236 research outputs found
The experimental challenge of detecting solar axion-like particles to test cosmological ALP-photon oscillation hypothesis
We consider possible experimental tests of recent hypotheses suggesting that
TeV photons survive the pair production interaction with extragalactic
background light over cosmological distances by converting to axion-like
particles (ALPs) in galactic magnetic fields. We show that proposed giant
ultra-low background scintillation detectors will even have a difficult time
reaching the present CAST sensitivity, which is one to two orders of magnitude
less sensitive than necessary for a meaningful test of the ALP-photon
oscillation hypothesis. Potential alternative tests are briefly discussed.Comment: 4 pages, no figure
Can large scintillators be used for solar-axion searches to test the cosmological axion-photon oscillation proposal?
Solar-axion interaction rates in NaI, CsI and Xe scintillators via the
axio-electric effect were calculated. A table is presented with photoelectric
and axioelectric cross sections, solar-axion fluxes, and the interaction rates
from 2.0 to 10.0 keV. The results imply that annual-modulation data of large
NaI and CsI arrays, and large Xe scintillation chambers, might be made
sensitive enough to probe coupling to photons at levels required to explain
axion-photon oscillation phenomena proposed to explain the survival of
high-energy photons traveling cosmological distances. The DAMAA/LIBRA data are
used to demonstrate the power of the model-independent annual modulation due to
the seasonal variation in the earth sun distance.Comment: 7 pages and no figure
Theory for the Direct Detection of Solar Axions by Coherent Primakoff Conversion in Germanium Detectors
It is assumed that axions exist and are created in the Sun by Primakoff
conversion of photons in the Coulomb fields of nuclei. Detection rates are
calculated in germanium detectors due to the coherent conversion of axions to
photons in the lattice when the incident angle fulfills the Bragg condition for
a given crystalline plane. The rates are correlated with the relative positions
of the Sun and detector, yielding a characteristic recognizable sub-diurnal
temporal pattern. A major experiment is proposed based on a large detector
array.Comment: gzipped postscript file from Microsoft Word, 8 pages. Figures can be
obtained by fax from [email protected]. Submitted to Phys. Lett.
Status of CUORE Experiment and latest results from CUORE-0
Neutrinoless Double Beta Decay (0νββ) is a rare nuclear transition that if it occurs at all it will be very important for the exploration of the inverted hierarchy region of the neutrino mass pattern. The Cryogenic Underground Observatory for Rare Events (CUORE) is an experiment that aims to search for such a transition in 130Te together with other rare processes. In the present paper we will describe the basic features of CUORE Experiment, the status of the experiment as well as the latest results obtained from CUORE-0 detector, a smaller scale experiment constructed to test and demonstrate the expected performances of CUOR
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
Pulse Shape Analysis with scintillating bolometers
Among the detectors used for rare event searches, such as neutrinoless Double
Beta Decay (0DBD) and Dark Matter experiments, bolometers are very
promising because of their favorable properties (excellent energy resolution,
high detector efficiency, a wide choice of different materials used as
absorber, ...). However, up to now, the actual interesting possibility to
identify the interacting particle, and thus to greatly reduce the background,
can be fulfilled only with a double read-out (i.e. the simultaneous and
independent read out of heat and scintillation light or heat and ionization).
This double read-out could greatly complicate the assembly of a huge,
multi-detector array, such as CUORE and EURECA. The possibility to recognize
the interacting particle through the shape of the thermal pulse is then clearly
a very interesting opportunity.
While detailed analyses of the signal time development in purely thermal
detectors have not produced so far interesting results, similar analyses on
macro-bolometers (10-500 g) built with scintillating crystals showed that
it is possible to distinguish between an electron or -ray and an
particle interaction (i.e. the main source of background for 0DBD
experiments based on the bolometric technique). Results on pulse shape analysis
of a CaMoO crystal operated as bolometer is reported as an example. An
explanation of this behavior, based on the energy partition in the heat and
scintillation channels, is also presented.Comment: Presented at the 14th International Workshop on Low Temperature
Detectors, proceedings to be published in the Journal of Low Temperature
Physic
Search for Solar Axions Produced in the Reaction
A search for the axioelectric absorption of 5.5-MeV solar axions produced in
the reaction was performed with
two BGO detectors placed inside a low-background setup. A model independent
limit on axion-photon and axion-nucleon couplings was obtained: . Constraints on the axion-electron
coupling constant were obtained for axions with masses in the MeV
range: . The solar positron flux from
decay was determined for axions with masses . Using the existing experimental data on the interplanetary positron
flux, a new constraint on the axion-electron coupling constant for axions with
masses in the MeV range was obtained: .Comment: 6 pages, 5 figure
The neutrino signal at HALO: learning about the primary supernova neutrino fluxes and neutrino properties
Core-collapse supernova neutrinos undergo a variety of phenomena when they
travel from the high neutrino density region and large matter densities to the
Earth. We perform analytical calculations of the supernova neutrino fluxes
including collective effects due to the neutrino-neutrino interactions, the
Mikheev-Smirnov-Wolfenstein (MSW) effect due to the neutrino interactions with
the background matter and decoherence of the wave packets as they propagate in
space. We predict the numbers of one- and two-neutron charged and
neutral-current electron-neutrino scattering on lead events. We show that, due
to the energy thresholds, the ratios of one- to two-neutron events are
sensitive to the pinching parameters of neutrino fluxes at the neutrinosphere,
almost independently of the presently unknown neutrino properties. Besides,
such events have an interesting sensitivity to the spectral split features that
depend upon the presence/absence of energy equipartition among neutrino
flavors. Our calculations show that a lead-based observatory like the Helium
And Lead Observatory (HALO) has the potential to pin down important
characteristics of the neutrino fluxes at the neutrinosphere, and provide us
with information on the neutrino transport in the supernova core.Comment: 30 pages, 12 figures, 6 tables, minor correction
Present status of IGEX dark matter search at Canfranc Underground Laboratory
One IGEX 76Ge double-beta decay detector is currently operating in the
Canfranc Underground Laboratory in a search for dark matter WIMPs, through the
Ge nuclear recoil produced by the WIMP elastic scattering. A new exclusion plot
has been derived for WIMP-nucleon spin-independent interactions. To obtain this
result, 40 days of data from the IGEX detector (energy threshold 4 keV),
recently collected, have been analyzed. These data improve the exclusion limits
derived from all the other ionization germanium detectors in the mass region
from 20 GeV to 200 GeV, where a WIMP supposedly responsible for the annual
modulation effect reported by the DAMA experiment would be located. The new
IGEX exclusion contour enters, by the first time, the DAMA region by using only
raw data, with no background discrimination, and excludes its upper left part.
It is also shown that with a moderate improvement of the detector performances,
the DAMA region could be fully explored.Comment: 3 pages, 3 figures, talk delivered at the 7th International Workshop
on Topics in Astroparticle and Underground Physics (TAUP 2001), September
2001, Laboratori Nazionali del Gran Sasso, Italy (to appear in the Conference
Proceedings, Nucl. Phys. B (Proc. Suppl.)
Improved constraints on WIMPs from the International Germanium Experiment IGEX
One IGEX 76Ge double-beta decay detector is currently operating in the
Canfranc Underground Laboratory in a search for dark matter WIMPs, through the
Ge nuclear recoil produced by the WIMP elastic scattering. A new exclusion
plot, has been derived for WIMP-nucleon spin-independent interactions. To
obtain this result, 40 days of data from the IGEX detector (energy threshold E
\~ 4 keV), recently collected, have been analyzed. These data improve the
exclusion limits derived from all the other ionization germanium detectors in
the mass region from 20 GeV to 200 GeV, where a WIMP supposedly responsible for
the annual modulation effect reported by the DAMA experiment would be located.
The new IGEX exclusion contour enters, by the first time, the DAMA region by
using only raw data, with no background discrimination, and excludes its upper
left part. It is also shown that with a moderate improvement of the detector
performances, the DAMA region could be fully explored.Comment: 14 pages, 8 figures, submitted to Physics Letters B (revised version
after referee's comments, some figures added
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