Hadron Correlation in Jets inHeavy Ion Collisions

C.B. YangCollaborated with

R.C. Hwa

arXiv:0812.2205Phys. Rev. C79, 044908 (2009)

Outline

QGP formation and jet quenching Interactions between jets and medium Correlations in jets Recombination model considerations Correlations in Re/Co model Results Discussions

PHENIX

QGP formation and jet quenching

STAR

December 15, 2008 Chunbin Yang

v2 scaling21 2 ( )cos(2 )T

T T

dNv p

p dp d

K

Jets influenced by medium

Medium influenced by jets?

Near side: ridgeAway side: double bump

Interactions between jets and medium

dividing the away-side jet function into equal-sized head (|φ − π| < π/6, HR) and shoulder (π/6 < |φ − π| <π/2, SR) regions, as indicated in (c).

Pt>4 GeV/c

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 • Hard partons evolve into semi-hard showers

Relevant partonic and hadronic variables

1. Position of hard scattering can be different2. Hard momentum k=k’ fluctuates

Degraded parton distributionwith fixed length L

Only parameter L

( )if k given by pQCD

0

' '

0

' ' 2

( , ) ( ) ( , , ) ( , , )

1= ( ) ( )

L

L

i i

k

qeL

i

q

dtF q q dkkf k G q k t G q k L t

L

dkk f k qq qq k eL

Upper and lower limits in the integrationcorrespond to t=0 and L

Fix the parameter

L=2.9

Near side

/ 0.065t L

Away side

Dependence on system size and momenta

Centrality dependence

Determine =L distribution for each centrality

Not a geometrical problem

No first principle can be used

Away side jet (special case)

( , ) ( , )awayt bY p c Y p p p c

L=2.9

L=2.9

Near side jet (general case)

Away side jet (general case)

Discussions

• Based on recombination model, with only 2 parameters for dynamical length

• Fix 2 parameters by fitting more than 100 data points• We discussed the yields, parton momenta, traversing length

etc and their dependence on centrality, momenta of trigger and associates.

• Trigger bias and anti-trigger bias• Dominance of tangential jets

Discussions

• More observables on correlation?• What is the dependence of correlation on

rapidity?• angle distribution and s dependence• Ridge and double bump properties?• Correlation of ridge and jet?• At LHC, how many changes?