Mentor Connection 2007

Compton Scattering

UConn Mentor Connection 2007 brought Matt Harrigan and Lee Hyun Seok to Storrs to work with Prof. Richard Jones in the Nuclear Physics Laboratory. For their project, they chose to study how to measure the polarization of high-energy electrons using a laser beam (Compton polarimetry). This technique will be used by the Qweak experiment at Jefferson Lab, which scatters polarized electrons from a proton target in order to measure the weak charge (Qweak) of the proton.

Energy of Compton-scattered photons in relation to the Compton scattering angle

As a part of their project, Matt and Lee studied how the weak force is described by the exchange of heavy bosons called W and Z particles, and how the weak nuclear force distinguishes between quarks and leptons of different helicity in a surprising physical effect called parity violation. As an introductory problem, they came up with a function to determine the energies of scattered photons in relation to the scattering angle. The graph of this function can be seen to the right. Their second task was to understand the setup of the device, which would include four concave mirrors to focus and direct the laser beam and a chicane so the scattered particles could be detected. The third problem Matt and Lee set out to solve was the effect of a mirrors edge on the reflected laser beam. Matt wrote a Java program designed to simulate a wave using Huygens' principle.

In the end, the two students had a firm understanding of how Compton scattering from a polarized laser beam could be used to measure the degree of polarization of the high-energy electron beam. At the research conference that concluded the three week Mentor Connection experience, they presented what they learned in the form of a poster and an oral presentation.