Interesting RHIC Observations by xiaohuicaicai


									Interesting RHIC Observations
1. Suppression of high pT hadrons
2. Increased baryon production at
   high pT
3. Large v2 values and the pT
4. Strange Baryon Production
5. HBT measurement – short
   emission duration
           Suppression of High pT Charged Hadrons
                                                         Used UA1 p+p 200 GeV data
                                                           (pT<6 GeV/c) as reference
RAA=                                                         Strong Suppression
       Nbin Yieldpp                                             in central Au+Au


                                                             N-Binary Scaling
                                                              in peripheral Au+Au

                        Preliminary sNN = 200 GeV

          Similar suppression pattern for p0 and for 130 GeV Au+Au data
                        and also observed by PHENIX
Issues in High pT Hadron Suppression
1.   Uncertainties in p+p reference data
2.   Collision geometry – Npart and Nbinary
3.   Gluon shadowing – we do not know the gluon
     structure function of nuclei yet
4.   Cronin effect – partonic multiple scattering,
     lack of theoretical understanding: pA
5.   Theoretical calculation of parton energy loss
     (low Q2 region) (exp  DE ~ E ?)
6.   Jet quenching or “jet abortion”
7.   Heavy quark jet – energy loss different !
   Large Proton to Pion Ratio at pT > 2 GeV/c

        PHENIX Preliminary              PHENIX Preliminary

        Au+Au at sqrt(sNN) =200GeV      Au+Au at sqrt(sNN) =200GeV

Baryon yield ~ meson yield  Very different from string fragmentation !!!
  Issues on High pT Baryon Production

1. Why baryon/meson ratio > 1 at pT > 2
2. Hydrodynamical expansion vs exotic
   production dynamics
3. High mass meson production vs pions
4. Baryon and meson production at really
   high pT (> 4-5 GeV/c?) (KS and L)
5. At what pT pQCD will set in (p/pion ratio
   decreases with pT) ?
Increased High Mass Particles with Strangeness
         Issues in Elliptic Flow

1. Dynamics responsible from geometrical
   anisotropy to momentum anisotropy
2. Magnitude of v2? Validity of hydrodynamic
3. pT dependence of v2: why saturation?
4. Particle dependence of v2: does or doesn’t
   depend on final state hadronic cross
5. V2 for resonance particles?
Intriguing v2 as a function of pT

                   • Statistical errors only

                   • Finite v2 up to 12 GeV/c
                   in mid-peripheral bin
Issues in Strange Baryon Production

1. Dynamics of hyperon production:
   enhancement of high mass hyperons
2. Baryon production and multi-gluon
3. Net baryon number at mid-rapidity and
   dynamics for baryon number transport
4. Mechanism for transport initial baryon
   number to multiply-strange hyperons
5. Comparison of pp--AA
L Production from Au+Au Collisions

            L, L @ 130 GeV
“Large” Yield of X Particles vs L
             Dn/dy of Strange Baryons

Centrality   0-5%     5-10%     10-20%    20-35%     35-75%
  L        17.0+-0.4 13.0+-0.3 10.1+-0.2 5.9 +-0.2 1.61+-0.05
 anti-L    12.0+-0.3 9.6+-0.3 7.4+-0.2 4.6+-0.1 1.26+-0.04

Centrality       0-10%           10-25%           25-75%
   X           2.30+-0.09       1.29+-0.12      0.28+-0.02
 anti-X        1.89+-0.08       1.08+-0.11      0.24+-0.02

     Relative large yield of strange baryons !!
    Issues in HBT Measurement

• Is there a mixed-phase?

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