skip to main content


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

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±0.04 μ/crystal/day with a modulation amplitude of 12.3±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±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. Furthermore, 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.
 [1] ;  [2] ;  [3] ;  [4] ;  [5] ; ;  [3] ;  [6] ;  [7] ;  [4] ;  [7] ;  [4] ;  [8] ;  [6] ;  [6] ;  [6] ;  [7] ;  [3] ; ;  [7] more »;  [9] « less
  1. Univ. of Wisconsin-Madison, Stoughton, WI (United States)
  2. Univ. of Alberta, Edmonton, AB (Canada)
  3. Univ. of Wisconsin, Madison, WI (United States)
  4. Yale Univ., New Haven, CT (United States)
  5. Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States)
  6. Univ. of Wisconsin, Madison, WI (United States); Yale Univ., New Haven, CT (United States)
  7. Univ. of Sheffield, Sheffield (United Kingdom)
  8. STFC Boulby Underground Science Facility, Cleveland (United Kingdom)
  9. Univ. of Illinois at Urbana-Champaign, Urbana, IL (United States)
Publication Date:
Report Number(s):
FERMILAB-PUB-15-531-AE; arXiv:1509.02486
Journal ID: ISSN 2470-0010; PRVDAQ; 1392437
Grant/Contract Number:
AC02-07CH11359; FC52-08NA28752
Accepted Manuscript
Journal Name:
Physical Review D
Additional Journal Information:
Journal Volume: 93; Journal Issue: 4; Journal ID: ISSN 2470-0010
American Physical Society (APS)
Research Org:
Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States)
Sponsoring Org:
USDOE Office of Science (SC), High Energy Physics (HEP) (SC-25); USDOE National Nuclear Security Administration (NNSA)
Contributing Orgs:
Country of Publication:
United States
79 ASTRONOMY AND ASTROPHYSICS; 46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY; 72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; DM-Ice; sodium iodide; muons; phosphorescence; annual modulation; dark matter; direct detection; WIMP; South Pole; IceCube
OSTI Identifier:
Alternate Identifier(s):
OSTI ID: 1236545