Measuring Eta A_LL with 2012 STAR Endcap Calorimeter Data
Arts and Sciences
Physics and Astronomy Department
This research project focused on measuring asymmetry (ALL) of eta (η) particles from products of longitudinally polarized proton-proton collisions (√s = 510 GeV) at the Solenoidal Tracker at RHIC (STAR), located at Brookhaven National Laboratory. The η particles decay into two photons (mean lifetime = 5 × 10-19 s), which are detected by the Encap Electromagnetic Calorimeter (EEMC). The EEMC, positioned at one end of the detector, measures the energy and position of an incoming photon’s electromagnetic shower. From these measurements the two-photon invariant mass spectrum can be reconstructed. These spectra are then fitted using a Gaussian peak and a background polynomial function to determine the total number of η particles (mass = 0.545 GeV) produced by the initial collision. ALL is then calculated from the number of η particles produced in collisions of protons with different spin alignments, and gives information about the gluon contribution to the spin of the proton. The status of the analysis of the 2012 data set to measure the η ALL will be presented.
Bliese, Maggie, "Measuring Eta A_LL with 2012 STAR Endcap Calorimeter Data" (2021). Summer Interdisciplinary Research Symposium. 111.