STAR Experiment and Forward Upgrade at RHIC


Arts and Sciences


Physics and Astronomy

Presentation Type

Poster Presentation

Symposium Date

Summer 7-29-2019


The Solenoidal Tracker at RHIC (STAR) located at Brookhaven National Laboratory in New York uses longitudinally polarized proton-proton collisions to determine the gluon contribution to the spin of the proton. One analysis of the 2012 data set, at a proton-proton center of mass energy of 510 GeV, studies the production of neutral pions (πœ‹β°) which immediately (~10-16s) decay into two photons. The neutral pion asymmetry, ALL, can be determined through data collected by the Endcap Electromagnetic Calorimeter (EEMC). The EEMC, positioned in an intermediate pseudorapidity range of 1 < Ξ· < 2, is able to measure the energy and position of each photon’s electromagnetic shower. By using this information as well as the angle between the photons, the two-photon invariant mass can be reconstructed. The invariant mass spectra are fitted using a skewed Gaussian plus a background function to determine the total number of πœ‹β°s present. The πœ‹β° asymmetry is calculated from the number of πœ‹β°s in collisions with different polarization directions of the colliding proton beams. The status of the measurement of ALL of the πœ‹β°s as a function of the transverse momentum, pT, of the πœ‹β° will be presented.

This document is currently not available here.