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Search Results: 1 - 10 of 87704 matches for " I. Dafinei "
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Performance of a large TeO2 crystal as a cryogenic bolometer in searching for neutrinoless double beta decay
L. Cardani,L. Gironi,J. W. Beeman,I. Dafinei,Z. Ge,G. Pessina,S. Pirro,Y. Zhu
Physics , 2011, DOI: 10.1088/1748-0221/7/01/P01020
Abstract: Bolometers are ideal devices in the search for neutrinoless Double Beta Decay. Enlarging the mass of individual detectors would simplify the construction of a large experiment, but would also decrease the background per unit mass induced by alpha-emitters located close to the surfaces and background arising from external and internal gamma's. We present the very promising results obtained with a 2.13 kg TeO2 crystal. This bolometer, cooled down to a temperature of 10.5 mK in a dilution refrigerator located deep underground in the Gran Sasso National Laboratories, represents the largest thermal detector ever operated. The detector exhibited an energy resolution spanning a range from 3.9 keV (at 145 keV) to 7.8 keV (at the 2615 gamma-line of 208Tl) FWHM. We discuss the decrease in the background per unit mass that can be achieved increasing the mass of a bolometer.
Measurements of the Cerenkov light emitted by a TeO2 crystal
F. Bellini,N. Casali,I. Dafinei,M. Marafini,S. Morganti,F. Orio,D. Pinci,M. Vignati,C. Voena
Physics , 2012, DOI: 10.1088/1748-0221/7/11/P11014
Abstract: Bolometers have proven to be good instruments to search for rare processes because of their excellent energy resolution and their extremely low intrinsic background. In this kind of detectors, the capability of discriminating alpha particles from electrons represents an important aspect for the background reduction. One possibility for obtaining such a discrimination is provided by the detection of the Cerenkov light which, at the low energies of the natural radioactivity, is only emitted by electrons. In this paper, the results of the analysis of the light emitted by a TeO2 crystal at room temperature when transversed by a cosmic ray are reported. Light is promptly emitted after the particle crossing and a clear evidence of its directionality is also found. These results represent a strong indication that Cerenkov light is the main, if not even the only, component of the light signal in a TeO2 crystal. They open the possibility to make large improvements in the performance of experiments based on this kind of materials
Discrimination of alpha and beta/gamma interactions in a TeO$_2$ bolometer
J. W. Beeman,F. Bellini,L. Cardani,N. Casali,I. Dafinei,S. Di Domizio,F. Ferroni,F. Orio,G. Pessina,S. Pirro,C. Tomei,M. Vignati
Physics , 2011, DOI: 10.1016/j.astropartphys.2011.12.004
Abstract: TeO$_2$ crystals have proven to be superb bolometers for the search of neutrinoless double beta decay in many respects. However, if used alone, they do not exhibit any feature that allows to discriminate an alpha energy deposit from a beta/gamma one. This fact limits their ability to reject the background due to natural radioactivity and eventually affects the sensitivity of the search. In this paper we show the results of a TeO$_2$ crystal where, in coincidence with its bolometric heat signal, also the luminescence light escaping the crystal is recorded. The results show that we are able to measure the light produced by beta/gamma particles, which can be explained as due to Cerenkov emission. No light is detected from alpha particles, allowing the rejection of this background source.
Response of a TeO_2 bolometer to alpha particles
F. Bellini,M. Biassoni,C. Bucci,N. Casali,I. Dafinei,Z. Ge,P. Gorla,F. Ferroni,F. Orio,C. Tomei,M. Vignati,Y. Zhu
Physics , 2010, DOI: 10.1088/1748-0221/5/12/P12005
Abstract: $TeO_2$ crystals are used as bolometers in experiments searching for Double Beta Decay without emission of neutrinos. One of the most important issues in this extremely delicate kind of experiments is the characterization of the background. The knowledge of the response to $\alpha$ particles in the energy range where the signal is expected is therefore a must. In this paper we report the results on the response function of a $TeO_2$ bolometer to $\alpha$'s emitted by $^{147}$Sm dissolved in the crystal at the growth phase. A Quenching Factor of ($1.0076\pm 0.0005$) is found, independent of the temperature in the investigated range. The energy resolution on $\alpha$ peaks shows a standard calorimeter energy dependence: $\sigma\; [\rm{keV}] = (0.56 \pm 0.02) \oplus (0.010 \pm 0.002)\sqrt{E[\rm{keV}]} $. Signal pulses show no difference between $\alpha$ and $\beta\gamma$ particles
Measurements and optimization of the light yield of a TeO$_2$ crystal
F. Bellini,L. Cardani,N. Casali,I. Dafinei,M. Marafini,S. Morganti,F. Orio,D. Pinci,G. Piperno,D. Santone,C. Tomei,M. Vignati
Physics , 2014, DOI: 10.1088/1748-0221/9/10/P10014
Abstract: Bolometers have proven to be good instruments to search for rare processes because of their excellent energy resolution and their extremely low intrinsic background. In this kind of detectors, the capability of discriminating alpha particles from electrons represents an important aspect for the background reduction. One possibility for obtaining such a discrimination is provided by the detection of the Cherenkov light which, at the low energies of the natural radioactivity, is only emitted by electrons. This paper describes the method developed to evaluate the amount of light produced by a crystal of TeO$_2$ when hit by a 511 keV photon. The experimental measurements and the results of a detailed simulation of the crystal and the readout system are shown and compared. A light yield of about 52 Cherenkov photons per deposited MeV was measured. The effect of wrapping the crystal with a PTFE layer, with the aim of maximizing the light collection, is also presented.
TeO$_2$ bolometers with Cherenkov signal tagging: towards next-generation neutrinoless double beta decay experiments
N. Casali,M. Vignati,J. W. Beeman,F. Bellini,L. Cardani,I. Dafinei,S. Di Domizio,F. Ferroni,L. Gironi,S. Nagorny,F. Orio,L. Pattavina,G. Pessina,G. Piperno,S. Pirro,C. Rusconi,K. Sch?ffner,C. Tomei
Physics , 2014, DOI: 10.1140/epjc/s10052-014-3225-4
Abstract: 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.
Performances of a large mass ZnSe bolometer to search for rare events
J. W. Beeman,F. Bellini,L. Cardani,N. Casali,I. Dafinei,S. Di Domizio,F. Ferroni,L. Gironi,A. Giuliani,S. Nagorny,F. Orio,L. Pattavina,G. Pessina,G. Piperno,S. Pirro,E. Previtali,C. Rusconi,C. Tomei,M. Vignati
Physics , 2013, DOI: 10.1088/1748-0221/8/05/P05021
Abstract: Scintillating bolometers of ZnSe are the baseline choice of the LUCIFER experiment, whose aim is to observe the neutrinoless double beta decay of 82Se. The independent read-out of the heat and scintillation signals allows to identify and reject alpha particle interactions, the dominant background source for bolometric detectors. In this paper we report the performances of a ZnSe crystal operated within the LUCIFER R&D. We measured the scintillation yield, the energy resolution and the background in the energy region where the signal from neutrinoless double beta decay of 82Se is expected with an exposure of 9.4 kg x days. With a newly developed analysis algorithm we improved the rejection of alpha events, and we estimated the increase in energy resolution obtained by the combination of the heat and light signals. For the first time we measured the light emitted by nuclear recoils, and found it to be compatible with zero. We conclude that the discrimination of nuclear recoils from beta/gamma interactions in the WIMPs energy region is possible, but low-noise light detectors are needed.
Characterization of bolometric Light Detectors for rare event searches
J. W. Beeman,F. Bellini,N. Casali,L. Cardani,I. Dafinei,S. Di Domizio,F. Ferroni,L. Gironi,S. Nagorny,F. Orio,L. Pattavina,G. Pessina,G. Piperno,S. Pirro,E. Previtali,C. Rusconi,C. Tomei,M. Vignati
Physics , 2013, DOI: 10.1088/1748-0221/8/07/P07021
Abstract: Bolometers have proven to be very good detectors to search for rare processes thanks to their excellent energy resolution and their low intrinsic background. Further active background rejection can be obtained by the simultaneous readout of the heat and light signals produced by particles interacting in scintillating bolometers, as proposed by the LUCIFER experiment. In this framework, the choice of the light detector and the optimization of its working conditions play a crucial role. In this paper, we report a study of the performances of a Germanium bolometric light detector in terms of signal amplitude, energy resolution and signal time development. The impact of various operational parameters on the detector performances is discussed.
Current Status and Future Perspectives of the LUCIFER Experiment
J. W. Beeman,F. Bellini,P. Benetti,L. Cardani,N. Casali,D. Chiesa,M. Clemenza,I. Dafinei,S. Di Domizio,F. Ferroni,A. Giachero,L. Gironi,A. Giuliani,C. Gotti,M. Maino,S. Nagorny,S. Nisi,C. Nones,F. Orio,L. Pattavina,G. Pessina,G. Piperno,S. Pirro,E. Previtali,C. Rusconi,M. Tenconi,C. Tomei,M. Vignati
Advances in High Energy Physics , 2013, DOI: 10.1155/2013/237973
Abstract: In the field of fundamental particle physics, the neutrino has become more and more important in the last few years, since the discovery of its mass. In particular, the ultimate nature of the neutrino (if it is a Dirac or a Majorana particle) plays a crucial role not only in neutrino physics, but also in the overall framework of fundamental particle interactions and in cosmology. The only way to disentangle its ultimate nature is to search for the neutrinoless double beta decay. The idea of LUCIFER is to combine the bolometric technique proposed for the CUORE experiment with the bolometric light detection technique used in cryogenic dark matter experiments. The bolometric technique allows an extremely good energy resolution while its combination with the scintillation detection offers an ultimate tool for background rejection. The goal of LUCIFER is not only to build a background-free small-scale experiment but also to directly prove the potentiality of this technique. Preliminary tests on several detectors containing different interesting DBD emitters have clearly demonstrated the excellent background rejection capabilities that arise from the simultaneous, independent, double readout of heat and scintillation light. 1. State of the Art The double beta transition, which is the rarest nuclear weak process, takes place between two even-even isobars, when the decay to the intermediate nucleus is energetically forbidden due to the pairing interaction, which opens a gap between the even-even and the odd-odd mass parabolas in a given isobaric chain. The two-neutrino decay conserves the lepton number and was originally proposed by Goeppert-Mayer in 1935 [1]. It is a second-order weak process—that explains its low rate—and it has been observed for a dozen of nuclei, with lifetimes in the range of 1018–1022?y [2]. Besides the two-neutrino decay, a much more intriguing process, the so-called neutrinoless double beta decay 0 -DBD [3–6], was proposed by Furry [7] shortly after the Majorana theory of the neutrino [8]. In this case, the simultaneous transformation of two neutrons into two protons is accompanied by the emission of two electrons and nothing else. The main feature of 0 -DBD is just the violation of the lepton number. In the modern (standard model) perspective, this is as important as the violation of the baryon number. In full generality, we can imagine this process as a mechanism capable of creating electrons in a nuclear transition. It is remarkable that 0 -DBD is not necessarily due to the exchange of Majorana neutrinos (mass mechanism) as a leading
ZnMoO4: a promising bolometer for neutrinoless double beta decay searches
J. W. Beeman,F. Bellini,S. Capelli,L. Cardani,N. Casali,I. Dafinei,S. Di Domizio,F. Ferroni,E. N. Galashov,L. Gironi,F. Orio,L. Pattavina,G. Pessina,G. Piperno,S. Pirro,V. N. Shlegel,Ya. V. Vasilyev,C. Tomei,M. Vignati
Physics , 2012, DOI: 10.1016/j.astropartphys.2012.02.013
Abstract: We investigate the performances of two ZnMoO4 scintillating crystals operated as bolometers, in view of a next generation experiment to search the neutrinoless double beta decay of Mo-100. We present the results of the alpha vs beta/gamma discrimination, obtained through the scintillation light as well as through the study of the shape of the thermal signal alone. The discrimination capability obtained at the 2615 keV line of Tl-208 is 8 sigma, using the heat-light scatter plot, while it exceeds 20 sigma using the shape of the thermal pulse alone. The achieved FWHM energy resolution ranges from 2.4 keV (at 238 keV) to 5.7 keV (at 2615 keV). The internal radioactive contaminations of the ZnMoO4 crystals were evaluated through a 407 hours background measurement. The obtained limit is < 32 microBq/kg for Th-228 and Ra-226. These values were used for a Monte Carlo simulation aimed at evaluating the achievable background level of a possible, future array of enriched ZnMoO4 crystals.
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