228 research outputs found
Preserving the gauge invariance of meson production currents in the presence of explicit final-state interactions
A comprehensive formalism is developed to preserve the gauge invariance of
currents describing the photo- or electroproduction of mesons off the nucleon
when the final-state interactions of mesons and nucleons is taken into account
explicitly. Replacing exchange currents by auxiliary currents, it is found that
all contributions due to explicit final-state interactions are purely
transverse and do not contain a Kroll-Ruderman-type contact current. The
relation of the present formulation to tree-level-type prescriptions is shown.Comment: 6 pages, 2 figures; published versio
Updated and novel limits on double beta decay and dark matter-induced processes in platinum
A 510 day long-term measurement of a 45.3 g platinum foil acting as the
sample and high voltage contact in an ultra-low-background high purity
germanium detector was performed at Laboratori Nazionali del Gran Sasso
(Italy). The data was used for a detailed study of double beta decay modes in
natural platinum isotopes. Limits are produced in the range
a for double beta decay to excited states (90%
C.L.) confirming, and partially extending existing limits. The highest
sensitivity, greater than a, was achieved for the and resonant
modes of double electron capture involving KL shell electrons.
Additionally, novel limits for inelastic dark matter scattering on Pt
are placed up to mass splittings of approximately 500 keV. We analyze several
techniques to extend the sensitivity and propose a few approaches for future
medium-scale experiments with platinum-group elements.Comment: 15 pages, 3 figure
Background suppression in massive TeO bolometers with Neganov-Luke amplified light detectors
Bolometric detectors are excellent devices for the investigation of
neutrinoless double-beta decay (0). The observation of such
decay would demonstrate the violation of lepton number, and at the same time it
would necessarily imply that neutrinos have a Majorana character. The
sensitivity of cryogenic detectors based on TeO is strongly limited by the
alpha background in the region of interest for the 0 of
Te. It has been demonstrated that particle discrimination in TeO
bolometers is possible measuring the Cherenkov light produced by particle
interactions. However an event-by-event discrimination with NTD-based light
detectors has to be demonstrated. We will discuss the performance of a
highly-sensitive light detector exploiting the Neganov-Luke effect for signal
amplification. The detector, being operated with NTD-thermistor and coupled to
a 750 g TeO crystal, shows the ability for an event-by-event identification
of electron/gamma and alpha particles. The extremely low detector baseline
noise, RMS 19 eV, demonstrates the possibility to enhance the sensitivity of
TeO-based 0 experiment to an unprecedented level
New experimental limits on the alpha decays of lead isotopes
For the first time a PbWO4 crystal was grown using ancient Roman lead and it
was run as a cryogenic detector. Thanks to the simultaneous and independent
read-out of heat and scintillation light, the detector was able to discriminate
beta/gamma interactions with respect to alpha particles down to low energies.
New more stringent limits on the alpha decays of the lead isotopes are
presented. In particular a limit of T_{1/2} > 1.4*10^20 y at a 90% C.L. was
evaluated for the alpha decay of 204Pb to 200Hg
Cryogenic Detectors for Rare Alpha Decay Search: A New Approach
The detection of Sm alpha decay with a precise measured half-life of and a Q-value of 1987.3 0.5 keV was achieved by a new experimental approach, where a conventional ZnWO scintillating crystal doped with enriched Sm isotope is operated as a cryogenic scintillating bolometer (phonon and light channel) at mK-temperatures
TeO bolometers with Cherenkov signal tagging: towards next-generation neutrinoless double beta decay experiments
CUORE, an array of 988 TeO bolometers, is about to be one of the most
sensitive experiments searching for neutrinoless double-beta decay. Its
sensitivity could be further improved by removing the background from
radioactivity. A few years ago it has been pointed out that the signal from
s can be tagged by detecting the emitted Cherenkov light, which is not
produced by s. In this paper we confirm this possibility. For the first
time we measured the Cherenkov light emitted by a CUORE crystal, and found it
to be 100 eV at the -value of the decay. To completely reject the
background, we compute that one needs light detectors with baseline noise below
20 eV RMS, a value which is 3-4 times smaller than the average noise of the
bolometric light detectors we are using. We point out that an improved light
detector technology must be developed to obtain TeO bolometric experiments
able to probe the inverted hierarchy of neutrino masses.Comment: 5 pages, 4 figures. Added referee correction
First bolometric measurement of the two neutrino double beta decay of Mo with a ZnMoO crystals array
The large statistics collected during the operation of a ZnMoO array, for
a total exposure of 1.3 kg day of Mo, allowed the first
bolometric observation of the two neutrino double beta decay of Mo. The
observed spectrum of each crystal was reconstructed taking into account the
different background contributions due to environmental radioactivity and
internal contamination. The analysis of coincidences between the crystals
allowed the assignment of constraints to the intensity of the different
background sources, resulting in a reconstruction of the measured spectrum down
to an energy of 300 keV. The half-life extracted from the data is
T= [7.15 0.37 (stat) 0.66 (syst)] 10
y.Comment: 6 pages, 2 figure, Accepted for publication in Journal of Physics G:
Nuclear and Particle Physic
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