# DNP2016 Abstract

LaTeX pasted below, pdf attached.

v3.0

Double-Spin Asymmetry in Neutral Pion Production at Intermediate Pseudorapidity in Longitudinally Polarized $p+p$ Collisions in the STAR Detector at RHIC

Adam Gibson for the STAR Collaboration

Department of Physics and Astronomy, Valparaiso University, Valparaiso, IN 46383, USA

One of the outstanding problems in nuclear physics is to explain the helicity of the proton in terms of its constituents. It has long been known that the helicity of the quarks is insufficient, initially a puzzling result. In recent years it has become clear that the gluon plays an important role, but the uncertainty on the contribution from low $x$ gluons in particular has remained large. The STAR and PHENIX detectors at RHIC have been critical in illuminating the role of the gluon. STAR published an analysis of neutral pions in the intermediate pseudorapidity Endcap Electromagnetic Calorimeter (EEMC, 1.09 $< \eta <$ 2.00) using a dataset from 2006 at $\sqrt{s} = 200$ GeV that was complimentary to results using jets and pions at mid-rapidity and at forward pseudorapidites. Our present analysis extends that earlier EEMC result using a much larger dataset in the EEMC at $\sqrt{s} = 510$, extending the reach of the analysis to lower gluon $x$. We will present the status of this analysis of the double-spin asymmetry in neutral pion production in longitudinally polarized $p+p$ collisions in the STAR detector at RHIC ($\pi^0$ $A_{LL}$), and discuss prospects for the future.
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v2.0

Double-Spin Asymmetry in Neutral Pion Production at Intermediate Pseudorapidity in Longitudinally Polarized $p+p$ Collisions in the STAR Detector at RHIC

Adam Gibson for the STAR Collaboration

Department of Physics and Astronomy, Valparaiso University, Valparaiso, IN 46383, USA

One of the outstanding problems in nuclear physics is to explain the helicity of the proton in terms of its constituents. It has long been known that the helicity of the quarks is insufficient, initially a puzzling result. In recent years it has become clear that the gluon plays an important role, but the uncertainty on the contribution from low parton $x$ gluons in particular has remained large. The STAR and PHENIX detectors at RHIC have been critical in illuminating the role of the gluon. At STAR, a paper analyzing neutral pions in the intermediate pseudorapidity Endcap Electromagnetic Calorimeter (EEMC, 1.09 $< \eta <$ 2.00) using a dataset from 2006 at $\sqrt{s} = 200$ GeV was complimentary to results using jets and pions at mid-rapidity and at forward pseduorapidites. Our present analysis extends that earlier EEMC result using a much larger dataset in the EEMC at $\sqrt{s} = 510$, extending the reach of the analysis to lower gluon $x$. We will present the status of this analysis of the double-spin asymmetry in neutral pion production in longitudinally polarized $p+p$ collisions in the STAR detector at RHIC ($\pi^0$ $A_{LL}$), and discuss prospects for the future.

v1.0

Double-Spin Asymmetry in Neutral Pion Production at Intermediate Pseudorapidity in Longitudinally Polarized $p+p$ Collisions in the STAR Detector at RHIC

Adam Gibson for the STAR Collaboration

Department of Physics and Astronomy, Valparaiso University, Valparaiso, IN 46383, USA

One of the outstanding problems in nuclear physics is to explain the helicity of the proton in terms of its constituents. It has long been known that the helicity of the quarks is insufficient, initially a puzzling result. In recent years it has become clear that the gluon plays an important role, but the uncertainty on the contribution from low parton $x$ gluons in particular has remained large. The STAR and PHENIX detectors at RHIC have been critical in illuminating the role of the gluon. At STAR, a paper analyzing neutral pions in the intermediate pseudorapidity Endcap Electromagnetic Calorimeter (EEMC) using a dataset from 2006 at $\sqrt{s} = 200$ GeV complimentary to results using jets and pions at mid-rapidity and at forward pseduorapidites. Our present analysis extends that earlier EEMC result using a much larger dataset in the EEMC at $\sqrt{s} = 510$, extending the reach of the analysis to lower gluon $x$. We will present the status of this analysis of the double-spin asymmetry in neutral pion production in longitudinally polarized $p+p$ collisions in the STAR detector at RHIC ($\pi^0$ $A_{LL}$), and discuss prospects for the future.