The ZEPLIN-III Anti-Coincidence Veto Detector
Abstract
The design, optimisation and construction of an anti-coincidence veto detector to complement the ZEPLIN-III direct dark matter search instrument is described. One tonne of plastic scintillator is arranged into 52 bars individually read out by photomultipliers and coupled to a gadolinium-loaded passive polypropylene shield. Particular attention has been paid to radiological content. The overall aim has been to achieve a veto detector of low threshold and high efficiency without the creation of additional background in ZEPLIN-III, all at a reasonable cost. Extensive experimental measurements of the components have been made, including radioactivity levels and performance characteristics. These have been used to inform a complete end-to-end Monte Carlo simulation that has then been used to calculate the expected performance of the new instrument, both operating alone and as an anti-coincidence detector for ZEPLIN-III. The veto device will be capable of rejecting over 65% of coincident nuclear recoil events from neutron background in the energy range of interest in ZEPLIN-III. This will reduce the background in ZEPLIN-III from ~0.4 to ~0.14 events per year in the WIMP acceptance region, a significant factor in the event of a non-zero observation. Furthermore, in addition to providing valuable diagnostic capabilities, the veto is capable of tagging over 15% for gamma-ray rejection, all whilst contributing no significant additional background. In conjunction with the replacement of the internal ZEPLIN-III photomultiplier array, the new veto is expected to improve significantly the sensitivity of the ZEPLIN-III instrument to dark matter, allowing spin independent WIMP-nucleon cross sections below 1E-8 pb to be probed.
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Cite
@article{arxiv.1004.4207,
title = {The ZEPLIN-III Anti-Coincidence Veto Detector},
author = {D. Yu. Akimov and H. M. Araujo and E. J. Barnes and V. A. Belov and A. A. Burenkov and V. Chepel and A. Currie and B. Edwards and V. Francis and C. Ghag and A. Hollingsworth and M. Horn and G. E. Kalmus and A. S. Kobyakin and A. G. Kovalenko and V. N. Lebedenko and A. Lindote and M. I. Lopes and R. Luscher and K. Lyons and P. Majewski and A. StJ. Murphy and F. Neves and S. M. Paling and J. Pinto da Cunha and R. Preece and J. J. Quenby and L. Reichhart and P. R. Scovell and V. N. Solovov and N. J. T. Smith and P. F. Smith and V. N. Stekhanov and T. J. Sumner and R. Taylor and C. Thorne and R. J. Walker},
journal= {arXiv preprint arXiv:1004.4207},
year = {2011}
}