Neutral Pion Asymmetries at Intermediate Pseudorapidity in Transversely Polarized p+p Collisions at sqrt(s)=200 GeV

Faculty Sponsor

Jim Drachenberg


Arts and Sciences



Presentation Type

Poster Presentation

Symposium Date

Spring 5-2-2015


Among the unanswered questions pertaining to nucleon spin physics is the origin of large azimuthal asymmetries (A_N) found in neutral pions produced at forward pseudorapidity from high-energy transversely polarized p+p collisions. One possible explanation is offered by twist-3 parton distribution and fragmentation functions. In order to test these and other mechanisms, it is important to study how the asymmetry changes over a range of pion kinematics. The STAR Endcap Electromagnetic Calorimeter (EEMC) is the only RHIC detector with the ability to study A_N for neutral pions in the kinematic range available at intermediate pseudorapidity. STAR recently published the first measurement of A_N for neutral pions at intermediate pseudorapidity using data collected in 2006 with collision energy sqrt(s)=200 GeV. In 2012 STAR collected a high-statistics dataset with transverse beam polarization at sqrt(s)=200 GeV. This offers over a five-fold increase in integrated luminosity relative to the 2006 dataset and a chance to enhance the precision of the previous results. The primary objective of this study is to determine the quality of the data from 2012 and to estimate the final statistical uncertainty. Preliminary results from this study indicate a significant improvement over the 2006 results.

Biographical Information about Author(s)

Samuel Brandt is a sophomore physics and humanities major from Portland, OR. He conducted this research over the past summer and presented it at the DNP conference in October. He was drawn to this research by the faculty in the Physics Department and will be interning at Pacific Northwest National Lab this coming summer.

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