On the alpha activity of natural tungsten isotopes

The indication for the alpha decay of 180-W with a half-life T1/2=1.1+0.8-0.4(stat)+-0.3(syst)x10^18 yr has been observed for the first time with the help of the super-low background 116-CdWO_4 crystal scintillators. In conservative approach the lower limit on half-life of 180-W has been established as T1/2>0.7x10^18 yr at 90% C.L. Besides, new T1/2 bounds were set for alpha decay of 182-W, 183-W, 184-W and 186-W at the level of 10^20 yr.Comment: 16 pages, 8 figures, accepted in Phys. Rev.

New limits on nucleon decays into invisible channels with the BOREXINO Counting Test Facility

The results of background measurements with the second version of the BOREXINO Counting Test Facility (CTF-II), installed in the Gran Sasso Underground Laboratory, were used to obtain limits on the instability of nucleons, bounded in nuclei, for decays into invisible channels ($inv$): disappearance, decays to neutrinos, etc. The approach consisted of a search for decays of unstable nuclides resulting from $N$ and $NN$ decays of parents $^{12}$C, $^{13}$C and $^{16}$O nuclei in the liquid scintillator and the water shield of the CTF. Due to the extremely low background and the large mass (4.2 ton) of the CTF detector, the most stringent (or competitive) up-to-date experimental bounds have been established: $\tau(n \to inv) > 1.8 \cdot 10^{25}$ y, $\tau(p \to inv) > 1.1 \cdot 10^{26}$ y, $\tau(nn \to inv) > 4.9 \cdot 10^{25}$ y and $\tau(pp \to inv) > 5.0 \cdot 10^{25}$ y, all at 90% C.L.Comment: 22 pages, 3 figures,submitted to Phys.Lett.

Probing New Physics Models of Neutrinoless Double Beta Decay with SuperNEMO

The possibility to probe new physics scenarios of light Majorana neutrino exchange and right-handed currents at the planned next generation neutrinoless double beta 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 beta decay by measuring the decay half-life and the electron angular and energy distributions.Comment: 17 pages, 14 figures, to be published in E.P.J.

Background rejection in NEXT using deep neural networks

[EN] We investigate the potential of using deep learning techniques to reject background events in searches for neutrinoless double beta decay with high pressure xenon time projection chambers capable of detailed track reconstruction. The differences in the topological signatures of background and signal events can be learned by deep neural networks via training over many thousands of events. These networks can then be used to classify further events as signal or background, providing an additional background rejection factor at an acceptable loss of efficiency. The networks trained in this study performed better than previous methods developed based on the use of the same topological signatures by a factor of 1.2 to 1.6, and there is potential for further improvement.The NEXT Collaboration acknowledges support from the following agencies and institutions: the European Research Council (ERC) under the Advanced Grant 339787-NEXT; the Ministerio de Economia y Competitividad of Spain and FEDER under grants CONSOLIDER-Ingenio 2010 CSD2008-0037 (CUP), FIS2014-53371-C04 and the Severo Ochoa Program SEV-2014-0398; GVA under grant PROMETEO/2016/120. Fermilab is operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy. JR acknowledges support from a Fulbright Junior Research Award.Renner, J.; Farbin, A.; Muñoz Vidal, J.; Benlloch-Rodríguez, J.; Botas, A.; Ferrario, P.; Gómez-Cadenas, J.... (2017). Background rejection in NEXT using deep neural networks. Journal of Instrumentation. 12. https://doi.org/10.1088/1748-0221/12/01/T01004S1

Investigations on temperature dependences of parameters of ¹²⁷I NQR spectrum of (BiI₃)(₁₋ₓ)(PbI₂)ₓ mixed layered semiconductor and alkaline halogens crystals

Results of investigations of the temperature dependence of NQR frequencies in the temperature range of 4.2-150 K for ¹²⁷I and ⁷⁹Br of the (BiI₃)(₁₋ₓ)(PbI₂)ₓ mixed layered semiconductor and the crystals of alkaline halogens are presented. The abnormally large absolute values of temperature coefficients of the NQR frequency for (BiI₃)(₁₋ₓ)(PbI₂)ₓ have been detected. It can be explained by influence of the point charges and interlayer fluctuations. It is concluded that the quasi-two-dimensional nature of the vibration states at PbI₂ contents of x ≤0.08 is persistent. The value of the orientation and translational vibrations frequency of the halogen ions assuming the correctness of the two-frequency model Bayer-Kushida has been calculated

The CAMEO Project: high sensitivity quest for majorana neutrino mass with the Borexino Counting Test Facility

The unique features of the CTF and BOREXINO set-ups are used for a high sensitivity study of 100Mo and 116Cd neutrinoless 2\u3b2 decay. Pilot measurements with 116Cd and Monte Carlo simulation show that the sensitivity of the CAMEO experiment (in terms of the T1/2 limit for 0\u3bd2\u3b2 decay) is (3\uc45)\ub71024 y with a 1 kg source of 100Mo (116Cd, 82Se, 150Nd) and 481026 y with 65 kg of 116CdWO4 crystals placed in the CTF. The last value corresponds to a limit on the neutrino mass of m\u3bd 64 0.06 eV. Moreover, with 1000 kg of 116CdWO4 crystals located in the BOREXINO apparatus, the neutrino mass limit can be pushed down to m\u3bd 64 0.02 eV

High sensitivity quest for Majorana neutrino mass with the BOREXINO counting test facility

The unique features of the CTF and BOREXINO set ups are used for a high sensitivity study of 100Mo and 116Cd neutrinoless 2\u3b2 decay. Pilot measurements with 116Cd and Monte Carlo simulation show that the sensitivity of the CAMEO experiment (in terms of the T1/2 limit for 0\u3bd2\u3b2 decay) is (3\u20135) 71024 yr with a 1 kg source of 100Mo (116Cd, 82Se, 150Nd) and 481026 yr with 65 kg of 116CdWO4 crystals placed in the CTF. The last value corresponds to a limit on the neutrino mass of m\u3bdless-than-or-equals, slant0.06 eV. Moreover, with 1000 kg of 116CdWO4 crystals located in the BOREXINO apparatus the neutrino mass limit can be pushed down to m\u3bdless-than-or-equals, slant0.02 eV

Elastic and inelastic scattering of

The angular distributions of the 14C + 18O elastic and inelastic scattering at the energy E lab( ^18O) = 105 MeV were measured firstly. The data were analyzed within the optical model and the coupled-reaction-channels method. The parameters of the 14C + 18O optical potential were deduced. The contributions of one- and two-step transfers of nucleons and clusters in the 14C + 18O elastic and inelastic scattering were calculated. The isotopic differences between the 14C + 18O and 12, 13, 14C + 18O potentials were studied