26-Oct-07W.A. Zajc Introduction and Welcome AdS/CFT Intersects Nuclear Beams at Columbia W.A. Zajc Columbia University

26-Oct-07W.A. Zajc RHIC Perspectives W.A. Zajc Columbia University RHIC Perspectives W.A. Zajc Columbia University

26-Oct-07W.A. Zajc Outline of My Talk

26-Oct-07W.A. Zajc Really, It’s A Meta-Talk Introduction, Motivation, Definition of terms up to here Two major discoveries: Flow Jet quenching

26-Oct-07W.A. Zajc Really, It’s A Meta-Talk Flow, v 2 scaling with n q

26-Oct-07W.A. Zajc Really, It’s A Meta-Talk Jet quenching, away-side disappearance, direct photons Mach cones, re-appearance of the away side

26-Oct-07W.A. Zajc Really, It’s A Meta-Talk Perfect liquid, KSS bound as QM result Viscosity primer

26-Oct-07W.A. Zajc Really, It’s A Meta-Talk The dénouement! AdS/CFT connection  /s values

26-Oct-07W.A. Zajc The Primacy of QCD lWlWhile the (conjectured) bound is a purely quantum mechanical result... FIFI t was derived in and motivated by the Anti-de Sitter space / Conformal Field Theory correspondence lWlWeak form: q“q“Four-dimensional N =4 supersymmetric SU(N c ) gauge theory is equivalent to IIB string theory with AdS 5 x S 5 boundary conditions.” ( The Large N limit of superconformal field theories and supergravity, J. Maldacena, Adv. Theor. Math. Phys. 2, 231, 1998 hep-th/ ) lSlStrong form: q“q“Hidden within every non-Abelian gauge theory, even within the weak and strong nuclear interactions, is a theory of quantum gravity.” ( Gauge/gravity duality, G.T. Horowitz and J. Polchinski, gr-qc/ ) lSlStrongest form: Only with QCD can we explore experimentally these fascinating connections over the full range of the coupling constant to study QGP  Quantum Gauge Phluid

26-Oct-07W.A. Zajc The (Assumed) Connection l Exploit Maldacena’s “D-dimensional strongly coupled gauge theory  (D+1)-dimensional stringy gravity” l Thermalize with massive black brane l Calculate viscosity  = “Area”/16  G l Normalize by entropy (density) s = “Area” / 4G l Dividing out the infinite “areas” : l Conjectured to be a lower bound “for all relativistic quantum field theories at finite temperature and zero chemical potential”. l See “Viscosity in strongly interacting quantum field theories from black hole physics”, P. Kovtun, D.T. Son, A.O. Starinets, Phys.Rev.Lett.94:111601, 2005, hep-th/ hep-th/ Infinite “Area” ! hh AA A

26-Oct-07W.A. Zajc New Dimensions in RHIC Physics l “The stress tensor of a quark moving through N =4 thermal plasma”, J.J. Friess et al., hep-th/ Our 4-d world String theorist’s 5+5-d world The stuff formerly known as QGP Heavy quark moving through the medium Energy loss from string drag Jet modifications from wake field

26-Oct-07W.A. Zajc Measuring  /s l Damping (flow, fluctuations, heavy quark motion) ~  /s q FLOW: Has the QCD Critical Point Been Signaled by Observations at RHIC?, R. Lacey et al., Phys.Rev.Lett.98:092301,2007 (nucl-ex/ )nucl-ex/ q The Centrality dependence of Elliptic flow, the Hydrodynamic Limit, and the Viscosity of Hot QCD, H.-J. Drescher et al., (arXiv: )arXiv: q FLUCTUATIONS: Measuring Shear Viscosity Using Transverse Momentum Correlations in Relativistic Nuclear Collisions, S. Gavin and M. Abdel-Aziz, Phys.Rev.Lett.97:162302,2006 (nucl-th/ )nucl-th/ q DRAG, FLOW: Energy Loss and Flow of Heavy Quarks in Au+Au Collisions at √s NN = 200 GeV (PHENIX Collaboration), A. Adare et al., to appear in Phys. Rev. Lett. (nucl-ex/ )nucl-ex/ CHARM!CHARM!

26-Oct-07W.A. Zajc Has the QCD Critical Point Been Signaled by Observations at RHIC?, R. Lacey et al., Phys.Rev.Lett.98:092301,2007 (nucl-ex/ )nucl-ex/ l Signature: FLOW l Calculation: l Payoff Plot: Fit v 2 ~I 1 (w)/I 0 (w); w = m T /2T On-shell transport model for gluons, Z. Xu and C. Greiner, hep-ph/ PHENIX v 2 /  data (nucl-ex/ ) compared to R.S. Bhalerao et al. (nucl-th/ )

26-Oct-07W.A. Zajc Measuring Shear Viscosity Using Transverse Momentum Correlations in Relativistic Nuclear Collisions, S. Gavin and M. Abdel-Aziz, Phys.Rev.Lett.97:162302,2006 (nucl-th/ )nucl-th/ l Signature: FLUCTUATIONS l Calculation: l Payoff Plot: Diffusion eq. for fluctuations g Compare to STAR data on centrality dependence of rapidity width  of p T fluctuations Difference in correlation widths for central and peripheral collisions

26-Oct-07W.A. Zajc The Centrality dependence of Elliptic flow, the Hydrodynamic Limit, and the Viscosity of Hot QCD, H.-J. Drescher et al., (arXiv: )arXiv: l Signature: FLOW l Calculation: l Payoff Plot: Knudsen number K Fits to PHOBOS v2 data to determine  for Glauber and CGC initial conditions Decrease in flow due to finite size

26-Oct-07W.A. Zajc Moore and Teaney Phys.Rev.C71: ,2005 (perturbative, argue ~valid non-perturbatively) Energy Loss and Flow of Heavy Quarks in Au+Au Collisions at √s NN = 200 GeV (PHENIX Collaboration), A. Adare et al., Phys. Rev. Lett. 98:172301,2007 (nucl-ex/ )nucl-ex/ l Signature: FLOW, ENERGY LOSS l Calculation: l Payoff Plot: Rapp and van Hees Phys.Rev.C71: ,2005, to fit both PHENIX v 2 (e) and R AA (e)

26-Oct-07W.A. Zajc (Some) Things I’d Like To Know l Are there better ways to extract  /s ? l Can these existing estimates be improved ? l (In particular, can systematic errors be understood?) l All of these methods rely on  +P = Ts. F How does this change in the presence of a conserved charge ? l In ordinary fluids,  /s has a pronounced minimum near the critical point. F Can AdS/CFT say anything about this for gauge fluids?

26-Oct-07W.A. Zajc (More) Things I’d Like To Know l Are AdS/CFT predictions falsifiable ? q What if Song and Heinz  /s < 1/4  is correct? u Suppression of elliptic flow in a minimally viscous quark-gluon plasma, H. Song and U. Heinz, arXiv: v1.arXiv: v1 q What if Mach cone angles different from data ? q What if 1/√  not seen in J/  suppression ? l What data can best constrain initial conditions? l (Will we ever be able to eliminate this source of ambiguity between Glauber, CGC, … ?) l Are there AdS/CFT setups to do elliptic flow dynamically? F Can they say anything about the observed scaling ?

26-Oct-07W.A. Zajc The “Flow” Is Perfect l The “fine structure” v 2 (p T ) for different mass particles shows good agreement with ideal (“perfect fluid”) hydrodynamics l Roughly: ∂ T  =0  Work-energy theorem    P d(vol) =  E K  m T – m 0   KE T ~

26-Oct-07W.A. Zajc The “Flow” Knows Quarks l The “fine structure” v 2 (p T ) for different mass particles shows good agreement with ideal (“perfect fluid”) hydrodynamics l Scaling flow parameters by quark content n q resolves meson-baryon separation of final state hadrons baryons mesons

26-Oct-07W.A. Zajc (More) Things I’d Like To Know l What does flow scaling tell us about degrees of freedom? q Hadronic Modes and Quark Properties in the Quark-Gluon Plasma, M. Mannarelli and R. Rapp, arXiv:hep-ph/ v2 : m ~ 150 MeV,  ~ 200 MeV.arXiv:hep-ph/ v2 F Is any form of quasiparticle consistent with KSS bound? l All(?) AdS/CFT calculations find drag ~ √ = √g 2 N C. l What is this telling us about the degrees of freedom ? l Is there a unique prescription for fixing coupling ? q Is there well-controlled expansion away from ‘t Hooft limit? q Calibrate it with lattice ‘data’ ? F ASIDE: Those who most often pronounce “AdS/CFT is useless because the coupling doesn’t run” are those most likely to do calculations with  s = 0.5.

26-Oct-07W.A. Zajc (Big ) Things I’d Like To Know l Can one start from confining, chiral Sakai-Sugimoto and push it through a phase transition ? l Hod tells us  > 1 /  T. q Universal Bound on Dynamical Relaxation Times and Black-Hole Quasinormal Ringing, S. Hod, arXiv:gr-qc/ v1arXiv:gr-qc/ v1 F Can AdS/CFT address this ? l What does it mean to have a gravity dual ? F In particular, how do I find it ? F What is the impact of the KSS conjecture on other fields ?

26-Oct-07W.A. Zajc What Follows is the Un-Meta-Talk…

26-Oct-07W.A. Zajc Working Title: The Fluid Nature of QGP l From the Oxford English Dictionary: 1) Primary definition: (adj.) fluid : "Having the property of flowing; consisting of particles that move freely among themselves, so as to give way before the slightest pressure. (A general term including both gaseous and liquid substances.)” 2) Secondary definition: (adj.) "Flowing or moving readily; not solid or rigid; not fixed, firm, or stable.” l SUMMARY: Following a) a discovery period, during which time our understanding of “quark-gluon plasma” was fluid(2), and b) a paradigm shift, we are now developing a solid understanding of the extraordinary fluid(1) produced at RHIC.

26-Oct-07W.A. Zajc Expectations circa 2000 As encoded in the Nuclear Physics Wall Chart, RHIC would create a quark-gluon plasma; a “gas” of weakly interacting quarks and gluons

26-Oct-07W.A. Zajc The Plan circa 2000 l Use RHIC’s unprecedented capabilities q Large √s  u Access to reliable pQCD probes u Clear separation of valence baryon number and glue u To provide definitive experimental evidence for/against Quark Gluon Plasma (QGP) q Polarized p+p collisions l Two small detectors, two large detectors q Complementary capabilities q Small detectors envisioned to have 3-5 year lifetime q Large detectors ~ facilities u Major capital investments u Longer lifetimes u Potential for upgrades in response to discoveries See earlier talk by M. Grosse Perdekamp

26-Oct-07W.A. Zajc RHIC and Its Experiments STAR

26-Oct-07W.A. Zajc Since Then… l Accelerator complex q Routine operation at 2-4 x design luminosity (Au+Au) q Extraordinary variety of operational modes u Species: Au+Au, d+Au, Cu+Cu, p  +p  u Energies: 22 GeV (Au+Au, Cu+Cu, p  ), 56 GeV (Au+Au), 62 GeV (Au+Au,Cu+Cu, p  +p  ), 130 GeV (Au+Au), 200 GeV (Au+Au, Cu+Cu, d+Au, p  +p  ), 410 GeV (p  ), 500 GeV (p  ) l Experiments: q Worked ! l Science q >160 refereed publications, among them > 90 PRL’s q Major discoveries l Future q Demonstrated ability to upgrade q Key science questions identified q Accelerator and experimental upgrade program underway to perform that science

26-Oct-07W.A. Zajc Approach Will present sample of results from various points of the collision process: 1.Final State Yields of produced particles Thermalization, Hadrochemistry 2. Initial State Hydrodynamic flow from initial spatial asymmetries 3. Probes of dense matter

26-Oct-07W.A. Zajc Assertion l In these complicated events, we have (a posteriori ) control over the event geometry: q Degree of overlap q Orientation with respect to overlap Reaction Plane “Central” “Peripheral”

26-Oct-07W.A. Zajc Language l We all have in common basic nuclear properties q A, Z … l But specific to heavy ion physics q v 2 q R AA q T q Bq B q q  q s 1 if yield = perturbative value from initial parton-parton flux Fourier coefficient of azimuthal anisotropies  “flow” Temperature (MeV) Baryon chemical potential (MeV) ~ net baryon density Viscosity ( MeV 3 ) Entropy density ( MeV 3 ) ~ “particle” density

26-Oct-07W.A. Zajc Final State Does the huge abundance of final state particles reflect a thermal distribution?: 1.Final State Yields of produced particles Thermalization, Hadrochemistry Consistent with thermal production T ~ 170 MeV,  B ~ 30 MeV

26-Oct-07W.A. Zajc RHIC’s Two Major Discoveries lDlDiscovery of strong “elliptic” flow: qEqElliptic flow in Au + Au collisions at √s NN = 130 GeV, STAR Collaboration, (K.H. Ackermann et al.). Phys.Rev.Lett.86: ,2001 q3q318 citations lDlDiscovery of “jet quenching” qSqSuppression of hadrons with large transverse momentum in central Au+Au collisions at √s NN = 130 GeV, PHENIX Collaboration (K. Adcox et al.), Phys.Rev.Lett.88:022301,2002 q3q384 citations

26-Oct-07W.A. Zajc Initial State How are the initial state densities and asymmetries imprinted on the detected distributions? 3. Initial State Hydrodynamic flow from initial spatial asymmetries

26-Oct-07W.A. Zajc Motion Is Hydrodynamic x y z l When does thermalization occur? q Strong evidence that final state bulk behavior reflects the initial state geometry l Because the initial azimuthal asymmetry persists in the final state dn/d  ~ v 2 (p T ) cos (2  ) v 2

26-Oct-07W.A. Zajc The “Flow” Is Perfect l The “fine structure” v 2 (p T ) for different mass particles shows good agreement with ideal (“perfect fluid”) hydrodynamics l Roughly: ∂ T  =0  Work-energy theorem    P d(vol) =  E K  m T – m 0   KE T ~

26-Oct-07W.A. Zajc The “Flow” Knows Quarks l The “fine structure” v 2 (p T ) for different mass particles shows good agreement with ideal (“perfect fluid”) hydrodynamics l Scaling flow parameters by quark content n q resolves meson-baryon separation of final state hadrons baryons mesons

26-Oct-07W.A. Zajc Probes of Dense Matter Q. How dense is the matter? A. Do pQCD Rutherford scattering on deep interior using “auto-generated” probes: 2. Probes of dense matter

26-Oct-07W.A. Zajc Baseline p+p Measurements with pQCD l Consider measurement of  0 ’s in p+p collisions at RHIC. l Compare to pQCD calculation l Phys. Rev. Lett. 91, (2003) Phys. Rev. Lett. 91, (2003) parton distribution functions, for partons a and b measured in DIS, universality perturbative cross-section (NLO) requires hard scale factorization between pdf and cross section fragmentation function measured in e+e-

26-Oct-07W.A. Zajc Au+Au: Systematic Suppression Pattern q  constancy for pT > 4 GeV/c for all centralities? Suppressed Enhanced

26-Oct-07W.A. Zajc The Matter is Opaque l STAR azimuthal correlation function shows ~ complete absence of “away-side” jet F Partner in hard scatter is completely absorbed in the dense medium GONE  =0   =   = 

26-Oct-07W.A. Zajc Schematically (Partons) Scattered partons on the “near side” lose energy, but emerge; those on the “far side” are totally absorbed

26-Oct-07W.A. Zajc Control: Photons shine, Pions don’t l Direct photons are not inhibited by hot/dense medium l Rather: shine through consistent with pQCD

26-Oct-07W.A. Zajc Schematically (Photons) Scattered partons on the “near side” lose energy, but emerge; the direct photon always emerges

26-Oct-07W.A. Zajc l This one figure encodes rigorous control of systematics l in four different measurements over many orders of magnitude Precision Probes central N coll = 975  94 = =

26-Oct-07W.A. Zajc Connecting Soft and Hard Regimes Scattered partons on the “near side” lose energy, but emerge; those on the “far side” are totally absorbed  Really ?

26-Oct-07W.A. Zajc l Mach cone? ☑ Jets travel faster than the speed of sound in the medium. ☑ While depositing energy via gluon radiation.  QCD “sonic boom” (?) F To be expected in a dense fluid which is strongly-coupled Fluid Effects on Jets ?

26-Oct-07W.A. Zajc High p T Parton  Low p T “Mach Cone”? l The “disappearance” is that of the high p T partner l But at low p T, see re-appearance l and l “Side-lobes” (Mach cones?)

26-Oct-07W.A. Zajc Suggestion of Mach Cone? l Modifications to di-jet hadron pair correlations in Au+Au collisions at √s NN = 200 GeV, PHENIX Collaboration (S.S. Adler et al.), Phys.Rev.Lett.97:052301,2006S.S. Adler et al. A “perfect” fluid response! 

26-Oct-07W.A. Zajc How Perfect is “Perfect” ? l All “realistic” hydrodynamic calculations for RHIC fluids to date have assumed zero viscosity q  = 0  “perfect fluid” q But there is a (conjectured) quantum limit: “A Viscosity Bound Conjecture”, P. Kovtun, D.T. Son, A.O. Starinets, hep-th/ P. KovtunD.T. SonA.O. Starinetshep-th/ q Where do “ordinary” fluids sit wrt this limit? q RHIC “fluid” might be at ~1 on this scale (!) T=10 12 K (4 

26-Oct-07W.A. Zajc l Remove your organic prejudices q Don’t equate viscous with “sticky” ! l Think instead of a not-quite-ideal fluid: q “not-quite-ideal”  “supports a shear stress” q Viscosity  then defined as q Dimensional estimate: F small viscosity  Large cross sections F Large cross sections  strong couplings F Strong couplings  perturbation theory difficult ! Viscosity Primer

26-Oct-07W.A. Zajc The Primacy of QCD lWlWhile the (conjectured) bound is a purely quantum mechanical result... FIFI t was derived in and motivated by the Anti-de Sitter space / Conformal Field Theory correspondence lWlWeak form: q“q“Four-dimensional N =4 supersymmetric SU(N c ) gauge theory is equivalent to IIB string theory with AdS 5 x S 5 boundary conditions.” ( The Large N limit of superconformal field theories and supergravity, J. Maldacena, Adv. Theor. Math. Phys. 2, 231, 1998 hep-th/ ) lSlStrong form: q“q“Hidden within every non-Abelian gauge theory, even within the weak and strong nuclear interactions, is a theory of quantum gravity.” ( Gauge/gravity duality, G.T. Horowitz and J. Polchinski, gr-qc/ ) lSlStrongest form: Only with QCD can we explore experimentally these fascinating connections over the full range of the coupling constant to study QGP  Quantum Gauge Phluid

26-Oct-07W.A. Zajc The (Assumed) Connection l Exploit Maldacena’s “D-dimensional strongly coupled gauge theory  (D+1)-dimensional stringy gravity” l Thermalize with massive black brane l Calculate viscosity  = “Area”/16  G l Normalize by entropy (density) s = “Area” / 4G l Dividing out the infinite “areas” : l Conjectured to be a lower bound “for all relativistic quantum field theories at finite temperature and zero chemical potential”. l See “Viscosity in strongly interacting quantum field theories from black hole physics”, P. Kovtun, D.T. Son, A.O. Starinets, Phys.Rev.Lett.94:111601, 2005, hep-th/ hep-th/ Infinite “Area” ! hh AA A See next talk: QGP- Theoretical Overview, U. Wiedemann

26-Oct-07W.A. Zajc New Dimensions in RHIC Physics l “The stress tensor of a quark moving through N =4 thermal plasma”, J.J. Friess et al., hep-th/ Our 4-d world String theorist’s 5+5-d world The stuff formerly known as QGP Heavy quark moving through the medium Energy loss from string drag Jet modifications from wake field

26-Oct-07W.A. Zajc Measuring  /s l Damping (flow, fluctuations, heavy quark motion) ~  /s q FLOW: Has the QCD Critical Point Been Signaled by Observations at RHIC?, R. Lacey et al., Phys.Rev.Lett.98:092301,2007 (nucl-ex/ )nucl-ex/ q The Centrality dependence of Elliptic flow, the Hydrodynamic Limit, and the Viscosity of Hot QCD, H.-J. Drescher et al., (arXiv: )arXiv: q FLUCTUATIONS: Measuring Shear Viscosity Using Transverse Momentum Correlations in Relativistic Nuclear Collisions, S. Gavin and M. Abdel-Aziz, Phys.Rev.Lett.97:162302,2006 (nucl-th/ )nucl-th/ q DRAG, FLOW: Energy Loss and Flow of Heavy Quarks in Au+Au Collisions at √s NN = 200 GeV (PHENIX Collaboration), A. Adare et al., to appear in Phys. Rev. Lett. (nucl-ex/ )nucl-ex/ CHARM!CHARM!

26-Oct-07W.A. Zajc Has the QCD Critical Point Been Signaled by Observations at RHIC?, R. Lacey et al., Phys.Rev.Lett.98:092301,2007 (nucl-ex/ )nucl-ex/ l Signature: FLOW l Calculation: l Payoff Plot: Fit v 2 ~I 1 (w)/I 0 (w); w = m T /2T On-shell transport model for gluons, Z. Xu and C. Greiner, hep-ph/ PHENIX v 2 /  data (nucl-ex/ ) compared to R.S. Bhalerao et al. (nucl-th/ )

26-Oct-07W.A. Zajc Measuring Shear Viscosity Using Transverse Momentum Correlations in Relativistic Nuclear Collisions, S. Gavin and M. Abdel-Aziz, Phys.Rev.Lett.97:162302,2006 (nucl-th/ )nucl-th/ l Signature: FLUCTUATIONS l Calculation: l Payoff Plot: Diffusion eq. for fluctuations g Compare to STAR data on centrality dependence of rapidity width  of p T fluctuations Difference in correlation widths for central and peripheral collisions

26-Oct-07W.A. Zajc The Centrality dependence of Elliptic flow, the Hydrodynamic Limit, and the Viscosity of Hot QCD, H.-J. Drescher et al., (arXiv: )arXiv: l Signature: FLOW l Calculation: l Payoff Plot: Knudsen number K Fits to PHOBOS v2 data to determine  for Glauber and CGC initial conditions Decrease in flow due to finite size

26-Oct-07W.A. Zajc Moore and Teaney Phys.Rev.C71: ,2005 (perturbative, argue ~valid non-perturbatively) Energy Loss and Flow of Heavy Quarks in Au+Au Collisions at √s NN = 200 GeV (PHENIX Collaboration), A. Adare et al., Phys. Rev. Lett. 98:172301,2007 (nucl-ex/ )nucl-ex/ l Signature: FLOW, ENERGY LOSS l Calculation: l Payoff Plot: Rapp and van Hees Phys.Rev.C71: ,2005, to fit both PHENIX v 2 (e) and R AA (e)

26-Oct-07W.A. Zajc RHIC and the Phase “Transition” l The lattice tells us that collisions at RHIC map out the interesting region from l High T init ~ 300 MeV to l Low T final ~ 100 MeV Recall per massless degree of freedom ?

26-Oct-07W.A. Zajc LHC l How could we not choose to investigate “QGP” at every opportunity? l LHC offers unparalleled increase in √s l Will this too create a strongly-coupled fluid? l Active pursuit via q Dedicated experiment (ALICE) q Targeted studies (CMS, ATLAS)

26-Oct-07W.A. Zajc World Context : 2009  : 2000  RHIC II  : 2012 

26-Oct-07W.A. Zajc RHIC Physics for Many INPC’s To Come! l Exploration q ~ Completed q Discovery! l Characterization q Photon+Jet q Heavy Flavor q Energy Scans l Exploitation (of upgrade potential) q Source q Detectors q Luminosity RHIC  RHIC II l Preparation l l (Anticipation) l Exploration q ~ Completed q Discovery! l Characterization q Photon+Jet q Heavy Flavor q Energy Scans l Exploitation l (of upgrade potential) q Source q Detectors q Luminosity LHC l Preparation l l (Anticipation) l Exploration q ~ Completed q Discovery! l Characterization q Photon+Jet q Heavy Flavor q Energy Scans l Exploitation l (of upgrade potential) q Source q Detectors q Luminosity GSI-FAIR