PHENIX Measurements of the Double Longitudinal Helicity Asymmetry in Neutral Pion Production in Polarized p+p Collisions at $\sqrt{s} =$ 200 and 500 GeV

Measurement of the gluon spin contribution to the proton spin, $\Delta G$, is an important component of the RHIC spin program. One particular focus is measuring the $\pi^{0}$ double longitudinal helicity asymmetry, $A_{LL}$, which is proportional to $\Delta G$. The large $p+p \rightarrow \pi^{0}$ cross section coupled with the high resolution of the PHENIX EM-Calorimeter make this an attractive avenue for constraining $\Delta G$. Significant constraints have already come from 2005 and 2006 PHENIX measurements of $\sqrt{s} =$ 200 GeV polarized proton collisions. In 2009, $\sqrt{s} =$ 200 GeV running saw a more than 60\% increase in the figure of merit ($P^4 L$) due a large increase in luminosity ($L$) with $\sim$55\% polarization ($P$). Also, the first data at $\sqrt{s} =$ 500 GeV were recorded and will push the constraints to lower momentum fraction x. After a brief review of past results, the status of the 2009 analysis will be presented.