D. J. Auty

Search for Neutrinoless Double-Beta Decay in 136 Xe with EXO-200

We report on a search for neutrinoless double-beta decay of 136Xe with EXO-200. No signal is observed for an exposure of 32.5 kgu2009yr, with a background of ∼1.5×10(-3)u2009u2009kg(-1)u2009yr(-1) u2009keV(-1) in the ±1σ region of interest. This sets a lower limit on the half-life of the neutrinoless double-beta decay T(1/2)(0νββ)(136Xe)>1.6×10(25)u2009u2009yr (90% C.L.), corresponding to effective Majorana masses of less than 140-380 meV, depending on the matrix element calculation.

Search for Neutrinoless Double-Beta Decay in 136Xe with EXO-200

We report on a search for neutrinoless double-beta decay of 136Xe with EXO-200. No signal is observed for an exposure of 32.5 kgu2009yr, with a background of ∼1.5×10(-3)u2009u2009kg(-1)u2009yr(-1) u2009keV(-1) in the ±1σ region of interest. This sets a lower limit on the half-life of the neutrinoless double-beta decay T(1/2)(0νββ)(136Xe)>1.6×10(25)u2009u2009yr (90% C.L.), corresponding to effective Majorana masses of less than 140-380 meV, depending on the matrix element calculation.

The EXO-200 detector, part I: detector design and construction

EXO-200 is an experiment designed to search for double beta decay of 136Xe with a single-phase, liquid xenon detector. It uses an active mass of 110 kg of xenon enriched to 80.6% in the isotope 136 in an ultra-low background time projection chamber capable of simultaneous detection of ionization and scintillation. This paper describes the EXO-200 detector with particular attention to the most innovative aspects of the design that revolve around the reduction of backgrounds, the efficient use of the expensive isotopically enriched xenon, and the optimization of the energy resolution in a relatively large volume.

An improved measurement of the 2\nu \beta \beta\ half-life of Xe-136 with EXO-200

We report on an improved measurement of the 2nu beta beta half-life of Xe-136 performed by EXO-200. The use of a large and homogeneous time projection chamber allows for the precise estimate of the fiducial mass used for the measurement, resulting in a small systematic uncertainty. We also discuss in detail the data analysis methods used for double-beta decay searches with EXO-200, while emphasizing those directly related to the present measurement. The Xe-136 2nu beta beta half-life is found to be 2.165 +- 0.016 (stat) +- 0.059 (sys) x 10^21 years. This is the most precisely measured half-life of any 2nu beta beta decay to date.

An RF-only ion-funnel for extraction from high-pressure gases

An RF ion-funnel technique has been developed to extract ions from a high-pressure (10 bar) noble-gas environment into a vacuum (10(-6) mbar). Detailed simulations have been performed and a prototype has been developed for the purpose of extracting Ba-136 ions from Xe gas with high efficiency. With this prototype, ions have been extracted for the first time from high-pressure xenon gas and argon gas. Systematic studies have been carried out and compared to simulations. This demonstration of extraction of ions, with mass comparable to that of the gas generating the high-pressure, has applications to Ba tagging from a Xe-gas time-projection chamber for double-beta decay, as well as to the general problem of recovering trace amounts of an ionized element in a heavy (m > 40 u) carrier gas

Spectroscopy of Ba and Ba + deposits in solid xenon for barium tagging in nEXO

Progress on a method of barium tagging for the nEXO double beta decay experiment is reported. Absorption and emission spectra for deposits of barium atoms and ions in solid xenon matrices are presented. Excitation spectra for prominent emission lines, temperature dependence, and bleaching of the fluorescence reveal the existence of different matrix sites. A regular series of sharp lines observed in

Cosmogenic backgrounds to 0νββ in EXO-200

{mathrm{Ba}}^{+}

Measurements of the ion fraction and mobility of alpha and beta decay products in liquid xenon using EXO-200

deposits is identified with some type of barium hydride molecule. Lower limits for the fluorescence quantum efficiency of the principal Ba emission transition are reported. Under current conditions, an image of fewer than or equal to

An apparatus to manipulate and identify individual Ba ions from bulk liquid Xe

{10}^{4}

Measurements of the ion fraction and mobility of α− and β -decay products in liquid xenon using the EXO-200 detector

Ba atoms can be obtained. Prospects for imaging single Ba atoms in solid xenon are discussed.