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Marino, M. G.

Publications and source records attributed to Marino, M. G..

11 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Search for Neutrinoless Double-ß Decay in 76Ge with the Majorana Demonstrator

The Majorana Collaboration is operating an array of high purity Ge detectors to search for neutrinoless double-beta decay in 76Ge. The Majorana Demonstrator is comprised of 44.8 kg (29.7 kg enriched in 76Ge) of Ge detectors in total, split between two modules contained in a low background shield at the Sanford Underground Research Facility in Lead, South Dakota. Here we present results from data taken during construction, commissioning, and the start of full operations. Given the unprecedented energy resolution at Q of 2.5 keV FWHM and the very low background with no observed candidate events in 10 kg yr of enriched Ge exposure, we find a lower limit on the half-life of 1:9 x 1025 yr (90% CL). This result constrains the effective Majorana neutrino mass to below 250 to 550 meV, depending on the matrix elements used. In our experimental configuration with the lowest background, the background is 4:0 +3:1(superscript) -2:5 (subscript) counts/(FWHM t yr) at 68% CL.

Aalseth, Craig E.↗
DOE OSTI2017

Searches for double beta decay of Xe 134 with EXO-200

Searches for double beta decay of 134 Xe were performed with EXO-200, a single-phase liquid xenon detector designed to search for neutrinoless double beta decay of 136 Xe. Using an exposure of 29.6 kg ∙ yr , the lower limits of T$2νββ\atop{1/2}$ > 8.7 × 10 20 yr and T$0νββ\atop{1/2}$ > 1.1 × 10 23 yr at 90% confidence level were derived, with corresponding half-life sensitivities of 1.2 × 10 21 yr and 1.9 × 10 23 yr . In conclusion, these limits exceed those in the literature for 134 Xe , improving by factors of nearly 10 5 and 2 for the two antineutrino and neutrinoless modes, respectively.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Trace radioactive impurities in final construction materials for EXO-200

Here, we report results from a systematic measurement campaign conducted to identify low radioactivity materials for the construction of the EXO-200 double beta decay experiment. Partial results from this campaign have already been reported in a 2008 paper by the EXO collaboration. Here we release the remaining data, collected since 2007, to the public. The data reported were obtained using a variety of analytic techniques. The measurement sensitivities are among the best in the field. We concluded the construction of the EXO-200 detector and Phase-I data was taken from 2011 to 2014. The detector’s extremely low background implicitly verifies the measurements and the analysis assumptions made during construction and reported in this paper.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2017

Measurement of the drift velocity and transverse diffusion of electrons in liquid xenon with the EXO-200 detector

The EXO-200 Collaboration is searching for neutrinoless double β decay using a liquid xenon (LXe) time projection chamber. This measurement relies on modeling the transport of charge deposits produced by interactions in the LXe to allow discrimination between signal and background events. In this paper, we present measurements of the transverse diffusion constant and drift velocity of electrons at drift fields between 20 V/cm and 615 V/cm using EXO-200 data. Finally, at the operating field of 380 V/cm EXO-200 measures a drift velocity of 1.705 +0.014 –0.010 mm/μs and a transverse diffusion coefficient of 55 ± 4 cm 2 /s.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2016

Cosmogenic backgrounds to $0νββ$ in EXO-200

As neutrinoless double-beta decay experiments become more sensitive and intrinsic radioactivity in detector materials is reduced, previously minor contributions to the background must be understood and eliminated. With this in mind, cosmogenic backgrounds have been studied with the EXO-200 experiment. Using the EXO-200 TPC, the muon flux (through a flat horizontal surface) underground at the Waste Isolation Pilot Plant (WIPP) has been measured to be $Φ$ = 4.07±0.14 (sys)±0.03 (stat)×10 -7 cm -2 s -1 , with a vertical intensity of $I_v$ = 2.97+0.14-0.13 (sys) ± 0.02 (stat) × 10 -7 cm -2 s -1 sr -1 . Simulations of muon-induced backgrounds identified several potential cosmogenic radionuclides, though only 137 Xe is a significant background for the 136 Xe $0νββ$ search with EXO-200. Muon-induced neutron backgrounds were measured using $γ$-rays from neutron capture on the detector materials. This provided a measurement of 137 Xe yield, and a test of the accuracy of the neutron production and transport simulations. The independently measured rates of 136 Xe neutron capture and of 137 Xe decay agree within uncertainties. Geant4 and FLUKA simulations were performed to estimate neutron capture rates, and these estimates agreed to within ~ 40% or better with measurements. The ability to identify 136 Xe($n,γ$) events will allow for rejection of 137 Xe backgrounds in future $0νββ$ analyses.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2016

Search for 2 ν β β decay of Xe 136 to the 0 1 + excited state of Ba 136 with the EXO-200 liquid xenon detector

EXO-200 is a single phase liquid xenon detector designed to search for neutrinoless ββ decay of 136 Xe to the ground state of 136 Ba. We report here on a search for the two-neutrino ββ decay of 136 Xe to the first 0 + excited state, 0 + 1 , of Ba136 based on a 100 kg yr exposure of 136 Xe. Using a specialized analysis employing a machine learning algorithm, we obtain a 90% CL half-life sensitivity of 1.7×10 24 yr. We find no statistically significant evidence for the 2νββ decay to the excited state resulting in a lower limit of T 2ν 1/2 (0 + → 0 + 1 ) > 6.9 ×10 23 yr at 90% CL. In conclusion, this observed limit is consistent with the estimated half-life of 2.5×10 25 yr.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2015

Investigation of radioactivity-induced backgrounds in EXO-200

The search for neutrinoless double-beta decay ( 0 ν β β ) requires extremely low background and a good understanding of their sources and their influence on the rate in the region of parameter space relevant to the 0 ν β β signal. We report on studies of various β and γ backgrounds in the liquid-xenon-based EXO- 200 0 ν β β experiment. With this work we try to better understand the location and strength of specific background sources and compare the conclusions to radioassay results taken before and during detector construction. Finally, we discuss the implications of these studies for EXO-200 as well as for the next-generation, tonne-scale nEXO detector.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2015

Minimizing magnetic fields for precision experiments

An increasing number of measurements in fundamental and applied physics rely on magnetically shielded environments with sub nano-Tesla residual magnetic fields. State of the art magnetically shielded rooms (MSRs) consist of up to seven layers of high permeability materials in combination with highly conductive shields. Proper magnetic equilibration is crucial to obtain such low magnetic fields with small gradients in any MSR. Here, we report on a scheme to magnetically equilibrate MSRs with a 10 times reduced duration of the magnetic equilibration sequence and a significantly lower magnetic field with improved homogeneity. For the search of the neutron's electric dipole moment, our finding corresponds to a 40% improvement of the statistical reach of the measurement. However, this versatile procedure can improve the performance of any MSR for any application.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2015

A large-scale magnetic shield with 10{sup 6} damping at millihertz frequencies

We present a magnetically shielded environment with a damping factor larger than 1 × 10{sup 6} at the mHz frequency regime and an extremely low field and gradient over an extended volume. This extraordinary shielding performance represents an improvement of the state-of-the-art in the difficult regime of damping very low-frequency distortions by more than an order of magnitude. This technology enables a new generation of high-precision measurements in fundamental physics and metrology, including searches for new physics far beyond the reach of accelerator-based experiments. We discuss the technical realization of the shield with its improvements in design.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗