Abstract Using data from the NEMO-3 experiment, we have measured the two-neutrino double beta decay ($$2\nu \beta \beta $$ 2νββ ) half-life of $$^{82}$$ 82 Se as $$T_{\smash {1/2}}^{2\nu } \!=\! ...\left 9.39 \pm 0.17\left( \text{ stat }\right) \pm 0.58\left( \text{ syst }\right) \right \times 10^{19}$$ T1/22ν=9.39±0.17stat±0.58syst×1019 y under the single-state dominance hypothesis for this nuclear transition. The corresponding nuclear matrix element is $$\left| M^{2\nu }\right| = 0.0498 \pm 0.0016$$ M2ν=0.0498±0.0016 . In addition, a search for neutrinoless double beta decay ($$0\nu \beta \beta $$ 0νββ ) using 0.93 kg of $$^{82}$$ 82 Se observed for a total of 5.25 y has been conducted and no evidence for a signal has been found. The resulting half-life limit of $$T_{1/2}^{0\nu } > 2.5 \times 10^{23} \,\text{ y } \,(90\%\,\text{ C.L. })$$ T1/20ν>2.5×1023y(90%C.L.) for the light neutrino exchange mechanism leads to a constraint on the effective Majorana neutrino mass of $$\langle m_{\nu } \rangle < \left( 1.2{-}3.0\right) \,\text{ eV }$$ ⟨mν⟩<1.2-3.0eV , where the range reflects $$0\nu \beta \beta $$ 0νββ nuclear matrix element values from different calculations. Furthermore, constraints on lepton number violating parameters for other $$0\nu \beta \beta $$ 0νββ mechanisms, such as right-handed currents, majoron emission and R-parity violating supersymmetry modes have been set.
Abstract The NEMO-3 results for the double- $$\beta $$ β decay of $$^{150}$$ 150 Nd to the 0 $$^+_1$$ 1 + and 2 $$^+_1$$ 1 + excited states of $$^{150}$$ 150 Sm are reported. The data recorded during ...5.25 year with 36.6 g of the isotope $$^{150}$$ 150 Nd are used in the analysis. The signal of the $$2\nu \beta \beta $$ 2 ν β β transition to the 0 $$^+_1$$ 1 + excited state is detected with a statistical significance exceeding 5 $$\sigma $$ σ . The half-life is measured to be $$T_{1/2}^{2\nu \beta \beta }(0^+_1) = \left 1.11 ^{+0.19}_{-0.14} \,\left( \hbox {stat}\right) ^{+0.17}_{-0.15}\,\left( \hbox {syst}\right) \right \times 10^{20}$$ T 1 / 2 2 ν β β ( 0 1 + ) = 1 . 11 - 0.14 + 0.19 stat - 0.15 + 0.17 syst × 10 20 year, which is the most precise value that has been measured to date. 90% confidence-level limits are set for the other decay modes. For the $$2\nu \beta \beta $$ 2 ν β β decay to the 2 $$^+_1$$ 1 + level the limit is $$T^{2\nu \beta \beta }_{1/2}(2^+_1) > 2.42 \times 10^{20}~\hbox {year}$$ T 1 / 2 2 ν β β ( 2 1 + ) > 2.42 × 10 20 year . The limits on the $$0\nu \beta \beta $$ 0 ν β β decay to the 0 $$^+_1$$ 1 + and 2 $$^+_1$$ 1 + levels of $$^{150}$$ 150 Sm are significantly improved to $$T_{1/2}^{0\nu \beta \beta }(0^+_1) > 1.36 \times 10^{22}~\hbox {year}$$ T 1 / 2 0 ν β β ( 0 1 + ) > 1.36 × 10 22 year and $$T_{1/2}^{0\nu \beta \beta }(2^+_1) > 1.26 \times 10^{22}~\hbox {year}$$ T 1 / 2 0 ν β β ( 2 1 + ) > 1.26 × 10 22 year .
The OPERA neutrino detector at the underground Gran Sasso Laboratory (LNGS) was designed to perform the first detection of neutrino oscillations in appearance mode, through the study of nu_mu to ...nu_tau oscillations. The apparatus consists of a lead/emulsion-film target complemented by electronic detectors. It is placed in the high-energy, long-baseline CERN to LNGS beam (CNGS) 730 km away from the neutrino source. In August 2006 a first run with CNGS neutrinos was successfully conducted. A first sample of neutrino events was collected, statistically consistent with the integrated beam intensity. After a brief description of the beam and of the various sub-detectors, we report on the achievement of this milestone, presenting the first data and some analysis results.
Using data from the NEMO-3 experiment, we have measured the two-neutrino double beta decay (
2
ν
β
β
) half-life of
82
Se as
T
1
/
2
2
ν
=
9.39
±
0.17
stat
±
0.58
syst
×
10
19
y under the ...single-state dominance hypothesis for this nuclear transition. The corresponding nuclear matrix element is
M
2
ν
=
0.0498
±
0.0016
. In addition, a search for neutrinoless double beta decay (
0
ν
β
β
) using 0.93 kg of
82
Se observed for a total of 5.25 y has been conducted and no evidence for a signal has been found. The resulting half-life limit of
T
1
/
2
0
ν
>
2.5
×
10
23
y
(
90
%
C.L.
)
for the light neutrino exchange mechanism leads to a constraint on the effective Majorana neutrino mass of
⟨
m
ν
⟩
<
1.2
-
3.0
eV
, where the range reflects
0
ν
β
β
nuclear matrix element values from different calculations. Furthermore, constraints on lepton number violating parameters for other
0
ν
β
β
mechanisms, such as right-handed currents, majoron emission and R-parity violating supersymmetry modes have been set.
This paper reviews the current experimental program envisaged with the future CERN neutrino beam called CNGS. Two detectors, OPERA and ICARUS, are under preparation and should investigate the ...neutrino properties coming from the CNGS to shed light on neutrino oscillation physics.
This paper reviews the current status of the OPERA detector preparation, which is designed to investigate the neutrino oscillation properties using the future CERN neutrino beam called CNGS. The ...physics potential and performances for neutrino oscillation studies, including
ν
μ
→
ν
e
search, will also be presented.
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