Accessing the Gluon Polarization in the Proton through the Measurement of the Double Helicity Asymmetry in Neutral Pion Production in Polarized Proton Collisions at PHENIX

A primary goal of the RHIC Spin program is to measure the gluon spin contribution ($\Delta G$) to the spin of the proton through the measurement of double helicity asymmetries ($A_{LL} $) in polarized proton collisions. Pions are abundantly produced in proton-proton collisions and so are a good candidate for a high statistics analysis. The PHENIX EMCal has good energy resolution and high granularity which, when used with a high energy photon trigger, yield a substantial $\pi^0$ sample over a wide range in transverse momentum ($p_T$). The 2005 and 2006 polarized proton runs (at $\sqrt{s}=200$ GeV) saw large increases in luminosity ($L$) and polarization ($P$) compared to previous runs, resulting in a high figure of merit ($P^4 L$). $\pi^0$ $A_{LL}$ from 2005 and 2006 are precise enough to be sensitive to $\Delta G$. Results from 2005 and 2006 for $\pi^0$ $A_{LL}$ at mid rapidity will be shown.