Initial performance of the CUORE-0 experiment Artusa, D. R.; Avignone, F. T.; Azzolini, O. ...
European physical journal. C, Particles and fields,
08/2014, Letnik:
74, Številka:
8
Journal Article
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CUORE-0 is a cryogenic detector that uses an array of tellurium dioxide bolometers to search for neutrinoless double-beta decay of
130
Te
. We present the first data analysis with
7.1
kg
·
y
of total
...TeO
2
exposure focusing on background measurements and energy resolution. The background rates in the neutrinoless double-beta decay region of interest (2.47 to
2.57
MeV
) and in the
α
background-dominated region (2.70 to
3.90
MeV
) have been measured to be
0.071
±
0.011
and
0.019
±
0.002
counts
/
(
keV
·
kg
·
y
)
, respectively. The latter result represents a factor of 6 improvement from a predecessor experiment, Cuoricino. The results verify our understanding of the background sources in CUORE-0, which is the basis of extrapolations to the full CUORE detector. The obtained energy resolution (full width at half maximum) in the region of interest is
5.7
keV
. Based on the measured background rate and energy resolution in the region of interest, CUORE-0 half-life sensitivity is expected to surpass the observed lower bound of Cuoricino with one year of live time.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Gamma-ray bursts (GRBs) are likely to have made a number of significant impacts on the Earth during the last billion years. The gamma radiation from a burst within a few kiloparsecs would quickly ...deplete much of the Earth's protective ozone layer, allowing an increase in solar UVB radiation reaching the surface. This radiation is harmful to life, damaging DNA and causing sunburn. In addition, NO sub(2) produced in the atmosphere would cause a decrease in visible sunlight reaching the surface and could cause global cooling. Nitric acid rain could stress portions of the biosphere, but the increased nitrate deposition could be helpful to land plants. We have used a two-dimensional atmospheric model to investigate the effects on the Earth's atmosphere of GRBs delivering a range of fluences, at various latitudes, at the equinoxes and solstices, and at different times of day. We have estimated DNA damage levels caused by increased solar UVB radiation, reduction in solar visible light due to NO sub(2) opacity, and deposition of nitrates through rainout of HNO sub(3). For the "typical" nearest burst in the last billion years, we find globally averaged ozone depletion up to 38%. Localized depletion reaches as much as 74%. Significant global depletion (at least 10%) persists up to about 7 yr after the burst. Our results depend strongly on time of year and latitude over which the burst occurs. The impact scales with the total fluence of the GRB at the Earth but is insensitive to the time of day of the burst and its duration (1-1000 s). We find DNA damage of up to 16 times the normal annual global average, well above lethal levels for simple life forms such as phytoplankton. The greatest damage occurs at mid- to low latitudes. We find reductions in visible sunlight of a few percent, primarily in the polar regions. Nitrate deposition similar to or slightly greater than that currently caused by lightning is also observed, lasting several years. We discuss how these results support the hypothesis that the Late Ordovician mass extinction may have been initiated by a GRB.
To better understand the contribution of cosmic ray muons to the CUORICINO background, 10 plastic scintillator detectors were installed at the CUORICINO site and operated during the final 3
months of ...the experiment. From these measurements, an upper limit of 0.0021
counts/(keV
kg
yr) (95% CL) was obtained on the cosmic ray-induced background in the neutrinoless double beta decay region of interest. The measurements were also compared to
Geant4 simulations.
We report the results of a search for neutrinoless double-beta decay in a 9.8 kg yr exposure of Te-130 using a bolometric detector array, CUORE-0. The characteristic detector energy resolution and ...background level in the region of interest are 5.1 +/- 0.3 keV FWHM and 0.058 +/- 0.004(stat) +/- 0.002(syst)counts/(keV kg yr), respectively. The median 90% C.L. lower-limit half-life sensitivity of the experiment is 2.9 x 10(24) yr and surpasses the sensitivity of previous searches. We find no evidence for neutrinoless double-beta decay of Te-130 and place a Bayesian lower bound on the decay half-life, T-1/2(0 nu) > 2.7 x 10(24) yr at 90% C.L. Combining CUORE-0 data with the 19.75 kg yr exposure of Te-130 from the Cuoricino experiment we obtain T-1/2(0 nu) > 4.0 x 10(24) yr at 90% C.L. (Bayesian), the most stringent limit to date on this half-life. Using a range of nuclear matrix element estimates we interpret this as a limit on the effective Majorana neutrino mass, m beta beta < 270-760 meV.
Neutrinoless double beta decay (
0
ν
β
β
) is one of the most sensitive probes for physics beyond the Standard Model, providing unique information on the nature of neutrinos. In this paper we review ...the status and outlook for bolometric
0
ν
β
β
decay searches. We summarize recent advances in background suppression demonstrated using bolometers with simultaneous readout of heat and light signals. We simulate several configurations of a future CUORE-like bolometer array which would utilize these improvements and present the sensitivity reach of a hypothetical next-generation bolometric
0
ν
β
β
experiment. We demonstrate that a bolometric experiment with the isotope mass of about 1 ton is capable of reaching the sensitivity to the effective Majorana neutrino mass (
|
m
e
e
|
) of order 10–20 meV, thus completely exploring the so-called inverted neutrino mass hierarchy region. We highlight the main challenges and identify priorities for an R&D program addressing them.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
We report the final result of the CUORICINO experiment. Operated between 2003 and 2008, with a total exposure of 19.75 kg*y of Te, CUORICINO was able to set a lower bound on the Te Ovββhalf-life of ...2.8 ×10years at 90% C.L. The limit here reported includes the effects of systematic uncertainties that are examined in detail in the paper. The corresponding upper bound on the neutrino Majorana mass is in the range 300-710 meV, depending on the adopted nuclear matrix element evaluation.
Gamma-ray bursts (GRBs) directed at Earth from within a few kiloparsecs may have damaged the biosphere, primarily through changes in atmospheric chemistry that admit greatly increased solar UV. ...However, GRBs are highly variable in spectrum and duration. Recent observations indicate that short ( 60.1 s) burst GRBs, which have harder spectra, may be sufficiently abundant at low redshift that they may offer an additional significant effect. A much longer timescale is associated with shock breakout luminosity observed in the soft X-ray (610 super(3) s) and UV (610 super(5) s) emission and radioactive decay gamma-ray line radiation emitted during the light-curve phase of supernovae (610 super(7) s). Here, we generalize our atmospheric computations to include a broad range of peak photon energies and investigate the effect of burst duration while holding total fluence and other parameters constant. The results can be used to estimate the probable impact of various kinds of ionizing events (such as short GRBs, X-ray flashes, and supernovae) on the Earth's atmosphere. We find that the ultimate intensity of atmospheric effects varies only slightly with burst duration from 10 super(-1) to 10 super(8) s. Therefore, the effect of many astrophysical events causing atmospheric ionization can be approximated without including time development. Detailed modeling requires specification of the season and latitude of the event. Harder photon spectra produce greater atmospheric effects for spectra with peaks up to about 20 MeV because of greater penetration into the stratosphere.
The CUORE experiment, a ton-scale cryogenic bolometer array, recently began operation at the Laboratori Nazionali del Gran Sasso in Italy. The array represents a significant advancement in this ...technology, and in this work we apply it for the first time to a high-sensitivity search for a lepton-number-violating process: 130Te neutrinoless double-beta decay. Examining a total TeO2 exposure of 86.3 kg yr, characterized by an effective energy resolution of (7.7 ± 0.5) keV FWHM and a background in the region of interest of (0.014 ± 0.002) counts /(keV kg yr), we find no evidence for neutrinoless double-beta decay. Including systematic uncertainties, we place a lower limit on the decay half-life of T $0ν\atop{1/2}$ (130 Te) > 1.3 × 1025 yr (90% C.L.); the median statistical sensitivity of this search is 7.0 × 1024 yr. In conclusion, combining this result with those of two earlier experiments, Cuoricino and CUORE-0, we find T $0ν\atop{1/2}$ (130Te) > 1.5 × 1025 yr (90% C.L.), which is the most stringent limit to date on this decay. Interpreting this result as a limit on the effective Majorana neutrino mass, we find mββ < (110 - 520) meV , where the range reflects the nuclear matrix element estimates employed.
The CUORE experiment, a ton-scale cryogenic bolometer array, recently began operation at the Laboratori Nazionali del Gran Sasso in Italy. The array represents a significant advancement in this ...technology, and in this work we apply it for the first time to a high-sensitivity search for a lepton-number-violating process: Te130 neutrinoless double-beta decay. Examining a total TeO2 exposure of 86.3 kg yr, characterized by an effective energy resolution of (7.7±0.5) keV FWHM and a background in the region of interest of (0.014±0.002) counts/(keV kg yr), we find no evidence for neutrinoless double-beta decay. Including systematic uncertainties, we place a lower limit on the decay half-life of T1/20ν(Te130)>1.3×1025 yr (90% C.L.); the median statistical sensitivity of this search is 7.0×1024 yr. Combining this result with those of two earlier experiments, Cuoricino and CUORE-0, we find T1/20ν(Te130)>1.5×1025 yr (90% C.L.), which is the most stringent limit to date on this decay. Interpreting this result as a limit on the effective Majorana neutrino mass, we find mββ<(110-520) meV, where the range reflects the nuclear matrix element estimates employed.
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