Measurement of the Longitudinal Double-spin Asymmetry for Neutral Pion Production in Polarized Proton Collisions at √s = 510 GeV

Date of Award


Project Type

Departmental Honors Paper/Project


Department of Physics & Astronomy

First Advisor

Adam Gibson-Even


Beyond the valence quarks' spin contribution to the total spin of a proton, gluon and sea quark contributions are becoming clear as well. For proton+proton collisions at a center of mass energy of 510 GeV , neutral pion production is dominated by gluon-gluon and gluon-quark scattering. An avenue to constrain the gluon polarization is the asymmetry, ALL, in the production of neutral pions from collisions of longitudinally spin-polarized proton beams. Our experiment was performed with the STAR detector at the Relativistic Heavy Ion Collider (RHIC), unique for its ability to collide spin-polarized proton beams. The Endcap Electromagnetic Calorimeter (EEMC) of the STAR detector with its pseudo-rapidity (η) range between 1.09 and 2.00 and full azimuthal coverage measures energies of photons from π0 decays. We consider the invariant mass of all photon pairs in the EEMC as we identify π0 candidates. We will present the current status of the analysis of the π0 ALL as measured by the EEMC at STAR in 2012 data with center-of-mass energy of 510 GeV.