Mon·Jul 27, 2009Monday·July 27, 2009

1. 01*

   Observation of hypertritons in Au+Au collisions at \sqrt{s_{NN}} = 200 GeV

   J. H. Chen (for the STAR Collaboration)🇨🇳

   We report preliminary results of hypertriton observation in heavy-ion collisions at RHIC. We have identified 157 +- 30 candidates in the current sample containing ~10^8 Au+Au events at \sqrt{s_{NN}} = 200 GeV. The production rate of hypertriton is close to that of helium 3. No extra penalty factor is observed for hypertriton, in contrast to results observed at the AGS.

   nucl-exNPA(2009)·14 citations
2. 02*

   Direct gamma and gamma-jet measurement capability of ATLAS for Pb+Pb collisions

   Mark D. Baker (for the ATLAS collaboration)🇺🇸

   The ATLAS detector at the LHC is capable of efficiently separating photons and neutral hadrons based on their shower shapes over a wide range in eta, phi, ET, either in addition to or instead of isolation cuts. This provides ATLAS with a unique strength for direct photon and gamma-jet physics as well as access to the unique capability to measure non-isolated photons from fragmentation or from the medium. We present a first look at the ATLAS direct photon measurement capabilities in Pb+Pb and, for reference, p+p collisions at sqrt(sNN)=5.5 TeV over the region |eta|<2.4.

   nucl-exhep-exNPA(2009)·4 citations
3. 03*

   Commissioning and Calibration of the ALICE TPC

   J. Wiechula (for the ALICE TPC Collaboration)🇩🇪

   ALICE (A Large Ion Collider Experiment) is the dedicated heavy ion experiment at the Large Hadron Collider at CERN. The main tracking device of ALICE is a large volume TPC. The milestones of the TPC commissioning as well as the current status of the detector calibration are presented. The obtained resolutions in transverse momentum, position as well as in specific energy loss (dE/dx) are presented and results from noise and electron drift velocity measurements are addressed.

   nucl-exNPA(2009)·5 citations
4. 04*

   Influence of the nucleon-nucleon collision geometry on the determination of the nuclear modification factor for nucleon-nucleus and nucleus-nucleus collisions

   Jiangyong Jia🇺🇸

   The influence of the underlying nucleon-nucleon collision geometry on evaluations of the nuclear overlap function ($T_{AB}$) and number of binary collisions ($N_{coll}$) is studied. A narrowing of the spatial distribution of the hard-partons with large light-cone fraction $x$ in nucleons leads to a downward correction for $N_{coll}$ and $T_{AB}$, which in turn, results in an upward correction for the nuclear modification factor $R_{AB}$. The size of this correction is estimated for several experimentally motivated nucleon-nucleon overlap functions for hard-partons. It is found to be significant in peripheral nucleus-nucleus and nucleon-nucleus collisions, and are much larger at the LHC energy of $\sqrt{s}=5.5$ TeV than for the RHIC energy of $\sqrt{s}$=200 GeV. The implications for experimental measurements are also discussed.

   ↳ nucl-thhep-phnucl-exPLB(2009)·16 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.