1,153 research outputs found
New results from DAMA/LIBRA
DAMA/LIBRA is running at the Gran Sasso National Laboratory of the I.N.F.N..
Here the results obtained with a further exposure of 0.34 ton x yr are
presented. They refer to two further annual cycles collected one before and one
after the first DAMA/LIBRA upgrade occurred on September/October 2008. The
cumulative exposure with those previously released by the former DAMA/NaI and
by DAMA/LIBRA is now 1.17 ton x yr, corresponding to 13 annual cycles. The data
further confirm the model independent evidence of the presence of Dark Matter
(DM) particles in the galactic halo on the basis of the DM annual modulation
signature (8.9 sigma C.L. for the cumulative exposure). In particular, with the
cumulative exposure the modulation amplitude of the single-hit events in the (2
-- 6) keV energy interval measured in NaI(Tl) target is (0.0116 +- 0.0013)
cpd/kg/keV; the measured phase is (146 +- 7) days and the measured period is
(0.999 +- 0.002) yr, values well in agreement with those expected for the DM
particles.Comment: presented at the Int. Conf. Beyond the Standard Models of Particle
Physics, Cosmology and Astrophysics (BEYOND 2010), 1-6 February 2010, Cape
Town, South Afric
Technical aspects in dark matter investigations
Some theoretical and experimental aspects regarding the direct dark matter
field are mentioned. In particular some arguments, which play a relevant role
in the evaluation of model dependent interpretations of experimental results
and in comparisons, are shortly addressed.Comment: Proceedings of TAUP 2011 Conferenc
A comprehensive analysis of the dark matter direct detection experiments in the mirror dark matter framework
Mirror dark matter offers a framework to explain the existing dark matter
direct detection experiments. Here we confront this theory with the most recent
experimental data, paying attention to the various known systematic
uncertainties, in quenching factor, detector resolution, galactic rotational
velocity and velocity dispersion. We perform a detailed analysis of the DAMA
and CoGeNT experiments assuming a negligible channeling fraction and find that
the data can be fully explained within the mirror dark matter framework. We
also show that the mirror dark matter candidate can explain recent data from
the CDMS/Ge, EdelweissII and CRESSTII experiments and we point out ways in
which the theory can be further tested in the near future.Comment: about 30 page
WIMPs search by scintillators: possible strategy for annual modulation search with large-mass highly-radiopure NaI(Tl)
The DAMA experiments are running deep underground in the Gran Sasso National
Laboratory. Several interesting results have been achieved so far. Here a
maximum likelihood method to search for the WIMP annual modulation signature is
discussed and applied to a set of preliminary test data collected with large
mass highly radiopure NaI(Tl) detectors. Various related technical arguments
are briefly addressed.Comment: 6 pages, 4 figures, LaTex. Contributed paper to TAUP97; to appear in
the Proceeding
Possible implications of the channeling effect in NaI(Tl) crystals
The channeling effect of low energy ions along the crystallographic axes and
planes of NaI(Tl) crystals is discussed in the framework of corollary
investigations on WIMP Dark Matter candidates. In fact, the modeling of this
existing effect implies a more complex evaluation of the luminosity yield for
low energy recoiling Na and I ions. In the present paper related
phenomenological arguments are developed and possible implications are
discussed at some extent.Comment: 16 pages, 10 figures, preprint ROM2F/2007/15, submitted for
publicatio
Sensitivity plots for WIMP direct detection using the annual modulation signature
Annual modulation due to the Earth's motion around the Sun is a well known
signature of the expected WIMP signal induced in a solid state underground
detector. In the present letter we discuss the prospects of this technique on
statistical grounds, introducing annual-modulation sensitivity plots for the
WIMP-nucleon scalar cross section for different materials and experimental
conditions. The highest sensitivity to modulation is found in the WIMP mass
interval 10 GeV< m_W < 130 GeV, the actual upper limit depending from the
choice of the astrophysical parameters, while the lowest values of the
explorable WIMP-nucleon elastic cross-sections fall in most cases within one
order of magnitude of the sensitivities of present direct detection WIMP
searches.Comment: 24 pages, ReVTeX, 9 figures, submitted to Astroparticle Physic
The XENON100 exclusion limit without considering Leff as a nuisance parameter
In 2011, the XENON100 experiment has set unprecedented constraints on dark
matter-nucleon interactions, excluding dark matter candidates with masses down
to 6 GeV if the corresponding cross section is larger than 10^{-39} cm^2. The
dependence of the exclusion limit in terms of the scintillation efficiency
(Leff) has been debated at length. To overcome possible criticisms XENON100
performed an analysis in which Leff was considered as a nuisance parameter and
its uncertainties were profiled out by using a Gaussian likelihood in which the
mean value corresponds to the best fit Leff value smoothly extrapolated to zero
below 3 keVnr. Although such a method seems fairly robust, it does not account
for more extreme types of extrapolation nor does it enable to anticipate on how
much the exclusion limit would vary if new data were to support a flat
behaviour for Leff below 3 keVnr, for example. Yet, such a question is crucial
for light dark matter models which are close to the published XENON100 limit.
To answer this issue, we use a maximum Likelihood ratio analysis, as done by
the XENON100 collaboration, but do not consider Leff as a nuisance parameter.
Instead, Leff is obtained directly from the fits to the data. This enables us
to define frequentist confidence intervals by marginalising over Leff.Comment: 10 pages;, 9 figures; references adde
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