Liquid xenon scintillation measurements and pulse shape discrimination in the LUX dark matter detector

• Published in: Physical review. D 2018-06, Vol.97 (11), Article 112002
• Main Authors: Akerib, D. S., Alsum, S., Araújo, H. M., Bai, X., Bailey, A. J., Balajthy, J., Beltrame, P., Bernard, E. P., Bernstein, A., Biesiadzinski, T. P., Boulton, E. M., Brás, P., Byram, D., Carmona-Benitez, M. C., Chan, C., Currie, A., Cutter, J. E., Davison, T. J. R., Dobi, A., Druszkiewicz, E., Edwards, B. N., Fallon, S. R., Fan, A., Fiorucci, S., Gaitskell, R. J., Genovesi, J., Ghag, C., Gilchriese, M. G. D., Hall, C. R., Haselschwardt, S. J., Hertel, S. A., Hogan, D. P., Horn, M., Huang, D. Q., Ignarra, C. M., Jacobsen, R. G., Ji, W., Kamdin, K., Kazkaz, K., Khaitan, D., Knoche, R., Lenardo, B. G., Lesko, K. T., Liao, J., Lindote, A., Lopes, M. I., Manalaysay, A., Mannino, R. L., Marzioni, M. F., McKinsey, D. N., Mei, D.-M., Mock, J., Moongweluwan, M., Morad, J. A., Murphy, A. St. J., Nehrkorn, C., Nelson, H. N., Neves, F., O’Sullivan, K., Oliver-Mallory, K. C., Palladino, K. J., Pease, E. K., Rhyne, C., Shaw, S., Shutt, T. A., Silva, C., Solmaz, M., Solovov, V. N., Sorensen, P., Sumner, T. J., Szydagis, M., Taylor, D. J., Taylor, W. C., Tennyson, B. P., Terman, P. A., Tiedt, D. R., To, W. H., Tripathi, M., Tvrznikova, L., Utku, U., Uvarov, S., Velan, V., Verbus, J. R., Webb, R. C., White, J. T., Whitis, T. J., Witherell, M. S., Wolfs, F. L. H., Xu, J., Yazdani, K., Young, S. K., Zhang, C.
• Format: Article
• Language: English
• Subjects: ASTRONOMY AND ASTROPHYSICS; Calibration; Dark matter; Discrimination; INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY; NUCLEAR PHYSICS AND RADIATION PHYSICS; Photons; PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; Pulse shape; Recoil; Scintillation; Time measurement; Weakly interacting massive particles; Xenon
• ISSN: 2470-0010; 2470-0029
• DOI: 10.1103/PhysRevD.97.112002

Weakly interacting massive particles (WIMPs) are a leading candidate for dark matter and are expected to produce nuclear recoil (NR) events within liquid xenon time-projection chambers. We present a measurement of the scintillation timing characteristics of liquid xenon in the LUX dark matter detector and develop a pulse shape discriminant to be used for particle identification. To accurately measure the timing characteristics, we develop a template-fitting method to reconstruct the detection times of photons. Analyzing calibration data collected during the 2013–2016 LUX WIMP search, we provide a new measurement of the singlet-to-triplet scintillation ratio for electron recoils (ER) below 46 keV, and we make, to our knowledge, a first-ever measurement of the NR singlet-to-triplet ratio at recoil energies below 74 keV. We exploit the difference of the photon time spectra for NR and ER events by using a prompt fraction discrimination parameter, which is optimized using calibration data to have the least number of ER events that occur in a 50% NR acceptance region. We then demonstrate how this discriminant can be used in conjunction with the charge-to-light discrimination to possibly improve the signal-to-noise ratio for nuclear recoils.