Nuclear Theory·nucl-th

Monday·December 11, 2017

10 papers—6 primary·4 cross-listed

01
[Submitted on 7 Dec 2017]
Microscopic optical potentials derived from ab initio translationally invariant nonlocal one-body densities
Michael Gennari · Matteo Vorabbi · Angelo Calci · Petr Navratil
We derive a microscopic optical potential for intermediate energies using ab initio translationally invariant nonlocal one-body nuclear densities computed within the no-core shell model (NCSM) approach utilizing two- and three-nucleon chiral interactions as the only input. The optical potential is derived at first-order within the spectator expansion of the non-relativistic multiple scattering theory by adopting the impulse approximation and using the same chiral nucleon-nucleon interaction as that used to compute densities. The ground state local and nonlocal densities of 4,6,8He, 12C, and 16O are calculated and applied to optical potential construction. The differential cross sections and the analyzing powers for the elastic proton scattering off of these nuclei are then calculated for different values of the incident proton energy. The impact of nonlocality and the COM removal is discussed. The use of nonlocal densities has a substantial impact on the differential cross sections and improves agreement with experiment in comparison to results generated with the local densities especially for light nuclei.
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1712.02879 [pdf]
PRC(2018)·50 citations
02
[Submitted on 8 Dec 2017]
Comparative study of the requantization of the time-dependent mean field for the dynamics of nuclear pairing
F. Ni · T. Nakatsukasa
To describe quantal collective phenomena, it is useful to requantize the time-dependent mean-field dynamics. We study the time-dependent Hartree-Fock-Bogoliubov (TDHFB) theory for the two-level pairing Hamiltonian, and compare results of different quantization methods. The one constructing microscopic wave functions, using the TDHFB trajectories fulfilling the Einstein-Brillouin-Keller quantization condition, turns out to be the most accurate. The method is based on the stationary-phase approximation to the path integral. We also examine the performance of the collective model which assumes that the pairing gap parameter is the collective coordinate. The applicability of the collective model is limited for the nuclear pairing with a small number of single-particle levels, because the pairing gap parameter represents only a half of the pairing collective space.
Comments:
28 pages, 13 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1712.02954 [pdf]
PRC(2018)·4 citations
03
[Submitted on 8 Dec 2017]
Two-body contributions to the effective mass in nuclear effective interactions
D. Davesne🇫🇷 · J. Navarro🇪🇸 · J. Meyer🇫🇷 · K. Bennaceur🇫🇷 · A. Pastore🇬🇧
Starting from general expressions of well-chosen symmetric nuclear matter quantities derived for both zero- and finite-range effective theories, we derive the contributions to the effective mass. We first show that, independently of the range, the two-body contribution is enough to describe correctly the saturation mechanism but gives an effective mass value around $m^{*} / m ≃ 0.4$ . Then, we show that the full interaction (by instance, an effective two-body density-dependent term on top of the pure two-body term) is needed to reach the accepted value $m^{*} / m ≃ 0.7 - 0.8$ .
Comments:
Minor typos fixed
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1712.03003 [pdf]
PRC(2018)·19 citations
04
[Submitted on 8 Dec 2017]
Combining symmetry breaking and restoration with configuration interaction: extension to z-signature symmetry in the case of the Lipkin Model
Julien Ripoche🇫🇷 · Thomas Duguet🇧🇪 · Jean-Paul Ebran🇫🇷 · Denis Lacroix🇫🇷
Background: Ab initio many-body methods whose numerical cost scales polynomially with the number of particles have been developed over the past fifteen years to tackle closed-shell mid-mass nuclei. Open-shell nuclei have been further addressed by implementing variants based on the concept of spontaneous symmetry breaking (and restoration). Purpose: In order to access the spectroscopy of open-shell nuclei more systematically while controlling the numerical cost, we design a novel many-body method that combines the merit of breaking and restoring symmetries with those brought about by low-rank individual excitations. Methods: The recently proposed truncated configuration-interaction method based on optimized symmetry-broken and -restored states is extended to the z-signature symmetry associated with a discrete subgroup of SU(2). The highly-truncated N-body Hilbert subspace within which the Hamiltonian is diagonalized is spanned by a z-signature broken and restored Slater determinant vacuum and associated low-rank excitations. Results: The proposed method provides an excellent reproduction of the ground-state energy and of low-lying excitation energies of various z-signatures and total angular momenta. In doing so, the successive benefits of (i) breaking the symmetry, (ii) restoring the symmetry, (iii) including low-rank particle-hole excitations and (iv) optimizing the amount by which the underlying vacuum breaks the symmetry are illustrated. Conclusions: The numerical cost of the newly designed variational method is polynomial with respect to the system size. The present study confirms the results obtained previously for the attractive pairing Hamiltonian in connection with the breaking and restoration of U(1) global gauge symmetry. These two studies constitute a strong motivation to apply this method to realistic nuclear Hamiltonians.
Comments:
14 pages, 10 figures, full abstract available in text
Subjects:
Nuclear Theory (nucl-th); Superconductivity (cond-mat.supr-con)
arXiv:
1712.03101 [pdf]
PRC(2018)·9 citations
05
[Submitted on 8 Dec 2017]
Meson effect in the proto neutron star PSR J0348+0432
Xian-Feng Zhao🇨🇳
The effect of mesons $f_{0} (975)$ (named as $f$ ), $ϕ (1020)$ (named as $ϕ$ ) and $δ$ on the moment of inertia of the PNS PSR J0348+0432 is examined in the framework of the relativistic mean field theory considering the baryon octet. It is found that the energy density $ε$ and pressure $p$ will increase considering the mesons $δ$ whereas will decrease as the mesons $f$ and $ϕ$ being considered. When the mesons $f, ϕ$ and $δ$ are considered, the energy density and pressure will all decrease. It is also found that the contribution of mesons $f$ , $ϕ$ and $δ$ to the central energy density is only the central energy density's 0.06 $\sim$ 0.6\% whereas the contribution of mesons $f$ , $ϕ$ and $δ$ to the central pressure is the central pressure's 4 $\sim$ 7\%. For the radius, it will decrease when the contributions of mesons $f$ , $ϕ$ and $δ$ are considered. The moment of inertia $I$ will increase considering the mesons $δ$ whereas will decrease as the mesons $f$ and $ϕ$ being considered. When the mesons $f$ , $ϕ$ and $δ$ are all considered, the moment of inertia will decrease. It is found that the contribution of mesons $f$ and $ϕ$ to moment of inertia is 4 $\sim$ 9 times larger than that of mesons $δ$ . Our results show that the mesons $f$ , $ϕ$ and $δ$ contribute to the moment of inertia's 2 $\sim$ 5\%.
Comments:
13 pages, 7 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1712.03110 [pdf]
Int.J.Theor.Phys.(2017)·2 citations
06
[Submitted on 8 Dec 2017]
Microscopic analysis of Li nuclei cluster photodisintegration reaction characteristics in broad energy range: from threshold until 100 MeV
M.A. Zhusupov · K.A. Zhaksybekova · R.S. Kabatayeva
On the base of potential theory of light nuclei cluster photodisintegration the characteristics of Lithium nuclei cluster photodisintegration reactions are considered in the range of low and intermediate energies. For the inverse reaction the interference has an opposite character: in forward semisphere it is deconstructive, and in backward semisphere it is constructive. In the energy range above several MeV the E2-multipole becomes dominating. The effect of appearance of the node structure of the wave function of relative motion has been considered in the characteristics of Li cluster photodisintegration reaction with polarized and non-polarized photons.
Comments:
9 pages, 9 figures, 17 references
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1712.03184 [pdf]
0 citations
07
[Submitted on 7 Dec 2017] (cross-list from hep-ph)
What is the right formalism to search for resonances?
JPAC Collaboration: M. Mikhasenko🇩🇪 · A. Pilloni🇺🇸 · J. Nys🇧🇪 · M. Albaladejo🇪🇸 · C. Fernandez-Ramirez🇲🇽 · A. Jackura🇺🇸 · V. Mathieu🇺🇸 · N. Sherrill🇺🇸 · T. Skwarnicki🇺🇸 · A. P. Szczepaniak🇺🇸
Hadron decay chains constitute one of the main sources of information on the QCD spectrum. We discuss the differences between several partial wave analysis formalisms used in the literature to build the amplitudes. We match the helicity amplitudes to the covariant tensor basis. Hereby, we pay attention to the analytical properties of the amplitudes and separate singularities of kinematical and dynamical nature. We study the analytical properties of the spin-orbit (LS) formalism, and some of the covariant tensor approaches. In particular, we explicitly build the amplitudes for the B -> psi pi K and B -> Dbar pi pi decays, and show that the energy dependence of the covariant approach is model dependent. We also show that the usual recursive construction of covariant tensors explicitly violates crossing symmetry, which would lead to different resonance parameters extracted from scattering and decay processes.
Comments:
14 pages, 3 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Theory (nucl-th)
arXiv:
1712.02815 [pdf]
EPJC(2018)·20 citations
08
[Submitted on 7 Dec 2017] (cross-list from hep-ph)
Parton correlations in double parton scattering
Tomas Kasemets🇩🇪 · Sergio Scopetta🇮🇹
Double parton scattering events are directly sensitive to the correlations between two partons inside a proton and can answer fundamental questions on the connections between the proton constituents. In this chapter, the different types of possible correlations, our present knowledge of them, and the processes where they are likely to be important, are introduced and explained. The increasing integrated luminosity at the LHC and the refinements of the theory of double parton scattering, lead to interesting prospects for measuring, or severely constraining, two-parton correlations in the near future.
Comments:
Prepared for: Multiple Parton Interactions at the LHC, Eds. P. Bartalini and J. R. Gaunt, World Scientific, Singapore; v2: references added
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1712.02884 [pdf]
Adv.Ser.Direct.High Energy Phys.(2018)·20 citations
09
[Submitted on 7 Dec 2017] (cross-list from nucl-ex)
Elliptic Flow and the Nuclear Equation of State
W. Trautmann🇩🇪 · H. H. Wolter🇩🇪
New constraints for the nuclear equation of state at suprasaturation densities have been obtained by measuring collective particle flows in heavy-ion reactions at relativistic energies. Ratios and differences of neutron and hydrogen flows in 197Au + 197Au collisions at 400 MeV/nucleon were used in studies of the asymmetric-matter equation of state. The comparison with predictions of transport models favors a moderately soft to linear density dependence, consistent with ab-initio nuclear matter theories. Model predictions suggest that comprehensive data sets collected at higher bombarding energies will provide information on the asymmetric-matter equation of state in the density range up to two or three times the saturation value.
Comments:
20 pages, 9 figures, paper dedicated to the memory of Prof. Walter Greiner, to appear in Walter Greiner Memorial Volume (World Scientific). arXiv admin note: substantial text overlap with arXiv:1205.2585
Subjects:
Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1712.03093 [pdf]
4 citations
10
[Submitted on 8 Dec 2017] (cross-list from hep-lat)
Nuclear modification of scalar, axial and tensor charges from lattice QCD
Emmanuel Chang🇺🇸 · Zohreh Davoudi🇺🇸 · William Detmold🇺🇸 · Arjun S. Gambhir🇺🇸 · Kostas Orginos🇺🇸 · Martin J. Savage🇺🇸 · Phiala E. Shanahan🇺🇸 · Michael L. Wagman🇺🇸 · Frank Winter🇺🇸
Complete flavour decompositions of the scalar, axial and tensor charges of the proton, deuteron, diproton and $^{3}$ He at SU(3)-symmetric values of the quark masses corresponding to a pion mass $m_{π} \sim 806$ MeV are determined using lattice QCD. At the physical quark masses, the scalar charges constrain mean-field models of nuclei and the low-energy interactions of nuclei with potential dark matter candidates. The axial and tensor charges of nuclei constrain their spin content, integrated transversity and the quark contributions to their electric dipole moments. External fields are used to directly access the quark-line connected matrix elements of quark bilinear operators, and a combination of stochastic estimation techniques is used to determine the disconnected sea-quark contributions. Significant nuclear modifications are found, with particularly large, O(10%), effects in the scalar charges. Typically, these nuclear effects reduce the effective charge of the nucleon (quenching), although in some cases an enhancement is not excluded. Given the size of the nuclear modifications of the scalar charges resolved here, contributions from correlated multi-nucleon effects should be quantified in the analysis of dark matter direct-detection experiments using nuclear targets.
Comments:
published version
Subjects:
High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1712.03221 [pdf]
PRL(2018)·67 citations

Affiliations

first authorsco-authorsvia INSPIRE