238 research outputs found
Multiple CP non-conserving mechanisms of (ββ)0ν -decay and nuclei with largely different nuclear matrix elements
No full textWe investigate the possibility to discriminate between different pairs of CP non-conserving mechanisms inducing the neutrinoless double beta (ββ)0ν -decay by using data on (ββ) 0ν -decay half-lives of nuclei with largely different nuclear matrix elements (NMEs). The mechanisms studied are: light Majorana neutrino exchange, heavy left-handed (LH) and heavy right-handed (RH) Majorana neutrino exchanges, lepton charge non-conserving couplings in SUSY theories with R-parity breaking giving rise to the "dominant gluino exchange" and the "squark-neutrino" mechanisms. The nuclei considered are 76Ge, 82Se, 100Mo, 130Te and 136Xe. Four sets of nuclear matrix elements (NMEs) of the decays of these five nuclei, derived within the Self-consistent Renormalized Quasiparticle Random Phase Approximation (SRQRPA), were employed in our analysis. While for each of the five single mechanisms discussed, the NMEs for 76Ge, 82Se, 100Mo and 130Te differ relatively little, the relative difference between the NMEs of any two nuclei not exceeding 10%, the NMEs for 136 Xe differ significantly from those of 76Ge, 82 Se, 100Mo and 130Te, being by a factor ~ (1.3 - 2.5) smaller. This allows, in principle, to draw conclusions about the pair of non-interfering (interfering) mechanisms possibly inducing the (ββ)0ν -decay from data on the half-lives of 136 Xe and of at least one (two) more isotope(s) which can be, e.g., any of the four, 76 Ge, 82 Se, 100 Mo and 130 Te. Depending on the sets of mechanisms considered, the conclusion can be independent of, or can depend on, the NMEs used in the analysis. The implications of the EXO lower bound on the half-life of 136 Xe for the problem studied are also exploited. © 2013 SISSA, Trieste, Italy
Real-space cluster dynamical mean-field theory: Center-focused extrapolation on the one- and two particle-levels
No full textWe revisit the cellular dynamical mean-field theory (CDMFT) for the single-band Hubbard model on the square lattice at half filling, reaching real-space cluster sizes of up to 9 x 9 sites. Using benchmarks against direct lattice diagrammatic Monte Carlo at high temperature, we show that the self-energy obtained from a cluster center-focused extrapolation converges faster with the cluster size than the periodization schemes previously introduced in the literature. The same benchmark also shows that the cluster spin susceptibility can be extrapolated to the exact result at large cluster size, even though its spatial extension is larger than the cluster size
Statistics of neutrinos and the double beta decay
No full textWe assume that the Pauli exclusion principle is violated for neutrinos, and thus, neutrinos obey at least partly the Bose-Einstein statistics. The parameter sin^2 chi is introduced that characterizes the bosonic (symmetric) fraction of the neutrino wave function. Consequences of the violation of the exclusion principle for the two-neutrino double beta decays are considered. This violation strongly changes the rates of the decays and modifies the energy and angular distributions of the emitted electrons. Pure bosonic neutrinos are excluded by the present data. In the case of partly bosonic (or mixed-statistics) neutrinos the analysis of the existing data allows to put the conservative upper bound sin^2 chi < 0.6. The sensitivity of future measurements of the two-neutrino double beta decay to sin^2 chi is evaluated
Mott Insulating States with Competing Orders in the Triangular Lattice Hubbard Model
No full textThe physics of the triangular lattice Hubbard model exhibits a rich phenomenology, ranging from a metal-insulator transition, intriguing thermodynamic behavior, and a putative spin liquid phase at intermediate coupling, ultimately becoming a magnetic insulator at strong coupling. In this multimethod study, we combine a finite-temperature tensor network method, minimally entangled thermal typical states (METTS), with two Green-function-based methods, connected-determinant diagrammatic Monte Carlo and cellular dynamical mean-field theory, to establish several aspects of this model. We elucidate the evolution from the metallic to the insulating regime from the complementary perspectives brought by these different methods. We compute the full thermodynamics of the model on a width-four cylinder using METTS in the intermediate to strong coupling regime. We find that the insulating state hosts a large entropy at intermediate temperatures, which increases with the strength of the coupling. Correspondingly, and consistently with a thermodynamic Maxwell relation, the double occupancy has a minimum as a function of temperature which is the manifestation of the Pomeranchuk effect of increased localization upon heating. The intermediate coupling regime is found to exhibit both pronounced chiral as well as stripy antiferromagnetic spin correlations. We propose a scenario in which time-reversal symmetry-broken states compete with stripy-spin states at lowest temperatures
Paul Schaefer Collection, 1870-1997
No full textThe Paul Schaefer collection consists of ca. 62 cu ft of correspondence, maps, litigation manuscripts, legislative documents, pamphlets, circulars, published materials, photographic material, audio recordings, video recordings, and art prints. The collection is in good condition, however some of the material exhibits water or insect damage. The dates within the collection range from 1870 to1997, with the bulk of the collection falling between 1940 and 1997. This collection documents Schaefer\u27s lengthy career as an environmental grass roots organizer and author, his work in home building and historic restoration projects, and his family life.https://digitalworks.union.edu/arl_findingaids/1036/thumbnail.jp
Neutrino Mass Matrix in Neutrino-Related Processes
No full textTechniques are developed for constructing amplitudes of neutrino-related
processes in terms of the neutrino mass matrix, with no reference to the
neutrino mixing matrix. The amplitudes of neutrino oscillations in vacuum and
medium, quasi-elastic neutrino scattering, decays and double-
decays are considered. The proposed approach makes extensive use of Frobenius
covariants within the framework of Sylvester's theorem on matrix functions. The
in-medium dispersion laws are found in terms of elementary functions for three
flavors of Majorana neutrinos as an application of the developed formalism. The
in-medium dispersion laws for Dirac neutrinos can be determined in the general
case by searching for the roots of a polynomial of degree 6. In the rest frame
of baryon matter, the minimum energy of both Majorana and Dirac neutrinos is
achieved at a finite neutrino momentum. In such cases, Dirac neutrinos occupy a
hollow Fermi sphere at zero temperature and low densities. Fitting experimental
data in terms of the neutrino mass matrix can provide better statistical
accuracy in determining the neutrino mass matrix compared to methods using the
neutrino mixing matrix at intermediate stages.Comment: 19 pages; two references, one footnote added, misprints remove
Searching for New Physics in Two-Neutrino Double Beta Decay
No full textMotivated by nonzero neutrino masses and the possibility of new physics discovery, a number of experiments search for neutrinoless double beta decay. While hunting for this hypothetical nuclear process, a significant amount of two-neutrino double beta decay data have become available. Although these events are regarded and studied mostly as the background of neutrinoless double beta decay, they can also be used to probe physics beyond the standard model. In this Letter, we show how the presence of right-handed leptonic currents would affect the energy distribution and angular correlation of the outgoing electrons in two-neutrino double beta decay. Consequently, we estimate constraints imposed by currently available data on the existence of right-handed neutrino interactions without having to assume their nature. In this way, our results complement the bounds coming from the nonobservation of neutrinoless double beta decay as they limit also the exotic interactions of Dirac neutrinos. We perform a detailed calculation of two-neutrino double beta decay under the presence of exotic (axial-) vector currents, and we demonstrate that current experimental searches can be competitive to existing limits
Production of monodisperse polyurea microcapsules using microfluidics.
No full textMethods to make microcapsules - used in a broad range of healthcare and energy applications - currently suffer from poor size control, limiting the establishment of size/property relationships. Here, we use microfluidics to produce monodisperse polyurea microcapsules (PUMC) with a limonene core. Using varied flow rates and a commercial glass chip, we produce capsules with mean diameters of 27, 30, 32, 34, and 35 µm, achieving narrow capsule size distributions of ±2 µm for each size. We describe an automated method of sizing droplets as they are produced using video recording and custom Python code. The sustainable generation of such size-controlled PUMCs, potential replacements for commercial encapsulated systems, will allow new insights into the effect of particle size on performance
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