Neutrinoless double beta decay is one of the most sensitive probes for new physics beyond the Standard Model of particle physics. One of the isotopes under investigation is ^136Xe, which would double beta decay into ^136Ba. Detecting the single ^136Ba daughter provides a sort of ultimate tool in the discrimination against backgrounds. Previous work demonstrated the ability to perform single atom imaging of Ba atoms in a single-vacancy site of a solid xenon matrix. In this paper, the effort to identify signal from individual barium atoms is extended to Ba atoms in a hexa-vacancy site in the matrix and is achieved despite increased photobleaching in this site. Abrupt fluorescence turn-off of a single Ba atom is also observed. Significant recovery of fluorescence signal lost through photobleaching is demonstrated upon annealing of Ba deposits in the Xe ice. Following annealing, it is observed that Ba atoms in the hexa-vacancy site exhibit antibleaching while Ba atoms in the tetra-vacancy site exhibit bleaching. This may be evidence for a matrix site transfer upon laser excitation. Our findings offer a path of continued research toward tagging of Ba daughters in all significant sites in solid xenon.

Neutrinoless double beta decay is one of the most sensitive probes for new physics beyond the Standard Model of particle physics. One of the isotopes under investigation is Xe-136, which would double beta decay into Ba-136. Detecting the single Ba-136 daughter provides a sort of ultimate tool in the discrimination against backgrounds. Previous work demonstrated the ability to perform single atom imaging of Ba atoms in a single-vacancy site of a solid xenon matrix. In this paper, the effort to identify signal from individual barium atoms is extended to Ba atoms in a hexa-vacancy site in the matrix and is achieved despite increased photobleaching in this site. Abrupt fluorescence turn-off of a single Ba atom is also observed. Significant recovery of fluorescence signal lost through photobleaching is demonstrated upon annealing of Ba deposits in the Xe ice. Following annealing, it is observed that Ba atoms in the hexa-vacancy site exhibit antibleaching while Ba atoms in the tetra-vacancy site exhibit bleaching. This may be evidence for a matrix site transfer upon laser excitation. Our findings offer a path of continued research toward tagging of Ba daughters in all significant sites in solid xenon.

We report on the performance of silicon photomultiplier (SiPM) light sensors operating in electric field strength up to 30 kV/cm and at a temperature of 149 K, relative to their performance in the absence of an external electric field. The SiPM devices used in this study show stable gain, photon detection efficiency, and rates of correlated pulses, when exposed to external fields, within the estimated uncertainties. No visible damage to the surface of the devices was caused by the exposure.

The possibility of double-beta (ββ) decay was recognized in the mid 1930s, and by 1939 something of its potential to reveal fundamental properties of the neutrino was known as well. But experimental observation of the phenomenon was out of reach. Despite numerous attempts over the next 30 years, and strong suggestions of its existence from geochemical experiments, ββ decay had not been observed to occur in the laboratory. Our group at UC Irvine took up the search in the early 1970s, first with a cloud chamber and then with a time-projection chamber. The following narrative traces a discovery process that unfolded over the ensuing 15 years—a sequence of setbacks and false starts punctuated by occasional victories and, ultimately, by a definitive laboratory observation of two-neutrino ββ decay, in August 1987.

The Enriched Xenon Observatory (EXO) will search for double beta decays of 136Xe. We report the results of a systematic study of trace concentrations of radioactive impurities in a wide range of raw materials and finished parts considered for use in the construction of EXO-200, the first stage of the EXO experimental program. Analysis techniques employed, and described here, include direct gamma counting, alpha counting, neutron activation analysis, and high-sensitivity mass spectrometry.

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 similar to 5 min (similar to 1 min) are achieved using He (Ar) as a buffer gas at pressures in the range 8x10(-5)-4x10(-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.

Cosmology provides an excellent laboratory for testing various aspects of neutrino physics. Here, I review the current status of cosmological searches for neutrino mass, as well as other properties of neutrinos. Future cosmological probes of neutrino properties are also discussed in detail.

Technique and Application of Xenon Detectors, pp. 179-191 (2003) No AccessPROGRESS ON THE ENRICHED XENON OBSERVATORY DOUBLE-BETA DECAY EXPERIMENTP. VOGEL, R. DEVOE, E. CONTI, F. PIETROPAOLO, M. DANILOV, A. DOLGOLENKO, O. ZELDOVICH, G. BOWER, M. BREIDENBACH, R. CONLEY, A. ODIAN, C. PRESCOTT, P. ROWSON, T. SANCHEZ, K. SKARPAAS, K. WAMBA, G. GRATTA, T. KOFFAS, S. WALDMAN, Y-F. WANG, J. WODIN, Z. DJURCIC, A. PIEPKE, M. MOE, J-L. VUILLEUMIER, P. PICCHI, G. GIANNINI, and R. NELSONP. VOGELCaltech, USA, R. DEVOEIBM Almaden, USA, E. CONTIINFN Padova, Italy, F. PIETROPAOLOINFN Padova, Italy, M. DANILOVITEF Moscow, Russia, A. DOLGOLENKOITEF Moscow, Russia, O. ZELDOVICHITEF Moscow, Russia, G. BOWERSLAC, USA, M. BREIDENBACHSLAC, USA, R. CONLEYSLAC, USA, A. ODIANSLAC, USA, C. PRESCOTTSLAC, USA, P. ROWSONSLAC, USA, T. SANCHEZSLAC, USA, K. SKARPAASSLAC, USA, K. WAMBASLAC, USA, G. GRATTAStanford University, USA, T. KOFFASStanford University, USA, S. WALDMANStanford University, USA, Y-F. WANGStanford University, USA, J. WODINStanford University, USA, Z. DJURCICU. of Alabama, USA, A. PIEPKEU. of Alabama, USA, M. MOEU. of California Irvine, USA, J-L. VUILLEUMIERU. of Neuchatel, Switzerland, P. PICCHIU. of Torino, Italy, G. GIANNINIU. of Trieste, Italy, and R. NELSONWIPP Carlsbad, USAhttps://doi.org/10.1142/9789812705075_0016Cited by:0 (Source: Crossref) PreviousNext AboutSectionsPDF/EPUB ToolsAdd to favoritesDownload CitationsTrack CitationsRecommend to Library ShareShare onFacebookTwitterLinked InRedditEmail Abstract: This paper presents the research and development progress towards the Enriched Xenon Observatory. A brief review of double beta decay theory and the experimental requirements for the observation of neutrinoless double beta decay will be followed by an overview of the research and development experiments currently underway. FiguresReferencesRelatedDetails Recommended Technique and Application of Xenon DetectorsMetrics History PDF download

We comment on the recent claim for the experimental observation of neutrinoless double-beta decay. We discuss several limitations in the analysis provided in that paper and conclude that there is no basis for the presented claim.

48Ca, the lightest double beta decay candidate, has been until now the only one simple enough to be treated exactly in the nuclear shell model. Thus, theββ(2ν) half-life measurement, reported here, provides a unique test of the nuclear physics involved in theββ matrix element calculation. Enriched48Ca sources of two different thicknesses have been exposed in a time projection chamber, and yieldT 1 2/2ν =(4.3 −1.1 +2.4 [stat.] ± 1.4[syst.]) × 1019 years, compatible with the shell model calculations. The consequences of this result for the shell model calculation of theββ(2ν) rate are briefly discussed.

Ca-48 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 beta beta(2v) measurement of this isotope provides a unique test of the nuclear physics involved in beta beta matrix element calculations. Enriched Ca-48 sources of two different thicknesses have been exposed in a time projection chamber, and yield a preliminary T-1/2(2v) = (5.5(-1.5)(+3.5)) x 10(19) y, in agreement with shell model calculations.

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.

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〉 < 7.0 × 10−5. The strengths and weaknesses of the TPC, and the feasibility of a larger TPC for neutrinoless double beta decay are discussed.

Substantial progress has been made in double beta decay experiments in the past few years, including the beginning of sensitive new searches for neutrinoless double beta decay, and several additional positive detections of the two-neutrino mode by geochemical, radiochemical, and direct-counting techniques. This review discusses the recent experimental activity.

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 axe now underway to determine its origin.

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.