A Program of measurement of high energy electron and gamma ray interactions with matter

University Of Massachusetts Amherst, Amherst MA

Investigators

Abstract

This award will support preparing, carrying out, and analyzing a series of measurements of electromagnetic structure of matter by the University of Massachusetts Group, primarily at the Stanford Linear Accelerator Center (SLAC) and for conducting a program of graduate and undergraduate education in experimental high energy nuclear physics. This work has as a common thread the use of high energy (sometimes polarized) electrons and gamma rays to probe matter. A major area of work will be the data runs, analysis, and publications for SLAC Experiment E158 that will use the SLAC high intensity polarized electron beam and a new dedicated spectrometer and detector system to measure parity violating asymmetry in electron-electron scattering. This high precision data will provide important tests of the Standard Model of matter at low momentum transfer in the electromagnetic coupling via the interference between exchange of virtual photons and Z bosons. The UMass Group has contributed to the design of the spectrometer and beamline instrumentation, to the calibration systems, and to implementation of the data acquisition system. The UMass Group is taking a leading role in developing a new high intensity, high energy quasi-monoenergic polarized photon beam facility to be build at SLAC for a program of experiments: 1) to measure the high energy contribution to the Gerasimov-Drell-Hearn sum rule 2) to measure the nuclear dependence of the photoproduction of charmed mesons and 3) to measure the gluon spin distribution using polarized photoproduction of charmed mesons.