Nuclear Theory·nucl-th

Friday·December 5, 2014

10 papers—5 primary·5 cross-listed

01
Electromagnetic production of $K Σ$ on the nucleon near threshold
T. Mart🇮🇩
Photo- and electroproduction of $K Σ$ have been investigated near their production thresholds by using an effective Lagrangian approach. For this purpose, the background amplitude is constructed from suitable Feynman diagrams, whereas the resonance terms are calculated by means of the Breit-Wigner form of multipoles. Experimental data available in the proton channels ( $K^{+} Σ^{0}$ and $K^{0} Σ^{+}$ ) with energies up to 50 MeV above the thresholds have been utilized to extract the unknown parameters. In these proton channels the calculated observables fit nicely the experimental data, whereas in the neutron channels ( $K^{+} Σ^{-}$ and $K^{0} Σ^{0}$ ) the predicted observables contain some uncertainties due to the the uncertainties in the values of helicity photon couplings. To this end, new $K^{0} Σ^{+}$ photoproduction data are urgently required. The present analysis indicates the validity of the $P_{Λ} = - \frac{1}{3} P_{Σ}$ relation derived a long time ago. In the electroproduction sector the present analysis confirms the smooth transition between photoproduction and low $Q^{2}$ electroproduction data. The effect of new Crystal Ball data is shown to be mild at the backward angles. It is also found that the electroproductions of $K^{0} Σ^{+}$ and $K^{0} Σ^{0}$ are practically not the suitable reactions for investigating the $K^{0}$ charge form factor, since the effect is small.
nucl-thhep-phPRC(2014)·27 citations
02
The $η^{'} N$ interaction from a chiral effective model and $η^{'}$ - $N$ bound state
Shuntaro Sakai🇯🇵 · Daisuke Jido🇯🇵
The $η^{'}$ mass reduction in the nuclear medium is expected from the degeneracy of the pseudoscalar-singlet and octet mesons when chiral symmetry is manifest. In this study, we investigate the $η^{'} N$ 2body interaction which is the foundation of the in-medium $η^{'}$ properties using the linear sigma model as a chiral effective model. The $η^{'} N$ interaction in the linear sigma model comes from the scalar meson exchange with U $_{A}$ (1) symmetry effect and is found to be fairly strong attraction. Moreover, the $η N$ transition is included in our calculation, and is important for the imaginary part of the $η^{'}$ -optical potential. The transition amplitude of $η^{'} N$ to the $η N$ channel is relatively small compared to that of elastic channel. From the analysis of the $η^{'} N$ 2body system, we find a $η^{'} N$ bound state with the binding energy $12.3 - 3.3 i$ MeV. We expect that this strongly attractive two body interaction leads to a deep and attractive optical potential.
nucl-thHyperfine Interact.(2015)·8 citations
03
Effects of three-nucleon spin-orbit interaction on isotope shifts of Pb nuclei
H. Nakada · T. Inakura
We investigate effects of the $3 N$ interaction, which effectively adds a density-dependent term to the LS channel, on the isotopes shifts of the Pb nuclei. With the strength so as to keep the $ℓ s$ splitting of the single-nucleon orbits, the density-dependence in the LS channel tends to shrink the wave functions of the $j = ℓ + 1/2$ orbits while makes the $j = ℓ - 1/2$ functions distribute more broadly. Thereby the kink in the isotope shifts of the Pb nuclei at $N = 126$ becomes stronger, owing to the attraction from neutrons occupying $0 i_{11/2}$ in $N > 126$ . The density-dependence in the LS channel enables us to reproduce the data of the isotope shifts by the Hartree-Fock-Bogolyubov calculations in a long chain of neutron numbers, even without degeneracy between the $n 1 g_{9/2}$ and $n 0 i_{11/2}$ levels. We exemplify it by the semi-realistic M3Y-P6 interaction.
nucl-thPRC(2015)·42 citations
04
Directed Flow Indicates a Crossover Deconfinement Transition in Relativistic Nuclear Collisions
Yu. B. Ivanov🇷🇺 · A. A. Soldatov🇷🇺
Analysis of directed flow ( $v_{1}$ ) of protons, antiprotons and pions in heavy-ion collisions is performed in the range of incident energies $s_{N N}$ = 2.7--27 GeV. Simulations have been done within a three-fluid model employing a purely hadronic equation of state (EoS) and two versions of the EoS involving deconfinement transitions: a first-order phase transition and a smooth crossover transition. High sensitivity of the directed flow, especially the proton one, to the EoS is found. The crossover EoS is favored by the most part of considered experimental data. A strong wiggle in the excitation function of the proton $v_{1}$ slope at the midrapidity obtained with the first-order-phase-transition EoS and a smooth proton $v_{1}$ with positive midrapidity slope, within the hadronic EoS unambiguously disagree with the data. The pion and antiproton $v_{1}$ also definitely testify in favor of the crossover EoS. The results obtained with deconfinement EoS's apparently indicate that these EoS's in the quark-gluon sector should be stiffer at high baryon densities than those used in the calculation.
nucl-thhep-phnucl-exPRC(2015)·77 citations
05
Time-dependent HF approach to SHE dynamics
A.S. Umar · V.E. Oberacker
We employ the time-dependent Hartree-Fock (TDHF) method to study various aspects of the reactions utilized in searches for superheavy elements. These include capture cross-sections, quasifission, prediction of $P_{CN}$ , and other interesting dynamical quantities. We show that the microscopic TDHF approach provides an important tool to shed some light on the nuclear dynamics leading to the formation of superheavy elements.
nucl-thNPA(2015)·47 citations
06
Phenomenological QCD equation of state for massive neutron stars
Toru Kojo🇺🇸 · Philip D. Powell🇺🇸 · Yifan Song🇺🇸 · Gordon Baym🇺🇸
We construct an equation of state for massive neutron stars based on quantum chromodynamics phenomenology. Our primary purpose is to delineate the relevant ingredients of equations of state that simultaneously have the required stiffness and satisfy constraints from thermodynamics and causality. These ingredients are: (i) a repulsive density-density interaction, universal for all flavors; (ii) the color-magnetic interaction active from low to high densities; (iii) confining effects, which become increasingly important as the baryon density decreases; (iv) non-perturbative gluons, which are not very sensitive to changes of the quark density. We use the following "3-window" description: At baryon densities below about twice normal nuclear density, 2n_0, we use the Akmal-Pandharipande-Ravenhall (APR) equation of state, and at high densities, > (4-7)n_0, we use the three-flavor Nambu-Jona-Lasinio (NJL) model supplemented by vector and diquark interactions. In the transition density region, we smoothly interpolate the hadronic and quark equations of state in the chemical potential-pressure plane. Requiring that the equation of state approach APR at low densities, we find that the quark pressure in non-confining models can be larger than the hadronic pressure, unlike in conventional equations of state. We show that consistent equations of state of stiffness sufficient to allow massive neutron stars are reasonably tightly constrained, suggesting that gluon dynamics remains non-perturbative even at baryon densities ~10n_0.
↳ hep-phastro-ph.SRhep-thnucl-thPRD(2015)·189 citations
07
Extracting meson-baryon contributions to the electroexcitation of the $N (1675) \frac{5}{2}^{-}$ nucleon resonance
I. G. Aznauryan🇺🇸 · V. D. Burkert🇺🇸
We report on the determination of the electrocouplings for the transition from the proton to the $N (1675) \frac{5}{2}^{-}$ resonance state using recent differential cross section data on $e p \to e π^{+} n$ by the CLAS collaboration at $1.8 \leq Q^{2} < 4.5$ GeV $^{2}$ . The data have been analyzed using two different approaches, the unitary isobar model and fixed-t dispersion relations. The extracted $γ^{*} p \to N (1675) \frac{5}{2}^{-}$ helicity amplitudes show considerable coupling through the $A_{1/2}^{p}$ amplitude, that is significantly larger than predicted three-quark contribution to this amplitude. The amplitude $A_{3/2}^{p}$ is much smaller. Both results are consistent with the predicted sizes of the meson-baryon contributions at $Q^{2} \geq 1.8$ GeV $^{2}$ from the dynamical coupled-channel model.
↳ nucl-thhep-phPRC(2015)·25 citations
08
A unified approach to nuclei: The BPS Skyrme Model
C. Adam🇪🇸 · C. Naya🇪🇸 · J. Sanchez-Guillen🇬🇧 · J.M. Speight🇪🇸 · R. Vazquez🇪🇸 · A. Wereszczynski🇵🇱
We present a concrete model of a low energy effective field theory of QCD, the well-known Skyrme Model. Specifically, we will work with the BPS submodel in order to describe the binding energies of nuclei. This BPS Skyrme model is characterized by having a saturated bound for the energy proportional to the baryon number of the nuclei. After presenting this classical result, we will proceed with a semi-classical quantization of the coordinates of spin and isospin. Then, with the further inclusion of the Coulomb interaction as well as a small explicit breaking of the isospin symmetry, we finally calculate the binding energies of nuclei, where an excellent agreement has been found for the nuclei with high baryon number. Besides this, we also apply this model to the study of some thermodynamic properties and to neutron stars.
↳ hep-thnucl-thNucl.Part.Phys.Proc.(2016)·3 citations
09
Boson star at finite temperature
S. Latifah🇮🇩 · A. Sulaksono🇮🇩 · T. Mart🇮🇩
By using a simple thermodynamical method we confirm the finding of Chavanis and Harko that stable Bose-Einstein condensate stars can form. However, by using a thermodynamically consistent boson equation of state, we obtain a less massive Bose-Einstein condensate star compared to the one predicted by Chavanis and Harko. We also obtain that the maximum mass of a boson star is insensitive to the change of matter temperature. However, the mass of boson star with relatively large radius depends significantly on the temperature of the boson matter.
↳ astro-ph.SRhep-phnucl-thPRD(2014)·34 citations
10
(Inverse) Magnetic Catalysis in Bose-Einstein Condensation of Neutral Bound Pairs
Bo Feng🇨🇳 · Defu Hou🇨🇳 · Hai-cang Ren🇺🇸
The Bose-Einstein condensation of bound pairs made of oppositely charged fermions in a magnetic field is investigated. We find that the condensation temperature shows the magnetic catalysis effect in weak coupling and the inverse magnetic catalysis effect in strong coupling. The different responses to the magnetic field can be attributed to the competition between the dimensional reduction by Landau orbitals in pairing dynamics and the anisotropy of the kinetic spectrum of fluctuations (bound pairs in the normal phase)
↳ cond-mat.quant-gascond-mat.str-elhep-phnucl-thPRD(2015)·19 citations

Affiliations

first authorsco-authorsvia INSPIRE