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Recombination models

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Recombination models Powered By Docstoc
					Particle Production and Correlation
  from the Recombination Model

              C.B. Yang

        CCNU ,Wuhan, China


        PRC81, 024908 (2010)
                     Outline

•   Data and our motivation
•   Quark recombination model
•   Scaling of dynamical path length dis
•   Particle spectrum
•   Correlations in jet
•   Discussion
PHENIX
PHENIX
                    Our aim
•   Find simplifying features of the data
•   Relation with nuclear geometry
•   Dynamical hadronization mechanism
•   New understanding of the data
•   Implications for LHC/ALICE
          Recombination models
• Hadrons formed by combining two (three)
  constituent quarks
• Combining probabilities, determined by wave
  functions, called the recombination functions
• There are soft and hard partons
• Hard parton will lose energy in traversing the
  medium
• There are different implementations
• Hard partons evolve into semi-hard showers
 Relevant partonic and hadronic variables




1. Position of hard scattering can be different
2. Hard momentum k=k’ fluctuates
   dN                    dq
          (b)            Fi (q, b,  ) H i ( q, pT )
pT dpT d
                jet
                         q i


                        Hadronization dynamics,
                        independent of centrality
                        and azimuthal angle
             Degraded parton distribution

Fi (q, b,  )   dxdyQ( x, y) dkkfi (k )G(q, k , l ( x, y, b,  ))


                fi (k )givenby pQCD


   Hard parton energy loss (model)
    depending on the traversed length

            Weight for each point (Geometry)
        Last equation can be rewritten as

Fi (q, b,  )   d P( , b,  ) Fi (q,  )
Fi (q,  )   dkkfi (k )G(k , q,  )

     ξcalled dynamical length
     P( , b,  )   dxdyQ( x, y) (   l ( x, y, b,  ))
    Dynamical path length distribution
TA (s)  A dz  (s, z )
                        1
LA, B ( x, y ) 
                     o         dz  ( s, z )

                   TA ( x, y, b / 2)TB ( x, y, b / 2)
Q ( x, y , b ) 
                   d       sTA ( s  b / 2)TB ( s  b / 2)
                        2


                                                   LB ( x , y )
 D( x, y)   LA ( x, y )(1  e                                     )
                             LA ( x , y )
                                                                         ω=4.6
  LB ( x, y)(1  e                           )

                    l ( x0 , y0 , b,  )   dtD( x(t ), y(t ))
 d P( , b,  )  1    d P( , b, )
z  /    ( z )   P ( , b,  )
Scaling dynamical path length distribution!
Scaling of RAA (Theoretical results)
         RAA vs NP (Th vs Data)




γ=0.11
                        i
    if f i ( k )  k
                                ( i  2)
          Fi (q,  )  (qe )

           R ( pT ,  )   dz ( z )e
             i
             AA
                                               z  ( i  2)




with  ( z) scaling, one gets RAA scaling
                   Back-to-Back Jets
       dN           dq1 dq2
pt pb dpt dpb d
                 
                    q1 q2
                                   F (q , q , b,  ) H (q , q , p , p )
                                    i
                                        i   1   2           i   1   2    t   b




                                                      Hadronization
                                                      dynamics
 Fi (q1 , q2 , b,  )   d 1d  P(1 ,  2 , b,  ) Fi (q1 , q2 , 1 ,  2 )
                                    2

 Fi (q1 , q2 , 1 ,  2 )   dkkf i (k )G (k , q1 , 1 )G (k , q2 ,  2 )
C=0.05,φ=π/24
    z j   j /  (b,  )
                                         2
     P(1 , 2 , b,  )  ( z1 , z2 ) /  (b,  )
Boundary of last plot
     z  z1  z2




2d path length dis is of scaling
Yield per trigger
       Trigger-normalized FF
     D ( zT ,  )  pt pbY ( pt , pb ,  )
                             away




Data: 8GeV/c<pt<16GeV/c, 0-10%
      Two-jet recombination at LHC

•   At LHC/ALICE, # of init hard partons is huge
•   They may overlap in space-time
•   Huge p/π ratio
•   New signal?
     2j
  dN AA           dq dq '
pT dpT d
          (b)            Fi (q, b, ) Fi ' (q ', b,  )Hii ' (q, q ', pT )
                  q q ' i ,i '



     Two-jet overlap probability Γ
                 Discussions
RAA at large pT depend on 
 Scaling of RAA seen at RHIC
b and φdependence of RAA encoded in mean
    path length
Yield per trigger depends on ξ-bar universally
At LHC, RAA can be huge and its scaling may be
  violated due to overlap of two-jets
 Can be checked easily!

				
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