A. R. Smith

New limit on the neutrinoless betabeta decay of 130Te.

We report the present results of CUORICINO, a search for neutrinoless double-beta (0nu betabeta) decay of 130Te. The detector is an array of 62 TeO2 bolometers with a total active mass of 40.7 kg. The array is cooled by a dilution refrigerator shielded from environmental radioactivity and energetic neutrons, operated at approximately 8 mK in the Gran Sasso Underground Laboratory. No evidence for (0nu betabeta) decay was found and a new lower limit, T(1/2)(0nu) > or = 1.8 x 10(24) yr (90% C.L.) is set, corresponding to [m(nu)] < or = 0.2 to 1.1 eV, depending on the theoretical nuclear matrix elements used in the analysis.

Neutron background for a dark matter experiment at a shallow depth site

Abstract The neutron flux in the Stanford Underground Facility, a shallow depth site with an overburden of 17 ± 1 m.w.e., has been measured using a moderated BF 3 proportional counter. This counter has also been used to measure the neutron flux inside various shielding configurations required for a dark matter search at this site. These measurements demonstrate that lead shielding, used for photon attenuation, acts as a strong neutron source, with the neutrons being produced primarily by cosmic ray muon interactions within the lead. We have determined the production rate of cosmic ray induced neutrons in lead at this depth. Fortunately, these measurements also demonstrate that it is possible to moderate and capture these neutrons so that the resulting neutron flux is no longer sensitive to the presence of the lead shielding. For a dark matter search, however, care still has to be taken to minimize the inactive mass near the detector.

Recebt results from the UCSB/LBL double beta decay experiment

Abstract A new limit has been set on neutrinoless double beta decay, a process which would require lepton number nonconservation, plus one other piece of new physics. That second item might be light Majorana electron neutrino mass, a very heavy Majorana neutrino, right-handed currents, or supersymmetric particles in theories with R-parity violation. Limits on all these quantities can be obtained from the result that the UCSB/LBL Ge multidetector system shows the halflife for 76 Ge → 76 Se + 2 e − to be > 1.2 × 10 24 y at the 90% confidence level or >2.4 × 1024y at the 68% confidence level.

Installation of the cryogenic dark matter search (CDMS)

Abstract We discuss the status of a cryogenic dark matter search beginning operation in the Stanford Underground Facility. The detectors will be cooled in a specially designed cryostat connected to a modified side access Oxford 400 dilution refrigerator. We discuss two detector designs and performance, the cryostat construction and operation, and the multi-level shield surrounding the cryostat. Finally, we will examine the limits which we will be able to set on WIMP dark matter with this experiment.

Results from a search for the 0 neutrino beta beta-decay of Te-130

A detailed description of the CUORICINO 130 Te neutrinoless double-beta (0 νββ) decay experiment is given and recent results are reported. CUORICINO is an array of 62 tellurium oxide (TeO 2 ) bolometers with an active mass of 40.7 kg. It is cooled to ∼8-10 mK by a dilution refrigerator shielded from environmental radioactivity and energetic neutrons. It is running in the Laboratori Nazionali del Gran Sasso (LNGS) in Assergi, Italy. These data represent an exposure of 11.83 kg yr or 91 mole-years of 130 Te. No evidence for 0 νββ-decay was observed and a limit of T 0ν 1/2 ( 130 Te) ≥ 3.0 x 1024 y (90% CL) is set. This corresponds to an upper limit on the effective mass, , between 0.19 and 0.68 eV when analyzed with the many published nuclear structure calculations. In the context of these nuclear models, the values fall within the range corresponding to the claim of evidence of 0 νββ-decay by H. V. Klapdor-Kleingrothaus et al. The experiment continues to acquire data.

A New Limit on the Neutrinoless DBD of 130Te

We report the present results of CUORICINO, a search for neutrinoless double-beta (0nu betabeta) decay of 130Te. The detector is an array of 62 TeO2 bolometers with a total active mass of 40.7 kg. The array is cooled by a dilution refrigerator shielded from environmental radioactivity and energetic neutrons, operated at approximately 8 mK in the Gran Sasso Underground Laboratory. No evidence for (0nu betabeta) decay was found and a new lower limit, T(1/2)(0nu) > or = 1.8 x 10(24) yr (90% C.L.) is set, corresponding to [m(nu)] < or = 0.2 to 1.1 eV, depending on the theoretical nuclear matrix elements used in the analysis.

The first cryogenic dark matter experiment

An experimental search for dark matter particle candidates using cryogenic detectors requires a low radioactive background environment. We discuss the status of a cryogenic dark matter experiment to be performed in the Stanford Underground Facility. The detectors will be cooled in a specially designed cryostat connected to a modified side access Oxford 400 dilution refrigerator. Details of the cryostat design and its operating performance are presented. The effectiveness of the multi-level shield surrounding the cryostat, as well as the background levels we expect to achieve in the pilot experiment are discussed. Finally, we examine the limits which can be set on dark matter candidates with such an experiment.

The LBL/UCSB 76Ge Double Beta Decay Experiment: First Results

A paper given at the IEEE Nuclear Science Symposium last year presented the scientific justification for this experiment and discussed the design of the detector system. At the present time two of the dual detector systems (i.e., four out of a final total of eight detectors) are operating in the complete active/ passive shield in the low background laboratory at LBL. Early results (1620 hrs) of an experiment using two detectors yield a limit of 4 × 1022 years (68% confidence) for the half life of the neutrinoless double beta decay (ßßo¿) of 76Ge. Although this experiment was carried out above ground, the result approaches those achieved by other groups in deep underground laboratories. Based on studies of the origins of background in our system, we hope to reach a limit of 3 × 1023 years (or more) in a two month/ four detector experiment to be carried out soon in an underground facility.

Production of solder and flux with low radioactivity

Abstract The problem of radioactivity in solder has been studied. A low-radioactive rosin-core solder has been produced. Low-radioactive alternatives for rosin-based flux have also been considered.

Identification and suppression of low-energy background from 210Pb contamination in lead

Abstract The importance of 210 Pb as a potential background source, particularly at low energies, is clearly demonstrated by both measurements and Monte Carlo simulations. A method for effectively suppressing this background source is also demonstrated.