Prospects with Heavy Ions at the LHC

The Quark-Gluon Plasma at RHIC & LHCSo far at RHIC:Elliptic Flow Near-perfect FluidHigh pT SuppressionStrongly-coupled QGPJet QuenchingStrongly-coupled QGPAway-side of jetEnergy dissipation/propagation in mediumMedium properties?Near-side RidgeSomething new, unresolvedHeating of the systemLongitudinal expansion?Initial parton distributions?Initial parton bremsstrahlung + flow? !!!!!!!!!!RHIC and LHC:Cover 2 3 decades of energy (sNN ~ 20 GeV 5.5 TeV)What are the properties of hot QCD in this temperature range (T ~ 150 600 MeV)?

BIG Physics Questions for RHIC & LHC Heavy Ions- How does the system evolve/decohere from its initial state?- Initial state saturation / color glass?- Rapid thermalization - how?- What are the properties & constituents (vs. T) of the QGP?- e.g., screening length, bulk/shear viscosity, vs, diff. coeff.,. How do partons lose energy in the QGP?- How does the QGP respond to large energy deposition (jet heating)- Response of medium (e.g. away-side, near-side ridge)?- How does hadronization take place?

Simple Expectations - Heavy Ion Physics at the LHC

Hard Scattering with Heavy Ion Physics at the LHCSignificant increase in hard scattering yields at LHC:

- jets & large pT processes

- sbb (LHC ) ~ 100 sbb (RHIC)

- scc (LHC) ~ 10 scc (RHIC)

How Will LHC Heavy Ions Contribute?- How does the system evolve/decohere from its initial state?

- What are the properties & constituents (vs. T) of the QGP?

- How do partons lose energy in the QGP?

- How does the QGP respond to jet heating response of medium (e.g. away-side, near-side ridge)?

- How does hadronization take place?- - LHC extends reach to very low-x phenomena- - LHC extends reach to higher T- LHC extends abundance & diversity of probes (e.g. flow of heavy quarks & quarkonia v2 scaling?)- - LHC extends reach in mass, flavor, and pT of hard probes(different parton probes, jets, Z-bosons, heavy quarks, quarkonia)-

- Trigger on hard probes (above) of different mass, flavor and pT-- Investigate intermediate pT (5 15 GeV/c) hadron production - Investigate fragmentation process in detail (hadrochemistry in jets)- Investigate production of new scaler and vector particles

LHC Heavy Ion Collider Program

LHC to start s = 14 TeV p + p operation in Spring 2008

LHC Heavy Ion operation sNN = 5.5 TeV Pb + Pb Anticipate 1 month per year

Detectors ATLAS CMS ALICE

LHC Heavy Ion Collider Experiments

AdS/CFT (and all theories)

Meets

Heavy Ions at the LHC

Prospects for AdS/CFT with LHC Heavy IonsLHC ions will investigatev2 for light & heavy particles(p,.f, W,.B, D, J/y,)PHENIX, PRL 98, 172301 (2007) From PHENIX non-g e-data, transport models require:small heavy quark relaxation timesmall diffusion coefficient DHQ x (2pT) ~ 4 6

constrain viscosity/entropy h/s ~ (1.5 3) / 4pwithin factor 2 - 3 of AdS/CFT conjectured lower bound*consistent with light hadron v2 analysis

* Kovtun, Son, Starinets, hep-th/0405231

Prospects for AdS/CFT with LHC Heavy IonsWhat about the v2 Quark Scaling at intermediate pT ?My navete : how does this work? Early flow & constituent quark scaling?

Prospects for AdS/CFT with LHC Heavy IonsWhat happens to the radiation? Interference effects? Dist. relative to parton?What about recoil energyof collisional E-loss?DEgluon > DEquark, m=0 > DEquark, m>0 What is dependenceon mass, flavor and energy of parton?How does parton lose energy?One parameterization of energy loss LWhat is the dynamical origin of parton energy loss (quenching, suppression)?

Jets & High pT Particles with LHC Heavy IonsJet Physics- Jets: measure parton E & E-loss, jet-tag (B vs. light quark, gluon) long. & transverse mod. of jet g-jet, Z0-jet, di-jet: parton E & E-loss Hadrochemistry in Jets fragmentation function mod. light flavored mesons gluons parents D-mesons quark parents (mc ~ 0) B-mesons quark parents (mb > 0)

Parameterization of Parton Energy Loss at RHICL

AdS5/CFT Parton Energy Loss Results & Future!H. Liu, K. Rajagopal and U. A. Wiedemann, arXiv:hep-ph/0605178, recent PRLfrom J. J. Friess, S. S. Gubser and G. Michalogiorgakis,arXiv:hep-th/0605292.Future for AdS/CFT:What is the velocity dependence of energy loss?What is the mass & flavor (q, g) dependence of energy loss?What is radiated from the partons?

A Near-side Ridge Appears at RHIC!Di-hadron correlationshJets: scale with # of binary collisions Ridge: exists to highest pT (trig) correlated with jetsBut ridge spectra ~ same as medium ( bulk-like, seen for mesons/baryons) thermal spectra + flow origin? jet-heating?........

Possible Ridge Mechanisms So FarRadiated gluons, broadened byLongitudinal flow, Armesto et al, PRL 93 (2004) Color magnetic fields, Majumder et al, hep-ph/0611035Medium heating + recombination, Chiu & Hwa, PRC72, 034903Radial flow + trigger particle bias, Voloshin, N.P. A749, 287, Shuryak nuc-th/07063531 Initial parton scatter + Jet-medium interactions, C.Y. Wong, hep-ph/07072385

References to proposed explanations so far:

Response of the Medium in AdS/CFTQuestions for AdS/CFT: Dependence on mass, flavor and velocity?hep-th/0706.4302

Heavy Flavors at the LHCRAA of D and B-mesons to large pT at LHC AdS/CFT dE/dx of heavy quarks - S. Gubser, Drag Force in AdS/CFT,hep-ph0605182, hep-th/0612023. - Chesler & Yaffe, hep-th/07060368. - Horowitz & Gyulassy, nuc-th/07062336. - .

Color Screening of the Medium?J/y and U Physics- Melting of quarkonium states: - initial T - suppression / regeneration - color screening of medium?

AdS/CFT & Color Screening of the Medium?

Medium Modification of Fragmentation from JetsFragmentation along jet axis: z = phadron / p partonIntroduce = ln(Ejet / phadron) ~ ln (1/z):Black line = radiative E-lossDashed line = flatCollisional E-loss?

Medium Modifications and Jet HadrochemistryParton energy loss can alter:partons color charge (flavor, baryon # ?)JAA RAA in jet cone

Hadronization, Fragmentation, Medium ModificationFragmentation at lower z in jets Hadronization of lower pT particlesfrom colored medium.

Both impacted by medium properties

Microscopic hadronization process?

At LHC: Is the QCD phase diagram feature-less at 1 4 Tc? What happens as we go up in T (e.g. coupling)? Are there new phenomena? Whats the range of theoretical validities (non-pQCD, pQCD, strings)? Measure/understand parton energy loss at the fundamental levelEstablish flavor (gluon and quark mass) dependenceUse jets and/or photons to establish hard-scattered parton energyJet modifications - longitudinal & transverse heating Medium response to jet-heating (near- and away-side) Measure/use open charm and beauty decays (also as jet-tags) cc and bb states (screening, suppression, enhancement?) Direct Photon Radiation?Developments in theory (lattice, hydro, parton E-loss, string theory) the next frontier!The Quark-Gluon Plasma at the LHC

AdS/CFT Meets Heavy Ions at the LHC Summary of Physics Questions for bothWhat is: - the velocity dependence of energy loss? the flavor (q, g) dependence of energy loss? radiated from partons in energy loss? the response of the medium? the color screening of the medium? the particle type dep. of viscosity (flow)? the basis for quark scaling of v2 at inter. pT hadronization mechanism?

The EndThe Beginning

Thanks for Discussions / Contributions to This Presentation!!Miklos GyulassyDima KharzeevPeter JacobsUrs Wiedemann

Gluon versus Quark Jets?LHC Gluon jets

Top energy RHICpT < 20 GeV Gluon jets pT > 20 GeV Quark jets Lower RHIC II energytransition from gluon to quark jetsUtilize RHIC versatility in s!

g-jet (hadron)h1 h2 correlations x1 x2 correlationsqg, gg, qq scattering

Three jet events?

Hadronization?Physics- : - -

Medium Modifications and Jet Hadrochemistry

How Will LHC Heavy Ions Contribute?- Properties of the Medium- bulk viscosity, entropy, T, ..- response to heating (away-side shock? Near side heating and flow?)- Parton Energy Loss- LHC extends reach in mass, flavor, and pT of hard probes(different parton probes, jets, Z-bosons, heavy quarks, quarkonia)- Hadronization- Investigate intermediate pT (5 15 GeV/c) hadron production - Investigate fragmentation process in detail (hadrochemistry in jets)- Investigate production of new scaler and vector particles