# Energy loss and in finite size QCD · PDF file Energy loss and in finite size QCD medium...

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Energy loss and in finite size QCD medium

Alejandro Ayala ICN-UNAM

November, 2006

Radiative vs. Collisional energy loss Single non-photonic electron puzzle at RHIC

S. Wicks, W. Horowitz, M. Djordjevic and M. Gyulassy, nucl-th/0512076

Energy loss issues

Collisional vs radiative energy losses Running of αs Non-perturbative calculations using AdS/CFT and duality arguments Finite size effects

S. Peigné, P.B. Gossiaux and T. Gousset, hep-ph/0509185

Energy loss computed by slowing down of parton induced by medium produced electric field in Abelian approximation

Retardation effects: A fast parton produced in the medium needs to travel some distance before losing energy at the highest rate. Conclusion: finite zise reduces the rate of energy loss.

M. Djordjevic, nucl-th/0603066 Perturbative collisional energy loss, 2 → 2 processes in a finite QCD medium

Condition for interaction between jet and medium parton to occur inside finite QCD medium of size L. Conclusion: finite size does not affect the rate of energy loss.

Finite size effects

AA

BB

Particle production region

Q: Does the size of the interaction region, where particles are produced, play a role in the description of particle spectra?

Finite size effects

Qualitatively, finite size effects produce a broader transverse momentum spectrum due to Heisenberg uncertainty principle since the more localized the states are in coordinate space, the wider their spread will be in momentum space.

Bosons

Momentum distribution

Thermal occupation factor includinng radial expansion

Wigner transform for bosons

A.A. E. Cuautle, J. Magnin, L.M. Montaño & A. Raya, Phys. Lett. B 634, 200 (2006)

Rπ=8 fm, βπ=0.6,Tπ=120 MeV

Fermions

Momentum distribution

Thermal occupation factor includinng radial expansion

Wigner transform for fermions

A.A., E. Cuautle, J. Magnin, L.M. Montaño, nucl-th/0603039, to appear in PRC

Rπ=Rp=8 fm βπ=0.6 βp=0.53 (10% smaller than βπ) Tπ=Tp=117 MeV

Scaling: R=R0 +C (Npart/2)1/3 R0 = 1fm, C = 1.28 fm

Two pion correlations

R vs PHENIX data

10 -7

10 -6

10 -5

10 -4

10 -3

10 -2

10 -1

1

10

10 2

10 3

0 1 2 3 4 5 6 7 8 9 10 Pt (GeV/c)

1/ 2π

*p td

N /d

p t

Conclusions Considering finite size of particle production region, proton and pion spectra well described. Spectra from discrete set of states. Similar analysis possible for heavy quark produced in finite QCD medium?

Energy loss and in finite size QCD medium Radiative vs. Collisional energy loss Energy loss issues S. Peigné, P.B. Gossiaux and T. Gousset, hep-ph/0509185 M. Djordjevic, nucl-th/0603066 Finite size effects Momentum distribution R?=8 fm, ??=0.6,T?=120 MeV Fermions Momentum distribution R?=Rp=8 fm??=0.6 ?p=0.53 (10% smaller than ??) T?=Tp=117 MeV Scaling: R=R0 +C (Npart/2)1/3R0 = 1fm, C = 1.28 fm Two pion correlations R vs PHENIX data Conclusions

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