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					                    Non-identical particle correlations
             in central Pb+Au collisions at 158 AGeV



                                                            Dariusz Antończyk
                                                      GSI Darmstadt, Germany
                                                                           for
                                                          CERES collaboration



Two-Pion Bose-Einstein Correlations at SPS Energies (Nucl. Phys. A715 (2003) 607c)
Universal Pion Freeze-Out in Heavy-Ion Collisions (PRL 90 (2003) 022301)
                                                              Outline




                      CERES setup
                      Data set
                      Non-identical particle correlations
                     Analysis variables
                      Correlation functions
                      Simulations
                      Discussion




05.10.2005   Non-identical particle correlation in central Pb+Au collisions at 158 AGeV   VI-SIM   Dariusz Antonczyk
                          TPC
 Acceptance                     2.03 <  < 2.65

 Gas                            Ne:CO2 (80:20)

 Dimensions                    length 2 m
                                inner radius 48.6 cm
                                outer radius 132 cm

 Readout                       20 pad rows in z
                                16*48 pads in 
 Radial drift field, azimuthal deflection




                                                                   Target                13 gold disks (diameter 600 m, thickness 25 m)

                                                                   SiDC1+2               Vertex reconstruction

                                                                   RICH1+2                Electron ID

                                                                   TPC                    Charge particle ID


                                                                   After 1999 no more B-field between RICHes




05.10.2005         Non-identical particle correlation in central Pb+Au collisions at 158 AGeV              VI-SIM          Dariusz Antonczyk
                                                               Data set


  System                             Pb+Au                             Track cuts
  Collision energy                  158 AGeV                                        good fit quality from the tracking

  Number of events                   23 M                                           high number of fitted hits = long track
                                                                                    matching between TPC and SD < 2 
  Centrality                         21 M 8 %
                                                                                    PID via dE/dx vs momentum
                                     2M          20 %

  Pair cuts                                                               Sailors                           Cowboys
             minimum opening angle




05.10.2005     Non-identical particle correlation in central Pb+Au collisions at 158 AGeV          VI-SIM        Dariusz Antonczyk
                             PID via dE/dx vs momentum


  Selected ranges were
  assigned to the given
  particle species
  based on the Bethe-
  Bloch formula




05.10.2005   Non-identical particle correlation in central Pb+Au collisions at 158 AGeV   VI-SIM   Dariusz Antonczyk
                          Non-identical particle correlation

                                            R.Lednicky at al. Phys. Lett. B 373, 30 (1996)

                                                                    Two cases

             Slower particle is emitted closer                                           Faster particle is emitted closer
             to the centre. Then the distance                                            to the centre. Then, it catches up.
             starts increasing. Interaction is                                           Interaction is stronger due to
             weaker due to longer distance of                                            shorter distance of closest
             closest approach                                                            approach




05.10.2005       Non-identical particle correlation in central Pb+Au collisions at 158 AGeV           VI-SIM        Dariusz Antonczyk
                                                    Analysis variables


                       Bertsch-Pratt, qlong-qside-qout coordinate system




                                                                                                          qout




                       Beam direction



             q           relative momentum in the pair centre of mass
             q ||        q component parallel to the transverse pair momentum, qout
             q          equal to        qside  qlong
                                             2           2




05.10.2005          Non-identical particle correlation in central Pb+Au collisions at 158 AGeV   VI-SIM          Dariusz Antonczyk
                                   Correlation functions (1)
                                    Definition of asymmetry




                                                                                          Lorentz function with
                                                                                               two widths


05.10.2005   Non-identical particle correlation in central Pb+Au collisions at 158 AGeV   VI-SIM    Dariusz Antonczyk
  Projection of 2 dimensional
  Non-identical correlation
  Functions in bins of pair
  transverse momentum

05.10.2005
                       Pair transverse momentum
                       dependence of asymmetry




05.10.2005   Non-identical particle correlation in central Pb+Au collisions at 158 AGeV   VI-SIM   Dariusz Antonczyk
                                                               Simulation

                      Generation of Track
                              • source position and momentum four-vectors
                              • source position generated according 3D Gauss distribution
                              • momentum and  obtained form experimental distributions
                              •  random generated in range from - to 


  Combining into Pairs
             • very similar algorithm as for data
             • applied shift between sources position
             • calculated Coulomb factor
                                                                                        Filling histograms
                                                                                                • with weight of calculated Coulomb
                                                                                                  factor and unity for signal and
                                                                                                  background distributions,
      Extracting asymmetry parameter                                                              respectively.
      exactly as for experimental data


05.10.2005         Non-identical particle correlation in central Pb+Au collisions at 158 AGeV           VI-SIM      Dariusz Antonczyk
    Generated correlated
         functions
  Projection of 2 dimensional
  non-identical correlation
  functions in bins of pair
  transverse momentum
05.10.2005
              Asymmetry as a function of the separation
             between pion & proton sources (simulation)




      Simulation for pair p between 0.8-1.0 GeV/c.
      Observed asymmetry corresponds to x=6.5 fm.


05.10.2005    Non-identical particle correlation in central Pb+Au collisions at 158 AGeV   VI-SIM   Dariusz Antonczyk
                                                          Discussion

             Asymmetry obtained in this analysis
                                                                                                     p
                                                                                                                 



                                                                                            6.5 fm
             STAR experiment                       :      Au+Au @
             nucl-exp/0212026                                 s = 130 AGeV/c                         p
                                                                                              7 fm                




             E887 experiment                        :      Au+Au @ 11 AGeV/c                                       p

             nucl-exp/9898993                                                                            

                                                                                                         10 fm

05.10.2005     Non-identical particle correlation in central Pb+Au collisions at 158 AGeV   VI-SIM           Dariusz Antonczyk
                         1 D vs 2 D asymmetry, comparison
                               between two methods



                                                                    Data



                                                              Simulation
   nucl-exp/0212026




05.10.2005   Non-identical particle correlation in central Pb+Au collisions at 158 AGeV   VI-SIM   Dariusz Antonczyk
                                                             Outlook


                  Asymmetry origin?
                              we see two candidates for that
                                       transverse flow                               STAR experiment
                                       protons are created at the beginning of the collision?
                      What next?
                              Blast wave parameterization
                              HBT analysis vs Reaction Plane




05.10.2005   Non-identical particle correlation in central Pb+Au collisions at 158 AGeV      VI-SIM    Dariusz Antonczyk
                                            CERES collaboration


                   D. Adamova, G. Agakichiev, D. Antończyk, A. Andronic, H. Appelshäuser,
                V. Belaga, J. Bielcikova, P. Braun-Munzinger, O. Busch, A. Castillo, A. Cherlin,
             S. Damjanovic, T. Dietel, L. Dietrich, A. Drees, S. Esumi, K. Filimonov, K. Fomenko,
             Z. Fraenkel, C. Garabatos, P. Glässel, G. Hering, J. Holeczek, V. Kushpil, B. Lenkeit,
               W. Ludolphs, A. Maas, A. Marin, J. Milosevic, A. Milov, D. Miśkowiec, R. Ortega,
             Yu. Panebrattsev, O. Petchenova, V. Petracek, A. Pfeiffer, M.Płoskoń, S. Radomski,
                J. Rak, Ravinovich, P. Rehak, W. Schmitz, J. Schukraft, H. Sako, S. Shimansky,
             S. Sedykh, J. Stachel, M. Sumbera, H. Tilsner, I. Tserruya, G. Tsiledakis, T. Wienold,
                    B. Windelband, J.P. Wessels, J.P. Wurm, W. Xie, S. Yurevich, V. Yurevich

                                                   NPI ASCR, Rez, Czech Republic
                                                      GSI Darmstadt, Germany
                                                    Frankfurt University, Germany
                                                   Heidelberg University, Germany
                                                        JINR Dubna, Russia
                                                  Weizmann Institute, Rehovot, Israel
                                                     SUNY at Stony Brook, USA
                                                         CERN, Switzerland
                                                          BNL, Upton, USA
                                                    Münster University, Germany
                                                      MPI Heidelberg, Germany

05.10.2005       Non-identical particle correlation in central Pb+Au collisions at 158 AGeV   VI-SIM   Dariusz Antonczyk
                                                        Backup




05.10.2005   Non-identical particle correlation in central Pb+Au collisions at 158 AGeV   VI-SIM   Dariusz Antonczyk

				
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