Nuclear Theory·nucl-th

Wednesday·January 11, 2017

8 papers—3 primary·5 cross-listed

01
New Empirical Formula for ({/gamma}, n) reaction cross section near to GDR Peak for elements with Z \geq 60
Rajnikant Makwana · S. Mukherjee · Jian-Song Wang · Zhi-Qiang Chen
A new empirical formula has been developed that describes the $(γ, n)$ nuclear reaction cross sections for the isotopes with $Z \geq 60$ . The results were supported by calculations using TALYS - 1.6, EMPIRE - 3.2.2 nuclear modular codes. The energy region for incident photon energy have been selected near to the giant dipole resonance (GDR) peak energy. The evaluated empirical data were compared with available data in the experimental data library - EXFOR. The data produced using TALYS - 1.6 and EMPIRE - 3.2.2 were in good agreement with experimental data. We have tested and presented the reproducibility of the present new empirical formula. We observed the reproducibility of the new empirical formula near to GDR peak energy is in good agreement with the experimental data and remarkable dependency on key nuclei properties: the neutron, proton and atomic number of the nuclei. The behavior of nucleus near GDR peak energy, and dependency of GDR peak on the isotopic nature were predicted. An effort has been made to explain the deformation of the GDR peak in $(γ, n)$ nuclear reaction cross section for some isotopes, which could not reproduce with TALYS - 1.6 and EMPIRE - 3.2.2. The evaluated data have been presented for the isotopes 180W, 183W, 202Pb, 203Pb, 204Pb, 205Pb, 231Pa, 232U, 237U and 239Pu that have no previous measurements.
nucl-thCPC(2017)·4 citations
02
Applications of nuclear physics to a wider context: from molecules to stars passing through hypernuclei
Lorenzo Fortunato
In this contribution I will review some of the researches that are currently being pursued in Padova (mainly within the In:Theory and Strength projects), focusing on the interdisciplinary applications of nuclear theory to several other branches of physics, with the aim of contributing to show the centrality of nuclear theory in the Italian scientific scenario and the prominence of this fertile field in fostering new physics. In particular, I will talk about: i) the recent solution of the long-standing "electron screening puzzle" that settles a fundamental controversy in nuclear astrophysics between the outcome of lab experiments on earth and nuclear reactions happening in stars; the application of algebraic methods to very diverse systems such as: ii) the supramolecular complex H2@C60, i.e. a diatomic hydrogen molecule caged in a fullerene and iii) to the spectrum of hypernuclei, i.e. systems made of a Lambda particles trapped in (heavy) nuclei.
nucl-thphysics.atm-clusJ.Phys.Conf.Ser.(2018)·0 citations
03
Doubly magic nuclei from Lattice QCD forces at $M_{P S} =$ 469 MeV/c $^{2}$
C. McIlroy🇯🇵 · C. Barbieri🇬🇧 · T. Inoue🇯🇵 · T. Doi🇯🇵 · T. Hatsuda🇯🇵
We perform ab initio self-consistent Green's function calculations of the closed shell nuclei $^{4}$ He, $^{16}$ O and $^{40}$ Ca, based on two-nucleon potentials derived from Lattice QCD simulations, in the flavor SU(3) limit and at the pseudo-scalar meson mass of 469~MeV/c $^{2}$ . The nucleon-nucleon interaction is obtained using the HAL QCD method and its short-distance repulsion is treated by means of ladder resummations outside the model space. Our results show that this approach diagonalises ultraviolet degrees of freedom correctly. Therefore, ground state energies can be obtained from infrared extrapolations even for the relatively hard potentials of HAL QCD. Comparing to previous Brueckner Hartree-Fock calculations, the total binding energies are sensibly improved by the full account of many-body correlations. The results suggest an interesting possible behaviour in which nuclei are unbound at very large pion masses and islands of stability appear at first around the traditional doubly-magic numbers when the pion mass is lowered toward its physical value. The calculated one-nucleon spectral distributions are qualitatively close to those of real nuclei even for the pseudo-scalar meson mass considered here.
nucl-thPRC(2018)·22 citations
04
Complex Langevin dynamics and zeroes of the fermion determinant
Gert Aarts🇬🇧 · Erhard Seiler🇩🇪 · Denes Sexty🇩🇪 · Ion-Olimpiu Stamatescu🇩🇪
QCD at nonzero baryon chemical potential suffers from the sign problem, due to the complex quark determinant. Complex Langevin dynamics can provide a solution, provided certain conditions are met. One of these conditions, holomorphicity of the Langevin drift, is absent in QCD since zeroes of the determinant result in a meromorphic drift. We first derive how poles in the drift affect the formal justification of the approach and then explore the various possibilities in simple models. The lessons from these are subsequently applied to both heavy dense QCD and full QCD, and we find that the results obtained show a consistent picture. We conclude that with careful monitoring, the method can be justified a posteriori, even in the presence of meromorphicity.
↳ hep-lathep-thnucl-thJHEP(2017)·99 citations
05
Euclidean to Minkowski Bethe-Salpeter amplitude and observables
J. Carbonell🇫🇷 · T. Frederico🇧🇷 · V. A. Karmanov🇷🇺
We propose a method to reconstruct the Bethe-Salpeter amplitude in Minkowski space given the Euclidean Bethe-Salpeter amplitude -- or alternatively the Light-Front wave function -- as input. The method is based on the numerical inversion of the Nakanishi integral representation and computing the corresponding weight function. This inversion procedure is, in general, rather unstable, and we propose several ways to considerably reduce the instabilities. In terms of the Nakanishi weight function, one can easily compute the BS amplitude, the LF wave function and the electromagnetic form factor. The latter ones are very stable in spite of residual instabilities in the weight function. This procedure allows both, to continue the Euclidean BS solution in the Minkowski space and to obtain a BS amplitude from a LF wave function.
↳ hep-phnucl-thEPJC(2017)·9 citations
06
pNRQCD determination of E1 radiative transitions
Sebastian Steinbeißer🇩🇪 · Jorge Segovia🇩🇪
This contribution contains the first numerical computation of the complete set of relativistic corrections of relative order $v^{2}$ for electric dipole (E1) transitions in heavy quarkonium; in particular, for the processes $χ_{b J} (1 P) \to Υ (1 S) + γ$ with $J = 0, 1, 2$ . We assume that the momentum transfer of the heavy mesons involved in the reactions lies in the weak-coupling regime of the low-energy effective field theory potential non-relativistic QCD (pNRQCD) and thus a full perturbative calculation can be performed.
↳ hep-phhep-exhep-latnucl-thEPJ Web Conf.(2017)·6 citations
07
Effect of strong magnetic field on competing order parameters in two-flavor dense quark matter
Tanumoy Mandal🇸🇪 · Prashanth Jaikumar🇺🇸
We study the effect of strong magnetic field on competing chiral and diquark order parameters in a regime of moderately dense quark matter. The inter-dependence of the chiral and diquark condensates through nonperturbative quark mass and strong coupling effects is analyzed in a two-flavor Nambu-Jona-Lasinio (NJL) model. In the weak magnetic field limit, our results agree qualitatively with earlier zero-field studies in the literature that find a critical coupling ratio $G_{D} / G_{S} \sim 1.1$ below which chiral or superconducting order parameters appear almost exclusively. Above the critical ratio, there exists a significant mixed broken phase region where both gaps are non-zero. However, a strong magnetic field $B ≳ 1 0^{18}$ G disrupts this mixed broken phase region and changes a smooth crossover found in the weak-field case to a first-order transition for both gaps at almost the same critical density. Our results suggest that in the two-flavor approximation to moderately dense quark matter, strong magnetic field enhances the possibility of a mixed phase at high density, with implications for the structure, energetics and vibrational spectrum of neutron stars.
↳ hep-phnucl-thAdv.High Energy Phys.(2017)·12 citations
08
Nuclear Structure Studies of Neutron-Rich Nuclei : Astrophysical Implications
O. Sorlin (GANIL)🇫🇷
It is proposed here to investigate three major properties of the nuclear force that influence the amplitude of shell gaps, the nuclear binding energies as well as the nuclear $β$ -decay properties far from stability, that are all key ingredients for modeling the r-process nucleosynthesis. These properties are derived from experiments performed in different facilities worldwide, using several various state-of-the-art experimental techniques including transfer and knockout reactions. Expected consequences on the r process nucleosynthesis as well as on the stability of super heavy elements are discussed.
↳ nucl-exnucl-thJPS Conf.Proc.(2017)·0 citations

Affiliations

first authorsco-authorsvia INSPIRE