Undergraduate Research at Jefferson Lab

A New Vertical Drift Chamber Algorithm for the APEX Experiment

Student: Seth Hall

School: Texas A&M University

Mentored By: Bogdan Wojsekhowski

The APEX experiment is a search for new <1 GeV-scale vector bosons, named the 'Dark Photon', which may mediate Standard-Model particle with dark matter. 2.2 GeV beam electrons from CEBAF interacted with a tungsten target, producing positron-electron pairs; some of which may be the direct result of a Dark Photon decay. In the twin High-Resolution Spectrometers used in APEX, the rate of tracks was as high as 2 MHz in the e-arm spectrometers. The software used to analyze this data, the Hall-A Analyzer, reconstructs tracks from VDC (Vertical Drift Chamber) clusters. It works well for track-rates up to 50-100 kHz, in which most events have one track. This is not the case for 2 MHz events with multiple tracks per event; when the Analyzer is fed APEX data, it is far too inefficient. This project outlines a new technique which uses S2m Scintillator hits to eliminate the extra VDC-clusters, thereby allowing the Hall-A Analyzer to efficiently reconstruct only those tracks necessary for APEX's analysis.