M. K. Moe

Double β decays of100Moand150Nd

The double beta decays of Mo-100 and Nd-150 were studied in a time projection chamber located 72 m underground. A 3275 h exposure of a 16.7 g sample of metallic Mo enriched to 97.4 % in Mo-100 resulted in a two-neutrino half-life of (6.82 + 0.38 - 0.53 +/- 0.68) * 10**18 y. Similarly, a 6287 h exposure of 15.5 g of Nd2O3 enriched to 91 % in Nd-150 yielded (6.75 + 0.37 - 0.42 +/- 0.68) * 10**18 y. Lower limits on half-lives for neutrinoless decay with and without majoron emission also have been measured.

Double Beta Decay of 48 Ca

{sup 48}Ca, the lightest experimentally accessible double beta decay candidate, is the only one simple enough to be treated exactly in the nuclear shell model. Thus the {beta}{beta}{sub 2{nu}} half-life measurement, reported here, provides a unique test of the nuclear physics involved in the {beta}{beta} matrix element calculation. Enriched {sup 48}Ca sources of two different thicknesses have been exposed in a time projection chamber. We observe a half-life of T{sub 1/2}{sup 2{nu}}=(4.3{sub {minus}1.1}{sup +2.4}[stat]{plus_minus}1.4[syst]){times}10{sup 19} yr, consistent with shell model calculations. {copyright} {ital 1996 The American Physical Society.}

Tracking electrons from double beta decay — How far can you push the TPC?

Abstract New results are reported from time-projection-chamber measurements of the double beta decay of 100Mo and 150Nd. A previously-observed high-energy anomaly has been eliminated by improved energy resolution. Kurie plots of the two-neutrino spectra show end-point energies close to the reported parent-daughter mass differences. The 150Nd source has produced a new direct-counting 90% confidence neutrino-majoron coupling limit of 〈gν,χ〉

Observation of single collisionally cooled trapped ions in a buffer gas

Individual Ba ions are trapped in a gas-filled linear ion trap and observed with a high signal-to-noise ratio by resonance fluorescence. Single-ion storage times of {approx}5 min ({approx}1 min) are achieved using He (Ar) as a buffer gas at pressures in the range 8x10{sup -5}-4x10{sup -3} torr. Trap dynamics in buffer gases are experimentally studied in the simple case of single ions. In particular, the cooling effects of light gases such as He and Ar and the destabilizing properties of heavier gases such as Xe are studied. A simple model is offered to explain the observed phenomenology.

A time projection chamber for detection of double beta decay

Abstract A time projection chamber is being used to study double beta decay in 82 Se. The construction, operation, and performance of this device are described.

Double Beta Decay of 48Ca

{sup 48}Ca, the lightest experimentally accessible double beta decay candidate, is the only one simple enough to be treated exactly in the nuclear shell model. Thus the {beta}{beta}{sub 2{nu}} half-life measurement, reported here, provides a unique test of the nuclear physics involved in the {beta}{beta} matrix element calculation. Enriched {sup 48}Ca sources of two different thicknesses have been exposed in a time projection chamber. We observe a half-life of T{sub 1/2}{sup 2{nu}}=(4.3{sub {minus}1.1}{sup +2.4}[stat]{plus_minus}1.4[syst]){times}10{sup 19} yr, consistent with shell model calculations. {copyright} {ital 1996 The American Physical Society.}

Observed double beta decay spectra from 82Se, 100Mo, and 150Nd☆

Abstract Two-electron events resembling double beta decay are being observed at energies beyond the die-off of the spectrum predicted for the two-neutrino mode. The anomaly appears in three isotopes having different half lives and Q-values. Tests are now underway to determine its origin.

Double beta decay

The search for neutrinoless double beta decay has pushed the limit of the effective Majorana neutrino mass below 1 electron volt. Recent progress in double beta experiments is discussed, together with ideas for future attempts to reach tens of milli eV sensitivity.

Double beta decays of Mo-100 and Nd-150

The double beta decays of Mo-100 and Nd-150 were studied in a time projection chamber located 72 m underground. A 3275 h exposure of a 16.7 g sample of metallic Mo enriched to 97.4 % in Mo-100 resulted in a two-neutrino half-life of (6.82 + 0.38 - 0.53 +/- 0.68) * 10**18 y. Similarly, a 6287 h exposure of 15.5 g of Nd2O3 enriched to 91 % in Nd-150 yielded (6.75 + 0.37 - 0.42 +/- 0.68) * 10**18 y. Lower limits on half-lives for neutrinoless decay with and without majoron emission also have been measured.

A measurement of the double beta decay half-life of 48Ca

48 Ca is the lightest of the many double beta decay nuclei, and the only one simple enough to be treated exactly in the shell model without truncation. Thus a ββ 2 v measurement of this isotope provides a unique test of the nuclear physics involved in ββ matrix element calculations. Enriched 48 Ca sources of two different thicknesses have been exposed in a time projection chamber, and yield a preliminary T 1/2 2 v = (5.5 −1.5 +3.5 ) × 10 19 y, in agreement with shell model calculations.