Di-hadron fragmentation functions exhibit only a weak sensitivity to medium!  - jet and better jet energy (full jet) measurements necessary

5. 5 Extracting the medium density T. Renk, Hard Probes Singles Di-hadrons Box density Hydro profile Eskola et al., hep-ph/0406319 Limited sensitivity to medium density Points of origin for detected high-p T particles Surface bias in single particle suppression Di-hadrons have smaller surface bias I.e. probe entire interaction zone: better for extracting medium density

6. John Harris (Yale) HEP Workshop, Valparaiso, Chile, 11 - 15 Dec. 2006 High p T Physics with Heavy Ions at the LHC Real Jets! Role of LHC heavy ions? Larger  s Extend to much larger p T and “real” jets Abundant production of heavy quarks  increased statistics for differential studies

7. John Harris (Yale) HEP Workshop, Valparaiso, Chile, 11 - 15 Dec. 2006 The Future of RHI‘s at the LHC: Dedicated HI experiment - ALICE Two pp experiments with HI program: ATLAS and CMS

8. John Harris (Yale) HEP Workshop, Valparaiso, Chile, 11 - 15 Dec. 2006 ALICE Set-up HMPID Muon Arm TRD PHOS PMD ITS TOF TPC Size: 16 x 26 meters Weight: 10,000 tons

9. John Harris (Yale) HEP Workshop, Valparaiso, Chile, 11 - 15 Dec. 2006 Simple Expectations - Heavy Ion Physics at the LHC  QGP (fm/c)  (GeV/fm 3 ) T / T c t form (fm/c) √ s NN (GeV) factor 28 2-4 5 1.9 0.2 200 RHIC ≤ 2 3 1.1 1 17 LHCSPS 5500 0.1 shorter 3.0 - 4.2hotter 15-60denser > 10 longer Significant increase in hard scattering yields at LHC: - jets & large p T processes -  bb (LHC ) ~ 100  bb (RHIC) -  cc (LHC) ~ 10  cc (RHIC)

10. John Harris (Yale) HEP Workshop, Valparaiso, Chile, 11 - 15 Dec. 2006 Physics with the ALICE EMCal 10+1/2+1/2=11 super-modules 8 SM from US 3 SM from Europe Lead-scintillator sampling calorimeter  = 1.4,  =110 o Shashlik geometry, APD photosensor ~13K towers (  x  ~ 0.014 x 0.014) EMCal Technical Proposal approved by LHCC 9/28/06!!

11. John Harris (Yale) HEP Workshop, Valparaiso, Chile, 11 - 15 Dec. 2006 Capabilities of ALICE Extended by EMCal EMCal improves detector capabilities: - Fast trigger ~10 -100 enhancement of jets - Improves jet reconstruction (plus TPC) - Good   discrimination increases coverage - Good electron/hadron discrimination EMCal extends the physics of ALICE: 10 4 /year in minbias Pb+Pb: inclusive jets: E T ~ 200 GeV dijets: E T ~ 170 GeV   : p T ~ 75 GeV inclusive  : p T ~ 45 GeV inclusive e: p T ~ 30 GeV Thanks – Peter Jacobs

12. John Harris (Yale) HEP Workshop, Valparaiso, Chile, 11 - 15 Dec. 2006 New and Extended ALICE Physics from EMCal Pb + Pb collisions: medium-induced modification of jets response of medium to large energy deposition from parton energy loss mechanisms photon physics and photon-tagged jets heavy flavor physics using semi-leptonic decays into electrons measured in the EMCal and b-tagged jets. Also important to understand reference data in p + p, p + A and light A + A collisions

13. John Harris (Yale) HEP Workshop, Valparaiso, Chile, 11 - 15 Dec. 2006 Jet Reconstruction Fragmentation: p(hadron) p (parton) z = =  (  2 +  2 ) Large background in RHI Collisions – must limit jet cone radius R, track p T cut  only measure fraction of parton energy - calibrate

14. John Harris (Yale) HEP Workshop, Valparaiso, Chile, 11 - 15 Dec. 2006 Medium Modification of Fragmentation from Jets Fragmentation along jet axis: z = p hadron / p parton Introduce  = ln(E jet / p hadron ) ~ ln (1/z):  = ln( E jet / p hadron ) p T hadron ~2 GeV “Jet quenching” modifies spectrum for p T (hadron) ~ 1-5 GeV jet direction z - MLLA vacuum fragmentation (basis of PYTHIA) - Medium effects at parton splitting Borghini and Wiedemann, hep-ph/0506218 Thanks – Joern Putschke

15. John Harris (Yale) HEP Workshop, Valparaiso, Chile, 11 - 15 Dec. 2006 Simulations on Jet Quenching Measured in ALICE E jet ~175 GeV Solid: unquenched (p+p) Dashed: quenched jet (Pb+Pb) Pythia-based simulation with quenching Measure dashed / solid Ratio = PbPb (central) / pp Thanks – Joern Putschke

16. John Harris (Yale) HEP Workshop, Valparaiso, Chile, 11 - 15 Dec. 2006 Reminder - Gluon versus Quark Jets LHC  Gluon jets Top energy RHIC p T < 20 GeV  Gluon jets p T > 20 GeV  Quark jets Lower RHIC energy transition from gluon to quark jets Utilize RHIC versatility in √s!  -jet and di-hadrons     correlations  x  x  correlations qg, gg, qq scattering 3-jet events?

17. John Harris (Yale) HEP Workshop, Valparaiso, Chile, 11 - 15 Dec. 2006 Use b-jets to Tag Quark Jets Radiative quark energy loss different for heavy and light quarks - Y.L.Dokshitzer and D.E. Kharzeev, hep-ph/0106202 Reconstruct jets, tag heavy quark (c,b) - jets via Hadronic decay: secondary vertices from charged tracks Leptonic decay: muons with displaced vertices Compare jet shapes / properties of heavy quark jets and light quark jets. Exploit parton mass dependence to study parton energy loss mechanism. b b B D 

18. Photon-tagged jets Why  -jet ? Why  -jet ? Medium effects redistribute (  qL) the parton energy, E jet, inside the hadron jet (multiplicity, k T ). Medium effects redistribute (  qL) the parton energy, E jet, inside the hadron jet (multiplicity, k T ). Jet Measure E  = E jet. Prompt  ^ Redistribution can be best measured in the Fragmentation Function... If we know E jet. Redistribution can be best measured in the Fragmentation Function... If we know E jet. HI environment hinders precise reconstruction of E jet. AB ALICE-INT-2005-014 Thanks - Gustavo Conesa Balbastre – INFN Frascati

19. Tagging jet with photon  Search identified prompt photon (PHOS) with largest p T (E  > 20 GeV). Strategy (event by event) : Strategy (event by event) :  min  max leading Search leading particle :   -  leading  180º E leading > 0.1 E  R Reconstruct the jet: Particles around the leading with p T > 0.5 GeV/c, inside a cone of R = 0.3. 2 configurations: charged and neutral hadrons (TPC+EMCAL) and charged only (TPC). IP PHOS EMCal TPC ALICE-INT-2005-014 Thanks - Gustavo Conesa Balbastre – INFN Frascati

20. John Harris (Yale) HEP Workshop, Valparaiso, Chile, 11 - 15 Dec. 2006 Special thanks for contributors: Marco Leeuwen Joern Putschke Gustavo Conesa Balbastre Peter Jacobs

21. John Harris (Yale) HEP Workshop, Valparaiso, Chile, 11 - 15 Dec. 2006 Summary and Future Hard pQCD probes require for in-depth, differential studies better statistics better jet energy determination Still a lot to understand with present and upcoming RHIC data Significant high p T physics still to be done at upgraded RHIC (& detectors) luminosity at LHC

22. John Harris (Yale) HEP Workshop, Valparaiso, Chile, 11 - 15 Dec. 2006 Back-up Slides

23.  -distribution: qhat variation Need ~10% resolution at large 

24. Reference systems Jet trigger Compare central Pb+Pb to reference measurements Pb+Pb peripheral: vary system size and shape p+A: cold nuclear matter effects p+p (14 TeV): no nuclear effects, but different energy p+p (5.5 TeV): ideal reference, but limited statistics Includes acceptance, efficiency, dead time, energy resolution All reference systems are required for a complete systematic study

25. Jet yields: one LHC year Jet yield in 20 GeV bin Large gains due to jet trigger Large variation in statistical reach for different reference systems

26. John Harris (Yale) HEP Workshop, Valparaiso, Chile, 11 - 15 Dec. 2006 Di-hadron Correlations and Fragmentation Function 8 < p T,trig < 15 GeV Near-side – no modification Away-side quenched by factor 4 – 5, but no shape modification Near-sideAway-side STAR nucl-ex/0604018 X.N. Wang nucl-th/0511001