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John Koster is a graduate student at the University of Illinois at Urbana-Champaign, and a member of the PHENIX collaboration.

Report From the PHENIX Collaboration Meeting

By John Koster

The PHENIX collaboration meeting was held last week in Urbana-Champaign, Illinois with over 70 collaborators and five theorists in attendance to review past achievements and to plan for exciting future measurements. The meeting included sessions devoted to collaboration news and planning, as well as sessions on specific physics topics. The physics sessions included talks on measurements in progress, the current theoretical understanding and the measurements that can be accessed with detector upgrades. Highlights of the sessions will be touched upon in this article. Further information on publicly available talks can be accessed on the meeting webpage and all talks are available to PHENIX collaborators through the CDS agenda.

The collaboration news talks reviewed the experimentís excellent track record in discovery and prompt publication of new physics. To date, the RHIC experiments have published 15 papers with 250 or more citations on a variety of topics. Recent PHENIX highlights include: first measurement of thermal photon radiation in Au+Au collisions, showing that the initial temperature is at least 300 MeV; quantifying energy loss in the hot, dense medium based on several models; observation of the onset of high pT hadron suppression between 22.4 and 62.4 GeV collision energy; mapping the medium response to jets; and PHENIX neutral pion ALL constraints on global fits of ΔG. The list of highly cited papers is sure to expand with time and also with the recent Run 08 dataset which saw one-day peak integrated luminosities greater than that from all of Run 03. Also discussed was the installation of new detector systems between scheduled shutdowns, an approach that extends the physics reach of the experiment without slowing down the pace of data-collection. Notable recent upgrades are the Time of Flight West MRPC-based detector for charged hadron identification, the Reaction Plane Detector for use in heavy ion collisions, the Hadron Blind Detector for di-electron spectrum measurements and the Muon Piston Calorimeter for forward/backward electromagnetic calorimetry.

Several theory talks emphasized the need for measurements in the forward region. On the heavy ion side, measurements in the forward region will improve our understanding of the sQGP through flow and cross-section measurements of neutral pions and direct photons. Gamma-jet measurements can also be used with longitudinally polarized protons to access the functional form of ΔG(x) and its low-x behavior. An exciting measurement and DOE milestone in transverse spin physics are gamma-jet correlations which can study the process dependence of the Sivers effect. Forward detectors and in particular forward calorimetry will be well positioned to answer these compelling questions. The first PHENIX forward calorimeter, the muon piston calorimeter, with rapidity 3.1 to 3.8, follows the PHENIX tradition of modular calorimeters and was successfully installed for Runs 6 (only South) and 7 (also North). The second forward calorimeter will be a silicon tungsten sampling calorimeter with rapidity 1 to 3. Its design will be based on advanced calorimeter technology currently in development for the ILC and already in use studying cosmic rays in balloon experiments.

In addition to electromagnetic measurements in the forward region, the theorists in attendance also pushed for measurements of hadrons with heavy flavor content. In heavy ion collisions, these particles are expected to be produced early in the collision. Their subsequent propagation through the hot, dense matter produced at RHIC will provide additional insight into its properties. In polarized proton collisions, charm and bottom quarks are expected to be formed through gluon-gluon fusion. Their high mass sets a hard scale which can be used to connect back to the gluon polarization in a theoretically clean way which can confirm the current RHIC results on the gluon polarization. Significantly enhanced signals using the upcoming FVTX and VTX detector upgrades will provide precision flavor-separated measurements of displaced vertices that should provide exciting measurements in the future.

The meeting also included an important discussion on the planned DAQ2010 > system that will enable PHENIX to maintain its highly efficient data taking capability despite the additional data volume from detector upgrades and luminosity increases.

The collaboration meeting's planners should be thanked for all their hard work organizing an enjoyable and enlightening meeting. In particular, the Illinois students: Aaron Veicht, Nicholas Mucia, George Deinlein and Cameron McKinney took great care to ensure a smoothly run meeting.