Measurement of muon annual modulation and muon-induced phosphorescence in NaI(Tl) crystals with DM-Ice17

J. Cherwinka, D. Grant, F. Halzen, K. M. Heeger, L. Hsu, A. J. F. Hubbard, A. Karle, M. Kauer, V. A. Kudryavtsev, K. E. Lim, C. Macdonald, R. H. Maruyama, S. M. Paling, W. Pettus, Z. P. Pierpoint, B. N. Reilly, M. Robinson, P. Sandstrom, N. J. C. Spooner, S. Telfer, and L. Yang (DM-Ice Collaboration)

Phys. Rev. D 93, 042001 – Published 1 February 2016

Abstract

We report the measurement of muons and muon-induced phosphorescence in DM-Ice17, a NaI(Tl) direct detection dark matter experiment at the South Pole. Muon interactions in the crystal are identified by their observed pulse shape and large energy depositions. The measured muon rate in DM-Ice17 is $2.93 \pm 0.04 μ / crystal / day$ with a modulation amplitude of $12.3 \pm 1.7 %$ , consistent with expectation. Following muon interactions, we observe long-lived phosphorescence in the NaI(Tl) crystals with a decay time of $5.5 \pm 0.5 s$ . The prompt energy deposited by a muon is correlated to the amount of delayed phosphorescence, the brightest of which consist of tens of millions of photons. These photons are distributed over tens of seconds with a rate and arrival timing that do not mimic a scintillation signal above $2 {keV}_{ee}$ . While the properties of phosphorescence vary among individual crystals, the annually modulating signal observed by DAMA cannot be accounted for by phosphorescence with the characteristics observed in DM-Ice17.

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Received 16 October 2015

DOI:https://doi.org/10.1103/PhysRevD.93.042001

Physics Subject Headings (PhySH)

Muons

Cosmic ray & astroparticle detectors Dark matter detectors

Particles & FieldsAccelerators & Beams

Authors & Affiliations

J. Cherwinka¹, D. Grant², F. Halzen³, K. M. Heeger⁴, L. Hsu⁵, A. J. F. Hubbard^3,4,*, A. Karle³, M. Kauer^3,4, V. A. Kudryavtsev⁶, K. E. Lim⁴, C. Macdonald⁶, R. H. Maruyama^4,†, S. M. Paling⁷, W. Pettus^3,4, Z. P. Pierpoint^3,4,‡, B. N. Reilly^3,4, M. Robinson⁶, P. Sandstrom³, N. J. C. Spooner⁶, S. Telfer⁶, and L. Yang⁸ (DM-Ice Collaboration)

¹Physical Sciences Laboratory, University of Wisconsin-Madison, Stoughton, Wisconsin 53589, USA
²Department of Physics, University of Alberta, Edmonton, Alberta T6G 2E1, Canada
³Department of Physics and Wisconsin IceCube Particle Astrophysics Center, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
⁴Department of Physics, Yale University, New Haven, Connecticut 06520, USA
⁵Fermi National Accelerator Laboratory, Batavia, Illinois 60510, USA
⁶Department of Physics and Astronomy, University of Sheffield, Sheffield S10 2TN, United Kingdom
⁷STFC Boulby Underground Science Facility, Boulby Mine, Cleveland TS13 4UZ, United Kingdom
⁸Department of Physics, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA

^*Corresponding author. antonia.hubbard@northwestern.edu Present address: Department of Physics and Astronomy, Northwestern University, Evanston, Illinois 60208, USA.
^†Corresponding author. reina.maruyama@yale.edu
^‡Present address: Department of Physics and Astronomy, University of Wisconsin-Fox Valley, Menasha, Wisconsin 54952, USA.

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Vol. 93, Iss. 4 — 15 February 2016

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