Measuring Eta A_LL with 2012 STAR Endcap Calorimeter Data

Faculty Sponsor

Shirvel Stanislaus


Arts and Sciences


Physics and Astronomy Department

Presentation Type

Poster Presentation

Symposium Date

Summer 7-23-2021


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.

Biographical Information about Author(s)

Maggie Bliese is a senior in the Physics and Astronomy Department. She has done research at Valparaiso University for the past three summers, but is new to the STAR project. She plans on pursuing her PhD in galactic astrophysics after graduation.

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