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Nuclear Theory·nucl-th

Monday·April 9, 2018

5 papers—3 primary·2 cross-listed

All5Primary3Cross-lists2
  1. 01

    Towards Reliable Nuclear Matrix Elements for Neutrinoless Decay

    Javier Menéndez🇯🇵

    The calculated nuclear matrix elements for the neutrinoless double-beta () decay suffer from several limitations. Predicted matrix-element values depend on the many-body method used to calculate them and, in addition, they may need to be "quenched", albeit by an unknown amount due to the relatively high momentum transferred in the decay. These uncertainties are hard to figure out from theoretical calculations alone because of the unique character of decay, not clearly related to other nuclear structure observables. We present recent progress in the determination of the nuclear matrix elements. First, we report improved shell model calculations in an extended configuration space of two harmonic oscillator shells. Second, we note the relation between the decay and double Gamow-Teller transitions that can in principle be measured in double charge-exchange reactions. These new insights pave the way for a more reliable estimation of the value of the nuclear matrix elements.

    nucl-thhep-exhep-phnucl-exJPS Conf.Proc.(2018)·2 citations
  2. 02

    Neutrinoless decay mediated by the exchange of light and heavy neutrinos: The role of nuclear structure correlations

    Javier Menéndez🇯🇵

    Neutrinoless decay nuclear matrix elements calculated with the shell model and energy-density functional theory typically disagree by more than a factor of two in the standard scenario of light-neutrino exchange. In contrast, for a decay mediated by sterile heavy neutrinos the deviations are reduced to about 50\%, an uncertainty similar to the one due to short-range effects. We compare matrix elements in the light- and heavy-neutrino-exchange channels, exploring the radial, momentum transfer and angular momentum-parity matrix element distributions, and considering transitions that involve correlated and uncorrelated nuclear states. We argue that the shorter-range heavy-neutrino exchange is less sensitive to collective nuclear correlations, and that discrepancies in matrix elements are mostly due to the treatment of long-range correlations in many-body calculations. Our analysis supports previous studies suggesting that isoscalar pairing correlations, which affect mostly the longer-range part of the neutrinoless decay operator, are partially responsible for the differences between nuclear matrix elements in the standard light-neutrino-exchange mechanism.

    nucl-thhep-exhep-phnucl-exJ.Phys.G(2018)·125 citations
  3. 03

    Study of hot thermally fissile nuclei using relativistic mean field theory

    Abdul Quddus · K. C. Naik · S. K. Patra

    We have studied the properties of hot U and Pu nuclei in the framework of relativistic mean field formalism. The recently developed FSUGarnet and IOPB-I parameter sets are implemented for the first time to deform nuclei at finite temperature. The results are compared with the well-known NL3 set. The said isotopes are structurally important because of the thermally fissile nature of U and Pu as these nuclei (U and Pu) are formed after the absorption of a thermal neutron, which undergoes fission. Here, we have evaluated the nuclear properties, such as shell correction energy, neutron-skin thickness, quadrupole and hexadecapole deformation parameters and asymmetry energy coefficient for these nuclei as a function of temperature.

    nucl-thJ.Phys.G(2018)·12 citations

Affiliations

first authorsco-authorsvia INSPIRE