The Heavy Photon Search Test Detector
Abstract
The Heavy Photon Search (HPS), an experiment to search for a hidden sector photon in fixed target electroproduction, is preparing for installation at the Thomas Jefferson National Accelerator Facility (JLab) in the Fall of 2014. As the first stage of this project, the HPS Test Run apparatus was constructed and operated in 2012 to demonstrate the experiment's technical feasibility and to confirm that the trigger rates and occupancies are as expected. This paper describes the HPS Test Run apparatus and readout electronics and its performance. In this setting, a heavy photon can be identified as a narrow peak in the ee invariant mass spectrum, above the trident background or as a narrow invariant mass peak with a decay vertex displaced from the production target, so charged particle tracking and vertexing are needed for its detection. In the HPS Test Run, charged particles are measured with a compact forward silicon microstrip tracker inside a dipole magnet. Electromagnetic showers are detected in a PbW0 crystal calorimeter situated behind the magnet, and are used to trigger the experiment and identify electrons and positrons. Both detectors are placed close to the beam line and split top-bottom. This arrangement provides sensitivity to low-mass heavy photons, allows clear passage of the unscattered beam, and avoids the spray of degraded electrons coming from the target. The discrimination between prompt and displaced ee pairs requires the first layer of silicon sensors be placed only 10~cm downstream of the target. The expected signal is small, and the trident background huge, so the experiment requires very large statistics. Accordingly, the HPS Test Run utilizes high-rate readout and data acquisition electronics and a fast trigger to exploit the essentially 100% duty cycle of the CEBAF accelerator at JLab.
Cite
@article{arxiv.1406.6115,
title = {The Heavy Photon Search Test Detector},
author = {Marco Battaglieri and Sergey Boyarinov and Stephen Bueltmann and Volker Burkert and Andrea Celentano and Gabriel Charles and William Cooper and Chris Cuevas and Natalia Dashyan and Raffaella DeVita and Camille Desnault and Alexandre Deur and Hovanes Egiyan and Latifa Elouadrhiri and Rouven Essig and Vitaliy Fadeyev and Clive Field and Arne Freyberger and Yuri Gershtein and Nerses Gevorgyan and Francois-Xavier Girod and Norman Graf and Mathew Graham and Keith Griffioen and Alexander Grillo and Michel Guidal and Gunther Haller and Per Hansson Adrian and Ryan Herbst and Maurik Holtrop and John Jaros and Scott Kaneta and Mahbub Khandaker and Alexey Kubarovsky and Valery Kubarovsky and Takashi Maruyama and Jeremy McCormick and Ken Moffeit and Omar Moreno and Homer Neal and Timothy Nelson and Silvia Niccolai and Al Odian and Marco Oriunno and Rafayel Paremuzyan and Richard Partridge and Sarah Phillips and Emmanuel Rauly and Benjamin Raydo and Joseph Reichert and Emmanuel Rindel and Philippe Rosier and Carlos Salgado and Philip Schuster and Youri Sharabian and Daria Sokhan and Stepan Stepanyan and Natalia Toro and Sho Uemura and Maurizio Ungaro and Hakop Voskanyan and Dieter Walz and Larry Weinstein and Bogdan Wojtsekhowski},
journal= {arXiv preprint arXiv:1406.6115},
year = {2015}
}
Comments
Revised version to match published version, 16 pages, 18 figures, published in Nuclear Instruments and Methods in Physics Research Section A, editor: Per Hansson Adrian