STAR Experiment and Forward Upgrade at RHIC
Arts and Sciences
Physics and Astronomy
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 (𝜋⁰) 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 < η < 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 𝜋⁰s present. The 𝜋⁰ asymmetry is calculated from the number of 𝜋⁰s in collisions with different polarization directions of the colliding proton beams. The status of the measurement of ALL of the 𝜋⁰s as a function of the transverse momentum, pT, of the 𝜋⁰ will be presented.
Kovarik, Claire; Edwards, Andrew; and Snaidauf, JD, "STAR Experiment and Forward Upgrade at RHIC" (2019). Summer Interdisciplinary Research Symposium. 65.