Double Longitudinal Spin Asymmetries of Inclusive Charged Pion Production in Polarized p+p Collisions at 200 GeV

A primary goal of the STAR Spin program at RHIC is the measurement of the polarized gluon distribution function $\Delta $G, which can be obtained from a global analysis incorporating measurements of the double spin asymmetry A$_{LL}$ in various final state channels of polarized p+p collisions. Final states with large production cross sections such as inclusive jet and hadron production are analyzed as the program moves towards the measurement of A$_{LL}$ in the theoretically clean channel of prompt photon production. The channels p+p$\to \pi ^{+/-}$+X are unique in that the ordering of the measurements of A$_{LL}$ in these two channels is sensitive to the sign of $\Delta $G. Moreover, STAR has already established the procedure for the identification of charged pions and the calculation of their production cross-sections over a broad kinematic range. This contribution will present first measurements of double longitudinal spin asymmetries for inclusive charged pion production extracted from 3 pb$^{-1}$ of data at $\surd $s=200 GeV and 50{\%} beam polarizations. The asymmetries are calculated over the transverse momentum region 2$<$p$_{T}<$12 GeV/c and compared with theoretical predictions incorporating several gluon polarization scenarios. A systematic bias introduced by the selection of charged pions from events satisfying electromagnetic energy triggers will be discussed and estimated using Monte Carlo.