Fri·Jul 3, 2009Friday·July 3, 2009

1. 01*

   Scaling patterns of the suppression of ${\pi }^0$ yields in Au+Au collisions at $\sqrt{s_{NN}}=200$ GeV: links to the transport properties of the QGP

   Roy A. Lacey🇺🇸 · N. N. Ajitanand🇺🇸 · J. M. Alexander🇺🇸 · X. Gong🇺🇸 · J. Jia🇺🇸 · A. Taranenko🇺🇸 · Rui Wei🇺🇸

   Suppression measurements for neutral pions (${\pi }^0$) are used to investigate the predicted path length ($L$) and transverse momentum ($p_T$) dependent jet quenching patterns of the hot QCD medium produced in Au+Au collisions at $\sqrt{s_{NN}}=200$ GeV. The observed scaling patterns show the predicted trends for jet-medium interactions dominated by radiative energy loss. They also allow simple estimates of the transport coefficient $\hat{q}$ and the ratio of viscosity to entropy density $\eta /s$. These estimates indicate that the short mean free path ($\lambda$) in the QCD medium leading to hydrodynamic-like flow with a small value of $\eta /s$, is also responsible for the strong suppression observed.

   nucl-exhep-phnucl-thPRC(2009)·15 citations
2. 02*

   Beam-Helicity Asymmetries in Double Pion Photoproduction off the Proton

   D. Krambrich🇩🇪 · F. Zehr🇨🇭 · A. Fix🇷🇺 · L. Roca🇪🇸 · P. Aguar🇩🇪 · J. Ahrens🇩🇪 · J.R.M. Annand🇬🇧 · H.J. Arends🇩🇪 · R. Beck🇩🇪 · V. Bekrenev🇷🇺 · B. Boillat🇨🇭 · A. Braghieri🇮🇹 and 49 other authors

   Beam-helicity asymmetries have been measured at the MAMI accelerator in Mainz in the three isospin channels $\vec{\gamma }p\to {\pi }^{+}{\pi }^{0}n$, $\vec{\gamma }p\to {\pi }^0{\pi }^{0}p$ and $\vec{\gamma }p\to {\pi }^{+}{\pi }^{-}p$ . The circularly polarized photons, produced from bremsstrahlung of longitudinally polarized electrons, were tagged with the Glasgow magnetic spectrometer. Charged pions and the decay photons of ${\pi }^0$ mesons were detected in a $4\pi$ electromagnetic calorimeter which combined the Crystal Ball detector with the TAPS detector. The precisely measured asymmetries are very sensitive to details of the production processes and are thus key observables in the modeling of the reaction dynamics.

   nucl-exPRL(2009)·53 citations

* Reconstructed cohort: no mailing for this day survives in the archive. Papers are grouped by their submission times and arXiv's announcement cut-off, assuming announcement without delay; positions follow identifier order. Validated at ~91% exact-day agreement against the archived era.