Background model of the CUPID-0 experiment Azzolini, O.; Beeman, J. W.; Bellini, F. ...
The European physical journal. C, Particles and fields,
07/2019, Letnik:
79, Številka:
7
Journal Article
Recenzirano
Odprti dostop
CUPID-0 is the first large mass array of enriched Zn
82
Se scintillating low temperature calorimeters, operated at LNGS since 2017. During its first scientific runs, CUPID-0 collected an exposure of ...9.95 kg year. Thanks to the excellent rejection of
α
particles, we attained the lowest background ever measured with thermal detectors in the energy region where we search for the signature of
82
Se
neutrinoless double beta decay. In this work we develop a model to reconstruct the CUPID-0 background over the whole energy range of experimental data. We identify the background sources exploiting their distinctive signatures and we assess their extremely low contribution down to
∼
10
-
4
counts/(keV kg year) in the region of interest for
82
Se
neutrinoless double beta decay search. This result represents a crucial step towards the comprehension of the background in experiments based on scintillating calorimeters and in next generation projects such as CUPID.
An accurate characterization of the neutron fields at spallation sources is crucial for many applications based on neutron irradiations, such as radiation damage tests that need a precise dose ...estimate. In this work, we present the neutron flux measurements performed with the multi-foil activation technique in the ROTAX and ChipIr beamlines of the ISIS spallation source, characterized by moderated and unmoderated spectra, respectively. We selected many different activation reactions to cover a wide energy range, from thermal to very fast neutrons up to about 100 MeV. By applying a Bayesian unfolding algorithm, we demonstrate the effectiveness of this technique in measuring the neutron flux intensity and energy spectrum with precision and accuracy.
In the framework of rare event searches, the identification of radioactive contaminants in ultra-pure samples is a challenging task, because the signal is often at the same level of the instrumental ...background. This is a rather common situation for
α
-spectrometers and other detectors used for low-activity measurements. In order to obtain the target sensitivity without extending the data taking live-time, analysis strategies that highlight the presence of the signal sought should be developed. In this paper, we show how to improve the contaminant tagging capability relying on the time-correlation of radioactive decay sequences. We validate the proposed technique by measuring the impurity level of both contaminated and ultra-pure copper samples, demonstrating the potential of this analysis tool in disentangling different background sources and providing an effective way to mitigate their impact in rare event searches.
CUPID-Mo, located in the Laboratoire Souterrain de Modane (France), was a demonstrator for the next generation
0
ν
β
β
decay experiment, CUPID. It consisted of an array of 20 enriched Li
2
100
MoO
4
...bolometers and 20 Ge light detectors and has demonstrated that the technology of scintillating bolometers with particle identification capabilities is mature. Furthermore, CUPID-Mo can inform and validate the background prediction for CUPID. In this paper, we present a detailed model of the CUPID-Mo backgrounds. This model is able to describe well the features of the experimental data and enables studies of the
2
ν
β
β
decay and other processes with high precision. We also measure the radio-purity of the Li
2
100
MoO
4
crystals which are found to be sufficient for the CUPID goals. Finally, we also obtain a background index in the region of interest of 3.7
-
0.8
+
0.9
(stat)
-
0.7
+
1.5
(syst)
×
10
-
3
counts/
Δ
E
FWHM
/
mol
iso
/
year
,
the lowest in a bolometric
0
ν
β
β
decay experiment.
Localization and modeling of radioactive contaminations is a challenge that ultra-low background experiments are constantly facing. These are fundamental steps both to extract scientific results and ...to further reduce the background of the detectors. Here we present an innovative technique based on the analysis of
α
-
α
delayed coincidences in
232
Th and
238
U decay chains, developed to investigate the contaminations of the ZnSe crystals in the CUPID-0 experiment. This method allows to disentangle surface and bulk contaminations of the detectors relying on the different probability to tag delayed coincidences as function of the
α
decay position.
The LUCIFER project aims at deploying the first array of enriched scintillating bolometers for the investigation of neutrinoless double-beta decay of Formula: see textSe. The matrix which embeds the ...source is an array of ZnSe crystals, where enriched Formula: see textSe is used as decay isotope. The radiopurity of the initial components employed for manufacturing crystals, that can be operated as bolometers, is crucial for achieving a null background level in the region of interest for double-beta decay investigations. In this work, we evaluated the radioactive content in 2.5 kg of 96.3 % enriched Formula: see textSe metal, measured with a high-purity germanium detector at the Gran Sasso deep underground laboratory. The limits on internal contaminations of primordial decay chain elements of Formula: see textTh, Formula: see textU and Formula: see textU are respectively: Formula: see text61, Formula: see text110 and Formula: see text74 Formula: see textBq/kg at 90 % C.L. The extremely low-background conditions in which the measurement was carried out and the high radiopurity of the Formula: see textSe allowed us to establish the most stringent lower limits on the half-lives of the double-beta decay of Formula: see textSe to 0Formula: see text, 2Formula: see text and 2Formula: see text excited states of Formula: see textKr of 3.4Formula: see text10Formula: see text, 1.3Formula: see text10Formula: see text and 1.0Formula: see text10Formula: see text y, respectively, with a 90 % C.L.
Abstract
CUPID-Mo, located in the Laboratoire Souterrain de Modane (France), was a demonstrator for the next generation
$$0\nu \beta \beta $$
0
ν
β
β
decay experiment, CUPID. It consisted of an array ...of 20 enriched Li
$$_{2}$$
2
$$^{100}$$
100
MoO
$$_4$$
4
bolometers and 20 Ge light detectors and has demonstrated that the technology of scintillating bolometers with particle identification capabilities is mature. Furthermore, CUPID-Mo can inform and validate the background prediction for CUPID. In this paper, we present a detailed model of the CUPID-Mo backgrounds. This model is able to describe well the features of the experimental data and enables studies of the
$$2\nu \beta \beta $$
2
ν
β
β
decay and other processes with high precision. We also measure the radio-purity of the Li
$$_{2}$$
2
$$^{100}$$
100
MoO
$$_4$$
4
crystals which are found to be sufficient for the CUPID goals. Finally, we also obtain a background index in the region of interest of 3.7
$$^{+0.9}_{-0.8}$$
-
0.8
+
0.9
(stat)
$$^{+1.5}_{-0.7}$$
-
0.7
+
1.5
(syst)
$$\times ~10 ^{-3}$$
×
10
-
3
counts/
$$\Delta E_{\text {FWHM}}/\text {mol}_{\text {iso}}/\text {year},$$
Δ
E
FWHM
/
mol
iso
/
year
,
the lowest in a bolometric
$$0\nu \beta \beta $$
0
ν
β
β
decay experiment.
Initial performance of the CUORE-0 experiment Artusa, D. R.; Avignone, F. T.; Azzolini, O. ...
The European physical journal. C, Particles and fields,
08/2014, Letnik:
74, Številka:
8
Journal Article
Recenzirano
Odprti dostop
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.
The CUPID-Mo experiment to search for 0
ν
β
β
decay in
100
Mo has been recently completed after about 1.5 years of operation at Laboratoire Souterrain de Modane (France). It served as a demonstrator ...for CUPID, a next generation 0
ν
β
β
decay experiment. CUPID-Mo was comprised of 20 enriched
Li
2
100
MoO
4
scintillating calorimeters, each with a mass of
∼
0.2
kg, operated at
∼
20
mK. We present here the final analysis with the full exposure of CUPID-Mo (
100
Mo exposure of 1.47
kg
×
year
) used to search for lepton number violation via 0
ν
β
β
decay. We report on various analysis improvements since the previous result on a subset of data, reprocessing all data with these new techniques. We observe zero events in the region of interest and set a new limit on the
100
Mo 0
ν
β
β
decay half-life of
T
1
/
2
0
ν
>
1.8
×
10
24
year (stat. + syst.) at 90% CI. Under the light Majorana neutrino exchange mechanism this corresponds to an effective Majorana neutrino mass of
m
β
β
<
(
0.28
-
0.49
)
eV, dependent upon the nuclear matrix element utilized.
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