collisional energy loss in a finite size qcd medium revisited
DESCRIPTION
Collisional energy loss in a finite size QCD medium revisited. Alejandro Ayala Instituto de Ciencias Nucleares, UNAM. Radiative and collisional energy losses. Mass and color charge effects…. Energy loss issues. Collisional vs radiative energy losses Mass and color charge effects - PowerPoint PPT PresentationTRANSCRIPT
Collisional energy loss in a finite size QCD medium revisited
Alejandro AyalaInstituto de Ciencias Nucleares, UNAM
Radiative and collisional energy losses
Mass and color charge effects…
Energy loss issues
Collisional vs radiative energy losses Mass and color charge effects Running of s
Non-perturbative calculations using AdS/CFT and duality arguments
... Finite size effects
A
A
B
B
Particle production region
Q: How does the size of the interaction region play a role in the description of parton energy losses?
Finite size effects
S. Peigné, P.B. Gossiaux and T. Gousset, JHEP04, 011 (2006)
Energy loss computed by slowing down of parton induced by medium produced chromoelectric field in Abelian approximation
Retardation effects: A fast parton produced in the mediumneeds to travel some distance before losing energy at thehighest rate.Conclusion: finite size reduces the rate of energy loss.
Conserved current
M. Djordjevic, PRC 74, 064907 (2006)
Condition for interaction between jet and medium parton to occur inside finite QCDmedium of size L.Conclusion: finite size does not affect the rateof energy loss.
Perturbative collisional energy loss, 2 2 processesin a finite QCD medium
Particle source
Scattering diagram
Source: J (t, x )
Classical, conserved current
Simple model: Color singlet dipole, i.e., two partonsin color singlet state traveling with velocities v1 and v2
In Fourier space, this is:
+ (retarded prescription)
But suppose ( finite)
Current life-time:
In Fourier space:
Parton should travel length of plasma
Interaction rate involves ratio of currents after and without collision
Explicit dependence on current life-time
Scattering diagram
Source: J (t, x )
Modified matrix elementCurrent life-time
Interaction within the plasma
Modified matrix element
Modified matrix element squared
Differential rate
Elementary scattering process
Auxiliary functions for average over velocity directions
Summary
Incorporate an explicit conserved current into the description of collisional energy loss
The above requires considering the time the current spends within the plasma
Predictions?... Not yet, working on them.