884 research outputs found
DAMA annual modulation effect and asymmetric mirror matter
The long-standing model-independent annual modulation effect measured by DAMA
Collaboration is examined in the context of asymmetric mirror dark matter,
assuming that dark atoms interact with target nuclei in the detector via
kinetic mixing between mirror and ordinary photons, both being massless. The
relevant ranges for the kinetic mixing parameter are obtained taking into
account various existing uncertainties in nuclear and particle physics
quantities as well as characteristic density and velocity distributions of dark
matter in different halo models.Comment: 27 pages, 5 figures, 2 tables; version in publication on Eur. Phys.
J.
Observations of annual modulation in direct detection of relic particles and light neutralinos
The long-standing model-independent annual modulation effect measured by the
DAMA Collaboration, which fulfills all the requirements of a dark matter annual
modulation signature, and the new result by the CoGeNT experiment that shows a
similar behavior are comparatively examined under the hypothesis of a dark
matter candidate particle interacting with the detectors' nuclei by a coherent
elastic process. The ensuing physical regions in the plane of the dark
matter-particle mass versus the dark matter-particle nucleon cross-section are
derived for various galactic halo models and by taking into account the impact
of various experimental uncertainties. It is shown that the DAMA and the CoGeNT
regions agree well between each other and are well fitted by a supersymmetric
model with light neutralinos which satisfies all available experimental
constraints, including the most recent results from CMS and ATLAS at the CERN
Large Hadron Collider.Comment: 13 pages, 7 figure
Preliminary study of feasibility of an experiment looking for excited state double beta transitions in tin
An attempt to study the feasibility of a new experiment to search for double
beta decay in Sn and Sn was carried out by using ultra-low
background HPGe detector (244 cm) inside the Gran Sasso National
Laboratory (LNGS) of the INFN (Italy). A small sample of natural Sn was
examined for 2367.5 h. The radioactive contamination of the sample has been
estimated. The data has also been considered to calculate the present
sensitivity for the proposed search; half-life limits years for EC and EC-EC processes in Sn and
years for transition in Sn were
measured. In the last section of the paper the enhancement of the sensitivity
for a proposed experiment with larger mass to reach theoretically estimated
values of half-lives is discussed.Comment: 20 pages, 11 figures, 4 tables, accepted for publication in NIMA (in
press
DAMA/NaI results
The DAMA/NaI set-up of the DAMA experiment has been operative during seven
annual cycles and has investigated several rare processes. In particular, it
has been realised in order to investigate the model independent annual
modulation signature for Dark Matter particles in the galactic halo. With the
total exposure collected in the seven annual cycles (107731 kg day) a model
independent evidence for the presence of a Dark Matter particle component in
the galactic halo has been pointed out at 6.3 sigma C.L.. Some of the many
possible corollary model dependent quests for the candidate particle have been
presented as well.Comment: Contributed paper to the Rencontres de Moriond "Electroweak
Interactions and Unified Theories", La Thuile, Aosta Valley, Italy, March
200
Final results of an experiment to search for 2beta processes in zinc and tungsten with the help of radiopure ZnWO4 crystal scintillators
A search for the double beta decay of zinc and tungsten isotopes has been
performed with the help of radiopure ZnWO4 crystal scintillators (0.1-0.7 kg)
at the Gran Sasso National Laboratories of the INFN. The total exposure of the
low background measurements is 0.529 kg yr. New improved half-life limits on
the double beta decay modes of 64Zn, 70Zn, 180W, and 186W have been established
at the level of 10^{18}-10^{21} yr. In particular, limits on double electron
capture and electron capture with positron emission in 64Zn have been set:
T_{1/2}(2\nu 2K) > 1.1 10^{19} yr, T_{1/2} (0\nu 2\epsilon) > 3.2 10^{20} yr,
T_{1/2} (2\nu \epsilon \beta^+) > 9.4 10^{20} yr, and T_{1/2} (0\nu \epsilon
\beta^+) > 8.5 10^{20} yr, all at 90% C.L. Resonant neutrinoless double
electron capture in 180W has been restricted on the level of T_{1/2} (0\nu
2\epsilon) > 1.3 10^{18} yr. A new half-life limit on alpha transition of 183W
to the metastable excited level 1/2^- 375 keV of 179Hf has been established:
T_{1/2} > 6.7 10^{20} yr.Comment: This is an author-created, un-copyedited version of an article
published in J. Phys. G: Nucl. Part. Phys. IOP Publishing Ltd is not
responsible for any errors or omissions in this version of the manuscript or
any version derived from it. The definitive publisher authenticated version
is available online at doi: 10.1088/0954-3899/38/11/11510
Investigation of rare nuclear decays with BaF crystal scintillator contaminated by radium
The radioactive contamination of a BaF scintillation crystal with mass of
1.714 kg was measured over 101 hours in the low-background DAMA/R&D set-up deep
underground (3600 m w.e.) at the Gran Sasso National Laboratories of INFN
(LNGS, Italy). The half-life of Po (present in the crystal scintillator
due to contamination by radium) was measured as Po) =
298.80.8(stat.)1.4(syst.) ns by analysis of the events' pulse
profiles. The Rn nuclide is known as 100% decaying via emission of
particle with = 3.82 d; however, its decay is also
energetically allowed with keV. Search for decay chains of
events with specific pulse shapes characteristic for or for
signals and with known energies and time differences allowed us
to set, for the first time, the limit on the branching ratio of Rn
relatively to decay as % at 90% C.L. (equivalent to
limit on partial half-life y). Half-life limits of
Pb, Rn and Ra relatively to decays are also
improved in comparison with the earlier results.Comment: 10 pages, 9 figures, 2 table
DAMA annual modulation and mirror Dark Matter
The DAMA experiment using ultra low background NaI(Tl) crystal scintillators has measured an annual modulation effect in the keV region which satisfies all the peculiarities of an effect induced by Dark Matter particles. In this paper we analyze this annual modulation effect in terms of mirror Dark Matter, an exact duplicate of ordinary matter from parallel hidden sector, which chemical composition is dominated by mirror helium while it can also contain significant fractions of heavier elements as Carbon and Oxygen. Dark mirror atoms are considered to interact with the target nuclei in the detector via Rutherford-like scattering induced by kinetic mixing between mirror and ordinary photons, both being massless. In the present analysis we consider various possible scenarios for the mirror matter chemical composition. For all the scenarios, the relevant ranges for the kinetic mixing parameter have been obtained taking also into account various existing uncertainties in nuclear and particle physics quantities
First search for double-beta decay of 184Os and 192Os
A search for double-beta decay of osmium has been realized for the first time
with the help of an ultra-low background HPGe gamma detector at the underground
Gran Sasso National Laboratories of the INFN (Italy). After 2741 h of data
taking with a 173 g ultra-pure osmium sample limits on double-beta processes in
184Os have been established at the level of T_{1/2} about 10^{14}-10^{17} yr.
Possible resonant double-electron captures in 184Os were searched for with a
sensitivity T_{1/2} about 10^{16} yr. A half-life limit T_{1/2} > 5.3 10^{19}
yr was set for the double-beta decay of 192Os to the first excited level of
192Pt. The radiopurity of the osmium sample has been investigated and
radionuclides 137Cs, 185Os and 207Bi were detected in the sample, while
activities of 40K, 60Co, 226Ra and 232Th were limited at the mBq/kg level.Comment: 12 pages, 7 figures, 2 table
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