Nuclear Theory·nucl-th

Tuesday·June 7, 2016

10 papers—6 primary·4 cross-listed

01
[Submitted on 3 Jun 2016]
Geometrical symmetries of nuclear systems: D(3h) and T(d) symmetries in light nuclei
Roelof Bijker
The role of discrete (or point-group) symmetries in alpha-cluster nuclei is discussed in the framework of the algebraic cluster model which describes the relative motion of the alpha-particles. Particular attention is paid to the discrete symmetry of the geometric arrangement of the alpha-particles, and the consequences for the structure of the corresponding rotational bands. The method is applied to study cluster states in the nuclei 12C and 16O. The observed level sequences can be understood in a simple way as a consequence of the underlying discrete symmetry that characterizes the geometrical configuration of the alpha-particles, i.e. an equilateral triangle with D(3h) symmetry for 12C, and a tetrahedron with T(d) symmetry for 16O. The structure of rotational bands provides a fingerprint of the underlying geometrical configuration of alpha-particles.
Comments:
27 pages, 20 figures, 3 tables. Invited comment, Physica Scripta, Focus Issue of Nuclear Structure: Celebrating the 75 Nobel Prize
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1606.01306 [pdf]
Phys.Scripta(2016)·13 citations
02
[Submitted on 4 Jun 2016]
Charmonium dissociation cross sections and charmonium dissociation rates in hadronic matter
Feng-Rong Liu🇨🇳 · Shi-Tao Ji🇨🇳 · Xiao-Ming Xu🇨🇳
K*-charmonium dissociation reactions in hadronic matter are studied in the Born approximation, in the quark-interchange mechanism, and with a temperature-dependent quark potential. We obtain the temperature dependence of unpolarized cross sections for K*-charmonium dissociation reactions which produce charmed mesons and charmed strange mesons. We use the cross sections for charmonium dissociation in collisions with pion, rho meson, kaon, vector kaon, and eta meson to calculate dissociation rates of charmonium with the five types of mesons. Because of the temperature dependence of the meson masses, dissociation cross sections, and meson distribution functions, the charmonium dissociation rates generally increase with the increase of temperature and decrease with the increase of charmonium momentum from 2.2 GeV/c. We find that the first derivative of the dissociation rate with respect to the charmonium momentum is zero when the charmonium is at rest. While the eta + psi' and eta + chi_c dissociation reactions can be neglected, the J/psi, psi', and chi_c dissociation are caused by the collisions with pion, rho meson, kaon, vector kaon, and eta meson.
Comments:
58 pages, 30 figures, 4 tables
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1606.01334 [pdf]
J.Korean Phys.Soc.(2016)·8 citations
03
[Submitted on 4 Jun 2016]
Constraining the surface properties of effective Skyrme interactions
R. Jodon🇫🇷 · M. Bender🇫🇷 · K. Bennaceur🇫🇮 · J. Meyer🇫🇷
The purpose of this study is threefold: first, to identify a scheme for the determination of the surface energy coefficient a_surf that offers the best compromise between robustness, precision, and numerical efficiency; second, to analyze the correlation between values for a_surf and the characteristic energies of the fission barrier of Pu240; and third, to lay out a procedure how the deformation properties of the Skyrme energy density functional (EDF) can be constrained during the parameter fit. There are several frequently used possibilities to define and calculate the surface energy coefficient a_surf of effective interactions. The most direct access is provided by the model system of semi-infinite nuclear matter, but a_surf can also be extracted from the systematics of binding energies of finite nuclei. Calculations can be carried out either self-consistently (HF), which incorporates quantal shell effects, or in one of the semi-classical Extended Thomas-Fermi (ETF) or Modified Thomas-Fermi (MTF) approximations. The surface energy coefficient of 76 parameterizations of the Skyrme EDF have been calculated. Values obtained with the HF, ETF and MTF methods are not identical, but differ by fairly constant systematic offsets. Despite having some drawbacks compared to the other methods studied here, the MTF approach provides sufficiently precise values for a_surf such that it can be used as a very robust constraint on surface properties during a parameter fit at negligible additional cost. Through the construction of a series of eight parameterizations SLy5s1-SLy5s8 of the standard Skyrme EDF with systematically varied a_surf value it is shown how to arrive at a fit with realistic deformation properties. [Note: The abstract has been abbreviated because of length restrictions imposed by the arXiv. See the paper for the full abstract.]
Comments:
18 pages, 9 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1606.01410 [pdf]
PRC(2016)·45 citations
04
[Submitted on 5 Jun 2016]
Two-nucleon scattering in a modified Weinberg approach with a symmetry-preserving regularization
J. Behrendt🇩🇪 · E. Epelbaum🇩🇪 · J. Gegelia🇩🇪 · Ulf-G. Meißner🇩🇪 · A. Nogga🇩🇪
We consider the nucleon-nucleon scattering problem by applying time-ordered perturbation theory to the Lorentz invariant formulation of baryon chiral perturbation theory. Using a symmetry preserving higher derivative form of the effective Lagrangian, we exploit the freedom of the choice of the renormalization condition and obtain an integral equation for the scattering amplitude with an improved ultraviolet behavior. The resulting formulation is used to quantify finite regulator artifacts in two-nucleon phase shifts as well as in the chiral extrapolations of the S-wave scattering lengths and the deuteron binding energy. This approach can be straightforwardly extended to analyze few-nucleon systems and processes involving external electroweak sources.
Comments:
16 pages, 3 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1606.01489 [pdf]
EPJA(2016)·16 citations
05
[Submitted on 6 Jun 2016]
Point kinetic model of the early phase of a spherically symmetric nuclear explosion
Andreas Aste
A concise point kinetic model of the explosion of a prompt supercritical sphere driven by a nuclear fission chain reaction is presented. The findings are in good agreement with the data available for Trinity, the first detonation of a nuclear weapon conducted by the United States Army as part of the Manhattan project. Results are presented for an implosion device containing pure plutonium-239, although the model can be easily applied to, e.g., uranium-235. The fizzle probability and corresponding yield of a fission bomb containing plutonium recovered from reactor fuel and therefore containing significant amounts of spontaneously fissioning plutonium-240 which can induce a predetonation of the device is illustrated by adding a corresponding source term in the presented model. Related questions whether a bomb could be made by developing countries or terrorist organizations can be tackled this way. Although the information needed to answer such questions is in the public domain, it is difficult to extract a consistent picture of the subject for members of organizations who are concerned about the proliferation of nuclear explosives.
Comments:
16 pages, 10 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1606.01670 [pdf]
0 citations
06
[Submitted on 6 Jun 2016]
Nuclear response functions with finite range Gogny force: tensor terms and instabilities
A. De Pace🇮🇹 · M. Martini🇫🇷
A fully-antisymmetrized random phase approximation calculation employing the continued fraction technique is performed to study nuclear matter response functions with the finite range Gogny force. The most commonly used parameter sets of this force, as well as some recent generalizations that include the tensor terms are considered and the corresponding response functions are shown. The calculations are performed at the first and second order in the continued fraction expansion and the explicit expressions for the second order tensor contributions are given. Comparison between first and second order continued fraction expansion results are provided. The differences between the responses obtained at the two orders turn to be more pronounced for the forces including tensor terms than for the standard Gogny ones. In the vector channels the responses calculated with Gogny forces including tensor terms are characterized by a large heterogeneity, reflecting the different choices for the tensor part of the interaction. For sake of comparison the response functions obtained considering a G-matrix based nuclear interaction are also shown. As first application of the present calculation, the possible existence of spurious finite-size instabilities of the Gogny forces with or without tensor terms has been investigated. The positive conclusion is that all the Gogny forces, but the GT2 one, are free of spurious finite-size instabilities. In perspective, the tool developed in the present paper can be inserted in the fitting procedure to construct new Gogny-type forces.
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1606.01880 [pdf]
PRC(2016)·11 citations
07
[Submitted on 5 Jun 2016] (cross-list from nucl-ex)
Optical model potential of deuteron with $1 p$ -shell nuclei
Y. Zhang🇨🇳 · D.Y. Pang🇨🇳 · J.L. Lou🇨🇳
A set of global optical potential parameters, DA1p, for deuterons with the $1 p$ -shell nuclei is obtained by simultaneously fitting 67 sets of experimental data of deuteron elastic scattering from \nuc{6}{Li}, \nuc{9}{Be}, \nuc{10}{B}, \nuc{11}{B}, \nuc{12}{C}, \nuc{13}{C}, \nuc{14}{N}, \nuc{16}{O} and \nuc{18}{O} with incident energies between 5.25 and 170 MeV. DA1p improves the description of the deuteron elastic scattering from the $1 p$ -shell nuclei with respect to the existing systematic deuteron potentials and can give satisfactory reproduction to the experimental data with radiative nuclei such as \nuc{9}{Li}, \nuc{10}{Be}, \nuc{14}{C} and \nuc{14}{O}.
Subjects:
Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1606.01507 [pdf]
PRC(2016)·40 citations
08
[Submitted on 6 Jun 2016] (cross-list from hep-th)
Energy loss of a nonaccelerating quark moving through a strongly coupled N=4 super Yang-Mills vacuum or plasma in strong magnetic field
Kiminad A. Mamo🇺🇸
Using AdS/CFT correspondence, we find that a massless quark moving at the speed of light $v = 1$ , in arbitrary direction, through a strongly coupled $N = 4$ super Yang-Mills (SYM) vacuum at $T = 0$ , in the presence of strong magnetic field $B$ , loses its energy at a rate linearly dependent on $B$ , i.e., $\frac{d E}{d t} = - \frac{λ}{6 π} B$ . We also show that a heavy quark of mass $M \neq = 0$ moving at near the speed of light $v^{2} = v_{*}^{2} = 1 - \frac{4 π ^{2} T ^{2}}{B} ≃ 1$ , in arbitrary direction, through a strongly coupled $N = 4$ SYM plasma at finite temperature $T \neq = 0$ , in the presence of strong magnetic field $B ≫ T^{2}$ , loses its energy at a rate linearly dependent on $B$ , i.e., $\frac{d E}{d t} = - \frac{λ}{6 π} B v_{*}^{2} ≃ - \frac{λ}{6 π} B$ . Moreover, we argue that, in the strong magnetic field $B ≫ T^{2}$ (IR) regime, $N = 4$ SYM and adjoint QCD theories (when the adjoint QCD theory has four flavors of Weyl fermions and is at its conformal IR fixed point $λ = λ^{*}$ ) have the same microscopic degrees of freedom (i.e., gluons and lowest Landau levels of Weyl fermions) even though they have quite different microscopic degrees of freedom in the UV when we consider higher Landau levels. Therefore, in the strong magnetic field $B ≫ T^{2}$ (IR) regime, the thermodynamic and hydrodynamic properties of $N = 4$ SYM and adjoint QCD plasmas, as well as the rates of energy loss of a quark moving through the plasmas, should be the same.
Comments:
6 pages; v2: a minor change to the title, explanation about the massless limit in the vacuum (without changing the conclusion) added, references added; v3: the equivalence between N=4 SYM and adjoint QCD in strong magnetic field discussed, published version in Rapid Communications PRD
Subjects:
High Energy Physics — Theory (hep-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1606.01598 [pdf]
PRD(2016)·25 citations
09
[Submitted on 6 Jun 2016] (cross-list from hep-lat)
Axial charges of hyperons and charmed baryons using $N_{f} = 2 + 1 + 1$ twisted mass fermions
C. Alexandrou (Univ. of Cyprus & The Cyprus Inst.)🇨🇾 · K. Hadjiyiannakou (Univ. of Cyprus & The Cyprus Inst.)🇨🇾 · Ch. Kallidonis (The Cyprus Inst.)🇨🇾
The axial couplings of the low lying baryons are evaluated using a total of five ensembles of dynamical twisted mass fermion gauge configurations. The simulations are performed using the Iwasaki gauge action and two degenerate flavors of light quarks, and a strange and a charm quark fixed to approximately their physical values at two values of the coupling constant. The lattice spacings, determined using the nucleon mass, are $a = 0.082$ fm and $a = 0.065$ fm and the simulations cover a pion mass in the range of about 210 MeV to 430 MeV. We study the dependence of the axial couplings on the pion mass in the range of about 210 MeV to 430 MeV as well as the $S U (3)$ breaking effects as we decrease the light quark mass towards its physical value.
Comments:
34 pages, 17 figures
Subjects:
High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1606.01650 [pdf]
PRD(2016)·28 citations
10
[Submitted on 6 Jun 2016] (cross-list from hep-th)
Quenching parameter in a holographic thermal QCD
Binoy Krishna Patra🇮🇳 · Bhaskar Arya🇮🇳
We have calculated the quenching parameter, $q^$ in a model-independent way using the gauge-gravity duality. In earlier calculations, the geometry in the gravity side at finite temperature was usually taken as the pure AdS blackhole metric for which the dual gauge theory becomes conformally invariant unlike QCD. Therefore we use a metric which incorporates the fundamental quarks by embedding the coincident D7 branes in the Klebanov-Tseytlin background and a finite temperature is switched on by inserting a black hole into the background, known as OKS-BH metric. Further inclusion of an additional UV cap to the metric prepares the dual gauge theory to run similar to thermal QCD. Moreover $q^$ is usually defined in the literature from the Glauber-model perturbative QCD evaluation of the Wilson loop, which has no reasons to hold if the coupling is large and is thus against the main idea of gauge-gravity duality. Thus we use an appropriate definition of $q^$ : $q^L^{-} = 1/ L^{2}$ , where $L$ is the separation for which the Wilson loop is equal to some specific value. The above two refinements cause $q^$ to vary with the temperature as $T^{4}$ always and to depend linearly on the light-cone time $L^{-}$ with an additional ( $1/ L^{-}$ ) correction term in the short-distance limit whereas in the long-distance limit, it depends only linearly on $L^{-}$ with no correction term. These observations agree with other holographic calculations directly or indirectly.
Comments:
16 pages
Subjects:
High Energy Physics — Theory (hep-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1606.01732 [pdf]
NPB(2017)·1 citation

Affiliations

first authorsco-authorsvia INSPIRE