Neutral Pion Helicity Asymmetry Analysis at STAR with an Emphasis on Integration of Updated Monte Carlo Simulation

Faculty Sponsor

Adam Gibson-Even


Arts and Sciences


Physics and Astronomy

ORCID Identifier(s)


Document Type

Poster Presentation

Symposium Date

Summer 7-30-2018


My research group and I, working through the STAR (Solenoidal Tracker at RHIC) collaboration, analyze data from the Endcap Electromagnetic Calorimeter to measure the asymmetry in neutral pion (π0) production as a function of spin alignment in longitudinally polarized proton beam collisions. This asymmetry can be used to determine the gluon contribution to the intrinsic spin of the proton. The π0’s decay into two photons. The invariant masses of all two photon candidates are calculated and plotted to give a π0 mass peak which includes the mass of diphoton background events. To identify the shape of the signal and backgrounds as a function of diphoton mass, proton collision event kinematics are simulated in a detailed computer model of the STAR detector. With this simulation data we are able to derive signal and background curve shapes which are fit to the aforementioned mass plots to determine an accurate count of the number of π0’s generated in differently spin aligned collisions. Simulation data generated to analyze the dataset from 2006 (4.8 pb-1) has been found inadequate for describing the 2012 dataset (82 pb-1). I will describe the π0 analysis and particularly our efforts to integrate simulation generated specifically for the 2012 dataset.

Biographical Information about Author(s)

Noah Strand is a Physics Major at Valparaiso University. He has marked two summers researching with the STAR group at Valpo. He sees this research as a phenomenal way to see the current state of the field he studies. He has and hopes to continue to benefit greatly from his time on the project. Noah is in the process of applying to seminary where he will study to obtain his Master of Divinity degree and ordination as a Missouri Synod Lutheran pastor.

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