The MAJORANA Project

Abstract

Building a 0νββ experiment with the ability to probe neutrino mass in the inverted hierarchy region requires the combination of a large detector mass sensitive to 0νββ, on the order of 1-tonne, and unprecedented background levels, on the order of or less than 1 count per year in the 0νββ signal region. The Majorana Collaboration proposes a design based on using high-purity enriched 76 Ge crystals deployed in ultra-low background electroformed Cu cryostats and using modern analysis techniques that should be capable of reaching the required sensitivity while also being scalable to a 1-tonne size. To demonstrate feasibility, the collaboration plans to construct a prototype system, the Majorana Demonstrator, consisting of 30 kg of 86% enriched 76 Ge detectors and 30 kg of natural or isotope-76-depleted Ge detectors. We plan to deploy and evaluate two different Ge detector technologies, one based on a p-type configuration and the other on n-type.

Arrival time and magnitude of airborne fission products from the Fukushima, Japan, reactor incident as measured in Seattle, WA, USA

“…Due to the uncertainty of the situation, limited quantitative information, and its potential impact on both local public health as well as our low-background fundamental physics program (Elliott et al, 2009), we began monitoring local air samples in Seattle, WA, USA, for the potential arrival of airborne radioactive fission products. In this paper we present data on key radionuclides associated with the nuclear accident and a brief discussion of the transport.…”

Searches on neutrino physics with cryogenic detectors

“…4. Double β β β β decay (DBD) This very rare process, amply discussed at this Symposium [10][11][12][13][14][15] consists, in the most common case, in the transition (Fig. 8) from the isotope (A, Z) to (A, Z+2) with contemporary emission of two electrons.…”

“…I leave to the reports by P. Vogel [18] and J. Engel [19] the discussion of the difficult calculations of the nuclear matrix elements for neutrinoless DBD. Most of the running and planned experiments aiming to detect neutrinoless DBD with the sensitivity suggested by the results of oscillations (Fig.12) are reported to this Symposium [10][11][12][13][14][15]. Let me only mention here those, running or in construction, which are based on the use of cryogenic detectors, whose mass has constantly increased with time as shown in Fig.…”

Neutron spallation measurements and impacts on low-background experiments

“…Solar neutrino experiments, neutrinoless double beta decay and dark matter searches are some of the physics experiments that expect event rates as low as a few per year [1]. The background-limited sensitivity goal of future neutrinoless double beta decay experiments is to probe effects with half-lives >10 27 years, equivalent to background rates of ~1 event/tonneyear [2,3]. The key to rare event searches lies in the ability to characterize and reduce the background rate [4].…”

“…The European 76 Ge neutrinoless double beta decay experiment (GERDA) has used Monte-Carlo simulations to design a transport shield, using ISABEL data and the SHIELD code [9]. The SHIELD result predicted an attenuation length for neutrons at 100 MeV in iron of about 240 g/cm 2 (0.30 m). Barabanov et al predict that the transport shield design would reduce production of 68 Ge and 60 Co by 10 and 15, respectively.…”