Photon and $\gamma$-Jet Reconstruction in the STAR Endcap EMC; Towards $\gamma$-Jet Constraints on $\Delta$G
ORAL
Abstract
The goal of determining the gluonic spin contribution to the proton is central to RHIC spin efforts. Recent results from inclusive jet measurements in polarized pp collisions at STAR and other experiments have indicated that gluons with momentum fraction x above $\sim 0.02$ do not contribute significantly to the integral $\Delta$G. $\gamma$-jet measurements provide a simpler although much more rare probe of the gluon spin contribution with sensitivity to the x dependence (event reconstruction of partonic kinematics) through measurements of the double longitudinal spin asymmetry A$_{LL}$. Several factors enhance the figure of merit of the primary gluon Compton process (g+q $\rightarrow$ q+$\gamma$) for these measurements in the Endcap and the detector itself was built to address various experimental difficulties, including suppressing the large $\pi^{\circ}$ backgrounds that grow at lower momentum transfer. The status of ongoing photon, direct $\gamma$ and $\gamma$-jet reconstruction and analyses efforts from the run 6 pp data sample and future prospects will be presented and discussed.
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Authors
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W.W. Jacobs
Indiana University Cyclotron Facility and Department of Physics