T. Shima

The MAJORANA DEMONSTRATOR Neutrinoless Double-Beta Decay Experiment

The MAJORANA DEMONSTRATOR will search for the neutrinoless double-beta decay of the isotope Ge with a mixed array of enriched and natural germanium detectors. The observation of this rare decay would indicate that the neutrino is its own antiparticle, demonstrate that lepton number is not conserved, and provide information on the absolute mass scale of the neutrino. The DEMONSTRATOR is being assembled at the 4850-foot level of the Sanford Underground Research Facility in Lead, South Dakota. The array will be situated in a low-background environment and surrounded by passive and active shielding. Here we describe the science goals of the DEMONSTRATOR and the details of its design.

Double beta decays of 100Mo

Abstract Double beta (ββ) decays of 100Mo were studied by means of ELEGANTS V. A finite half-life of T 2v 1 2 =(1.15 +0.30 −0.20 )×10 19 yr (68% CL ) for 2νββ decay and the most stringent lower limit of T 0v 1 2 > 4.7 × 10 21 yr (68% CL ) on the half-life for the 0vββ decay were obtained. The observed T 2ν 1 2 indicates very severe cancellation of the components of the relevant nuclear matrix element.

Big Bang nucleosynthesis with a new neutron lifetime

We show that the predicted primordial helium production is significantly reduced when new measurements of the neutron lifetime and the implied enhancement in the weak reaction rates are included in big-bang nucleosynthesis. Therefore, even if a narrow uncertainty in the observed helium abundance is adopted, this brings the constraint on the baryon-to-photon ratio from BBN and the observed helium into better accord with the independent determination of the baryon content deduced from the WMAP spectrum of power fluctuations in the cosmic microwave background and measurements of primordial deuterium in narrowline quasar absorption systems at high redshift.

The high sensitivity beta-gamma spectrometer ELEGANTS V for rare β(e) and ββ(ee) decays

Abstract The high sensitivity β-γ spectrometer ELEGANTS V (ELEctron GAmma-ray NeuTrino Spectrometer V) has been developed primarily for studying rare double-beta decays. It is a low background high sensitivity detector for low energy beta (β), electron (e) and gamma (γ) decays. ELEGANTS V is shown to be useful for the study of ultrarare nuclear β(e), ββ(ee), β(e)γ and ββ(ee)γ decays with decay rates of the order of T ∼ 10 −27–30 s −1 (t 1 2 ∼ 10 20–23 yr ) .

Double Beta Decays of 116Cd

Double beta decays (ββ) from the 0 + ground state in 116 Cd to the 0 + ground state in 116 Sn were studied by means of ELEGANT V. A finite half-life for the two-neutrino ββ(2νββ) and an upper limit on the neutrinoless one (0νββ) were obtained as T 2ν 1/2 =2.6 +0.9 -0.5 ×10 19 y and T 0ν 1/2 >6.3×10 21 y (68% C.L.), respectively. The nuclear matrix element M 2ν ββ was deduced as 0.069±0.009 in units of ( m e c 2 ) -1 . This supports the universal quenching of the 2νββ rates in this mass region, which is consistent with that previously measured in 100 Mo.

Simultaneous measurement of the photodisintegration of He-4 in the giant dipole resonance region

We have performed for the first time the simultaneous measurement of the two-body and three-body photodisintegration cross sections of

Limits on neutrino-less double beta decay of 100Mo

^{4}\mathrm{He}

Double beta decay of 76Ge(0+) to 0+ and 2+ states in 76Se studied by the β-γ coincidence method

in the energy range from 21.8 to 29.8 MeV using monoenergetic pulsed photons and a 4\ensuremath{\pi} time projection chamber containing

Multilayer Scintillator Responses for Mo Observatory of Neutrino Experiment Studied Using a Prototype Detector MOON-1

^{4}\mathrm{He}

Resonant Photonuclear Reactions for Isotope Transmutation

gas as an active target in an event-by-event mode. The photon beam was produced via the Compton backscattering of laser photons with high-energy electrons. The