A Measurement of π⁰ A_LL with the STAR 2013 Endcap Calorimeter Data

Longitudinally polarized protons are collided in the Solenoidal Tracker at RICH (STAR) located at Brookhaven National Laboratory to study the gluon spin contibution to the spin of the proton. Data have been collected in 2013 at √s = 510 GeV from which the spin-dependent assymetry of the neutral pion (π⁰) production, A_LL, can be measured. The neutral pions are reconstructed using photons from the π⁰ decays detected in the Endcap Electromagnetic Calorimeter (EEMC). The EEMC, covering an intermediate pseudorapidity range of 1.1 < μ < 2, is able to measure the energy and position of the elctromagnetic showers from incoming photons. From these measurements, the two-photon invariant mass spectrum can be obtained, which is then fit using a scewed Gaussian function to represent the π⁰ signal and a Chebyshev function to charcterize the random two-photon background. The total number of π⁰s is obtained by integrating the resulting Gaussian peak. The π⁰ A_LL is calculated from the number of π⁰s produced in collisions of protons with different spin alignments. Numerous checks must be carried out to ensure the quality of the very large data set used in this analysis. The current status of the analysis, focussing on the data quality assurance, will be presented.