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Title: Direct WIMP detection in directional experiments

Abstract

The recent WMAP data have confirmed that exotic dark matter together with the vacuum energy (cosmological constant) dominate in the flat Universe. Thus the direct dark matter search, consisting of detecting the recoiling nucleus, is central to particle physics and cosmology. Modern particle theories naturally provide viable cold dark matter candidates with masses in the GeV-TeV region. Supersymmetry provides the lightest supersymmetric particle (LSP), theories in extra dimensions the lightest Kaluza-Klein particle (LKP) etc. Unfortunately, however, in nuclear recoil measurements the interesting signal cannot be easily distinguished from the background. So, to minimize the background problems, one should exploit characteristic signatures of the reaction, such as the modulation effect and, in directional experiments, the correlation of the event rates with the sun's motion. In standard nondirectional experiments the modulation is small, less than two per cent and the location of the maximum depends on the unknown particle's mass. In directional experiments, in addition to the forward-backward asymmetry due to the sun's motion, one expects a larger modulation, which depends on the direction of observation. We study such effects both in the case of a light and a heavy target. Furthermore, since it now appears that the planned experiments may bemore » only partly directional, in the sense that they can only detect the line of the recoiling nucleus, but not the sense of direction on it, we study which of the above mentioned interesting features, if any, will persist in these less ambitious experiments.« less

Authors:
 [1];  [2];  [3]
  1. Theoretical Physics Division, University of Ioannina, Ioannina, Gr 451 10 (Greece)
  2. (Germany)
  3. Institute of Theoretical Physics, University of Tuebingen, Tuebingen (Germany)
Publication Date:
OSTI Identifier:
21020092
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review. D, Particles Fields; Journal Volume: 75; Journal Issue: 5; Other Information: DOI: 10.1103/PhysRevD.75.055007; (c) 2007 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; ASYMMETRY; CORRELATIONS; COSMOLOGICAL CONSTANT; COSMOLOGY; GEV RANGE; KALUZA-KLEIN THEORY; MODULATION; NONLUMINOUS MATTER; PARTICLE IDENTIFICATION; SPARTICLES; SUPERSYMMETRY; TEV RANGE; UNIVERSE

Citation Formats

Vergados, J. D., Institute of Theoretical Physics, University of Tuebingen, Tuebingen, and Faessler, Amand. Direct WIMP detection in directional experiments. United States: N. p., 2007. Web. doi:10.1103/PHYSREVD.75.055007.
Vergados, J. D., Institute of Theoretical Physics, University of Tuebingen, Tuebingen, & Faessler, Amand. Direct WIMP detection in directional experiments. United States. doi:10.1103/PHYSREVD.75.055007.
Vergados, J. D., Institute of Theoretical Physics, University of Tuebingen, Tuebingen, and Faessler, Amand. Thu . "Direct WIMP detection in directional experiments". United States. doi:10.1103/PHYSREVD.75.055007.
@article{osti_21020092,
title = {Direct WIMP detection in directional experiments},
author = {Vergados, J. D. and Institute of Theoretical Physics, University of Tuebingen, Tuebingen and Faessler, Amand},
abstractNote = {The recent WMAP data have confirmed that exotic dark matter together with the vacuum energy (cosmological constant) dominate in the flat Universe. Thus the direct dark matter search, consisting of detecting the recoiling nucleus, is central to particle physics and cosmology. Modern particle theories naturally provide viable cold dark matter candidates with masses in the GeV-TeV region. Supersymmetry provides the lightest supersymmetric particle (LSP), theories in extra dimensions the lightest Kaluza-Klein particle (LKP) etc. Unfortunately, however, in nuclear recoil measurements the interesting signal cannot be easily distinguished from the background. So, to minimize the background problems, one should exploit characteristic signatures of the reaction, such as the modulation effect and, in directional experiments, the correlation of the event rates with the sun's motion. In standard nondirectional experiments the modulation is small, less than two per cent and the location of the maximum depends on the unknown particle's mass. In directional experiments, in addition to the forward-backward asymmetry due to the sun's motion, one expects a larger modulation, which depends on the direction of observation. We study such effects both in the case of a light and a heavy target. Furthermore, since it now appears that the planned experiments may be only partly directional, in the sense that they can only detect the line of the recoiling nucleus, but not the sense of direction on it, we study which of the above mentioned interesting features, if any, will persist in these less ambitious experiments.},
doi = {10.1103/PHYSREVD.75.055007},
journal = {Physical Review. D, Particles Fields},
number = 5,
volume = 75,
place = {United States},
year = {Thu Mar 01 00:00:00 EST 2007},
month = {Thu Mar 01 00:00:00 EST 2007}
}
  • New techniques for the laboratory direct detection of dark matter weakly interacting massive particles (WIMPs) are sensitive to the recoil direction of the struck nuclei. We compute and compare the directional recoil rates dR/dcos{theta} (where {theta} is the angle measured from a reference direction in the sky) for several WIMP velocity distributions including the standard dark halo and anisotropic models such as Sikivie's late-infall halo model and logarithmic-ellipsoidal models. Since some detectors may be unable to distinguish the beginning of the recoil track from its end (lack of head-tail discrimination), we introduce a folded directional recoil rate dR/d|cos{theta}|, where |cos{theta}|more » does not distinguish the head from the tail of the track. We compute the CS{sub 2} and CF{sub 4} exposures required to distinguish a signal from an isotropic background noise, and find that dR/d|cos{theta}| is effective for the standard dark halo and some but not all anisotropic models.« less
  • In the earlier work on the development of a model-independent data analysis method for determining the mass of Weakly Interacting Massive Particles (WIMPs) by using measured recoil energies from direct Dark Matter detection experiments directly, it was assumed that the analyzed data sets are background-free, i.e., all events are WIMP signals. In this article, as a more realistic study, we take into account a fraction of possible residue background events, which pass all discrimination criteria and then mix with other real WIMP-induced events in our data sets. Our simulations show that, for the determination of the WIMP mass, the maximalmore » acceptable fraction of residue background events in the analyzed data sets of O(50) total events is ∼ 20%, for background windows of the entire experimental possible energy ranges, or in low energy ranges; while, for background windows in relatively higher energy ranges, this maximal acceptable fraction of residue background events can not be larger than ∼ 10%. For a WIMP mass of 100 GeV with 20% background events in the windows of the entire experimental possible energy ranges, the reconstructed WIMP mass and the 1σ statistical uncertainty are ∼ 97GeV{sup +61%}{sub −35%} ( ∼ 94GeV{sup +55%}{sub −33%} for background-free data sets)« less
  • We present a new method for determining Weakly Interacting Massive Particle (WIMP) properties in future tonne scale direct detection experiments which accounts for uncertainties in the Milky Way (MW) smooth dark matter distribution. Using synthetic data on the kinematics of MW halo stars matching present samples from the Sloan Digital Sky Survey, complemented by local escape velocity constraints, we demonstrate that the local dark matter density can be constrained to ∼ 20% accuracy. For low mass WIMPs, we find that a factor of two error in the assumed local dark matter density leads to a severely biased reconstruction of themore » WIMP spin-independent cross section that is incorrect at the 15σ level. We show that this bias may be overcome by marginalizing over parameters that describe the MW potential, and use this formalism to project the accuracy attainable on WIMP properties in future 1 ton Xenon detectors. Our method can be readily applied to different detector technologies and extended to more detailed MW halo models.« less
  • Cited by 15
  • The direction dependence of the event rate in WIMP direct detection experiments provides a powerful tool for distinguishing WIMP events from potential backgrounds. We use a variety of (nonparametric) statistical tests to examine the number of events required to distinguish a WIMP signal from an isotropic background when the uncertainty in the reconstruction of the nuclear recoil direction is included in the calculation of the expected signal. We consider a range of models for the Milky Way halo, and also study rotational symmetry tests aimed at detecting nonsphericity/isotropy of the Milky Way halo. Finally we examine ways of detecting tidalmore » streams of WIMPs. We find that if the senses of the recoils are known then of order ten events will be sufficient to distinguish a WIMP signal from an isotropic background for all of the halo models considered, with the uncertainties in reconstructing the recoil direction only mildly increasing the required number of events. If the senses of the recoils are not known the number of events required is an order of magnitude larger, with a large variation between halo models, and the recoil resolution is now an important factor. The rotational symmetry tests require of order a thousand events to distinguish between spherical and significantly triaxial halos, however a deviation of the peak recoil direction from the direction of the solar motion due to a tidal stream could be detected with of order a hundred events, regardless of whether the sense of the recoils is known.« less