The possibility to probe new physics scenarios of light Majorana neutrino exchange and right-handed currents at the planned next generation neutrinoless double β decay experiment SuperNEMO is discussed. Its ability to study different isotopes and track the outgoing electrons provides the means to discriminate different underlying mechanisms for the neutrinoless double β decay by measuring the decay half-life and the electron angular and energy distributions.a

The NEMO-3 detector, which had been operating in the Modane Underground Laboratory from 2003 to 2010, was designed to search for neutrinoless double-β (0νββ) decay. We report the final results of a search for 0νββ decays with 6.914 kg of 100 Mo using the entire NEMO-3 data set with a detector live time of 4.96 yr, which corresponds to an exposure of 34.3 kg · yr. We perform a detailed study of the expected background in the 0νββ signal region and find no evidence of 0νββ decays in the data. The level of observed background in the 0νββ signal region [2.8-3.2] MeV is 0.44 AE 0.13 counts=yr=kg, and no events are observed in the interval [3.2-10] MeV. We therefore derive a lower limit on the half-life of 0νββ decays in 100 Mo of * Deceased PHYSICAL REVIEW D 92, 072011 (2015) 1550-7998=2015=92 (7)=072011 (23) 072011-1 © 2015 American Physical Society T 1=2 ð0νββÞ > 1.1 × 10 24 yr at the 90% confidence level, under the hypothesis of decay kinematics similar to that for light Majorana neutrino exchange. Depending on the model used for calculating nuclear matrix elements, the limit for the effective Majorana neutrino mass lies in the range hm ν i < 0.33-0.62 eV. We also report constraints on other lepton-number violating mechanisms for 0νββ decays.

The full data set of the NEMO-3 experiment has been used to measure the half-life of the two-neutrino double beta decay of 100 Mo to the ground state of 100 Ru,

The half-life for double beta decay of 150 Nd has been measured by the NEMO-3 experiment at the Modane Underground Laboratory. Using 924.7 days of data recorded with 36.55 g of 150 Nd the half-life for 2νββ decay is measured to be T 2ν 1/2 = (9.11 +0.25 −0.22 (stat.) ± 0.63 (syst.)) × 10 18 years. The observed limit on the half-life for neutrinoless double beta decay is found to be T 0ν 1/2 > 1.8×10 22 years at 90% Confidence Level. This translates into a limit on the effective Majorana neutrino mass of mν < 4.0 − 6.3 eV if the nuclear deformation is taken into account. We also set limits on models involving Majoron emission, right-handed currents and transitions to excited states. Experiments studying atmospheric, solar, reactor and accelerator neutrinos have established the existence of neutrino oscillations as a direct evidence for a non-zero neutrino mass. These experiments, however, cannot distinguish between Dirac or Majorana neutrinos. They also provide no information on the absolute neutrino mass scale, since oscillations experiments measure the square of the mass difference between neutrino states. The half-life of neutrinoless double beta decay (0νββ) is inversely proportional to the effective Majorana neutrino mass squared, m ν 2 . Observation of this process would therefore directly constrain the neutrino mass scale and would be unambiguous evidence for the Majorana nature of neutrinos. The 0νββ process also violates lepton number and is therefore a direct probe for physics beyond the standard model of particle physics.The search for neutrinoless double beta decay of neodymium-150 ( 150 Nd) using the NEMO-3 detector is of special interest since 150 Nd is a candidate isotope for SuperNEMO [1], a next generation double beta decay experiment based on the NEMO-3 concept, and the SNO++ experiment at SNOLAB [2]. Its main advan-2 tages are the high Q ββ value for double beta decay, Q ββ = 3.368 MeV, which lies above the typical energies for many background sources, and the large phase space factor. The 2νββ half-life of 150 Nd has previously been measured using a Time Projection Chamber [3,4].The NEMO-3 experiment has been taking data since 2003 in the Modane Underground Laboratory (LSM) located in the Fréjus tunnel at a depth of 4800 m water equivalent. The detector has a cylindrical shape with 20 sectors that contain different isotopes in the form of thin foils with a total surface of about 20 m 2 [5]. In addition to ∼7 kg of 100 Mo and ∼1 kg of 82 Se, the detector contains smaller amounts of other isotopes. The neodymium source foil is composed of Nd 2 O 3 with an enrichement of (91 ± 0.5)%, corresponding to a 150 Nd mass of 36.55 ± 0.10 g. On each side of the foils is a ∼50 cm wide tracking volume comprising a total of 6180 drift cells operated in Geiger mode with helium as drift gas. A 25 Gauss magnetic field created by a solenoid provides charge identification. The calorimeter consists of 1940 plastic scintillators coupled to low radioactivity photomultipliers. For 1 MeV electrons the energy resolutio...

No abstract