RUI: Models of Hadron Structure and Interactions

Seattle University, Seattle WA

Investigators

Abstract

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5). In this project we study two topics in theoretical nuclear physics related to the structure of hadrons (e.g. protons, neutrons and their antiparticles) and to their interactions. The first topic is the fundamental question of how the properties of a hadron (e.g. momentum and spin) are distributed among its constituent partons: quarks, antiquarks and gluons. Two theoretical frameworks will be used. In the first, a hadron fluctuates into meson-baryon pairs, and the hadron's parton distribution is determined by the parton distributions of the mesons and baryons in the fluctuations. In the second, the hadron's parton distributions are calculated in a statistical model. This study will address one of the outstanding challenges to theory posed by recent experiment, the momentum-dependence of light quark distributions in the proton sea. The calculations will also provide predictions for experiments planned at Fermilab and JPARC. The second topic is the fundamental question of how spin and strangeness are related in the production of strange particles. We will consider reactions in which a hyperon and its antiparticle (e.g. Lambda and anti-Lambda) are created by the annihilation of an antiproton and a proton. Our calculations will focus on recent spin transfer measurements at CERN, which disagree with all theoretical predictions. We will also calculate cross sections and spin observables for the experiments planned by the PANDA collaboration at GSI/FAIR, which will extend the CERN measurements to higher energies. This work will be carried out with undergraduate research assistants from Seattle University, which has a diverse student population and a high percentage of women physics majors. The student research experience will be complementary to coursework, and provide an integration of classroom learning and the excitement of contemporary research. Students will receive training in research methods and scientific communication. They will work in teams, mentor younger students and present their work in papers, posters and talks at meetings of professional societies. They will also share their work with the local campus community in seminars and events sponsored by Seattle University student research organizations.