9 GeV Au+Au Collisions Run on March 11 th, 2008 Out of ~200k Events –11000 had Vertices –6700 had Vertices within 2 cm of the beamline –4150 appeared to be beam-pipe events Run details can be found at: Combinations of bbc,vpd,ctb triggers used Rosi Reed

9 GeV Au+Au Collisions

Be beam pipe extends from -75 cm to 75 cm

Beam-Pipe Collisions and Low Energy Considerations Why did we trigger on “empty” events? Why did we trigger on beam-pipe events Are the events labeled as beam-pipe events actually collisions between Au and the beam pipe? –We looked at the physics in these events to determine whether this was the case

Au-Al HBT Analysis (root S NN = 3.2) Event quality cuts: –|Vz| > 75 cm –Vr > 2 cm –Vz*TotalEventPz < 0 Track Quality cuts: –Assumed all negatively charged tracks were pions –nHits/nPossHits > 0.5 for either TPC or FTPC

Au-Al HBT Analysis – dE/dx

Au-Al HBT Analysis Fit does not use lowest 3 points due to track merging