Discussion Session on Parton Energy Loss contribution by Nestor Armesto, Carlos A. Salgado and Urs Achim Wiedemann Rules of the game: Four Slides maximum for 10 min Show (easy to understand) analytical results on total energy loss in limit of large E and L in static medium (for reasons explained, we show also 1-dim Bjorken expansion) Compare to other approaches (BDMPS and GLV are limiting cases of our calculation) What values can be derived from comparison to data
ASWBDMPS Wiedemann, NPB 588 (2000) 303 Radiation off produced parton 1. Medium-induced gluon energy distribution All info about medium in: density of scattering centers times effective interaction strength of single scatterer: Two approximation schemes: 2. Opacity expansion in powers of Harmonic oscillator approximation: BDMPS transport coefficient ASWGLV Salgado, Wiedemann, PRD68 (2003) 014008 Armesto, Salgado, Wiedemann, PRD69 (2004) 114003
ASWGLV ASWBDMPS 2. Average Energy Loss • Harmonic oscillator approximation (static medium) • N=1 opacity approximation (static medium) Salgado, Wiedemann, PRD68 (2003) 014008 • Harmonic oscillator approximation (Bjorken expansion) (A) • GLV-result for Bjorken expansion, nucl-th/0012092 (B) Compare (A) to (B) …
compare (A) to (B) for following numbers: 3. Comparison: ASW-BDMPS-GLV for Rough estimate from pocket formulas! for This estimate shows only that is same order as In comparison to data, distribution over L and deviations from average energy loss pocket formulas are important. • Where does the log come from?
4.Beyond Pocket Formulas- how we do it: Probability of parton energy loss: Salgado, Wiedemann, PRD68 (2003) 014008 Armesto, Salgado, Wiedemann, PRD69 (2004) 114003 For L=2 fm, R=1000, 40% probability that hard quark does not scatter on medium. (deviation from pocket formula!) Average energy loss is first moment:
5. Comparison to data: Eskola, Honkanen, Salgado, Wiedemann NPA747 (2005) 511
Expand path intergral: Zeroth order: 2 First order: Parton cascade limit: L 2 2 Rescattering of vacuum term + + + + Bertsch-Gunion 2 Wiedemann, NPB 588 (2000) 303 Opacity Expansion