Nuclear Theory·nucl-th

Tuesday·November 15, 2016

16 papers—12 primary·4 cross-listed

01
Self-consistent Green's function approaches
Carlo Barbieri🇬🇧 · Arianna Carbone🇩🇪
We present the fundamental techniques and working equations of many-body Green's function theory for calculating ground state properties and the spectral strength. Green's function methods closely relate to other polynomial scaling approaches discussed in chapters 8 and 10. However, here we aim directly at a global view of the many-fermion structure. We derive the working equations for calculating many-body propagators, using both the Algebraic Diagrammatic Construction technique and the self-consistent formalism at finite temperature. Their implementation is discussed, as well as the inclusion of three-nucleon interactions. The self-consistency feature is essential to guarantee thermodynamic consistency. The pairing and neutron matter models introduced in previous chapters are solved and compared with the other methods in this book.
nucl-thLect.Notes Phys.(2017)·31 citations
02
Transverse Momentum Distribution in Heavy Ion Collision using q-Weibull Formalism
Sadhana Dash🇮🇳 · D.P. Mahapatra🇮🇳
We have implemented the Tsallis q-statistics in the Weibull model of particle production known as the q-Weibull distribution to describe the transverse-momentum (pT ) distribution of the charged hadrons at mid-rapidity measured at RHIC and LHC energies. The model describes the data remarkably well for the entire pT range measured in nucleus-nucleus and nucleon-nucleon collisions. The proposed distribution is based on the non-extensive Tsallis q-statistics which replaces the usual thermal equilibrium assumption of hydrodynamical models. The parameters of the distribution can be related to the various aspects of complex dynamics associated with such collision process.
nucl-thhep-ph0 citations
03
Indication of Collective Flow and Transparency in p-p Collisions at LHC
Inam-ul Bashir🇮🇳 · Saeed Uddin🇮🇳
The mid-rapidity transverse momentum spectra of hadrons and the available rapidity distributions of the strange hadrons produced in p-p collisions at LHC energy root(snn) = 0.9 TeV and root(snn)= 7.0 TeV have been studied using a unified statistical thermal freeze-out model. The calculated results are found to be in good agreement with the experimental data. The theoretical fits of the transverse momentum spectra using the model calculations provide the thermal freeze-out conditions in terms of the temperature and collective flow parameters for different hadronic species. The study reveal the presence of significant collective flow and a well defined temperature in the system thus indicating the formation of a thermally equilibrated hydrodynamic system in p-p collisions at LHC. Moreover, the fits to the available experimental rapidity distributions data of strange hadrons show the effect of almost complete transparency in p-p collisions at LHC. The transverse momentum distributions of protons and Kaons produced in p-p collisions at root(snn) = 200 GeV and root(snn)= 2.76 TeV have also been reproduced successfully. The model incorporates longitudinal as well as a transverse hydrodynamic flow. The contributions from heavier decay resonances have also been taken into account. We have also imposed the criteria of exact strangeness conservation in the system.
nucl-thhep-phPoS(2017)·1 citation
04
Effect of gamma-strength on nuclear reaction calculations
Igor Kadenko · Vladimir Plujko · Borys Bondar · Oleksandr Gorbachenko · Borys Leshchenko · Kateryna Solodovnyk · Oleksandr Tkach · Viktor Zheltonozhskyi
The results of the study of gamma-transition description in fast neutron capture and photofission are presented. Recent experimental data were used, namely, the spectrum of prompt gamma-rays in the energy range 2{\div}18 MeV from 14-MeV neutron capture in natural Ni and isomeric ratios in primary fragments of photofission of the isotopes of U, Np and Pu by bremsstrahlung with end-point energies $E_{e}$ = 10.5, 12 and 18 MeV. The data are compared with the theoretical calculations performed within EMPIRE 3.2 and TALYS 1.6 codes. The mean value of angular momenta and their distributions were determined in the primary fragments $^{84}$ Br, $^{97}$ Nb, $^{90}$ Rb, $^{131, 133}$ Te, $^{132}$ Sb, $^{132, 134}$ I, $^{135}$ Xe of photofissions. An impact of the characteristics of nuclear excited states on the calculation results is studied using different models for photon strength function and nuclear level density.
nucl-th0 citations
05
The phase transition in hot $Λ$ hypernuclei within relativistic Thomas-Fermi approximation
Jinniu Hu · Zhaowen Zhang🇨🇳 · Shishao Bao🇨🇳 · Hong Shen🇨🇳
A self-consistent description for hot $Λ$ hypernuclei in hypothetical big boxes is developed within the relativistic Thomas-Fermi approximation in order to investigate directly the liquid-gas phase coexistence in strangeness finite nuclear systems. We use the relativistic mean-field model for nuclear interactions. The temperature dependence of $Λ$ hyperon density, $Λ$ hyperon radius, excitation energies, specific heat, and the binding energies of $Λ$ hypernuclei from $_{Λ}^{16}$ O to $_{Λ}^{208}$ Pb in phase transition region are calculated by using the subtraction procedure in order to separate the hypernucleus from the surrounding baryon gas. The $Λ$ central density is very sensitive to the temperature. The radii of $Λ$ hyperon at high temperature become very large. In the relativistic Thomas-Fermi approximation with the subtraction procedure, the properties of hypernuclei are independent of the size of the box in which the calculation is performed. The level density parameters of hypernuclei in the present work are confirmed to be almost constant at low temperature. It is also found that the single- $Λ$ binding energies of $Λ$ hypernuclei are largely reduced with increasing temperature.
nucl-thPRC(2016)·6 citations
06
Geometrical description of the phase transition in the Gaździcki Gorenstein model
Kacper Zalewski🇵🇱
The derivation of the phase transition in the model of Gaździcki and Gorenstein is generalized and simplified by using a geometrical construction.
nucl-thhep-phActa Phys.Polon.B(2016)·1 citation
07
Wobbling motion in $^{135}$ Pr within a collective Hamiltonian
Q. B. Chen · S. Q. Zhang · J. Meng
The recently reported wobbling bands in $^{135}$ Pr are investigated by the collective Hamiltonian, in which the collective parameters, including the collective potential and the mass parameter, are respectively determined from the tilted axis cranking (TAC) model and the harmonic frozen alignment (HFA) formula. It is shown that the experimental energy spectra of both yrast and wobbling bands are well reproduced by the collective Hamiltonian. It is confirmed that the wobbling mode in $^{135}$ Pr changes from transverse to longitudinal with the rotational frequency. The mechanism of this transition is revealed by analyzing the effective moments of inertia of the three principal axes, and the corresponding variation trend of the wobbling frequency is determined by the softness and shapes of the collective potential.
nucl-thnucl-exPRC(2016)·27 citations
08
Nuclear Energy Density Functional for KIDS
Hana Gil · Panagiota Papakonstantinou · Chang Ho Hyun · Tae-Sun Park · Yongseok Oh
The density functional theory (DFT) is based on the existence and uniqueness of a universal functional $E [ρ]$ , which determines the dependence of the total energy on single-particle density distributions. However, DFT says nothing about the form of the functional. Our strategy is to first look at what we know, from independent considerations, about the analytical density dependence of the energy of nuclear matter and then, for practical applications, to obtain an appropriate density-dependent effective interaction by reverse engineering. In a previous work on homogeneous matter, we identified the most essential terms to include in our "KIDS" functional, named after the early-stage participating institutes. We now present first results for finite nuclei, namely the energies and radii of $^{16, 28}$ O, $^{40, 60}$ Ca.
nucl-thActa Phys.Polon.B(2017)·28 citations
09
Systematic effects in the measurement of the negatively charged pion mass using laser spectroscopy of pionic helium atoms
Boyan Obreshkov🇧🇬
The collision-induced shift and broadening of selected dipole transition lines of pionic helium in gaseous helium at low temperatures up to $T = 12$ K and pressure up to a few bar are calculated within variable phase function approach. We predict blue shift of the resonance frequencies of the $(n, l) = (16, 15) \to (16, 14)$ and $(16, 15) \to (17, 14)$ unfavored transitions and red shift for the favored transition $(17, 16) \to (16, 15)$ . The result may be helpful in reducing the systematic error in proposed future experiments for determination of the negatively charged pion mass from laser spectroscopy of metastable pionic helium atoms.
nucl-thphysics.atom-phNucl.Theor.(2016)·0 citations
10
Amplitude reconstruction from complete experiments and truncated partial-wave expansions
R.L. Workman · L. Tiator · Y. Wunderlich · M. Doering · H. Haberzettl
We compare the methods of amplitude reconstruction, for a complete experiment and a truncated partial wave analysis, applied to the photoproduction of pseudo-scalar mesons. The approach is pedagogical, showing in detail how the amplitude reconstruction (observables measured at a single energy and angle) is related to a truncated partial-wave analysis (observables measured at a single energy and a number of angles).
nucl-thnucl-exPRC(2017)·32 citations
11
Effects of sterile neutrino and extra-dimension on big bang nucleosynthesis
Dukjae Jang🇰🇷 · Motohiko Kusakabe🇺🇸 · Myung-Ki Cheoun🇰🇷
By assuming the existence of extra-dimensional sterile neutrinos in big bang nucleosynthesis (BBN) epoch, we investigate the sterile neutrino ( $ν_{s}$ ) effects on the BBN and constrain some parameters associated with the $ν_{s}$ properties. First, for cosmic expansion rate, we take into account effects of a five-dimensional bulk and intrinsic tension of the brane embedded in the bulk, and constrain a key parameter of the extra dimension by using the observational element abundances. Second, effects of the $ν_{s}$ traveling on or off the brane are considered. In this model, the effective mixing angle between a $ν_{s}$ and an active neutrino depends on energy, which may give rise to a resonance effect on the mixing angle. Consequently, reaction rate of the $ν_{s}$ can be drastically changed during the cosmic evolution. We estimated abundances and temperature of the $ν_{s}$ by solving the rate equation as a function of temperature until the sterile neutrino decoupling. We then find that the relic abundance of the $ν_{s}$ is drastically enhanced by the extra-dimension and maximized for a characteristic resonance energy $E_{res} ≳ 0.01$ GeV. Finally, some constraints related to the $ν_{s}$ , mixing angle and mass difference, are discussed in detail with the comparison of our BBN calculations corrected by the extra-dimensional $ν_{s}$ to observational data on light element abundances.
nucl-thastro-ph.COhep-phPRD(2018)·11 citations
12
Optical potential from first principles
J. Rotureau · P. Danielewicz · G. Hagen · F. Nunes · T. Papenbrock
We develop a method to construct a microscopic optical potential from chiral interactions for nucleon-nucleus scattering. The optical potential is constructed by combining the Green's function approach with the coupled-cluster method. To deal with the poles of the Green's function along the real energy axis we employ a Berggren basis in the complex energy plane combined with the Lanczos method. Using this approach, we perform a proof-of-principle calculation of the optical potential for the elastic neutron scattering on $^{16} O$ . For the computation of the ground-state of $^{16} O$ , we use the coupled-cluster method in the singles-and-doubles approximation, while for the $A = \pm 1$ nuclei we use particle-attached/removed equation-of-motion method truncated at two-particle-one-hole and one-particle-two-hole excitations, respectively. We verify the convergence of the optical potential and scattering phase shifts with respect to the model-space size and the number of discretized complex continuum states. We also investigate the absorptive component of the optical potential (which reflects the opening of inelastic channels) by computing its imaginary volume integral and find an almost negligible absorptive component at low-energies. To shed light on this result, we computed excited states of $^{16} O$ using equation-of-motion coupled-cluster method with singles-and-doubles excitations and we found no low-lying excited states below 10~MeV. Furthermore, most excited states have a dominant two-particle-two-hole component, making higher-order particle-hole excitations necessary to achieve a precise description of these core-excited states. We conclude that the reduced absorption at low-energies can be attributed to the lack of correlations coming from the low-order cluster truncation in the employed coupled-cluster method.
nucl-thphysics.chem-phPRC(2017)·98 citations
13
Parity Breaking Medium and Squeeze Operators
A. A. Andrianov🇪🇸 · S. S. Kolevatov🇷🇺 · R. Soldati🇮🇹
The transition between a Minkowski space region and a parity breaking medium domain is thoroughly discussed. The requirement of continuity of the field operator content across the separating boundary of the two domains leads to Bogolyubov transformations, squeezed pairs states and squeeze operators that turn out to generate a functional SU(2) algebra. According to this algebraic approach, the reflection and transmission probability amplitude across the separating boundary are computed. The probability rate of the emission or absorption of squeezed pairs out of the vacuum (generalization of the Sauter-Schwinger-Nikishov formula) is obtained.
↳ hep-thastro-ph.HEhep-phnucl-thPRD(2017)·1 citation
14
Baryon-to-meson transition distribution amplitudes: formalism and models
B. Pire🇫🇷 · K. Semenov-Tian-Shansky🇷🇺 · L. Szymanowski🇵🇱
In specific kinematics, hard exclusive amplitudes may be factorized into a short distance dominated part computable in a perturbative way on the one hand, and universal, confinement related hadronic matrix elements on the other hand. The extension of this description to processes such as backward meson electroproduction and forward meson production in antiproton-nucleon scattering leads to define new hadronic matrix elements of three quark operators on the light cone, the nucleon-to-meson transition distribution amplitudes, which shed a new light on the nucleon structure.
↳ hep-phhep-exnucl-exnucl-thFew Body Syst.(2017)·3 citations
15
Charming quasi-exotic open-flavor mesons
Thomas Hilger🇦🇹 · Andreas Krassnigg🇦🇹
We discuss charmed mesons in the covariant Dyson-Schwinger-Bethe-Salpeter-equation approach. In particular we computed masses, leptonic decay constants, and an orbital-angular-momentum decomposition for a basic set of states. We also report an efficient way to treat the two coupled quark propagator dressing functions via a single function.
↳ hep-phnucl-thEPJ Web Conf.(2017)·8 citations
16
Heavy-Light Mesons in Chiral AdS/QCD
Yizhuang Liu🇺🇸 · Ismail Zahed🇺🇸
We discuss a minimal holographic model for the description of heavy-light and light mesons with chiral symmetry, defined in a slab of AdS space. The model consists of a pair of chiral Yang-Mills and tachyon fields with specific boundary conditions that break spontaneously chiral symmetry in the infrared. The heavy-light spectrum and decay constants are evaluated explicitly. In the heavy mass limit the model exhibits both heavy-quark and chiral symmetry and allows for the explicit derivation of the one-pion axial couplings to the heavy-light mesons.
↳ hep-phhep-thnucl-thPLB(2017)·24 citations

Affiliations

first authorsco-authorsvia INSPIRE