RUI: Studying the Strong Nuclear Force at Augustana University

Augustana University Association, Sioux Falls SD

Investigators

Abstract

This award continues the scientific program to study the strong nuclear force at Augustana University in Sioux Falls, South Dakota. The strong nuclear force is carried by particles called gluons that bind protons and neutrons together to form a nucleus at the core of every atom. Because atoms make up the majority of the observable matter, knowing the number of gluons inside a nucleus and their motion is necessary to understand matter at its fundamental level. The nuclear physics group at Augustana studies the gluon content of the nucleus by analyzing high energy nuclear collisions produced at the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory. The group will analyze data from deuterium + gold collisions measured with the PHENIX detector. The group will also participate in the building and installing the new sPHENIX detector, a next-generation detector that will measure results from collisions at RHIC beginning in approximately 2023. This program in strong nuclear physics is the only one of its kind in South Dakota. It provides those in the state and the region opportunities to study and participate in this physics. The proposal will support undergraduates studying physics or pre-engineering. The educational benefits for the students are broad. Students will gain practical skills such as computer programming, analysis of large data sets, electrical engineering application, and mechanical engineering design. These skills are transferable to other vocations of interest to the student, the state, and the nation. Students will participate in weekly collaboration meetings, present at national conferences, and visit collaborating institutions. Such opportunities will build their communication skills, grow their professional network, put them in contact with potential graduate schools, and prepare them for 21st-century technical jobs. An outstanding experimental question in strong-force physics is measuring the nuclear parton distribution function of gluons at low momentum fraction x. This award continues work by the PI and undergraduates to study this area in two ways. First, the measurement of pi0-hadron azimuthal correlations in d + Au at midrapidity of 200 GeV recorded by the PHENIX experiment at RHIC in 2016 will be completed and published. The analysis will utilize the Muon Piston Calorimeter (MPC) and the Muon Piston Calorimeter Extension (MPC-EX). The MPC is a PbWO4 crystal electromagnetic calorimeter. The MPC-EX is a Si-W pre-shower detector with high segmentation that can separate photons from pi-zero decays for E < 80 GeV. Using pairs of particles in different pseudorapidity, including the very forward MPC+MPC-EX region, the pair rate and azimuthal correlation shapes will be measured as a function of pair pseudorapidity. These measurements should yield insights to the kinematics of low-x gluons in the nucleus and allow tests of saturation physics or cold nuclear matter energy loss. Second, the group is transitioning from PHENIX to sPHENIX, a next-generation heavy ion detector that will take advantage of high-luminosity RHIC running to measure jets and heavy flavor physics. The group will spend significant time during the summers of 2021 and 2022 helping to build components and install the detector at the interaction region. First data is expected in early 2023. The group will focus on measurements of low-energy jets using two-particle correlations. In the future, the sPHENIX detector is expected to transform into a Day-1 physics detector the Electron-Ion Collider (EIC) that will be built at Brookhaven in the later 2020's. The main physics driver for the EIC is to measure the gluon content of the nucleus. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.