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Comparison of energy loss formalisms. Marco van Leeuwen, UU. TECHQM meeting LBNL, 15-16 Dec 2008. TECHQM `Brick Problem’. Idea: define a few ‘model systems’ to compare different calculational approaches. Fixed-length homogeneous ‘brick’ of QGP: L = 2 fm, L = 5 fm.
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Comparison of energy loss formalisms Marco van Leeuwen, UU TECHQM meeting LBNL, 15-16 Dec 2008
TECHQM `Brick Problem’ Idea: define a few ‘model systems’ to compare different calculational approaches Fixed-length homogeneous ‘brick’ of QGP: L = 2 fm, L = 5 fm Explore parton energy dependence: E = 10 GeV, E = 100 GeV (quarks) Compare models at ‘comparable phenomenology’, i.e. fixed DE/E (0.05, 0.1, 0.2, 0.4) Calculate P(DE) and P(Ngluon) (partial) results available for: WHDG/GLV, ASW/BDMPS, AMY, Higher Twist, YaJEM Note: not all models calculate P(DE)
Comparing P(DE) ASW-GLV and WHDG-GLV are different Due to treatment of DE/E →1? Note importance of P(0) Continuous part of P(DE) more sharply peaked for WHDG-GLV Are these differences significant?
L-dependence Increase L at constant <DE/E>: continuous part increases; peak at small values Difference WHDG-ASW persists
Energy-dependence Increase energy: reduces P(0), importance of DE/E → 1 Difference WHDG and ASW reduced at 100 GeV?
Towards phenomenology: fragmentation functions Artefact in KKP parametrisation Simple folding (only ‘loss term’): E = 10 GeV, WHDG steeper than ASW (reflects different P(DE) E = 100 GeV: shapes similar, normalisation difference?
Next steps Immediate future: • Compare to other formalisms (Higher twist, AMY, YaJEM) • Compare at same medium density? • Calculate RAA, IAA, g-jet • Use more realistic geometry Strategy towards future: To discuss in TECHQM and/or