arXiv subjects

C. Cattadori

Publications and source records attributed to C. Cattadori.

At least 37 records · Page 2Linked to original sources

arXiv2020

Cryogenic SiPM arrays for the DUNE photon detection system

In this paper we report on the characterization of SiPM tiles developed for the R & D on the DUNE Photon Detection System. The tiles were produced by Fondazione Bruno Kessler (FBK) employing NUV-HD-SF SiPMs. Special emphasis is given on cryo-reliability of the sensors, i.e. the stability of electric and mechanical properties after thermal cycles at room and 77K temperature. The characterization includes the determination of the I-V curve, a high sensitivity measurement of Dark Count Rate at different overvoltages, and correlated noise. The single p.e. sensitivity is measured as a function of the number of sensors connected to a single electronic channel, after amplification at 77K using a dedicated cold amplifier.

physics.ins-det↗

arXiv2019

Probing Majorana neutrinos with double-$β$ decay

A discovery that neutrinos are not the usual Dirac but Majorana fermions, i.e. identical to their antiparticles, would be a manifestation of new physics with profound implications for particle physics and cosmology. Majorana neutrinos would generate neutrinoless double-$β$ ($0νββ$) decay, a matter-creating process without the balancing emission of antimatter. So far, 0$νββ$ decay has eluded detection. The GERDA collaboration searches for the $0νββ$ decay of $^{76}$Ge by operating bare germanium detectors in an active liquid argon shield. With a total exposure of 82.4 kg$\cdot$yr, we observe no signal and derive a lower half-life limit of T$_{1/2}$ > 0.9$\cdot$10$^{26}$ yr (90% C.L.). Our T$_{1/2}$ sensitivity assuming no signal is 1.1$\cdot$10$^{26}$ yr. Combining the latter with those from other $0νββ$ decay searches yields a sensitivity to the effective Majorana neutrino mass of 0.07 - 0.16 eV, with corresponding sensitivities to the absolute mass scale in $β$ decay of 0.15 - 0.44 eV, and to the cosmological relevant sum of neutrino masses of 0.46 - 1.3 eV.

hep-ex↗

arXiv2019

Characterization of 30 $^{76}$Ge enriched Broad Energy Ge detectors for GERDA Phase II

The GERmanium Detector Array (GERDA) is a low background experiment located at the Laboratori Nazionali del Gran Sasso in Italy, which searches for neutrinoless double beta decay of $^{76}$Ge into $^{76}$Se+2e$^-$. GERDA has been conceived in two phases. Phase II, which started in December 2015, features several novelties including 30 new Ge detectors. These were manufactured according to the Broad Energy Germanium (BEGe) detector design that has a better background discrimination capability and energy resolution compared to formerly widely-used types. Prior to their installation, the new BEGe detectors were mounted in vacuum cryostats and characterized in detail in the HADES underground laboratory in Belgium. This paper describes the properties and the overall performance of these detectors during operation in vacuum. The characterization campaign provided not only direct input for GERDA Phase II data collection and analyses, but also allowed to study detector phenomena, detector correlations as well as to test the strength of pulse shape simulation codes.

physics.ins-det↗

arXiv2018

Improved limit on neutrinoless double beta decay of $^{76}$Ge from GERDA Phase II

The GERDA experiment searches for the lepton number violating neutrinoless double beta decay of $^{76}$Ge ($^{76}$Ge $\rightarrow$ $^{76}$Se + 2e$^-$) operating bare Ge diodes with an enriched $^{76}$Ge fraction in liquid argon. The exposure for BEGe-type detectors is increased threefold with respect to our previous data release. The BEGe detectors feature an excellent background suppression from the analysis of the time profile of the detector signals. In the analysis window a background level of $1.0_{-0.4}^{+0.6}\cdot10^{-3}$ cts/(keV$\cdot$kg$\cdot$yr) has been achieved; if normalized to the energy resolution this is the lowest ever achieved in any 0$νββ$ experiment. No signal is observed and a new 90 \% C.L. lower limit for the half-life of $8.0\cdot10^{25}$ yr is placed when combining with our previous data. The median expected sensitivity assuming no signal is $5.8\cdot10^{25}$ yr.

nucl-ex↗

arXiv2017

Upgrade for Phase II of the GERDA Experiment

The GERDA collaboration is performing a sensitive search for neutrinoless double beta decay of $^{76}$Ge at the INFN Laboratori Nazionali del Gran Sasso, Italy. The upgrade of the GERDA experiment from Phase I to Phase II has been concluded in December 2015. The first Phase II data release shows that the goal to suppress the background by one order of magnitude compared to Phase I has been achieved. GERDA is thus the first experiment that will remain background-free up to its design exposure (100 kg yr). It will reach thereby a half-life sensitivity of more than 10$^{26}$ yr within 3 years of data collection. This paper describes in detail the modifications and improvements of the experimental setup for Phase II and discusses the performance of individual detector components.

physics.ins-det↗

arXiv2017

Searching for neutrinoless double beta decay with GERDA

The GERmanium Detector Array (GERDA) experiment located at the INFN Gran Sasso Laboratory (Italy), is looking for the neutrinoless double beta decay of Ge76, by using high-purity germanium detectors made from isotopically enriched material. The combination of the novel experimental design, the careful material selection for radio-purity and the active/passive shielding techniques result in a very low residual background at the Q-value of the decay, about 1e-3 counts/(keV kg yr). This makes GERDA the first experiment in the field to be background-free for the complete design exposure of 100 kg yr. A search for neutrinoless double beta decay was performed with a total exposure of 47.7 kg yr: 23.2 kg yr come from the second phase (Phase II) of the experiment, in which the background is reduced by about a factor of ten with respect to the previous phase. The analysis presented in this paper includes 12.4 kg yr of new Phase II data. No evidence for a possible signal is found: the lower limit for the half-life of Ge76 is 8.0e25 yr at 90% CL. The experimental median sensitivity is 5.8e25 yr. The experiment is currently taking data. As it is running in a background-free regime, its sensitivity grows linearly with exposure and it is expected to surpass 1e26 yr within 2018.

nucl-ex↗

arXiv2017

The Large Enriched Germanium Experiment for Neutrinoless Double Beta Decay (LEGEND)

The observation of neutrinoless double-beta decay (0$νββ$) would show that lepton number is violated, reveal that neutrinos are Majorana particles, and provide information on neutrino mass. A discovery-capable experiment covering the inverted ordering region, with effective Majorana neutrino masses of 15 - 50 meV, will require a tonne-scale experiment with excellent energy resolution and extremely low backgrounds, at the level of $\sim$0.1 count /(FWHM$\cdot$t$\cdot$yr) in the region of the signal. The current generation $^{76}$Ge experiments GERDA and the MAJORANA DEMONSTRATOR utilizing high purity Germanium detectors with an intrinsic energy resolution of 0.12%, have achieved the lowest backgrounds by over an order of magnitude in the 0$νββ$ signal region of all 0$νββ$ experiments. Building on this success, the LEGEND collaboration has been formed to pursue a tonne-scale $^{76}$Ge experiment. The collaboration aims to develop a phased 0$νββ$ experimental program with discovery potential at a half-life approaching or at $10^{28}$ years, using existing resources as appropriate to expedite physics results.

physics.ins-det↗

arXiv2017

Background free search for neutrinoless double beta decay with GERDA Phase II

The Standard Model of particle physics cannot explain the dominance of matter over anti-matter in our Universe. In many model extensions this is a very natural consequence of neutrinos being their own anti-particles (Majorana particles) which implies that a lepton number violating radioactive decay named neutrinoless double beta ($0νββ$) decay should exist. The detection of this extremely rare hypothetical process requires utmost suppression of any kind of backgrounds. The GERDA collaboration searches for $0νββ$ decay of $^{76}$Ge ($^{76}\rm{Ge} \rightarrow\,^{76}\rm{Se} + 2e^-$) by operating bare detectors made from germanium with enriched $^{76}$Ge fraction in liquid argon. Here, we report on first data of GERDA Phase II. A background level of $\approx10^{-3}$ cts/(keV$\cdot$kg$\cdot$yr) has been achieved which is the world-best if weighted by the narrow energy-signal region of germanium detectors. Combining Phase I and II data we find no signal and deduce a new lower limit for the half-life of $5.3\cdot10^{25}$ yr at 90 % C.L. Our sensitivity of $4.0\cdot10^{25}$ yr is competitive with the one of experiments with significantly larger isotope mass. GERDA is the first $0νββ$ experiment that will be background-free up to its design exposure. This progress relies on a novel active veto system, the superior germanium detector energy resolution and the improved background recognition of our new detectors. The unique discovery potential of an essentially background-free search for $0νββ$ decay motivates a larger germanium experiment with higher sensitivity.

nucl-ex↗

arXiv2016

Limits on uranium and thorium bulk content in GERDA Phase I detectors

Internal contaminations of $^{238}$U, $^{235}$U and $^{232}$Th in the bulk of high purity germanium detectors are potential backgrounds for experiments searching for neutrinoless double beta decay of $^{76}$Ge. The data from GERDA Phase~I have been analyzed for alpha events from the decay chain of these contaminations by looking for full decay chains and for time correlations between successive decays in the same detector. No candidate events for a full chain have been found. Upper limits on the activities in the range of a few nBq/kg for $^{226}$Ra, $^{227}$Ac and $^{228}$Th, the long-lived daughter nuclides of $^{238}$U, $^{235}$U and $^{232}$Th, respectively, have been derived. With these upper limits a background index in the energy region of interest from $^{226}$Ra and $^{228}$Th contamination is estimated which satisfies the prerequisites of a future ton scale germanium double beta decay experiment.

physics.ins-det↗

arXiv2016

Limit on the Radiative Neutrinoless Double Electron Capture of $^{36}$Ar from GERDA Phase I

Neutrinoless double electron capture is a process that, if detected, would give evidence of lepton number violation and the Majorana nature of neutrinos. A search for neutrinoless double electron capture of $^{36}$Ar has been performed with germanium detectors installed in liquid argon using data from Phase I of the GERmanium Detector Array (GERDA) experiment at the Gran Sasso Laboratory of INFN, Italy. No signal was observed and an experimental lower limit on the half-life of the radiative neutrinoless double electron capture of $^{36}$Ar was established: $T_{1/2} > $ 3.6 $\times$ 10$^{21}$ yr at 90 % C.I.

nucl-ex↗

arXiv2016

Flux Modulations seen by the Muon Veto of the GERDA Experiment

The GERDA experiment at LNGS of INFN is equipped with an active muon veto. The main part of the system is a water Cherenkov veto with 66~PMTs in the water tank surrounding the GERDA cryostat. The muon flux recorded by this veto shows a seasonal modulation. Two effects have been identified which are caused by secondary muons from the CNGS neutrino beam (2.2 %) and a temperature modulation of the atmosphere (1.4 %). A mean cosmic muon rate of $I^0_μ = (3.477 \pm 0.002_{\textrm{stat}} \pm 0.067_{\textrm{sys}}) \times 10^{-4}$/(s$\cdot$m$^2$) was found in good agreement with other experiments at LNGS at a depth of 3500~meter water equivalent.

physics.ins-det↗

arXiv2015

LArGe - Active background suppression using argon scintillation for the GERDA $0νββ$-experiment

LArGe is a GERDA low-background test facility to study novel background suppression methods in a low-background environment, for future application in the GERDA experiment. Similar to GERDA, LArGe operates bare germanium detectors submersed into liquid argon (1 m$^3$, 1.4 tons), which in addition is instrumented with photomultipliers to detect argon scintillation light. The scintillation signals are used in anti-coincidence with the germanium detectors to effectively suppress background events that deposit energy in the liquid argon. The background suppression efficiency was studied in combination with a pulse shape discrimination (PSD) technique using a BEGe detector for various sources, which represent characteristic backgrounds to GERDA. Suppression factors of a few times $10^3$ have been achieved. First background data of LArGe with a coaxial HPGe detector (without PSD) yield a background index of (0.12$-$4.6)$\cdot 10^{-2}$ cts/(keV$\cdot$kg$\cdot$y) (90% C.L.), which is at the level of GERDA Phase I. Furthermore, for the first time we monitor the natural $^{42}$Ar abundance (parallel to GERDA), and have indication for the $2νββ$-decay in natural germanium. These results show the effectivity of an active liquid argon veto in an ultra-low background environment. As a consequence, the implementation of a liquid argon veto in GERDA Phase II is pursued.

physics.ins-det↗

arXiv2015

$2νββ$ decay of $^{76}$Ge into excited states with GERDA Phase I

Two neutrino double beta decay of $^{76}$Ge to excited states of $^{76}$Se has been studied using data from Phase I of the GERDA experiment. An array composed of up to 14 germanium detectors including detectors that have been isotopically enriched in $^{76}$Ge was deployed in liquid argon. The analysis of various possible transitions to excited final states is based on coincidence events between pairs of detectors where a de-excitation $γ$ ray is detected in one detector and the two electrons in the other. No signal has been observed and an event counting profile likelihood analysis has been used to determine Frequentist 90\,\% C.L. bounds for three transitions: ${0^+_{\rm g.s.}-2^+_1}$: $T^{2ν}_{1/2}>$1.6$\cdot10^{23}$ yr, ${0^+_{\rm g.s.}-0^+_1}$: $T^{2ν}_{1/2}>$3.7$\cdot10^{23}$ yr and ${0^+_{\rm g.s.}-2^+_2}$: $T^{2ν}_{1/2}>$2.3$\cdot10^{23}$ yr. These bounds are more than two orders of magnitude larger than those reported previously. Bayesian 90\,\% credibility bounds were extracted and used to exclude several models for the ${0^+_{\rm g.s.}-0^+_1}$ transition.

hep-ex↗

arXiv2015

Improvement of the Energy Resolution via an Optimized Digital Signal Processing in GERDA Phase I

An optimized digital shaping filter has been developed for the GERDA experiment which searches for neutrinoless double beta decay in 76Ge. The GERDA Phase I energy calibration data have been reprocessed and an average improvement of 0.3 keV in energy resolution (FWHM) at the 76Ge Q value for 0νββdecay is obtained. This is possible thanks to the enhanced low-frequency noise rejection of this Zero Area Cusp (ZAC) signal shaping fillter.

physics.ins-det↗

arXiv2015

Results on $ββ$ decay with emission of two neutrinos or Majorons in $^{76}$Ge from GERDA Phase I

A search for neutrinoless $ββ$ decay processes accompanied with Majoron emission has been performed using data collected during Phase I of the GERmanium Detector Array (GERDA) experiment at the Laboratori Nazionali del Gran Sasso of INFN (Italy). Processes with spectral indices n = 1, 2, 3, 7 were searched for. No signals were found and lower limits of the order of 10$^{23}$ yr on their half-lives were derived, yielding substantially improved results compared to previous experiments with $^{76}$Ge. A new result for the half-life of the neutrino-accompanied $ββ$ decay of $^{76}$Ge with significantly reduced uncertainties is also given, resulting in $T^{2ν}_{1/2} = (1.926 \pm 0.095)\cdot10^{21}$ yr.

nucl-ex↗

arXiv2014

Production, characterization and operation of $^{76}$Ge enriched BEGe detectors in GERDA

The GERmanium Detector Array (GERDA) at the Gran Sasso Underground Laboratory (LNGS) searches for the neutrinoless double beta decay (0νββ) of $^{76}$Ge. Germanium detectors made of material with an enriched $^{76}$Ge fraction act simultaneously as sources and detectors for this decay. During Phase I of the experiment mainly refurbished semi-coaxial Ge detectors from former experiments were used. For the upcoming Phase II, 30 new $^{76}$Ge enriched detectors of broad energy germanium (BEGe)-type were produced. A subgroup of these detectors has already been deployed in GERDA during Phase I. The present paper reviews the complete production chain of these BEGe detectors including isotopic enrichment, purification, crystal growth and diode production. The efforts in optimizing the mass yield and in minimizing the exposure of the $^{76}$Ge enriched germanium to cosmic radiation during processing are described. Furthermore, characterization measurements in vacuum cryostats of the first subgroup of seven BEGe detectors and their long-term behavior in liquid argon are discussed. The detector performance fulfills the requirements needed for the physics goals of GERDA Phase~II.

physics.ins-det↗

arXiv2014

The background in the neutrinoless double beta decay experiment GERDA

The GERmanium Detector Array (GERDA) experiment at the Gran Sasso underground laboratory (LNGS) of INFN is searching for neutrinoless double beta decay of 76Ge. The signature of the signal is a monoenergetic peak at 2039 keV, the Q-value of the decay, Q_bb. To avoid bias in the signal search, the present analysis does not consider all those events, that fall in a 40 keV wide region centered around Q_bb. The main parameters needed for the neutrinoless double beta decay analysis are described. A background model was developed to describe the observed energy spectrum. The model contains several contributions, that are expected on the basis of material screening or that are established by the observation of characteristic structures in the energy spectrum. The model predicts a flat energy spectrum for the blinding window around Q_bb with a background index ranging from 17.6 to 23.8*10^{-3} counts/(keV kg yr). A part of the data not considered before has been used to test if the predictions of the background model are consistent. The observed number of events in this energy region is consistent with the background model. The background at Q-bb is dominated by close sources, mainly due to 42K, 214Bi, 228Th, 60Co and alpha emitting isotopes from the 226Ra decay chain. The individual fractions depend on the assumed locations of the contaminants. It is shown, that after removal of the known gamma peaks, the energy spectrum can be fitted in an energy range of 200 kev around Q_bb with a constant background. This gives a background index consistent with the full model and uncertainties of the same size.

physics.ins-det↗

arXiv2013

GeFRO: a New Charge Sensitive Amplifier Design with a Minimal Number of Front-end Components

A new approach was developed for the design of front-end circuits for semiconductor radiation detectors. The readout scheme consists of a first stage made of only a few components located close to the detector, and of a remote second stage located far from the detector, several meters away. The second stage amplifies the signals from the first stage and closes the feedback loop to discharge the input node after each event. The circuit has two outputs: one gives a "fast" signal, with a bandwidth larger than 20 MHz, allowing to preserve the high frequency components of the detector signals, which may be useful for timing measurements, pile-up rejection or pulse shape discrimination. The second output gives a "slow" signal, whose gain depends only on the value of the feedback capacitor, as happens with a classic charge sensitive amplifier, allowing to obtain higher resolution and lower drift. The prototype was named GeFRO for Germanium front-end, and was tested with a BEGe detector from Canberra. The wide bandwidth of the "fast" signal gave a timing resolution of the order of 20 ns. The noise of the circuit at the "slow" output after a 10 us Gaussian shaping was close to 160 electrons RMS with an input capacitance of 26 pF.

physics.ins-det↗