Determining the Longitudinal Double-Spin Asymmetry (A_LL) for pi0 and eta Production from STAR 2013 Endcap Calorimeter Data

Faculty Sponsor

Dr. Shrivel Stanislaus


Arts and Sciences



Presentation Type

Oral Presentation

Symposium Date

Spring 4-27-2023


The Solenoidal Tracker at RHIC (STAR) located at Brookhaven National Laboratory uses longitudinally polarized proton-proton collisions to study the gluon spin contribution to the known proton spin of 1/2 h-bar. The relative contributions of the quarks and gluons to the spin of the proton remain uncertain. Using data from the 2013 longitudinally polarized proton-proton collisions we study the asymmetry of proton spin-dependent production of neutral pions (pi0s) from these collisions. pi0s rapidly (8.5 * 10-17s) decay into 2 photons that are detected by the Endcap Electromagnetic Calorimeter. By comparing the number of pi0s produced when protons collide with different helicities, the asymmetry of pi0 production (ALL), which can be related to the contribution of the gluon spin to the spin of the proton, can be measured. The two-photon invariant mass spectrum is reconstructed and then fit using a skewed Gaussian function to represent the pi0 signal and a Chebyshev function to characterize the background. Various checks must be made to assure the quality of the data being analyzed. The status of this analysis will be presented.

This document is currently not available here.