177 research outputs found
Channeling Effects in Direct Dark Matter Detectors
The channeling of the ion recoiling after a collision with a WIMP changes the
ionization signal in direct detection experiments, producing a larger signal
than otherwise expected. We give estimates of the fraction of channeled
recoiling ions in NaI (Tl), Si and Ge crystals using analytic models produced
since the 1960's and 70's to describe channeling and blocking effects. We find
that the channeling fraction of recoiling lattice nuclei is smaller than that
of ions that are injected into the crystal and that it is strongly temperature
dependent.Comment: 8 pages, 12 figures, To appear in the Proceedings of the sixth
International Workshop on the Dark Side of the Universe (DSU2010) Leon,
Guanajuato, Mexico 1-6 June 201
Channeling in direct dark matter detection I: channeling fraction in NaI (Tl) crystals
The channeling of the ion recoiling after a collision with a WIMP changes the
ionization signal in direct detection experiments, producing a larger signal
than otherwise expected. We give estimates of the fraction of channeled
recoiling ions in NaI (Tl) crystals using analytic models produced since the
1960's and 70's to describe channeling and blocking effects. We find that the
channeling fraction of recoiling lattice nuclei is smaller than that of ions
that are injected into the crystal and that it is strongly temperature
dependent.Comment: 37 pages, 35 figures, Accepted for publication in JCAP on 27 October
2010, Minor revisions: added an appendix, updated references, updated Fig. 9,
corrected a few typo
Recoiling Ion-Channeling in Direct Dark Matter Detectors
The channeling of the recoiling nucleus in crystalline detectors after a WIMP
collision would produce a larger scintillation or ionization signal in direct
detection experiments than otherwise expected. I present estimates of
channeling fractions obtained using analytic models developed from the 1960's
onwards to describe channeling and blocking effects. We find the fractions to
be too small to affect the fits to potential WIMP candidates. I also examine
the possibility of detecting a daily modulation of the dark matter signal due
to channeling.Comment: Talk presented at the DSU 2011 Conference, KITPC, Beijing, China,
Sept 26-30, 2011. 8 pages, 14 figures, jpconf.cls and jpconf11.clo necessary
to typese
Transient thermal effects in solid noble gases as materials for the detection of Dark Matter
The transient phenomena produced in solid noble gases by the stopping of the
recoils resulting from the elastic scattering processes of WIMPs from the
galactic halo were modelled, as dependencies of the temperatures of lattice and
electronic subsystems on the distance to the recoil's trajectory, and time from
its passage. The peculiarities of these thermal transients produced in Ar, Kr
and Xe were analysed for different initial temperatures and WIMP energies, and
were correlated with the characteristics of the targets and with the energy
loss of the recoils. The results were compared with the thermal spikes produced
by the same WIMPs in Si and Ge. In the range of the energy of interest, up to
tens of keV for the self-recoil, local phase transitions solid - liquid and
even liquid - gas were found possible, and the threshold parameters were
established.Comment: Minor corrections and updated references; accepted to JCA
Halo independent comparison of direct dark matter detection data
We extend the halo-independent method of Fox, Liu, and Weiner to include
energy resolution and efficiency with arbitrary energy dependence, making it
more suitable for experiments to use in presenting their results. Then we
compare measurements and upper limits on the direct detection of low mass
( GeV) weakly interacting massive particles with spin-independent
interactions, including the upper limit on the annual modulation amplitude from
the CDMS collaboration. We find that isospin-symmetric couplings are severely
constrained both by XENON100 and CDMS bounds, and that isospin-violating
couplings are still possible at the lowest energies, while the tension of the
higher energy CoGeNT bins with the CDMS modulation constraint remains. We find
the CRESST II signal is not compatible with the modulation signals of DAMA and
CoGeNT.Comment: version slightly longer than the first, with 3 additional figures and
the latest XENON100 bound added. 7 pages, 5 figure
Relevance of Ion-Channeling for Direct DM Detection
The channeling of the recoiling nucleus in crystalline detectors after a WIMP
collision would produce a larger scintillation or ionization signal in direct
detection experiments than otherwise expected. I present estimates of the
importance of this effect for the total direct detection rate and the daily
modulation of the signal using analytic models produced in the 1960's and 70's
to describe the effects of channeling and blocking in crystals.Comment: Talk given at the TAUP 2009 conference, Rome, Italy, July 1-5 2009. 3
pages, 4 figures. jpconf.cls and jpconf11.clo files need to typeset the tex
fil
Exploring nu signals in dark matter detectors
We investigate standard and non-standard solar neutrino signals in direct
dark matter detection experiments. It is well known that even without new
physics, scattering of solar neutrinos on nuclei or electrons is an irreducible
background for direct dark matter searches, once these experiments each the ton
scale. Here, we entertain the possibility that neutrino interactions are
enhanced by new physics, such as new light force carriers (for instance a "dark
photon") or neutrino magnetic moments. We consider models with only the three
standard neutrino flavors, as well as scenarios with extra sterile neutrinos.
We find that low-energy neutrino--electron and neutrino--nucleus scattering
rates can be enhanced by several orders of magnitude, potentially enough to
explain the event excesses observed in CoGeNT and CRESST. We also investigate
temporal modulation in these neutrino signals, which can arise from geometric
effects, oscillation physics, non-standard neutrino energy loss, and
direction-dependent detection efficiencies. We emphasize that, in addition to
providing potential explanations for existing signals, models featuring new
physics in the neutrino sector can also be very relevant to future dark matter
searches, where, on the one hand, they can be probed and constrained, but on
the other hand, their signatures could also be confused with dark matter
signals.Comment: 38 pages, 8 figures, 1 table; v3: eq 3 and nuclear recoil plots
corrected, footnote added, conclusions unchange
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