2-presentation by liamei12345

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									Physics with ALICE-PMD

      Basanta K. Nandi
         IIT Bombay
    For PMD collaboration
    Photon Multiplicity Detector (PMD) in ALICE




        PMD




                                      Distance from IP : 367 cm
                                      Approx. 9 sq.m.
                                      η Covergae : 2.3 to 3.9
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                    Photon Multiplicity Detector



                                          Cell depth : 0.5 cm
                                          Cell cross-section : 0.23 cm2
                                          Total no. of cells : 220 K
                                          Sensitive medium : Gas
                                           (Ar+CO2 in the ratio 70:30)




     Honeycomb
      chamber
    (48×96 cells)
3
    Principle of Photon Multiplicity Detector

                                    Energy deposition in PMD


                                                Hadron


                                                Photon




                                            Edep (a.u.)

               Particle       CPV               PRE
               Photon         No                Yes
               Ch Hadron      Yes               Yes



4
                     Photon Multiplicity Detector

     PMD measures:
      - Event-by-event number of photons produced
        in heavy-ion collisions
      - Spatial distribution (x,y) or (,) of photons

     Physics Capabilities:
       - Pseudo-rapidity density
       - Limiting Fragmentation
       - Fluctuation in the ratio of N/Nch in the common
         coverage of PMD & FMD
       - Azimuthal anisotropy and event plane determination
       - Charged particle multiplicity
       - Jet ???




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         Charged Particle pseudo-rapidity Density
                                                     Au + Au at mid-rapidity

                                                                               200 GeV
 Particle production mechanism                                                130 GeV

     Soft process : Nch/γ scales with Npart                                   19.6 GeV

     Hard process : Nch/γ scales with Ncoll

       dNch/d = A x Npart + B x Ncoll


• Hard processes contribution increases with
  centrality from ~30% to 50% in the mid-rapidity

        Rapidity distribution of charged particles and photons gives the input
         to the theorist to validate their model

Q. What happens at higher energy?


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        Charged Particle pseudo-rapidity Density




Q. What happens in the forward rapidity for photons?


7
               Pseudo-rapidity distributions of Photons

          900 GeV p+p                              7 TeV p+p




         ALICE PRELIMINARY




       At 0.9 TeV Phojet explains the data where as Pythia6D6T and
        Pythia6ATLAS underpredict.
       At 7 TeV both Pythia and Phojet under-predict the data.


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 Limiting Fragmentation

       Particle production is independent of beam energy near beam rapidity




    Q. Is the limiting fragmentation scenario valid for photons?


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             Limiting fragmentation (LF) behavior of photons




      Limiting fragmentation behavior of photons seems to be inline with the
       earlier measurement.

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                                 Elliptic Flow

 Flow is a phenomenon seen in nucleus-nucleus collisions, which correlates
 the momentum distributions of the produced particles with the
 spatial eccentricity of the overlap region.


     azimuthal dependence of the
     pressure gradient.
                                       y            py


                                            x
                        y

                                                  
                                                   
                            z
                       x
                                    
                                   2
                                   2
                                   yx                p
                                                      
                                                   1y
                                                 v , tan
                                                 2 2
                                                  cos ()
     Reaction plane: z-x plane      
                                   2
                                   y
                                    2
                                    x                 px




                            


             d1 
             3           
                                                            
                                                              
                                                              
                       
             NdN
             E
             3
               2 dy
             d p
                dp
              p tt
                    co s v cos
                     2 
                   1 n nRP 2
                    
                    1
                    n
                     2 
                     v  
                         
                               2       
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                Event Plane Determination from PMD




     PMD event plane determination codes are in the repository for global use




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                   Charged particle measurement
     FMD 1     FMD 2           FMD 3

                                   Outer ing


                                     Inner ring




                   PMD
                                                  Similar Eta acceptance of FMD2I and CPV
                          = 2.3




                          = 3.5   FMD2i
                                                                        Beam line
                                                         IP
                            FMD1                               FMD3i Z-axis

                                               FMD2             FMD3o
                                               o
             PRE           CPV
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           Method to determine primary Charged Particles


                                           I.P. @ z = 0




     CPV               FMD

                                     X-Y plane @ z = 0



             Principle – Three point straight line tracking

             Necessity – Magnetic Field OFF data


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     Method to determine primary Charged Particles



Y




                      X
     R = √(x2 + y2)



15
     Charged particle measurement using CPV




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           Jet Study using PMD ?




p                      p




     TPC                    PMD


17
 Physics studies other than PMD

         Fluctuation in mid-rapidity

         K* measurement

         Anti-Nuclei search




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            Centrality Dependence of νdyn




10% Centrality Bins                5% Centrality Bins
     Measurement of K*




20
               Anti-Nuclei Search in ALICE


          pp @ 7 TeV




      Approximately 350 M events are analyzed
      Various nuclei are nicely identified in ALICE
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     Summary:




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