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This paper gives a review of the double beta experimental techniques and projects, in the search for the Majorana neutrino. The purpose of this review is to detail, for each technique, the different origins of background, how they can be identified, and how they can be reduced. Advantages and limitations of the different techniques are discussed.

Phasic variations in dopamine levels are interpreted as a teaching signal reinforcing rewarded behaviors. However, behavior also depends on the motivational, neuromodulatory effect of phasic dopamine. In this study, we reveal a neurodynamical principle that unifies these roles in a recurrent network-based decision architecture embodied through an action-perception loop with the task space, the MAGNet model. Dopamine optogenetic conditioning in mice was accounted for by an embodied network model in which attractors encode internal goals. Dopamine-dependent synaptic plasticity created “latent” attractors, to which dynamics converged, but only locally. Attractor basins were widened by dopamine-modulated synaptic excitability, rendering goals accessible globally, i.e. from distal positions. We validated these predictions optogenetically in mice: dopamine neuromodulation suddenly and specifically attracted animals toward rewarded locations, without off-target motor effects. We thus propose that motivational dopamine reveals dopamine-built attractors representing potential goals in a behavioral landscape. The reason why manipulating dopamine (DA) activity can affect both action latency, action direction, and movement vigor, but only in certain animal states and behavioral settings is not fully understood. Here, the authors propose that DA signaling builds and reveals latent attractors representing potential goals. They validate their model predictions: activation of dopamine neurons exerts context- and state-dependent effects on mouse movements.

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, \\[T_{1/2} = \\left[ 6.81 \\pm 0.01\\,\\left( \\text{ stat }\\right) ^{+0.38}_{-0.40}\\,\\left( \\text{ syst }\\right) \\right] \\times 10^{18}\\] year. The two-electron energy sum, single electron energy spectra and distribution of the angle between the electrons are presented with an unprecedented statistics of \\[5\\times 10^5\\] events and a signal-to-background ratio of \\[\\sim \\] 80. Clear evidence for the Single State Dominance model is found for this nuclear transition. Limits on Majoron emitting neutrinoless double beta decay modes with spectral indices of \\[\\mathrm{n}=2,3,7\\], as well as constraints on Lorentz invariance violation and on the bosonic neutrino contribution to the two-neutrino double beta decay mode are obtained.

In the prefrontal cortex (PFC), higher-order cognitive functions and adaptive flexible behaviors rely on continuous dynamical sequences of spiking activity that constitute neural trajectories in the state space of activity. Neural trajectories subserve diverse representations, from explicit mappings in physical spaces to generalized mappings in the task space, and up to complex abstract transformations such as working memory, decision-making and behavioral planning. Computational models have separately assessed learning and replay of neural trajectories, often using unrealistic learning rules or decoupling simulations for learning from replay. Hence, the question remains open of how neural trajectories are learned, memorized and replayed online, with permanently acting biological plasticity rules. The asynchronous irregular regime characterizing cortical dynamics in awake conditions exerts a major source of disorder that may jeopardize plasticity and replay of locally ordered activity. Here, we show that a recurrent model of local PFC circuitry endowed with realistic synaptic spike timing-dependent plasticity and scaling processes can learn, memorize and replay large-size neural trajectories online under asynchronous irregular dynamics, at regular or fast (sped-up) timescale. Presented trajectories are quickly learned (within seconds) as synaptic engrams in the network, and the model is able to chunk overlapping trajectories presented separately. These trajectory engrams last long-term (dozen hours) and trajectory replays can be triggered over an hour. In turn, we show the conditions under which trajectory engrams and replays preserve asynchronous irregular dynamics in the network. Functionally, spiking activity during trajectory replays at regular timescale accounts for both dynamical coding with temporal tuning in individual neurons, persistent activity at the population level, and large levels of variability consistent with observed cognitive-related PFC dynamics. Together, these results offer a consistent theoretical framework accounting for how neural trajectories can be learned, memorized and replayed in PFC networks circuits to subserve flexible dynamic representations and adaptive behaviors.

H.A. Wilson, then R.H. Dicke, proposed to describe gravitation by a spatial change of the refractive index of the vacuum around a gravitational mass. Dicke extended this formalism in order to describe the apparent expansion of the universe by a cosmological time dependence of the global vacuum index. In this paper, we develop Dicke’s formalism. The metric expansion in standard cosmology (the time-dependent scale factor of the Friedmann–Lemaître curved spacetime metric) is replaced by a flat and static Euclidean metric with a change with time of the vacuum index. We show that a vacuum index increasing with time produces both the cosmological redshift and time dilation, and that the predicted evolution of the energy density of the cosmological microwave background is consistent with the standard cosmology. We then show that the type Ia supernovæ data, from the joint SDSS-II and SNLS SNe-Ia samples, are well modeled by a vacuum index varying exponentially as n(t)=exp(t/τ0), where τ0=8.0-0.8+0.2 Gyr. The main consequence of this formalism is that the cosmological redshift should affect any atom, with a relative decrease of the energy levels of about -210-18s-1. Possibilities for an experimental investigation of this prediction are discussed.

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.

The NEMO-3 results for the double- β decay of 150 Nd to the 0 1 + and 2 1 + excited states of 150 Sm are reported. The data recorded during 5.25 year with 36.6 g of the isotope 150 Nd are used in the analysis. The signal of the 2 ν β β transition to the 0 1 + excited state is detected with a statistical significance exceeding 5 σ . The half-life is measured to be 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 ν β β decay to the 2 1 + level the limit is T 1 / 2 2 ν β β ( 2 1 + ) > 2.42 × 10 20 year . The limits on the 0 ν β β decay to the 0 1 + and 2 1 + levels of 150 Sm are significantly improved to T 1 / 2 0 ν β β ( 0 1 + ) > 1.36 × 10 22 year and T 1 / 2 0 ν β β ( 2 1 + ) > 1.26 × 10 22 year .

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 NEMO-3 results for the double- β decay of¹⁵⁰ Nd to the 0 ⁺₁and 2 ⁺₁excited states of¹⁵⁰ Sm are reported. The data recorded during 5.25 year with 36.6 g of the isotope¹⁵⁰ Nd are used in the analysis. The signal of the2ν β β transition to the 0 ⁺₁excited state is detected with a statistical significance exceeding 5 σ . The half-life is measured to beT_(1/2)^(2ν β β)(0⁺₁) = \\left[ 1.11 ^(+0.19)_(-0.14) \\left( \\hbox stat\\right) ^(+0.17)_(-0.15) \\left( \\hbox syst\\right) \\right] × 10²⁰  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 the2ν β β decay to the 2 ⁺₁level the limit isT^(2ν β β)_(1/2)(2⁺₁) > 2.42 × 10²⁰ \\hbox year . The limits on the0ν β β decay to the 0 ⁺₁and 2 ⁺₁levels of¹⁵⁰ Sm are significantly improved toT_(1/2)^(0ν β β)(0⁺₁) > 1.36 × 10²² \\hbox yearandT_(1/2)^(0ν β β)(2⁺₁) > 1.26 × 10²² \\hbox year .

Using data from the NEMO-3 experiment, we have measured the two-neutrino double beta decay (\\[2\\nu \\beta \\beta \\]) half-life of \\[^{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}\\] 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\\]. In addition, a search for neutrinoless double beta decay (\\[0\\nu \\beta \\beta \\]) 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\\nu } > 2.5 \\times 10^{23} \\,\\text{ y } \\,(90\\%\\,\\text{ 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 }\\], where the range reflects \\[0\\nu \\beta \\beta \\] nuclear matrix element values from different calculations. Furthermore, constraints on lepton number violating parameters for other \\[0\\nu \\beta \\beta \\] mechanisms, such as right-handed currents, majoron emission and R-parity violating supersymmetry modes have been set.