Search results for "Parametrization"
showing 10 items of 99 documents
Solution of Hartree-Fock-Bogoliubov equations and fitting procedure using the N2LO Skyrme pseudopotential in spherical symmetry
2017
International audience; We present the development of the extended Skyrme N2LO pseudopotential in the case of spherical even-even nuclei calculations. The energy density functional is first presented. Then we derive the mean-field equations and discuss the numerical method used to solve the resulting fourth-order differential equation together with the behavior of the solutions at the origin. Finally, a fitting procedure for such an N2LO interaction is discussed and we provide a first parametrization. Typical ground-state observables are calculated and compared against experimental data.
Cranked Relativistic Hartree-Bogoliubov Theory: probing the gateway to superheavy nuclei
2003
The cranked relativistic Hartree+Bogoliubov theory has been applied for a systematic study of the nuclei around 254No, the heaviest elements for which detailed spectroscopic data are available. The deformation, rotational response, pairing correlations, quasi-particle and other properties of these nuclei have been studied with different parametrizations for the effective mean-field Lagrangian. Pairing correlations are taken into account by a finite range two-body force of Gogny type. While the deformation properties are well reproduced, the calculations reveal some deficiencies of the effective forces both in the particle-hole and particle-particle channels. For the first time, the quasi-pa…
Initial Conditions in the One-Fluid Hydrodynamical Description of Ultrarelativistic Nuclear Collisions
1997
We present a phenomenological model for the initial conditions needed in a one-fluid hydrodynamical description of ultrarelativistic nuclear collisions at CERN--SPS. The basic ingredient is the parametrization of the baryon stopping, i.e. the rapidity distribution, as a function of the thickness of the nuclei. We apply the model to S + S and Pb + Pb collisions and find after hydrodynamical evolution reasonable agreement with the data.
Bilarge neutrino mixing and the Cabibbo angle
2012
Recent measurements of the neutrino mixing angles cast doubt on the validity of the so-far popular tri-bimaximal mixing ansatz. We propose a parametrization for the neutrino mixing matrix where the reactor angle seeds the large solar and atmospheric mixing angles, equal to each other in first approximation. We suggest such bi-large mixing pattern as a model building standard, realized when the leading order value of the reactor angle equals the Cabibbo angle.
Neutrinoless double-beta decay and physics beyond the standard model
2012
Neutrinoless double beta decay is the most powerful tool to probe not only for Majorana neutrino masses but for lepton number violating physics in general. We discuss relations between lepton number violation, double beta decay and neutrino mass, review a general Lorentz invariant parametrization of the double beta decay rate, highlight a number of different new physics models showing how different mechanisms can trigger double beta decay, and finally discuss possibilities to discriminate and test these models and mechanisms in complementary experiments.
Nuclear Parton Distributions - a DGLAP Analysis
1999
Nuclear parton distributions $f_A(x,Q^2)$ are studied within a framework of the DGLAP evolution. Measurements of $F_2^A/F_2^D$ in deep inelastic $lA$ collisions, and Drell--Yan dilepton cross sections measured in $pA$ collisions are used as constraints. Also conservation of momentum and baryon number is required. It is shown that the calculated $Q^2$ evolution of $F_2^{\rm Sn}/F_2^{\rm C}$ agrees very well with the recent NMC data, and that the ratios $R_f^A=f_A/f$ are only moderately sensitive to the choice of a specific modern set of free parton distributions. For general use, we offer a numerical parametrization of $R_f^A(x,Q^2)$ for all parton flavours $f$ in $A>2$, and at $10^{-6}\l…
Masses, mixings, Yukawa couplings and their symmetries
1993
We present a method to find the number of real and imaginary observable parameters coming from the Yukawa sector in an arbitrary gauge theory. The method leads naturally to a classification of Yukawa couplings according to their symmetries and suggests a new parametrization of masses and mixings that is useful to study the behaviour of Yukawa couplings under the renormalization group. We apply it to some examples based on the Standard Model with Yukawa couplings obeying various chiral symmetries. We also show how our method of parameter counting can be used in some models with an enlarged leptonic sector.
A general parametrization for the long-range part of neutrinoless double beta decay
1997
Double beta decay has been proven to be a powerful tool to constrain $B-L$ violating physics beyond the standard model. We present a representation for the long-range part of the general $0\nu\beta\beta$ decay rate allowed by Lorentz-invariance. Combined with the short range part this general parametrization in terms of effective $B-L$ violating couplings will provide the $0\nu\beta\beta$ limits on arbitrary lepton number violating theories.
Skyrme-force parametrization: Least-squares fit to nuclear ground-state properties.
1986
We investigate systematically the possibilities and the limits of the Skyrme force for reproducing nuclear ground-state properties in a spherical Hartree-Fock calculation. This investigation is performed by means of least-squares fits of the force parameters to the measured binding energy, diffraction radius, and surface width of eight selected nuclei. Particular emphasis is put on the density dependence of the interaction, which turns out to be determined mainly by the surface width. The least-squares fitting procedure yields the best-fit parameters together with uncertainties on them, and it also allows one to estimate the uncertainties of an extrapolation to other fields, e.g., nuclear m…
Parameter Degeneracy in Flavor-Dependent Reconstruction of Supernova Neutrino Fluxes
2008
We reexamine the possibility of reconstructing the initial fluxes of supernova neutrinos emitted in a future core-collapse galactic supernova explosion and detected in a Megaton-sized water Cherenkov detector. A novel key element in our method is the inclusion, in addition to the total and the average energies of each neutrino species, of a "pinching" parameter characterizing the width of the distribution as a fit parameter. We uncover in this case a continuous degeneracy in the reconstructed parameters of supernova neutrino fluxes at the neutrinosphere. We analyze in detail the features of this degeneracy and show how it occurs irrespective of the parametrization used for the distribution …