skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Examining the time dependence of DAMA’s modulation amplitude

Abstract

If dark matter is composed of weakly interacting particles, Earth’s orbital motion may induce a small annual variation in the rate at which these particles interact in a terrestrial detector. The DAMA collaboration has identified at a confidence level such an annual modulation in their event rate over two detector iterations, DAMA/NaI and DAMA/LIBRA, each with years of observations. This data is well fit by a constant modulation amplitude for the two iterations of the experiment. We statistically examine the time dependence of the modulation amplitudes, which “by eye” appear to be decreasing with time in certain energy ranges. We perform a chi-squared goodness of fit test of the average modulation amplitudes measured by the two detector iterations which rejects the hypothesis of a consistent modulation amplitude at greater than 80, 96, and 99.6% for the 2–4, 2–5 and 2–6 keVee energy ranges, respectively. We also find that among the 14 annual cycles there are three departures from the average in our estimated data in the 5–6 keVee energy range. In addition, we examined several phenomenological models for the time dependence of the modulation amplitude. Using a maximum likelihood test, we find that descriptions of the modulation amplitude as decreasingmore » with time are preferred over a constant modulation amplitude at anywhere between and , depending on the phenomenological model for the time dependence and the signal energy range considered. A time dependent modulation amplitude is not expected for a dark matter signal, at least for dark matter halo morphologies consistent with the DAMA signal. New data from DAMA/LIBRA–phase2 will certainly aid in determining whether any apparent time dependence is a real effect or a statistical fluctuation.« less

Authors:
 [1];  [2];  [3];  [4];  [3]
  1. Univ. of North Florida, Jacksonville, FL (United States)
  2. Univ. of Michigan, Ann Arbor, MI (United States); Univ. of Utah, Salt Lake City, UT (United States)
  3. Univ. of Utah, Salt Lake City, UT (United States)
  4. Univ. of Michigan, Ann Arbor, MI (United States)
Publication Date:
Research Org.:
Univ. of Michigan, Ann Arbor, MI (United States)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
1433270
Alternate Identifier(s):
OSTI ID: 1506463
Grant/Contract Number:  
SC0007859; SC007859
Resource Type:
Journal Article: Published Article
Journal Name:
European Physical Journal. C, Particles and Fields
Additional Journal Information:
Journal Volume: 78; Journal Issue: 3; Journal ID: ISSN 1434-6044
Publisher:
Springer
Country of Publication:
United States
Language:
English
Subject:
79 ASTRONOMY AND ASTROPHYSICS

Citation Formats

Kelso, Chris, Savage, Christopher, Sandick, Pearl, Freese, Katherine, and Gondolo, Paolo. Examining the time dependence of DAMA’s modulation amplitude. United States: N. p., 2018. Web. doi:10.1140/epjc/s10052-018-5685-4.
Kelso, Chris, Savage, Christopher, Sandick, Pearl, Freese, Katherine, & Gondolo, Paolo. Examining the time dependence of DAMA’s modulation amplitude. United States. doi:10.1140/epjc/s10052-018-5685-4.
Kelso, Chris, Savage, Christopher, Sandick, Pearl, Freese, Katherine, and Gondolo, Paolo. Fri . "Examining the time dependence of DAMA’s modulation amplitude". United States. doi:10.1140/epjc/s10052-018-5685-4.
@article{osti_1433270,
title = {Examining the time dependence of DAMA’s modulation amplitude},
author = {Kelso, Chris and Savage, Christopher and Sandick, Pearl and Freese, Katherine and Gondolo, Paolo},
abstractNote = {If dark matter is composed of weakly interacting particles, Earth’s orbital motion may induce a small annual variation in the rate at which these particles interact in a terrestrial detector. The DAMA collaboration has identified at a confidence level such an annual modulation in their event rate over two detector iterations, DAMA/NaI and DAMA/LIBRA, each with years of observations. This data is well fit by a constant modulation amplitude for the two iterations of the experiment. We statistically examine the time dependence of the modulation amplitudes, which “by eye” appear to be decreasing with time in certain energy ranges. We perform a chi-squared goodness of fit test of the average modulation amplitudes measured by the two detector iterations which rejects the hypothesis of a consistent modulation amplitude at greater than 80, 96, and 99.6% for the 2–4, 2–5 and 2–6 keVee energy ranges, respectively. We also find that among the 14 annual cycles there are three departures from the average in our estimated data in the 5–6 keVee energy range. In addition, we examined several phenomenological models for the time dependence of the modulation amplitude. Using a maximum likelihood test, we find that descriptions of the modulation amplitude as decreasing with time are preferred over a constant modulation amplitude at anywhere between and , depending on the phenomenological model for the time dependence and the signal energy range considered. A time dependent modulation amplitude is not expected for a dark matter signal, at least for dark matter halo morphologies consistent with the DAMA signal. New data from DAMA/LIBRA–phase2 will certainly aid in determining whether any apparent time dependence is a real effect or a statistical fluctuation.},
doi = {10.1140/epjc/s10052-018-5685-4},
journal = {European Physical Journal. C, Particles and Fields},
issn = {1434-6044},
number = 3,
volume = 78,
place = {United States},
year = {2018},
month = {3}
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record at 10.1140/epjc/s10052-018-5685-4

Citation Metrics:
Cited by: 1 work
Citation information provided by
Web of Science

Save / Share: