Photodisintegration of the deuteron in the few GeV region using asymptotic amplitudes

Exclusive photodisintegration of the deuteron in the 1-4GeV range is described in terms of a simple covariant and gauge invariant approach using an effective counting rule as the hard part of the d-np vertex. At a scattering angle of theta_cm=90 degrees a prescaling behavior of the differential cross section proportional to 1/s^(n-2) with n ~ 12 is obtained; going away from 90 degrees the value of n decreases slowly, in qualitative agreement with the recent data.Comment: 10 pages, 3 figures, to appear in Physics Letters

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

Electromagnetic properties of off-shell particles and gauge invariance

Abstract: Electromagnetic properties of off-shell particles are discussed on the basis of a purely electromagnetic reaction: virtual Compton scattering off a proton. It is shown that the definition of off-shell electromagnetic form factors is not gauge invariant and that these cannot be investigated in practice. Using only fundamental requirements of gauge invariance it is demonstrated that off-shell effects are cancelled in the longitudinal components of the total conserved current by the minimal contact current, while the off-shellness appears only in the the transverse (gauge invariant) non-pole part. This provides the possibility to introduce an on-shell extrapolated form factor F_1^+(q^2) in a gauge invariant way for the unphysical time-like region, 4m_e^

On the possibility to search for double beta decay of initially unstable (alpha/beta radioactive) nuclei

Possibilities to search for double beta decay of alpha/beta unstable nuclei, many of which have higher energy release than "conventional" (beta stable) double beta decay candidates, are discussed. First experimental half-life limits on double beta decay of radioactive nuclides from U and Th families (trace contaminants of the CaWO_4, CdWO_4 and Gd_2SiO_5 scintillators) were established by reanalyzing the data of low-background measurements in the Solotvina Underground Laboratory with these detectors (1734 h with CaWO_4, 13316 h with CdWO_4, and 13949 h with Gd_2SiO_5 crystals).Comment: 15 pages, 6 figure

TeO2_2 bolometers with Cherenkov signal tagging: towards next-generation neutrinoless double beta decay experiments

CUORE, an array of 988 TeO$_2$ 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 $\alpha$ radioactivity. A few years ago it has been pointed out that the signal from $\beta$s can be tagged by detecting the emitted Cherenkov light, which is not produced by $\alpha$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 $Q$-value of the decay. To completely reject the $\alpha$ 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$_2$ bolometric experiments able to probe the inverted hierarchy of neutrino masses.Comment: 5 pages, 4 figures. Added referee correction

Development of a Li2MoO4 scintillating bolometer for low background physics

We present the performance of a 33 g Li2MoO4 crystal working as a scintillating bolometer. The crystal was tested for more than 400 h in a dilution refrigerator installed in the underground laboratory of Laboratori Nazionali del Gran Sasso (Italy). This compound shows promising features in the frame of neutron detection, dark matter search (solar axions) and neutrinoless double-beta decay physics. Low temperature scintillating properties were investigated by means of different alpha, beta/gamma and neutron sources, and for the first time the Light Yield for different types of interacting particle is estimated. The detector shows great ability of tagging fast neutron interactions and high intrinsic radiopurity levels (< 90 \muBq/kg for 238-U and < 110 \muBq/kg for 232-Th).Comment: revised versio