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					              Recent
            Discoveries
              at RHIC
Do they indicate a new
   state of matter?
                  W.A. Zajc
17-Oct-03          W.A. University
              ColumbiaZajc           1
                            It‟s In The News
  2




                                                           No.

                                                           7
                                                      Are there new
                                                     states of matter
  From the National Research Council Committee on
                                                       at ultrahigh
            The Physics of the Universe:              temperatures
            Connecting Quarks with the Cosmos:        and densities?
      Eleven Science Questions for the New Century


17-Oct-03                                                               W.A. Zajc
                            Fermi‟s Vision
  3




               (Almost) included RHIC physics
               See also remarks in his “statistical model” paper

                                                        RHIC




                                                 From Fermi notes on
                                                  Thermodynamics


17-Oct-03                                                              W.A. Zajc
                                   QCD is not QED
  4




           QED (Abelian):
               Photons have do not carry charge
               Flux is not confined  1/r potential  1/r2 force
           QCD (Non-Abelian):
               Gluons carry charge (red, green, blue)  (anti-red, anti-green, anti-blue)
               Flux tubes form      potential ~ r  constant force




           HOW TO LIBERATE ??


                  +               +…


17-Oct-03                                                                            W.A. Zajc
            The Landscape of QCD
  5




17-Oct-03                          W.A. Zajc
                            Relevant dimensions
  6




               Hadron masses ~ 1 GeV
               Hadron sizes ~ 10-15 meters
                 aka 1 femtometer
                 aka 1 fermi = 1 fm
               Characteristic velocity ~ c
                   Characteristic time ~ 1 fm/c


               Planck‟s constant       c = 0.2 GeV-fm
                 1 fm-1  200 MeV
                 200 MeV ~ characteristic scale associated
                             with confinement




17-Oct-03                                                     W.A. Zajc
  7

                             Relevant Nuclear Physics
               Nuclei are
                    (sort of) spherical
                    contain A=N+Z protons and neutrons
                     have ~ constant density r0 ~ 0.16 GeV / fm3


                  MPROTON ~ MNEUTRON ~ 1 GeV
                  R(A) = 0.92 A1/3 (rms) , where A = Atomic Number

                  <r2PROTON>1/2 ~ <r2NEUTRON>1/2 ~ 0.86 fm
                  Nuclei ~ close-packed “spheres” of protons and neutrons

               Nuclear potential
                  Short range ( ~ 1 fm)
                  Modest strength ( ~ 50 MeV depth)
                  Nuclei are loosely bound
                  Treat as ~free Fermi gas of protons and neutrons

             Nuclear physics is the “Large A, small Q 2” limit of QCD




17-Oct-03                                                                    W.A. Zajc
  8

                               Relevant Thermal Physics
      Q. How to liberate quarks and gluons from
          ~1 fm confinement scale?
      A. Create an energy density
        ~ ( / 1 fm )4 ~ 0.2 GeV / fm 3 ~ Normal nuclear density ??
       Need better control of dimensional analysis:
                2
       g            T4                    Energy density for “g” massless d.o.f
                 30
                                                              8 gluons, 2 spins;
                                                
                                                 2
                        7                                 2 quark flavors, anti-quarks,
             2  8 g   2 s  2 a  2 f  3 c  T 4
                       8                         30          2 spins, 3 colors

                     2                                            37 (!)
             37         T4
                     30                4
                                                             “Reasonable”
             12  T  12  
                      4
                                     2.4 GeV / fm 3
                             1 fm 
                                                                   estimate
17-Oct-03                                                                                  W.A. Zajc
  9


                                      Slightly More Refined Estimate
           Compare
                           2
               P  3           T4       Pressure of “pure” pion gas at temperature T
                           90
                              2                              Pressure in plasma phase with
               PQGP  g               T 4 - B, g  37
                               90                               “Bag constant” B ~ 0.2 GeV / fm3
              Select system with higher pressure:
               0.5
                         Pion Phase
                         QGP Phase
                                                   PQGP         Phase transition at T ~ 140 MeV
                                                                   with latent heat ~0.8 GeV / fm3
            0.25


 Pressure                                            P         Compare to best estimates (Karsch, QM01)
(GeV / fm 3)
                                                                    from lattice calculations:
                0
                     0            100              200
                                                                         T ~ 150-170 MeV
                                                                  latent heat ~ 0.70.3 GeV / fm3
                                         Temperature (MeV)



            -0.25
17-Oct-03                                                                                            W.A. Zajc
 10


                            ~1970: An Ultimate Temperature?
                                                                                         Hadron 'level' diagram
                The very rapid increase of                                  1500
                 hadron levels with mass

                ~ equivalent to an exponential
                                                                             1000

                                                                     Mass                              rw
                   level density                                     (MeV)                   fo
                                                                                             h
                                                                              500            K

                          dn
                      ρ
                      (m)
                            ~ ma e m / TH                                                   
                          dm                                                    0
                                                                                    0             10            20        30          40
                                                                                                       Degeneracy
                      ρ
                                                                                         Density of States vs Energy
                                       m / T
                        (m)e                    dm                              250


                                          1 1                                   200
                                       m(  )
                            ~  ma e     TH T
                                                  dm                 Number of 150
                                                                      available
                                                                       states 100
                    and would thus imply a
                     “limiting temperature”                                         50


                     TH ~ 170 MeV                        Hagedorn,                  0
                                                                                         0        500           1000      1500      2000
                                                        S. Fraustchi,
                                                 Phys.Rev.D3:2821-2834,1971                                  Mass (MeV)
17-Oct-03                                                                                                                        W.A. Zajc
                   (1970) TH  (2000) TC
 11




      That is: The „Hagedorn temperature‟ TH is now understood
        as a precursor of TC
      TC = Phase transition temperature of QCD
                                     0.66 TC     Study
                 T =0
                                                 confining
                                                 potential
                                                 in Lattice QCD
                                                 at various
                                    0.90 TC
                                                 temperatures
                                               Current estimates from
                                                lattice calculations:

                                    1.06 TC     TC ~ 150-170 MeV

                  F. Karsch, hep-              L ~ 0.70.3 GeV / fm3
                    ph/0103314
                                                     (latent heat)

17-Oct-03                                                            W.A. Zajc
 12


                                Making Something from Nothing
     Explore non-perturbative “vacuum”                 Non-perturbative Vacuum
      that confines color flux by melting it
      requires temperatur e T ~  / (1 fm ) ~ 200 MeV      c                c
             Particle production
             Our „perturbative‟ region
                                                            Perturbative Vacuum

               is filled with
                 gluons
                 quark-antiquark pairs
             which screen the “bare” interaction           c                c
             A Quark-Gluon Plasma (QGP)
      Experimental method:                                 Perturbative Vacuum
        Energetic collisions of heavy nuclei
      Experimental measurements:
       Use probes that are
                                                           c                c
           Auto-generated
           Sensitive to all time/length scales
                                                               Color Screening
17-Oct-03                                                                    W.A. Zajc
                      Previous Attempts
 13




   First attempt at QGP formation was successful

                              (~1010 years ago)
                                                                 
                                                  1                       E i ( p)              d3 p
                                      g* (T )  2 4
                                                T / 30
                                                            e
                                                          species 0
                                                                      ( E i   i ) / Ti
                                                                                            1 ( 2 )3
      g
                                                                         ( Effective
                                                                           number of
                                                                           degrees-
                The Early Universe,                                        of-
                 Kolb and Turner
                                                                           freedom
                                                                           per
                                                                           relativistic
                                                                           particle )

17-Oct-03                                                                                        W.A. Zajc
                               RHIC Specifications
 14




     3.83 km circumference
     Two independent rings
           120 bunches/ring
           106 ns crossing time
     Capable of colliding
      ~any nuclear species
      on
      ~any other species

     Energy:

         500 GeV for p-p
         200 GeV for Au-Au
            (per N-N collision)
     Luminosity
           Au-Au: 2 x 1026 cm-2 s-1
             p-p : 2 x 1032 cm-2 s-1
            (polarized)


17-Oct-03                                            W.A. Zajc
                           RHIC Runs To Date
 15




     Run-1 (2000):                               RHIC Successes (to date)
           Au-Au at 130 GeV ~ 1 b-1             based on ability to deliver
            (p-p equivalent: ~ 0.04 pb-1)          physics at ~all scales:
                                               barn    : Multiplicity (Entropy)
     Run-2 (2001-2):
            Au-Au at 200 GeV ~ 24 b-1        millibarn: Flavor yields
            (p-p equivalent:  ~ 1 pb-1)        (temperature)
                                               microbarn: Charm (transport)
         p-p      at 200 GeV 0.15 pb-1
                                               nanobarn: Jets (density)
     Run-3 (2002-3):                          picobarn: J/Psi (deconfinement)
           d-Au at 200 GeV        2.7 nb-1
            (p-p equivalent:       ~ 1 pb-1)

           p-p    at 200 GeV     0.35 pb-1




17-Oct-03                                                                         W.A. Zajc
                           How is RHIC Different?
 16




               Different from p-p, e-p colliders
                Atomic weight A introduces new scale Q2 ~ A1/3 Q02
               Different from previous (fixed target) heavy ion
                facilities
                ECM increased by order-of-magnitude
                                                             2 pT
                Accessible x (parton momentum fraction) x ~
                 decreases by ~ same factor                    s
                Access to perturbative phenomena
                     Jets                                         Jargon Alert:

                     Non-linear dE/dx           s = Center-of-mass energy (per nucleon collision)
                                                       pT = transverse momentum = |p| sin q
                                                            Q2 = (momentum transfer)2

               Its detectors are comprehensive
                ~All final state species measured with a suite of detectors that
                 nonetheless have significant overlap for comparisons


17-Oct-03                                                                                      W.A. Zajc
            RHIC‟s Experiments
 17




                    STAR




17-Oct-03                        W.A. Zajc
                               1 RHIC Event
 18




 Data Taken June 25, 2000.
 Pictures from STAR Level 3 online display.




                                              Q. How to take the measure
                                                 of such complexity??

                                                 (Is it possible?)
                                              A. (Yes.) Begin with
                                                 single-particle momentum
                                                 spectra

17-Oct-03                                                                  W.A. Zajc
                                Kinematics 101
 19




            Fundamental single-particle observable:
                 Momentum Spectrum

                                                   dn
              d 3s
             E 3                               d (cos q )
              dp
                           Kinematics

                                                            -1        -0.5          0        0.5
                                                                                  cosq
                 1  E  pz       d s
                                    3
            y    ln       
                    E p  
                                                   dn
                 2       z    d 2 pT dy          dy

                                        Dynamics            -6   -4          -2     0    2         4   6
                                                                                    y

                                  d 2s dn           dn
                                       
                                   2
                                 d pT dy            dy
                                                            -6   -4          -2     0    2         4   6
                                                                                     y

17-Oct-03                                                                                              W.A. Zajc
             (PID) Acceptances
 20




              PHOBOS Acceptance
                                  BRAHMS Acceptance




            STAR Acceptance




17-Oct-03                                             W.A. Zajc
                         Transverse Dynamics
 21




           The ability to
            access “jet” physics
            also clearly
            anticipated in RHIC
            design manual
               (vintage: ISAJET)
               a new perturbative
                probe of the
                colliding matter
           Most studies to date
            have focused on
            single-particle
            “high pT” spectra
             Please keep in mind:
            “High pT” is lower than
              you think
17-Oct-03                                      W.A. Zajc
 22


                          Predicting pT Distributions at RHIC
     Focus on some slice of the
      collision:
           Assume 3 nucleons struck in A,
            and 5 in B
           Do we weight this contribution
            as
              Npart ( = 3 + 5) ?
              Ncoll ( = 3 x 5 ) ?

     Answer is a function of pT :
           Low pT  large cross sections
             yield ~Npart
                Soft, non-perturbative,
                 “wounded nucleons”, ...
           High pT  small cross sections
             yield ~Ncoll
                Hard, perturbative,
                 “binary scaling”,
                 point-like, A*B, ...

17-Oct-03                                                       W.A. Zajc
                                     Luminosity
 23




           Consider collision of „A‟ ions per bunch
            with                  „B‟ ions per bunch:



                                                 Cross-sectional
                                                    area ‘S’


      
                    A
            Luminosity
                                                             B
                                       A B
                                    L~
                                        S
17-Oct-03                                                          W.A. Zajc
                            Change scale by ~ 109
 24




           Consider collision of „A‟ nucleons per nucleus
            with                  „B‟ nucleons per nucleus:

                                                      Cross-sectional
                                                         area ‘S’

                        A
           „Luminosity‟
                                                  B
                     A B                               Provided:
                  L~      ~ N Coll  A  B                    No shadowing
                      S
                                                              Small
                              not    N Part  A  B            cross-sections
17-Oct-03                                                                    W.A. Zajc
                        Q. Why did we build RHIC?
 25




                                                       p+p → 0+X (200 GeV)
 A: To gain access to „small‟ cross-sections*
    that are
        A) Fundamental
        B) Calculable
        C) Interesting
 which then allow us to use
                                     }
        Ncoll ( aka A*B or “binary” or “point-like”)
 scaling of yields as our

      baseline hypothesis

 for probing a new state of matter


     (This of course one of many possible answers…)




17-Oct-03                                                                     W.A. Zajc
 26


                        Systematizing our Knowledge
     All four RHIC experiments have
      carefully developed techniques                     Spectators

      for determining
                                                        Participants
           the number of participating
            nucleons NPART in each collision             Spectators
            (and thus the impact parameter)
           The number of binary nucleon-
            nucleon collisions NCOLL as a         Binary Collisions
            function of impact parameter
     This effort has been essential in
      making the QCD connection
           Soft physics ~ NPART
           Hard physics ~ NCOLL
     Often express impact
                                               Participants
      parameter b in terms of
      “centrality”, e.g., 10-20% most
17-Oct-03
                                                                       b (fm) Zajc
                                                                            W.A.
                           Example of Ncoll Scaling
 27




         Q: Are there rare probes at RHIC that scale as the number of binary
          collisions?
         A: Yes, charm production (for Ncoll from 71 to 975)



 PHENIX
 Run-2
 Preliminary
 Data
 presented
 at Quark
 Matter 2002




17-Oct-03                                                                       W.A. Zajc
                                     „Jets‟ at RHIC
 28




           Tremendous interest in hard
            scattering (and subsequent                    Jet
                                                      R   Axis
            energy loss in QGP) at RHIC
               Production rate calculable in
                pQCD
               But strong reduction predicted
                due to dE/dx ~ path-length
                (due to non-Abelian nature of
                medium)




           However:
               “Traditional” jet methodology
                very difficult at RHIC
               Dominated by the soft
                background
       Investigate by (systematics of)
            high-pT single particles

17-Oct-03                                                   W.A. Zajc
 29

                    Another Example of Ncoll Scaling

         PHENIX (Run-2) data on 0 production
          in peripheral collisions:
         Excellent agreement
          between
          PHENIX measured 0‟s
          in p-p

          and

          PHENIX measured 0‟s
          in Au-Au peripheral
          collisions scaled by
          the number of collisions

          over ~ 5 decades
                                                 PHENIX Preliminary


17-Oct-03                                                             W.A. Zajc
 30


                 Central Collisions Are Profoundly Different

 Q: Do all processes that should scale with Ncoll do just that?
 A: No!
 Central collisions
   are different .
   (Huge deficit at high pT)
  This is a clear discovery
   of new behavior at RHIC

         Suppression    of
          low-x gluons in
          the initial state?
         Energy loss in
          a new state of matter?    PHENIX Preliminary

17-Oct-03                                                      W.A. Zajc
 31

                     Energy Loss of Fast Partons
     Many approaches
                                                 dE 3 30 2       4 ET            4 ET 
                                                       S  ln 2  ~  S T 2 ln 2 
                                                                           2
           1983: Bjorken                        dx   4          M               M 
                                                             dE 4                 E          
            1991: Thoma and Gyulassy (1991)                       C F S T 2 ln             
                                                                          2
                                                                                            
                                                             dx   3                D          
                                                                             kT
                                                                                   2
           1993: Brodsky and Hoyer (1993)                        
                                                                      dE
                                                                         
                                                                      dx      2
                                                            dE      CR D
                                                                          2
                                                                                  L
           1997: BDMPS- depends on path length(!)             S         L ln  
                                                                                  
                                                            dx       8 g         g
                                                                                  kT
                                                                                           2
           1998: BDMS                                       
                                                                 dE     N
                                                                     s C
                                                                 dx      4             2

     Numerical values range from
               ~ 0.1 GeV / fm (Bj, elastic scattering of partons)
           ~several GeV / fm (BDMPS, non-linear interactions of gluons)




17-Oct-03                                                                                          W.A. Zajc
 32


                         Systematizing Our Expectations
             Describe in terms of
              scaled ratio RAA                “no effect”

               Yield in Au  Au Events
          
              A  B Yield in p  p Events


              = 1 for “baseline
              expectations”

             Will present most of
              suppression data in
              terms of this ratio



17-Oct-03                                                   W.A. Zajc
 33


                         Is The Suppression Unique to RHIC?
                                               Yes- all previous
                                                nucleus-nucleus
                                                measurements see
                                                enhancement,
                                                not suppression.
            SPS 17 GeV
                                               Effect at RHIC is
                             ISR 31 GeV         qualitatively new physics
                                                made accessible by RHIC‟s
                                                ability to produce
                                                       (copious) perturbative
                                                        probes
                                                       (New states of matter?)
                             RHIC 200 GeV      Run-2 results show that this
                                                effect persists (increases) to
                                                the highest available
                                                transverse momenta

                                               Describe in terms of
                                                scaled ratio RAA
                                                     Yield in Au  Au Events
                                                
                                                    A  B Yield in p  p Events
                                                = 1 for “baseline expectations”
17-Oct-03                                                                     W.A. Zajc
 34


                     Is The Suppression Always Seen at RHIC?
           NO!
           Run-3: a crucial control measurement via d-Au collisions




                       d+Au results from


                       presented at a press conference
                       at BNL on June, 18th, 2003




17-Oct-03                                                        W.A. Zajc
                               First Conclusion
 35




               The combined data from Runs 1-3 at RHIC on
                p-p, Au-Au and d-Au collisions establish that
                a new effect (a new state of matter?)
                is produced in central Au-Au collisions
                   Au + Au Experiment      d + Au Control Experiment




                  Final Data               Preliminary Data

17-Oct-03                                                              W.A. Zajc
 36


                           Theoretical Understanding?
            Both
                  Au-Au suppression (I. Vitev and M. Gyulassy, hep-ph/0208108)
                  d-Au enhancement (I. Vitev, nucl-th/0302002 )
            understood in an approach that combines multiple
              scattering with absorption in a dense partonic
              medium

             Our                                          d-Au
              high pT probes
              have been
              calibrated
              and are now                              Au-Au
              being used to
              explore the
              precise properties
17-Oct-03                                                                  W.A. Zajc
 37

                          Further Evidence
      STAR azimuthal
       correlation
       function shows
       ~ complete            G                                             G
       absence of            O
                             N
                                                                           O
                                                                           N
       “away-side” jet       E                                             E




                                 Pedestal&flow subtracted



                            C2 (Au  Au)  C2 (p  p)  A *(1 2v 2 cos(2 ))
                                                                  2
            
                            Surface emission only (?)
                            That is, “partner” in hard scatter
                           is absorbed in the dense medium
17-Oct-03                                                               W.A. Zajc
                                      Recombination
 38




         The in vacuo fragmentation of a
          high momentum quark to
          produce hadrons
          competes with the in medium
          recombination of lower
          momentum quarks to produce
          hadrons
         Example:
               Fragmentation: Dq→h(z)
                    produces a 6 GeV/c 
                     from a 10 GeV/c quark
                                               Fries, et al, nucl-th/0301087
               Recombination:                 Greco, Ko, Levai, nucl-th/0301093
                  produces a 6 GeV/c 
                   from two 3 GeV/c quarks
                  produces a 6 GeV/c proton
                   from three 2 GeV/c quarks

17-Oct-03                                                                      W.A. Zajc
                                                  Data
 39




           Provides a “natural” explanation of
               Spectrum of charged hadrons       ...requires the assumption of a thermalized
                                                  parton phase... (which) may be appropriately
               Enhancements seen in p/          called a quark-gluon plasma
               Momentum scale for same           Fries et al., nucl-th/0301087




                                                        “Extra” protons sampled
                                                               from ~pT/3




                  Fries, et al, nucl-th/0301087




17-Oct-03                                                                                   W.A. Zajc
                                   Hydrodynamics of Elliptic Flow
 40




 Parameterize azimuthal asymmetry of charged particles as
                          dn/d ~ 1 + 2 v2 cos (2 )                                 z




                                             asymmetry
                            (scaled) spatial Hydrodynamic limit
                                               STAR: PRL86 (2001) 402
                                                                          y
                                               PHOBOS preliminary
                                                                                            x
                                                                              Evidence that initial
                                                                              spatial asymmetry is
                                                                              translated quickly to
                                                                              momentum space
                                                                               ( as per a hydrodynamic
                                                                                 description)

       Compilation and Figure from M. Kaneta
                                    (PHOBOS : Normalized Paddle Signal)
17-Oct-03                                                                                          W.A. Zajc
                Recombination Tested
 41




  The complicated observed flow pattern in v2(pT)
      d2n/dpTd ~ 1 + 2 v2(pT) cos (2 )
  is predicted to be simple at the quark level under
      pT → pT / n , v2 → v2 / n , n = 2,3 for meson,baryon
  if the flow pattern is established at the quark level



                                                              Compilation
                                                             courtesy of H.
                                                                Huang




17-Oct-03                                                           W.A. Zajc
                               Second Conclusions
 42




               Suppression at high pT is characteristic of dense
                matter formation in Au-Au collisions
                (lack of suppression for heavy quarks, as observed in N coll
                   scaling of charm yields, also predicted)
               Recombination models operating at the parton level
                describe
                   “Anomalous” baryon/meson yields
                    (i.e., jet fragmentation is augmented by “other” partons)
                   Elliptic flow patterns for different mesons and baryons
                    (results from one primordial flow pattern established at the
                    parton level)
               Is there evidence that these (deconfined?) partons
                are also thermalized?



17-Oct-03                                                                      W.A. Zajc
 43


                          Results on Particle Composition




                                                      BRAHMS: 10% central
                                                      PHOBOS: 10%
                                                      PHENIX: 5%
                                                      STAR: 5%



                         200 GeV/A Au+Au




            Just a sample!
            There are also results on spectra of 0„s, K* ,  , L , LXX , …


17-Oct-03                                                                          W.A. Zajc
                       Longitudinal Dynamics
 44




     From the RHIC design
      manual:
           Emphasis on higher beam
            energy needed to develop
            “baryon-free” central region
           This theoretical argument is
            nicely confirmed by
            measurements from BRAHMS
           Aids in (future) comparisons to
              lattice gauge theory
              conditions in the early universe




17-Oct-03                                         W.A. Zajc
 45

                                 Is there a „Temperature‟?
     Apparently:
            Assume distributions described by one temperature T and

             one ( baryon) chemical potential  :      dn ~ e ( E μ) / T d 3 p

             One ratio (e.g., p / p ) determines  / T :                      p e  ( E μ ) / T
        
                                                                                 ( E μ) / T  e 2μ / T
       STAR preliminary    Systematic errors ~10-20%                           p e




                                                        Ratio (chemical fit)
            130 GeV RHIC : STAR / PHENIX /
                          PHOBOS / BRAHMS                                        Central
            17.4 GeV SPS : NA44, WA97                                              BRAHMS
                                                                                   PHENIX
                                                                                   PHOBOS
                                                                                   STAR



                                                                                                             K/h
                                                                                                 p/   K0s/h
                                                                                        K0/h



                                                                                                   Model:N.Xu and M.Kaneta
                                                                                        X/h      nucl-ex/0104021
            A second ratio (e.g., K /  ) provides T                               X/h
     Then predict all other hadronic yields and ratios:                                         Ratio (data)
17-Oct-03                                                                                                            W.A. Zajc
                  Locating RHIC on Phase Diagram
 46




 Previous figure  RHIC has net baryon density ~ 0:
     STAR preliminary Systematic errors ~10-20%
 TCH = 179 ± 4 MeV, B = 51 ± 4 MeV (M. Kaneta and N. Xu, nucl-ex/0104021)
            130 GeV RHIC : STAR / PHENIX /
                          PHOBOS / BRAHMS
            17.4 GeV SPS : NA44, WA97




                                                             RHIC is as
                                                              close as
                                                              we‟ll get to
                                                              the early
                                                              universe for
                                                              some time



17-Oct-03                                                                W.A. Zajc
                                        Questions
 47




               Do those many particles in the final state have
                anything to do with a state of matter?
               For example: Is there a well-defined
                   Energy density       
                   Temperature          T
                   Chemical potential 
                   Size                R
                   Transport coefficient 


               Answer: Yes (apparently)
                 The first round of RHIC experiments have determined
                  ~all of these parameters (and more)




17-Oct-03                                                               W.A. Zajc
                                   Open Questions
 48




               Is the quark-gluon plasma being formed in RHIC
                collisions? To be determined:
                   Does charmonium show the expected suppression from
                    (color) Debye screening?

                                                  RHIC




                   Is there direct (photon) radiation from the plasma?
                   Do the suppression effects extend to the highest pT‟s?
               What is the suppression pattern in cold nuclear
                matter? (proton-nucleus collisions) First results now available!
               What are the gluon and sea-quark contributions to
                the proton spin? (polarized proton running)

17-Oct-03                                                                          W.A. Zajc
                               Screening by the QGP
 49




            (An explicit test of deconfinement) In pictures:



                   r -->                         r -->                          r -->
  V(r)




                                   V(r)




                                                                 V(r)
                                                                        QCD potential at
            QCD potential at              QCD potential at                high T and
                 T=0                          high T                     high density




         Non-perturbative Vacuum



            c              c              c              c              c               c

             Perturbative Vacuum                                            Color Screening
                                           Perturbative Vacuum


17-Oct-03                                                                                     W.A. Zajc
                             Screening by the QGP
 50




 In first-order finger physics:
           Follow usual derivation of Debye screening

                             
       2  4r  4no e  e / kT  e  e / kT   
                                      1            kT
              4e 2no / kT  2  with D 
                   2                                    2

        
                                D assumptions:  4e 2 no
            Now put in QGP scales and        2
      4e 2  g 2 ~ 1
      no  3.6T 3  T 3 (Stefan - Boltzman for QGP)
      T  200 MeV
                  1 1
       D              0.4 fm
                  2 gT
         Hadrons with radii greater than
          ~ D will be dissolved
         Study “onium” bound states



17-Oct-03                                                    W.A. Zajc
 51

                           J/Y Measurements To Date
      p-p results:
               ~comparable
                to other hadron
                facilities
                (especially at low pT)


      Au-Au results:
               A limit only
               To be addressed in
                Run-4




17-Oct-03                                             W.A. Zajc
                                           Looking Ahead
 52




      Runs 1-5: EXPLORATION
               Well underway!
               “Complete” data sets for full energy
                    Au-Au
                    d-Au
               200 GeV p-p
                    “Complete” data set for A-A comparison
                    Strong start on G physics
      Runs 5-10: CHARACTERIZATION
               Ion program
                    Species scans
                    Energy “scans”
                    d-A, p-A
               Spin program
                    “Complete” program of G(x) at 200 GeV
                    500 GeV running, sea quark contributions
                    Study of G(x) via direct photons, heavy flavor (energy scan?)
               Upgrades (as available) to extend reach of both programs
      Runs 11-15: EXPLOITATION
               Full upgrades available
               Repeat “complete” measurements with x10-100 sensitivity


17-Oct-03                                                                            W.A. Zajc
                                                     Discovery
 53




                                                                       QCD Publications Versus Time




 
                                                   600

                                                   500


            Discovery of Top




                                  SPIRES Entries
                                                   400

                                                   300




 “Discovery” of QCD
                                                   200

                                                   100

                                                    0
                                                         1970   1975     1980       1985        1990   1995   2000
                                                                                       Year




     “Discovery(?)” that gluon Is massless

     It is clear that RHIC physics is on the cusp
           “Evidence for” QGP is abundant
           “Discovery of” same is imminent

17-Oct-03                                                                                                      W.A. Zajc
 54

               Provocative (non)-Questions
                   “It’s a Quark-Gluon-Plasma,
                              Period.”
                    QGP =PQCD + pQCD + dA
                            Miklos Gyulassy
                             Columbia University

                  Three major discoveries at RHIC
 1) Conclusive evidence for PQCD via v2 collective flow of 104 p, K, p
 2) Conclusive evidence for pQCD jet quenching in Au+Au at RHIC
 3) Conclusive evidence for dA via jet unquenching in dAu: Null Control

                 All 3 are explained by QCD dynamics

  Conclusion: AuAu at 200 AGeV made Bulk QGP Matter
                       e(t ~ 0.2 fm / c) : 100 e0
17-Oct-03                                                          W.A. Zajc
 55

                                    Open(?) Questions

                            New York Times 6/19/03
            "It is without a doubt the densest matter ever created in the
                                laboratory," said W. A. Zajc

       "We're creating matter that is tremendously denser," said Peter Jacobs, "It
            makes no sense to talk about individual protons and neutrons."

                  “If we were sure it was the quark-gluon plasma,
                         we would have said it was.“, W.A.Zajc.


       "Most of us aren't quite ready to make that leap," T. Hemmick said.

      “The experimentalists' caution may be due, in part, to fallout from a
      previous claim regarding quark soup at CERN [(6/20/00)] . Many
      physicists called the CERN data unconvincing.” (Newsday 6/17/03)

17-Oct-03                                                                        W.A. Zajc
                                Closed Questions
 56




        
             Has the accelerator worked?

         Have the experiments worked?
        



         Are the data analyzable?
        



        
             Are they being analyzed?

             Do the data validate the premise of RHIC?
            

               Collective, ~thermal behavior
              
               Contact with basic QCD phenomenology
              



             Are there new phenomena?
            



         Are there prospects for a long and fruitful
        
              experimental program?
17-Oct-03                                                 W.A. Zajc
 57

                    Is the Suppression New?
      Yes- in the sense that an enhancement is
       observed in proton-nucleus collisions:
      Known since 1975 that
       yields increase as A,  > 1




                                         J.W. Cronin et al.,
                                          Phys. Rev. D11, 3105 (1975)
                                         D. Antreasyan et al.,
                                          Phys. Rev. D19, 764 (1979)
17-Oct-03                                                         W.A. Zajc
                                 Other New Effects
 58




           Comparison of Au-Au, d-Au and p-p data indicate
               Dense matter uniquely formed in Au-Au collisions
               How dense? Sufficient to “extinguish” jets
  Q. Are there other anomalies observed in these collisions?
  A. Yes- the fragmentation function is drastically modified:

  Q. How to                                                        Central
      understand this?
                                                                    Peripheral
  A. Competition
      between
            Fragmentation
  and
            Recombination

            at the quark level

            (next slide)
17-Oct-03                                                               W.A. Zajc
 59

                          Experimental Gauge Theory
               QCD is the only fundamental gauge theory
                amenable to experimental study in both
                    Weak and strong coupling limits
                    Particle and bulk limits

                            Coupling Constant          Number Limit
                             Weak         Strong       Particle   Bulk
                Gravity                     X            X         
                Weak                        X                     X
                QED                         X                     
                QCD                                              

               RHIC
                    (Strong, bulk ) limit : heavy ion collisions
                    (Strong, particle) limit : spin physics
                    (Weak , particle) limit : W‟s as helicity probes
                    (Weak , bulk ) limit : high pT probes of plasma state
17-Oct-03                                                                    W.A. Zajc
 60


                      My 3 Part Definition of a QGP
                    QGP =PQCD + pQCD + dA
            1. A form of matter (many body dynamical system)
                    with a unique set of Bulk (collective)
                    phenomena and partonic diagnostics

            2. which are calculable in the deconfined
                   (Colored) quark-gluon basis of QCD

            3. And which can be turned on or off via
                   Control experiments

                 Examples of NON-QGP systems in QCD
            1.   e+e- -> q q g        2 ok but not 1
            2.   p+p -> pi, K, p     2 ok but not 1
            3.   e+A -> jets         2 ok but not 1
            4.   Nucleus A           1 ok but not 2
            5.   SIS,AGS res. gas    1 ok but not 2
            6.   SPS A+A             1 ok but 2~OK but not 3!
17-Oct-03                                                       W.A. Zajc
 61




17-Oct-03   W.A. Zajc
 62

                      Below RHIC energies, QCD hydro over-predicts elliptic
                      flow!
            v2(Ecm)           QGP hydro for the FIRST time at RHIC!




            CERES            17 AGeV



                           17 AGeV




                          CERES/SPS                        dNch / dyd2 x ^   (fm- 2 )


17-Oct-03                                                                        W.A. Zajc
 63


                      Yet Another Luminosity Limited Observable

           New PHENIX Run-2 result on v2 of 0‟s:

           Clearly would
            benefit
            from Run-4 statistics             PHENIX Preliminary




17-Oct-03                                                          W.A. Zajc

				
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