Nuclear Theory
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New submissions for Fri, 19 Jan 18
 [1] arXiv:1801.05933 [pdf, ps, other]

Title: Resonance properties including asymptotic normalization coefficients deduced from phaseshift data without the effectiverange functionComments: 7 pages, 3 figures and 1 tableSubjects: Nuclear Theory (nuclth)
Recently a new $\Delta$method for the calculation of asymptotic normalization coefficients (ANC) from phaseshift data has been formulated, proved and used for bound states. This method differs from the conventional one by fitting only the nuclear part of the effectiverange function which includes a partial phase shift. It should be applied to largecharge nuclei when the conventional effectiverange expansion or the Pad\'eapproximations using the effectiverange function $K_l(k^2)$ fitting do not work. A typical example is the nucleus vertex $\alpha+^{12}$C $\longleftrightarrow ^{16}$O. Here we extend the $\Delta$method, which totally excludes the effectiverange function, to resonance states. In fact, we return to the initial renormalized scattering amplitude with a denominator which defines the wellknown pole condition. Concrete calculations are made for the resonances observed in the $^3$He$^4$He, $\alpha$$\alpha$ and $\alpha$$^{12}$C collisions. The corresponding results are in a good agreement with those for the $S$matrix pole (SMP) method which uses the differing formalism. The simple formula for narrow resonances given in the literature is used to check the deduced results.
 [2] arXiv:1801.05960 [pdf, other]

Title: Influence of the coupling constant of $Δ$ to $δ$ meson on isospin dependent inmedium $\mbox{NN}\to \mbox{N}Δ$ cross sectionComments: 7 pages, 5 figuresSubjects: Nuclear Theory (nuclth)
The isospin dependent inmedium $NN\rightarrow N\Delta$ cross sections in isospin asymmetric nuclear matter are investigated within the framework of the one boson exchange model with the $\delta$ meson taken into account. The influence of the coupling constant of $\Delta$ to $\delta$ meson ($g_{\delta\Delta\Delta}$ or $\kappa=g_{\delta\Delta\Delta}/g_{\delta NN}$) on the inmedium $NN\rightarrow N\Delta$ cross sections is analyzed. Our results show that the strength of the coupling constant $g_{\delta\Delta\Delta}$ largely influences the inmedium cross section and the medium correction factor, R=$\sigma^*_{NN\rightarrow N\Delta}/\sigma^{free}_{NN\rightarrow N\Delta}$, near the threshold energy. In the case of $\kappa$=1, the $\sigma^*_{pp\rightarrow n\Delta^{++}}$ ($\sigma^*_{nn\rightarrow p\Delta^{}}$) is enhanced (suppressed) relative to its cross section in free space due to the shift of the spectral function of $\Delta$ resonance in medium. For $\kappa$=3, the medium correction has opposite effects, where the $\sigma^*_{pp\rightarrow n\Delta^{++}}$ ($\sigma^*_{nn\rightarrow p\Delta^{}}$) is suppressed (enhanced) relative to its cross section in free space. It could influence the prediction on the multiplicity of pion and the $\pi^/\pi^+$ ratio in the transport model simulations, and this uncertainty should be well understood in the transport models simulations before obtaining the accurate conclusion on the symmetry energy at suprasaturation density through the comparison with the pion data.
 [3] arXiv:1801.05964 [pdf, other]

Title: Investigation of the 9B nucleus and its clusternucleon correlationsAuthors: Qing Zhao, Zhongzhou Ren, Mengjiao Lyu, Hisashi Horiuchi, Yasuro Funaki, Gerd Röpke, Peter Schuck, Akihiro Tohsaki, Chang Xu, Taiichi Yamada, Bo ZhouComments: 16 pages, 8 figuresSubjects: Nuclear Theory (nuclth)
In order to study the correlation between clusters and nucleons in light nuclei, we formulate a new superposed THSR wave function which describes both spatial large spreading and clustercorrelated dynamics of valence nucleons. By using the new THSR wave function, the binding energy of 9B is essentially improved comparing with our previous studies. We calculate the excited states of 9B and obtain the energy spectrum of 9B which is consistent with the experimental results, including prediction of the 1/2+ excited state of 9B which is not fixed yet experimentally. We study the proton dynamics in 9B and find that the clusterproton correlation plays an essential role for the proton dynamics in the ground state of 9B. Further more, we discuss the density distribution of the valence proton with special attention to its tail structure. Finally, the resonance nature of excited states of 9B is illustrated by comparing rootmeansquare radii between the ground and excited states.
 [4] arXiv:1801.05969 [pdf, other]

Title: On the stability of superheavy nucleiComments: 17 pages, 16 figuresSubjects: Nuclear Theory (nuclth)
The potentialenergy surfaces of an extended set of heavy and superheavy eveneven nuclei with $92 \le Z \le 126$ and isospins $40 \le NZ \le 74$ are evaluated within the recently developed Fourier shape parametrization. Groundstate and decay properties are studied for 324 different eveneven isotopes in a fourdimensional deformation space, defined by nonaxiality, quadrupole, octupole, and hexadecapole degrees of freedom. Nuclear deformation energies are evaluated in the framework of the macroscopicmicroscopic approach, with the LublinStrasbourgDrop model and a Yukawafolded meanfield potential. The evolution of the groundstate equilibrium shape (and possible isomeric, metastable states) is studied as a function of $Z$ and $N$. Alphadecay $Q$values and halflives, as well as fissionbarrier heights, are deduced. In order to understand the transition from asymmetric to symmetric fission along the Fm isotopic chain, the properties of all identified fission paths are investigated. Good agreement is found with experimental data wherever available. New interesting features about the population of different fission modes for nuclei beyond Fm are predicted.
 [5] arXiv:1801.06096 [pdf, ps, other]

Title: Constraining Transfer Cross Sections Using Bayes' TheoremComments: 17 pages, 12 figures, submitted to PRCSubjects: Nuclear Theory (nuclth)
Being able to rigorously quantify the uncertainties in reaction models is crucial to moving this field forward. Even though Bayesian methods are becoming increasingly popular in nuclear theory, they are yet to be implemented and applied in reaction theory problems. The purpose of this work is to investigate, using Bayesian methods, the uncertainties in the optical potentials generated from fits to elastic scattering data and the subsequent uncertainties in the transfer predictions. We also study the differences in two reaction models where the parameters are constrained in a similar manner, as well as the impact of reducing the experimental error bars on the data used to constrain the parameters. We use Bayes' Theorem combined with a Markov Chain Monte Carlo to determine posterior distributions for the parameters of the optical model, constrained by neutron, proton, and/or deuterontarget elastic scattering. These potentials are then used to predict transfer cross sections within the adiabatic wave approximation or the distortedwave Born approximation. We study a number of reactions involving deuteron projectiles with energies in the range of $1025$ MeV/u on targets with mass $A=48208$. The case of $^{48}$Ca(d,p)$^{49}$Ca transfer to the ground state is described in detail. A comparative study of the effect of the size of experimental errors is also performed. Five transfer reactions are studied, and their results compiled in order to systematically identify trends. Uncertainties in transfer cross sections can vary significantly (25100\%) depending on the reaction. While these uncertainties are reduced when smaller experimental error bars are used to constrain the potentials, this reduction is not trivially related to the error reduction. We also find smaller uncertainties when using the adiabatic formulation than when using distortedwave Born approximation.
 [6] arXiv:1801.06142 [pdf, other]

Title: Neutron moderation spectrum considering inelastic scatteringAuthors: V.D. Rusov, V.A. Tarasov, S.A. Chernezhenko, A.A. Kakaev, V.P. Smolyar, V.V. Urbanevich, V.M. VashchenkoComments: 24 pages, 13 figuresSubjects: Nuclear Theory (nuclth)
For the first time an analytic expression for inelastic neutron scattering law for isotropic neutron source considering moderating medium temperature as a parameter was obtained in the present paper within gas model. The obtained scattering law is based on solution of kinematic problem of inelastic scattering of a neutron at a nucleus in laboratory coordinate system ($L$system) in general case. I.e. in case not only a neutron but also a nucleus have arbitrary velocity vector in $L$system. Analytic expression for neutron flux density and neutron moderation spectrum in reactor fission medium are found for elastic scattering law obtained by the authors before and for new law of inelastic scattering. They consider elastic and inelastic scattering and depend on medium temperature. The obtained expressions for neutron moderation spectra enable reinerpretation of physical nature of processes that determine the shape of neutron spectrum in thermal neutron energy range.
 [7] arXiv:1801.06175 [pdf, other]

Title: Nuclear deformation in the configurationinteraction shell modelComments: 6 pages, 4 figures, Proceedings of the Twelfth International Spring Seminar on Nuclear PhysicsSubjects: Nuclear Theory (nuclth); Mesoscale and Nanoscale Physics (condmat.meshall); Statistical Mechanics (condmat.statmech)
We review a method that we recently introduced to calculate the finitetemperature distribution of the axial quadrupole operator in the laboratory frame using the auxiliaryfield Monte Carlo technique in the framework of the configurationinteraction shell model. We also discuss recent work to determine the probability distribution of the quadrupole shape tensor as a function of intrinsic deformation $\beta,\gamma$ by expanding its logarithm in quadrupole invariants. We demonstrate our method for an isotope chain of samarium nuclei whose ground states describe a crossover from spherical to deformed shapes.
Crosslists for Fri, 19 Jan 18
 [8] arXiv:1705.05177 (crosslist from nuclex) [pdf, ps, other]

Title: Observation of Narrow $N^+(1685)$ and $N^0(1685)$ Resonances in $γ N \to ηπN$ ReactionsAuthors: V. Kuznetsov, F. Mammoliti, F. Tortorici, V. Bellini, V. Brio, A. Gridnev, N. Kozlenko, G. Russo, A.Spatafora, M.L.Sperduto, V.Sumachev, C.SuteraComments: Published versionJournalref: JETP Letters, 106, 693 (2017)Subjects: Nuclear Experiment (nuclex); High Energy Physics  Experiment (hepex); High Energy Physics  Phenomenology (hepph); Nuclear Theory (nuclth)
Observation of a narrow structure at $W\sim 1.68$ GeV in the excitation functions of some photon and pioninduced reactions may signal a new narrow isospin1/2 $N(1685)$ resonance. New data on the $\gamma N \to \pi \eta N$ reactions from GRAAL seems to reveal the signals of both $N^+(1685)$ and $N^0(1685)$ resonances.
 [9] arXiv:1801.06067 (crosslist from hepph) [pdf, other]

Title: The radiative corrections to doubleDalitz decays revisitedComments: 22 pages, 9 figuresSubjects: High Energy Physics  Phenomenology (hepph); High Energy Physics  Experiment (hepex); Nuclear Theory (nuclth)
In this study, we revisit and complete the full nexttoleading order corrections to pseudoscalar doubleDalitz decays within the softphoton approximation. Comparing to the previous study, we find small differences, which are nevertheless relevant for extracting information about the pseudoscalar transition form factors. Concerning the latter, these processes could offer the opportunity to test themfor the first timein their doublevirtual regime
 [10] arXiv:1801.06163 (crosslist from condmat.quantgas) [pdf, other]

Title: Nature of pairing correlations in the homogeneous Fermi gas at unitarityComments: 5 pages, 2 figures, and 3 pages, 5 figures of supplemental materialSubjects: Quantum Gases (condmat.quantgas); Superconductivity (condmat.suprcon); High Energy Physics  Lattice (heplat); Nuclear Theory (nuclth)
In the twocomponent Fermi gas with contact interactions a pseudogap regime, in which pairing correlations are present without superfluidity, can exist at temperatures between the superfluid critical temperature $T_c$ and a temperature $T^* > T_c$. However, the existence of a pseudogap in the unitary limit of infinite scattering length is debated. To help address this issue, we have used finitetemperature auxiliaryfield quantum Monte Carlo (AFMC) methods to study the thermodynamics of the spinbalanced homogeneous unitary Fermi gas on a lattice. We present results for the thermal energy, heat capacity, condensate fraction, a modelindependent pairing gap, and spin susceptibility, and compare them to experimental data when available. Our model space consists of the complete first Brillouin zone of the lattice, and our calculations are performed in the canonical ensemble of fixed particle number. We find that the energystaggering pairing gap vanishes above $T_c$ and that $T^*$ at unitarity, as determined from the spin susceptibility, is lower than previously reported in AFMC simulations.
 [11] arXiv:1801.06173 (crosslist from quantph) [pdf, ps, other]

Title: On the vacuumpolarization Uehling potential for a Fermi charge distributionAuthors: JeanChristophe PainComments: submitted to European Physical Journal DSubjects: Quantum Physics (quantph); High Energy Physics  Phenomenology (hepph); High Energy Physics  Theory (hepth); Nuclear Theory (nuclth); Atomic Physics (physics.atomph)
We present analytical formulas for the vacuumpolarization Uehling potential in the case where the finite size of the nucleus is modeled by a Fermi charge distribution. Using a Sommerfeldtype development, the potential is expressed in terms of multiple derivatives of a particular integral. The latter and its derivatives can be evaluated exactly in terms of BickleyNaylor functions, which connection to the Uehling potential was already pointed out in the pure Coulomb case, and of usual Bessel functions of the second kind. The cusp and asymptotic expressions for the Uehling potential with a Fermi charge distribution are also provided. Analytical results for the higherordercontribution K\"all\`enSabry potential are given.
Replacements for Fri, 19 Jan 18
 [12] arXiv:1704.08699 (replaced) [pdf, other]

Title: Fluid Dynamics far from Local EquilibriumAuthors: Paul RomatschkeComments: 7 pages, 2 figures; v2: minor changes; v3: matches published versionJournalref: Phys. Rev. Lett. 120, 012301 (2018)Subjects: High Energy Physics  Theory (hepth); Nuclear Theory (nuclth); Fluid Dynamics (physics.fludyn)
 [13] arXiv:1705.06522 (replaced) [pdf, other]

Title: Low energy peripheral scaling in NucleonNucleon Scattering and uncertainty quantificationComments: 16 pages, 12 figures. Extended discussion with SAID400 analysis and figures and references addedSubjects: Nuclear Theory (nuclth); High Energy Physics  Phenomenology (hepph)
 [14] arXiv:1710.03234 (replaced) [pdf, other]

Title: Relativistic Hydrodynamic Attractors with Broken Symmetries: NonConformal and NonHomogeneousAuthors: Paul RomatschkeComments: 13 pages, 2 figures; v2: minor changes (typos, etc.); v3: matches published versionSubjects: High Energy Physics  Theory (hepth); General Relativity and Quantum Cosmology (grqc); Nuclear Theory (nuclth)
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