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Radiative Energy Loss. Radiative Energy Loss. Radiative Energy Loss. Radiative Energy Loss. Radiative Energy Loss. Radiative Energy Loss. Radiative Energy Loss. Radiative Energy Loss. Radiative Energy Loss. at all orders in opacity. Simon Wicks, Yale-Columbia fest, May 2008
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Radiative Energy Loss Radiative Energy Loss Radiative Energy Loss Radiative Energy Loss Radiative Energy Loss Radiative Energy Loss Radiative Energy Loss Radiative Energy Loss Radiative Energy Loss at all orders in opacity Simon Wicks, Yale-Columbia fest, May 2008 Reference: arXiv:0804.4704
Radiative energy loss An opacity expansion ... ...the hard way
The Hard Way I 13 diagrams
The Hard Way II 135 diagrams
The Hard Way III ??? diagrams
An opacity expansion ... ... the clever way (once someone has done the hard way, and check with comparison to the hard way) Radiative energy loss
An opacity expansion ... ... the clever way (once someone has done the hard way, and check with comparison to the hard way) Find an operator recursion from order to order The 'reaction operator' Radiative energy loss
The Recursion Classical cascade Quantum source term(s)
The Quantum Source Term Sum over all opacities:
An opacity expansion is ... An opacity expansion is a Dyson expansion ... ... of an operator equation, similar to a Schrodinger equation ... ... that gives a nice form in impact parameter space.
Spot the difference GLV is equivalent to: BDMPS, at an intermediate stage, is:
Spot the difference II In q-space, BDMPS can be expressed as: AMY is:
Provides: 1) A method of derivation of the Schrodinger-like equation 2) A method of solution of the Schrodinger-like equation The opacity expansion To almost arbitrary precision!
Results – Orders in opacity (x/L) dN/dxdk Lambda = 1fm, mu = 0.5 GeV Bertsch-Gunion incoherent 'limit', L/x
Conclusion • Future work: • Different V(q) (Djodjevic's `dynamical medium'?) • Connection with 'thick medium' approximation in BDMPS • Variable density along path length • Effect on RAA • Multiple emission convolution • Convolution with collisional energy loss • Geometry integration
Q: Will the opacity expansion converge quickly? Naïve expectation: largest term is the L/lambda'th. BUT: Strong imaginary potential: strongly absorbing Hence, higher orders << lower orders