Search results for "multipole"
showing 10 items of 105 documents
Multipole analysis of pion photoproduction based on fixed t dispersion relations and unitarity
1997
We have analysed pion photoproduction imposing constraints from fixed t dispersion relations and unitarity. Coupled integral equations for the S and P wave multipoles were derived from the dispersion relations and solved by the method of Omnes and Muskhelishvili. The free parameters were determined by a fit to the most recent data for \pi^{+} and \pi^{0} production on the proton as well as \pi^{-} production on the neutron, in the energy We have analysed pion photoproduction imposing constraints from fixed t dispersion relations and unitarity. Coupled integral equations for the S and P wave multipoles were derived from the dispersion relations and solved by the method of Omnes and Muskhelis…
Universal features of the nuclear matrix elements governing the mass sector of the 0νββ decay
2005
In this work we report on manifest universal features found in the nuclear matrix elements which govern the mass sector of the neutrinoless double beta decay. The results are based on the analysis of the calculated matrix elements corresponding to the decays of 76Ge, 82Se, 100Mo, and 116Cd. The results suggest a dominance of few low-lying nuclear states of few multipoles in these matrix elements. Dedicated charge-exchange reactions could be used to probe these key states to determine experimentally the value of the nuclear matrix element.
Low energy collective modes of deformed superfluid nuclei within the finite amplitude method
2013
Background: The major challenge for nuclear theory is to describe and predict global properties and collective modes of atomic nuclei. Of particular interest is the response of the nucleus to a time-dependent external field that impacts the low-energy multipole and beta-decay strength. Purpose: We propose a method to compute low-lying collective modes in deformed nuclei within the finite amplitude method (FAM) based on the quasiparticle random-phase approximation (QRPA). By using the analytic property of the response function, we find the QRPA amplitudes by computing the residua of the FAM amplitudes by means of a contour integration around the QRPA poles in a complex frequency plane. Metho…
Charged-current neutrino-nucleus scattering off 95,97^Mo
2013
Background: Reliable cross sections for the neutrino-nucleus scattering off relevant nuclei for supernova neutrinos are essential for various applications in neutrino physics and astrophysics (e.g., supernova mechanisms). Studies of the nuclear responses for the stable molybdenum isotopes are of great interest for the planned MOON (Mo Observatory of Neutrinos) experiment.Purpose: The purpose of the present work is, thus, to perform a detailed study of the charged-current nuclear responses to supernova neutrinos for the stable odd molybdenum isotopes. A special effort will be devoted to discuss in detail the structures of the most relevant final states in the corresponding proton-odd nucleus…
Multipole modes in deformed nuclei within the finite amplitude method
2015
Background: To access selected excited states of nuclei, within the framework of nuclear density functional theory, the quasiparticle random phase approximation (QRPA) is commonly used. Purpose: We present a computationally efficient, fully self-consistent framework to compute the QRPA transition strength function of an arbitrary multipole operator in axially-deformed superfluid nuclei. Methods: The method is based on the finite amplitude method (FAM) QRPA, allowing fast iterative solution of QRPA equations. A numerical implementation of the FAM-QRPA solver module has been carried out for deformed nuclei. Results: The practical feasibility of the deformed FAM module has been demonstrated. I…
Nuclear matrix elements and the neutrinoless double beta decay
2005
Systematics of the nuclear matrix elements related to the neutrinoless double beta ( 0 ν β β ) decay are discussed. The calculation of the related nuclear matrix elements in the framework of the proton-neutron quasiparticle random-phase approximation (pnQRPA) is analyzed. In particular, the extraction of a proper value of the proton-neutron particle-particle interaction parameter in this theory is addressed. The relevance of different multipoles in the multipole decomposition of the 0 ν β β matrix element is also discussed.
Polarization Effects in Electromagnetic Deuteron Break-Up
1992
Polarization observables of deuteron photo- and electrodisintegration with polarized photons and electrons, respectively, and oriented deuterons are investigated with respect to their sensitivity to subnuclear degrees of freedom and relativistic effects, to the different electric and magnetic multipole contributions, to various realistic potential models and — in electrodisintegration — to e.m. form factors.
(e,e'f) Coincidence experiments on 235U and 238U
1990
Abstract Coincidence experiments for (e, e'f) on the actinide nuclei 235 U and 238 U have been performed at the Mainz Microtron (MAMI A) concentrating on three subjects: multipole strength distributions and form factors for the lowest multipolarities, the mass split in the fission decay of various giant multipole resonances, and the separation of near barrier fission channels. Data were taken at four values of momentum transfer ( q eff ≈ 0.20, 0.28, 0.53, and 0.71 fm −1 for 238 U, q eff ≈ 0.20, 0.44, 0.57, and 0.71 fm −1 for 235 U) for excitation energies ω = 4–22 MeV. The fission fragments have been detected using the Giessen PPAC-Ball. A model-independent multipole analysis yields both fo…
Muon-capture strength functions in intermediate nuclei of 0νββ decays
2019
Capture rates of ordinary muon capture (OMC) to the intermediate nuclei of neutrinoless double beta ($0\ensuremath{\nu}\ensuremath{\beta}\ensuremath{\beta}$) decays of current experimental interest are computed. The corresponding OMC (capture-rate) strength functions have been analyzed in terms of multipole decompositions. The computed low-energy OMC-rate distribution to $^{76}\mathrm{As}$ is compared with the available data of Zinatulina et al. [Phys. Rev. C 99, 024327 (2019)]. The present OMC computations are performed using the Morita-Fujii formalism by extending the original formalism beyond the leading order. The participant nuclear wave functions are obtained in extended no-core singl…
Constraints on electromagnetic form factors of sub-GeV dark matter from the cosmic microwave background anisotropy
2021
We consider dark matter which have non-zero electromagnetic form factors like electric/magnetic dipole moments and anapole moment for fermionic dark matter and Rayleigh form factor for scalar dark matter. We consider dark matter mass $m_\chi > \cal{ O}({\rm MeV})$ and put constraints on their mass and electromagnetic couplings from CMB and LSS observations. Fermionic dark matter with non-zero electromagnetic form factors can annihilate to $e^+ e^-$ and scalar dark matter can annihilate to $2\gamma$ at the time of recombination and distort the CMB. We analyze dark matter with multipole moments with Planck and BAO observations. We find upper bounds on anapole moment $g_{A}<7.163\times 10^{3} …