Undergraduate Research at Jefferson Lab

A Scintillating Fiber Detector for use in the A' Experiment

Student: Robert M. Karl, Jr.

School: Rochester Institute of Technology

Mentored By: Bogdan Wojtsekhowski

The A' boson is a hypothesized extension to the Standard Model. The A' is thought to have a weak coupling to the photon allowing the production of the A' in a process analogous to bremsstrahlung radiation. Once produced, the A' can decay into e⁺e^- pairs. The A' Experiment (APEX) is designed to measure the invariant mass of these e⁺e^- pairs to search for the A' within the mass range of 65 MeV ≲ m_A' ≲ 525 MeV and with a coupling strength of α' ≳ 9 × 10^-8α (α = e²/4π). To measure the invariant mass, the momenta and separation angle of the e⁺e^- pairs will be measured using the High Resolution Spectrometer (HRS) in Hall A of the Thomas Jefferson National Accelerator Facility (TJNAF). Precision in the measurement of the angle is the limiting factor on the mass resolution. This is limited by the current calibration method. In order to better calibrate the HRS, a Scintillating Fiber (SciFi) detector will be used. The purpose of this study is to develop and test the data acquisition (DAQ) system for the SciFi detector. The DAQ systemshows a plateau in efficiency, with probability of crosstalk at most 20% of that. The SciFi detector will be used in the full APEX run (projected 2016). If successful, the SciFi detector will revolutionize HRS optics calibration and be used in many other HRS experiments.