Nuclear Theory·nucl-th

Friday·March 4, 2016

12 papers—5 primary·7 cross-listed

01
[Submitted on 3 Mar 2016]
Multidimensionally-constrained relativistic mean-field study of spontaneous fission: coupling between shape and pairing degrees of freedom
Jie Zhao · Bing-Nan Lu · Tamara Niksic · Dario Vretenar · Shan-Gui Zhou
Studies of fission dynamics, based on nuclear energy density functionals, have shown that the coupling between shape and pairing degrees of freedom has a pronounced effect on the nonperturbative collective inertia and, therefore, on dynamic (least-action) spontaneous fission paths and half-lives. Collective potentials and nonperturbative cranking collective inertia tensors are calculated using the multidimensionally-constrained relativistic mean-field (MDC-RMF) model. Pairing correlations are treated in the BCS approximation using a separable pairing force of finite range. Pairing fluctuations are included as a collective variable using a constraint on particle-number dispersion. Fission paths are determined with the dynamic programming method by minimizing the action in multidimensional collective spaces. The dynamics of spontaneous fission of $^{264}$ Fm and $^{250}$ Fm are explored. Fission paths, action integrals and corresponding half-lives computed in the three-dimensional collective space of shape and pairing coordinates, using the relativistic functional DD-PC1 and a separable pairing force of finite range, are compared with results obtained without pairing fluctuations. Results for $^{264}$ Fm are also discussed in relation with those recently obtained using the HFB model. The inclusion of pairing correlations in the space of collective coordinates favors axially symmetric shapes along the dynamic path of the fissioning system, amplifies pairing as the path traverses the fission barriers, significantly reduces the action integral and shortens the corresponding SF half-life.
Comments:
10 pages, 8 figures. arXiv admin note: text overlap with arXiv:1511.05689
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1603.00992 [pdf]
PRC(2016)·83 citations
02
[Submitted on 3 Mar 2016]
Power counting for nuclear forces in chiral effective field theory
Bingwei Long
The present note summarizes the discourse on power counting issues of chiral nuclear forces, with an emphasis on renormalization-group invariance. Given its introductory nature, I will lean toward narrating a coherent point of view on the concepts, rather than covering comprehensively the development of chiral nuclear forces in different approaches.
Comments:
To appear in the special issue of the International Journal of Modern Physics E on "Effective Field Theory in Nuclear Physics", published version, added references
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1603.01002 [pdf]
IJMPE(2016)·14 citations
03
[Submitted on 3 Mar 2016]
Isotopic yield in cold binary fission of even-even $^{244 - 258}$ Cf isotopes
K. P. Santhosh · Annu Cyriac · Sreejith Krishnan
The cold binary fission of even-even 244-258Cf isotopes has been studied by taking the interacting barrier as the sum of Coulomb and proximity potential. The favorable fragment combinations are obtained from the cold valley plot (plot of driving potential vs. mass number of fragments) and by calculating the yield for charge minimized fragments. It is found that highest yield for 244,246,248Cf isotopes are for the fragments with isotope of Pb (Z=82) as one fragment, whereas for 250Cf and 252Cf isotopes the highest yield is for the fragments with isotope of Hg (Z=80) as one fragment. In the case of 254,256,258Cf isotopes the highest yield is for the fragments with Sn (Z=50) as one fragment. Thus, the fragment combinations with maximum yield reveal the role of doubly magic and near doubly magic nuclei in binary fission. It is found that asymmetric splitting is favoured for Cf isotopes with mass number A < 250 and symmetric splitting is favoured for Cf isotopes with A > 252. In the case of Cf isotope with A=252, there is an equal probability for asymmetric and symmetric splitting. The individual yields obtained for the cold fission of 252Cf isotope are compared with the experimental data taken from the {\gamma}- {\gamma}- {\gamma} coincidences technique using Gammasphere.
Comments:
18 pages, 9 figures in Nuclear Physics A (2016)
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1603.01162 [pdf]
NPA(2016)·13 citations
04
[Submitted on 3 Mar 2016]
Neutron stars: from the inner crust to the core with the (Extended) Nambu-Jona-Lasinio model
Helena Pais🇵🇹 · Débora P. Menezes🇧🇷 · Constança Providência🇵🇹
Nucleonic matter is described within a su(2) extended Nambu-Jona-Lasinio model. Several parametrizations with different nuclear matter saturation properties are proposed. At subsaturation, nuclear pasta phases are calculated within two methods: the coexistence-phases approximation and the compressible liquid drop model, with the surface tension coefficient determined using a geometrical approach at zero temperature. An unified equation of state of stellar matter for the inner crust, with the nuclear pasta phases, and the core is calculated. The mass and radius of neutron stars within this framework are obtained for several families of hadronic and hybrid stars. The quark phase of hybrid stars is described within the su(3) NJL model including a vector term. Stellar macroscopic properties are in accordance with some of the recent results in the literature.
Comments:
13 pages, 10 figures, published version
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1603.01239 [pdf]
PRC(2016)·27 citations
05
[Submitted on 3 Mar 2016]
Chiral Electroweak Currents in Nuclei
D.O. Riska🇫🇮 · R. Schiavilla🇺🇸
The development of the chiral dynamics based description of nuclear electroweak currents is reviewed. Gerald E. (Gerry) Brown's role in basing theoretical nuclear physics on chiral Lagrangians is emphasized. Illustrative examples of the successful description of electroweak observables of light nuclei obtained from chiral effective field theory are presented.
Comments:
34 pages, chapter for Gerry Brown memorial book
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1603.01253 [pdf]
IJMPE(2017)·5 citations
06
[Submitted on 28 Feb 2016] (cross-list from gr-qc)
Spin Precession of Slow Neutrons in Einstein-Cartan Gravity with Torsion, Chameleon and Magnetic Field
A. N. Ivanov🇦🇹 · M. Wellenzohn🇦🇹
We analyse a spin precession of slow neutrons in the Einstein-Cartan gravity with torsion, chameleon and magnetic field. For the derivation of the Heisenberg equation of motion of the neutron spin we use the effective low-energy potential, derived by Ivanov and Wellenzohn (Phys. Rev. D92, 125004 (2015)) for slow neutrons, coupled to gravitational, chameleon and torsion fields to order 1/m, where m is the neutron mass. In addition to this low-energy interactions we switch on the interaction of slow neutrons with a magnetic field. We show that to linear order approximation with respect to gravitational, chameleon and torsion fields the Dirac Hamilton operator for fermions (neutrons), moving in spacetimes created by rotating coordinate systems, contains the anti-Hermitian operators of torsion-fermion (neutron) interactions, caused by torsion scalar and tensor degrees of freedom. Such anti-Hermitian operators violate CP and T invariance. One may assume that in the rotating Universe and galaxies the obtained anti-Hermitian torsion-fermion interactions might be an origin of i) violation of CP and T invariance in the Universe and ii) of baryon asymmetry.
Comments:
14 pages, no figures
Subjects:
General Relativity and Quantum Cosmology (gr-qc); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th); Quantum Physics (quant-ph)
arXiv:
1602.08709 [pdf]
PRD(2016)·12 citations
07
[Submitted on 2 Mar 2016] (cross-list from nucl-ex)
Nucleon Resonance Physics
Volker D. Burkert🇺🇸
Recent results of meson photo-production at the existing electron machines with polarized real photon beams and the measurement of polarization observables of the final state baryons have provided high precision data that led to the discovery of new excited nucleon and $Δ$ states using multi-channel partial wave analyses procedures. The internal structure of several prominent excited states has been revealed employing meson electroproduction processes. On the theoretical front, lattice QCD is now predicting the baryon spectrum with very similar characteristics as the constituent quark model, and continuum QCD, such as is represented in the Dyson-Schwinger Equations approach and in light front relativistic quark models, describes the non-perturbative behavior of resonance excitations at photon virtuality of $Q^{2} > 1.5 G e V^{2}$ . In this talk I discuss the need to continue a vigorous program of nucleon spectroscopy and the study of the internal structure of excited states as a way to reveal the effective degrees of freedom underlying the excited states and their dependence on the distance scale probed.
Comments:
9 pages. 9 figures, ECT* 2015 Workshop on Nucleon Resonances, October 12-16, 2015, Trento, Italy
Subjects:
Nuclear Experiment (nucl-ex); High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1603.00919 [pdf]
Few Body Syst.(2016)·17 citations
08
[Submitted on 3 Mar 2016] (cross-list from hep-lat)
Hadron Interactions from lattice QCD
Sinya Aoki🇯🇵
We review our strategy to study hadron interactions from lattice QCD using newly proposed potential method. We first explain our strategy in the case of nuclear potentials and its application to nuclear physics. We then discuss the origin of the repulsive core, by adding strange quarks to the system. We also explore a possibility for H-dibaryon to exist in flavor SU(3) limit of lattice QCD. We conclude the paper with an application of our strategy to investigate the maximum mass of neutron stars.
Comments:
9 pages, 11 figures, A plenary talk given at "21st International Conference on Few-Body Problems in Physics", May 18-22, 2015, Chicago, USA
Subjects:
High Energy Physics — Lattice (hep-lat); Nuclear Theory (nucl-th)
arXiv:
1603.00989 [pdf]
EPJ Web Conf.(2016)·2 citations
09
[Submitted on 3 Mar 2016] (cross-list from hep-lat)
Axial U(1) symmetry in the chiral symmetric phase of 2-flavor QCD at finite temperature
Sinya Aok for JLQCD Collaboration🇯🇵
We discuss the fate of the axial U(1) symmetry in 2-flavor QCD at finite temperature, where the non-singlet chiral symmetry is restored. We first summarize the previous theoretical investigation on the relation between the eigenvalue density of the Dirac operator and the axial U(1) symmetry. We show that the eigenvalue density near the origin behaves as $λ^{γ}$ with $γ > 2$ in the chirally symmetric phase, where $λ$ is an eigenvalue. This implies that the axial U(1) symmetry is partially restored, so that the low energy symmetry of the theory becomes SU(2) $\otimes$ SU(2) $\otimes$ Z $_{4}$ . Secondly, we report recent numerical investigations on this issue by lattice QCD simulations with lattice chiral fermions such as Overlap or improved domain-wall fermions. Our preliminary results indicate that the eigenvalue density seems to have a gap at the origin just above $T_{c}$ , the temperature of the chiral symmetry restoration, which implies the axial U(1) symmetry is effectively restored at high temperature. We also point out an importance of the exact lattice chiral symmetry to obtain correct results on this issue.
Comments:
10 pages, 5 figures, A talk given at "The 8th International Workshop on Chiral Dynamics, CD2015", 29 June - 03 July, 2015, Pisa, Italy
Subjects:
High Energy Physics — Lattice (hep-lat); Nuclear Theory (nucl-th)
arXiv:
1603.00997 [pdf]
PoS(2016)·5 citations
10
[Submitted on 3 Mar 2016] (cross-list from hep-ph)
Effect of the $2 p 2 h$ cross-section uncertainties on an analysis of neutrino oscillations
Artur M. Ankowski🇺🇸 · Omar Benhar🇺🇸 · Camillo Mariani🇺🇸 · Erica Vagnoni🇮🇹
We report the results of a study aimed at quantifying the impact on the oscillation analysis of the uncertainties associated with the description of the neutrino-nucleus cross section in the two-particle--two-hole sector. The results of our calculations, based on the kinematic method of energy reconstruction and carried out comparing two data-driven approaches, show that the existing discrepancies in the neutrino cross sections have a sizable effect on the extracted oscillation parameters, particularly in the antineutrino channel.
Comments:
7 pages, 5 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Theory (nucl-th)
arXiv:
1603.01072 [pdf]
PRD(2016)·29 citations
11
[Submitted on 3 Mar 2016] (cross-list from hep-ph)
$X (5568)$ and and its partner states
Yan-Rui Liu🇨🇳 · Xiang Liu🇨🇳 · Shi-Lin Zhu🇨🇳
Stimulated by the recent observation of the $X (5568)$ , we study the $X (5568)$ and its partners under the tetraquark scenario. In the framework of the color-magnetic interaction, we estimate the masses of the partner states of the $X (5568)$ and discuss their decay pattern, which provide valuable information on the future experimental search of these states.
Comments:
7 pages, suggestions and comments are welcome
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); High Energy Physics — Lattice (hep-lat); Nuclear Theory (nucl-th)
arXiv:
1603.01131 [pdf]
PRD(2016)·64 citations
12
[Submitted on 3 Mar 2016] (cross-list from hep-th)
Thermodynamics, transport and relaxation in non-conformal theories
Maximilian Attems🇪🇸 · Jorge Casalderrey-Solana🇬🇧 · David Mateos🇪🇸 · Ioannis Papadimitriou🇮🇹 · Daniel Santos-Oliván🇪🇸 · Carlos F. Sopuerta🇪🇸 · Miquel Triana🇪🇸 · Miguel Zilhão🇪🇸
We study the equilibrium and near-equilibrium properties of a holographic five-dimensional model consisting of Einstein gravity coupled to a scalar field with a non-trivial potential. The dual four-dimensional gauge theory is not conformal and, at zero temperature, exhibits a renormalisation group flow between two different fixed points. We quantify the deviations from conformality both in terms of thermodynamic observables and in terms of the bulk viscosity of the theory. The ratio of bulk over shear viscosity violates Buchel's bound. We study relaxation of small-amplitude, homogeneous perturbations by computing the quasi-normal modes of the system at zero spatial momentum. In this approximation we identify two different relaxation channels. At high temperatures, the different pressures first become approximately equal to one another, and subsequently this average pressure evolves towards the equilibrium value dictated by the equation of state. At low temperatures, the average pressure first evolves towards the equilibrium pressure, and only later the different pressures become approximately equal to one another.
Comments:
22 pages, 29 figures; published version
Subjects:
High Energy Physics — Theory (hep-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1603.01254 [pdf]
JHEP(2016)·95 citations

Affiliations

first authorsco-authorsvia INSPIRE