Docstoc

Fachini

Document Sample
Fachini Powered By Docstoc
					   Resonance Production in Au+Au and
     p+p Collisions at sNN=200 GeV

               Patricia Fachini
       Brookhaven National Laboratory

                Motivation
               Data Analysis
                  Results
                Conclusions

STAR               Patricia Fachini     1
                              Motivation - I
• In-medium modification of mass and/or width  Chiral Symmetry
  Restoration, Collision Broadening or Phase Space?
                         +
                               -
               -                                                π-
                        ρ0         +                                 π+
                         π+   ρ0                  π-      ρ0    ρ0
                   π-
           -             ρ0
                                   ρ0 c = 1.3 fm
                         +                                     π+

•  ρ0(770)  Leptonic decay channel  probes all stages of the
  collision. Hadronic decay channel  probes only late stages of the
  collision
• Φ  Information from early time ?       Φ c = 44 fm
• f0(980)  KK molecule (bound state)  insight strangeness
  behavior in relativistic collisions
• K*0(892)  Regeneration and daughter rescattering  time scale ?

    STAR                               Patricia Fachini                   2
                                   Motivation - II
                                             • If resonance decays before
                                               kinetic freeze-out  not
                                    π          reconstructed due to
             K*                                rescattering of daughters
                      π             K K*     • K*0 (c = 4 fm) survival
           K*
                                    measured   probability  time between
                                               chemical and kinetic freeze-out,
                                    K*         source size and pT of K*0
       π                       K
                                   lost
  K*                                           • Chemical freeze-out  elastic
                π                   π
                          K*                     interactions πK  K*0 πK
       K
                                                 regenerate K*0(892) until kinetic
                  K            K K*              freeze-out
Chemical              Kinetic  measured •           K*0/K may reveal time between
freeze-out            freeze-out
                                                    chemical and thermal freeze-out
                                               • Λ*/Λ, ρ0/π, f0/π ?

    STAR                                  Patricia Fachini                    3
       Resonance Production at RHIC
0(770)  π+ π- B.R. ~1               c = 1.3 fm
K*0(892)  π K B.R. 2/3               c = 4 fm
f0(980)  π+ π- B.R. 2/3              c = 2.6 fm
Φ(1020)  K+ K- B.R. 0.492            c = 44 fm
Φ(1020)  e+ e- B.R. 0.000296 c = 44 fm
Λ(1520)  p K    B.R. 0.45            c = 12.6 fm
• |y| ≤ 0.5
• Mixed Event or Like Sign Technique

STAR               Patricia Fachini                 4
     Raw Invariant Mass Distribution from Data
P. Fachini, L. Gaudichet, J. Ma, C. Maguire, H. Zhang SQM2003                                                           Statistical error only

           p+p                                             40%-80% Au+Au                                                                p+p

                                                                                                               K*0              STAR Preliminary
    J. Adams et al.                                          J. Adams et al.
    nucl-exp/0307023                                         nucl-exp/0307023
                  STAR                                               STAR




                               Au+Au                                             p+p                                                Au+Au

                                      sNN = 200 GeV                        STAR Preliminary                   Φ              STAR Preliminary
     K*0                                                                           Φ
                                           |y|<0.5

  STAR Preliminary



       p+p                                60%-80% Au+Au                                        Au+Au                                  Au+Au
   STAR Preliminary                       STAR Preliminary                             PHENIX Preliminary                   PHENIX Preliminary

        Λ(1520)                               Λ(1520)                                      ΦK+K-                                      Φe+e-



    STAR                                                           Patricia Fachini                                                          5
           Invariant Mass (GeV/c2 )                  Invariant Mass (GeV/c2 )                Invariant Mass (GeV/c2 )                  Invariant Mass (GeV/c2 )
                         K*0 Mass and Width
H. Zhang, SQM2003


      STAR Preliminary                            STAR Preliminary




|y|<0.5                                  sNN = 200 GeV


  • K*0 mass  shifted in p+p and Au+Au at low pT
  • K*0 width  agrees with the MC (GEANT) calculation
  • Systematic and statistical error added in quadrature


    STAR                       Patricia Fachini                      6
                                          Phase Space
    P. Braun-Munzinger et.al., CERES Int. Note, March 2000, unpublished; E.V. Shuryak and G.E. Brown, Nucl.
    Phys. A 717 (2003) 322; P.K. Kolb and M. Prakash, nucl-th/0301007; H.W. Barz et al., Phys. Lett. B 265,
    219 (1991); R. Rapp, hep-ph/0305011.

                                                          -  M2 + pT2                  π+         ρ0        π+
                                          M              e      T
    Phase Space =                                                                        π-                  π-
                                    M2    + pT      2

•       M = Invariant Mass; pT = transverse momentum; T = Temperature
•       pp  particle composition reasonably reproduced by statistical
        model  T = 160 MeV
              F. Becattini, Nucl. Phys. A 702, 336 (2002); Z. Phys. C 69, 485 (1996); F. Becattini and U.
              Heinz, Z. Phys. C 76, 269 (1997)

•       Au+Au  between chemical and kinetic freeze-out  resonances
        formed until particles too far apart  resonances emitted
        T = 120 MeV
              E.V. Shuryak and G.E. Brown, Nucl. Phys. A 717 (2003) 322
                                                                                                    3
                                  Γ(M)                                            M2 – 4mπ2         2   Mρ
       BW(M) =                                                   Γ(M) = Γρ
                     (M2   – M   2)2 +   M   2   Γ(M)2                          Mρ2 – 4mπ2            M
     STAR                                           Patricia Fachini                                          7
                                         ρ0 Mass
J. Adams et al. nucl-exp/0307023

                                                        •     p+p at s = 27.5 GeV  M = 762.6
       10% of minimum bias p+p for |η|<0.5
                                                              ± 2.6 MeV/c2
                                                        •     PDG average hadroproduced ρ0 
                                                              M = 769.0 ± 0.9 MeV/c2
                                                        •     PDG average e +e- ρ  M = 775.9 ±
                                                              0.5 MeV/c2
                                                        •     ρ0 mass pt dependent and lower
                                   sNN = 200 GeV             than previous p+p measurement in
                                                              both p+p and peripheral Au+Au
                                                              collisions
                                                        •     ρ0 mass high multiplicity p+p lower
                                                              than minimum bias p+p 
                                                              multiplicity dependent
                                                        •     Systematic errors  common and
                                                              correlated between p+p and
                                                              peripheral Au+Au
                 |y|<0.5                                •     ρ0 width  no sensitivity for
                                                              systematic study
    STAR                                   Patricia Fachini                                   8
                                                   Mass Shift…
•   Dynamical Effect
    E.V. Shuryak and G.E. Brown, Nucl. Phys. A 717 (2003) 322; R. Rapp, hep-ph/0305011.

     – ρ0 interactions at late stages of the collision
         • nucleons, hyperons and baryon resonances
         • pions, kaons and ρ0-mesons
         • t-channel exchanges
 Distortion of the ρ0 spectral shape 
  mass shift and/or broadening

                                                         -23 MeV/c2 shift in the ρ0 mass

                                                                              -38 MeV/c2 shift in the ρ0 mass
                                                                              due to t-channel attraction

•   Interference between various π+π- scattering channels
    R. Longacre, nucl-exp/0305015

•   Bose-Einstein correlations between ρ0 decay daughters and pions in
    the surrounding matter
    G.D. Lafferty, Z. Phys. C 60, 659 (1993); R. Rapp, hep-ph/0305011; S. Pratt et al ., nucl-th/0308087.




     STAR                                                    Patricia Fachini                                   9
                                                   Spectra
          H. Zhang, SQM2003                         J. Ma, SQM2003                 J. Adams et al. nucl-exp/0307023
                                                                                           P. Fachini, SQM2003

           K*0                                         Φ
                                                                                                         ρ0

                                                                                                         f0

                                                  STAR Preliminary                    STAR Preliminary
              STAR Preliminary


                                                                        Statistical error only
|y|<0.5                          sNN = 200 GeV                                                  L. Gaudichet, SQM2003

• Au+Au  spectra fit to exponential in                                                                 Λ(1520)
  mT-m0
• p+p  spectra fit to power-law                                                           pp
  contribution pQCD processes larger than
                                                                                       STAR Preliminary
  soft processes ?
      STAR                                           Patricia Fachini                                         10
                                          Particle Ratios
                                                                             M. Bleicher et al. J. Phys. G 25 (1999) 1859
                                          J. Adams et al. nucl-exp/0307023
H. Zhang SQM2003 L. Gaudichet, SQM2003 J. Ma SQM2003 P. Fachini SQM2003




                                STAR Preliminary




   Statistical and systematic
   errors added in quadrature

     • Φ/K- independent of centrality  Φ not produced via kaon
       coalescence ?
     • Cross-section  regeneration or rescattering ?
       STAR                                          Patricia Fachini                                            11
             <pT> Charged Particle Dependence
H. Zhang, SQM2003       Statistical and systematic errors added in quadrature   J. Ma, SQM2003




              STAR Preliminary                                       STAR Preliminary



  • Φ and K*0  No centrality dependence
  • Φ  Flows differently ?
  • K*0  Rescattering dominates at peripheral collisions and
    regeneration becomes significant for central collisions ?
   STAR                                  Patricia Fachini                                 12
                        Thermal Models
                                                      Chemical freeze-out
                        K*0
                        K-                                Kinetic freeze-out


                                              ρ0
                                                          Chemical = kinetic
                                              π-          freeze-out

                                                            mρ=770MeV

                                                            mρ=700MeV




                                        f0
                 Φ                      π-               Λ(1520)
                 K-                                         Λ

sNN = 200 GeV

    • Short-lived resonances  Kinetic freeze-out ?    Statistical and systematic
                                                       errors added in quadrature


      STAR                     Patricia Fachini                     13
                   Conclusions
• Significant resonance production measured from
  hadronic interactions from RHIC data at sNN = 200
  GeV
• ρ0 and K*0  mass shift observed even after phase
  space correction in p+p and Au+Au collisions
• Lower mass expected due to in-medium modifications,
  interference and Bose-Einstein correlations ?
• Φ/K- independent of centrality  Φ not produced via
  kaon coalescence ?
• Short-lived resonances  Regeneration and
  rescattering  driven by hadronic cross sections ?
• Resonances can provide information on the collision
  dynamics
  STAR                 Patricia Fachini           14

				
DOCUMENT INFO
Shared By:
Categories:
Stats:
views:6
posted:6/26/2011
language:Dutch
pages:14