Nuclear Theory·nucl-th

Tuesday·April 4, 2017

15 papers—8 primary·7 cross-listed

01
Light Clusters and Pasta Phases in Warm and Dense Nuclear Matter
Sidney S. Avancini🇵🇹 · Márcio Ferreira🇵🇹 · Helena Pais🇵🇹 · Constança Providência🇵🇹 · Gerd Röpke🇩🇪
The pasta phases are calculated for warm stellar matter in a framework of relativistic mean-field models, including the possibility of light cluster formation. Results from three different semiclassical approaches are compared with a quantum statistical calculation. Light clusters are considered as point-like particles, and their abundances are determined from the minimization of the free energy. The couplings of the light-clusters to mesons are determined from experimental chemical equilibrium constants and many-body quantum statistical calculations. The effect of these light clusters on the chemical potentials is also discussed. It is shown that including heavy clusters, light clusters are present until larger nucleonic densities, although with smaller mass fractions.
nucl-thPRC(2017)·27 citations
02
Nuclear Effects in the Deuteron and Constraints on the d/u Ratio
S.I. Alekhin🇷🇺 · S.A. Kulagin🇷🇺 · R. Petti🇺🇸
We present a detailed study of nuclear corrections in the deuteron (D) by performing an analysis of data from deep inelastic scattering off proton and D, dilepton pair production in $pp$ and pD interactions, and W^+- and Z boson production in pp and p pbar collisions. In particular, we discuss the determination of the off-shell function describing the modification of the parton distribution functions in bound nucleons in the context of global QCD fits. Our results are consistent with the ones obtained independently from the study of deep inelastic scattering data off heavy nuclei with $A \geq 4$ , further confirming the universality of the off-shell function. We also study the sensitivity to the modeling of the deuteron wave function. As an important application we discuss the impact of nuclear corrections to the deuteron on the determination of the d quark distribution.
nucl-thhep-phPRD(2017)·54 citations
03
Covariant chiral kinetic equation in Wigner function approach
Jian-hua Gao🇨🇳 · Shi Pu🇯🇵 · Qun Wang🇨🇳
The covariant chiral kinetic equation (CCKE) is derived from the 4-dimensional Wigner function by an improved perturbative method under the static equilibrium conditions. The chiral kinetic equation in 3-dimensions can be obtained by intergation over the time component of the 4-momentum. There is freedom to add more terms to the CCKE allowed by conservation laws. In the derivation of the 3-dimensional equation, there is also freedom to choose coefficients of some terms in $d x_{0} / d τ$ and $d x / d τ$ ( $τ$ is a parameter along the worldline, and $(x_{0}, x)$ denotes the time-space position of a particle) whose 3-mometum integrals are vanishing. So the 3-dimensional chiral kinetic equation derived from the CCKE is not uniquely determined in the current approach. To go beyond the current approach, one needs a new way of building up the 3-dimensional chiral kinetic equation from the CCKE or directly from covariant Wigner equations.
nucl-thPRD(2017)·64 citations
04
New and efficient method for solving the eigenvalue problem for the two-center shell model with finite-depth potentials
K. Hagino · T. Ichikawa
We propose a new method to solve the eigen-value problem with a two-center single-particle potential. This method combines the usual matrix diagonalization with the method of separable representation of a two-center potential, that is, an expansion of the two-center potential with a finite basis set. To this end, we expand the potential on a harmonic oscillator basis, while single-particle wave functions on a combined basis with a harmonic oscillator and eigen-functions of a one-dimensional two-center potential. In order to demonstrate its efficiency, we apply this method to a system with two $^{16}$ O nuclei, in which the potential is given as a sum of two Woods-Saxon potentials.
nucl-thPRC(2017)·3 citations
05
Proton distributions in $d p$ dielectron production within Regge theory
A.P.Jerusalimov🇷🇺 · G.I.Lykasov🇷🇺
The processes of dielectron production in deuteron-proton collisions at intermediate incident deuteron beam energies are analyzed in the spectator model within the one-pion exchange reggeized approach. We focus mainly on the momentum and angle distributions of the proton-spectator and the proton emitted in quasi-free $N N$ processes at small angles in the laboratory frame. It is shown that the inclusion of many channels in quasi-free $N N$ interaction allows us to describe the HADES data quite satisfactorily at incident deuteron kinetic energies of about 2.5 GeV.
nucl-thhep-phInt.J.Mod.Phys.A(2017)·2 citations
06
The Cross Section Calculation of the $^{112}$ Sn( $α$ , $γ$ ) $^{116}$ Te Reaction with Different Nuclear Models at the Astrophysical Energy Range
C. Yalcin
The theoretical cross section calculations for the astrophysical $p$ process are needed because the most of the related reactions are technically very difficult to be measured in the laboratory. Even if the reaction was measured, most of the measured reactions have been carried out at the higher energy range from the astrophysical energies. Therefore, almost all cross sections needed for $p$ process simulation has to be theoretically calculated or extrapolated to the astrophysical energies. The $^{112}$ Sn( $α$ , $γ$ ) $^{116}$ Te is an important reaction for the $p$ process nucleosynthesis. The theoretical cross section of the $^{112}$ Sn( $α$ , $γ$ ) $^{116}$ Te reaction was investigated for different global optical model potentials, level density and strength function models at the astrophysically interested energies. Astrophysical $S$ factors were calculated and compared with experimental data available in EXFOR database. The calculation with the optical model potential of the dispersive model by Demetriou et al., and Back-shifted Fermi gas level density model and Brink-Axel Lorentzian strength function model best served to reproduce experimental results at astrophysically relevant energy region. The reaction rates were calculated with these model parameters at the $p$ process temperature and compared with the current version of the reaction rate library Reaclib and Starlib.
nucl-thastro-ph.HEnucl-exNucl.Sci.Tech.(2017)·6 citations
07
Fission properties of superheavy nuclei for r-process calculations
Samuel A. Giuliani · Gabriel Martinez-Pinedo · Luis M. Robledo
We computed a new set of static fission properties suited for r-process calculations. The potential energy surfaces and collective inertias of 3640 nuclei in the superheavy region are obtained from Self-Consistent Mean-Field calculations using the Barcelona-Catania-Paris-Madrid energy density functional. The fission path is computed as a function of the quadrupole moment by minimizing the potential energy and exploring octupole and hexadecapole deformations. The spontaneous fission lifetimes are evaluated employing different schemes for the collective inertias and vibrational energy corrections. This allows to explore the sensitivity of the lifetimes to those quantities together with the collective ground state energy along the superheavy landscape. We computed neutron induced stellar reaction rates relevant for r-process nucleosynthesis using the statistical approach and study the impact of collective inertias. The competition between different reaction channels including neutron induced rates, spontaneous fission and alpha decay is discussed for typical r-process conditions.
nucl-thPRC(2018)·101 citations
08
Microscopic Theory of Nuclear Fission
Aurel Bulgac · Shi Jin · Piotr Magierski · Kenneth J. Roche · Ionel Stetcu
We describe the fission dynamics of $^{240}$ Pu within an implementation of the Density Functional Theory (DFT) extended to superfluid systems and real-time dynamics. We demonstrate the critical role played by the pairing correlations, which even though are not the driving force in this complex dynamics, are providing the essential lubricant, without which the nuclear shape evolution would come to a screeching halt. The evolution is found to be much slower than previously expected in this fully non-adiabatic treatment of nuclear dynamics, where there are no symmetry restrictions and all collective degrees of freedom (CDOF) are allowed to participate in the dynamics.
nucl-thPoS(2017)·0 citations
09
Numerical calculation of the decay widths, the decay constants, and the decay energy spectra of the resonances of the delta-shell potential
Rafael de la Madrid🇺🇸
We express the resonant energies of the delta-shell potential in terms of the Lambert $W$ function, and we calculate their decay widths and decay constants. The ensuing numerical results strengthen the interpretation of such decay widths and constants as a way to quantify the coupling between a resonance and the continuum. We calculate explicitly the decay energy spectrum of the resonances of the delta-shell potential, and we show numerically that the lineshape of such spectrum is not the same as, and can be very different from, the Breit-Wigner (Lorentzian) distribution. We argue that the standard Golden Rule cannot describe the interference of two resonances, and we show how to describe such interference by way of the decay energy spectrum of two resonant states.
↳ quant-phhep-phnucl-thNPA(2017)·16 citations
10
Peeking into the Origins of IceCube Neutrinos: I. Buried Transient TeV Miniburst Rates
Matthew D. Kistler (KIPAC, Stanford, SLAC)🇺🇸 · Hasan Yuksel (Mimar Sinan)🇹🇷
Any interpretation of the astrophysical neutrinos discovered by IceCube must accommodate a variety of multimessenger constraints. We address implications of these neutrinos being produced in transient sources, principally if buried within supernovae so that gamma rays are absorbed by the star. This would alleviate tension with the isotropic Fermi GeV background that >10 TeV neutrinos rival in detected energy flux. We find that IceCube data constrain transient properties, implying buried GeV-TeV electromagnetic emission near or exceeding canonical SN explosion energies of ~10^51 erg, indicative of an origin within superluminous SNe. TeV neutrino bursts with dozens of IceCube events -- which would be of great use for understanding r-process nucleosynthesis and more -- may be just around the corner if they are a primary component of the flux.
↳ astro-ph.HEastro-ph.COastro-ph.GAhep-ph+12 citations
11
Experimental constraint on quark electric dipole moments
Tianbo Liu🇺🇸 · Zhiwen Zhao🇺🇸 · Haiyan Gao🇺🇸
The electric dipole moments (EDMs) of nucleons are sensitive probes of additional $C P$ violation sources beyond the standard model to account for the baryon number asymmetry of the universe. As a fundamental quantity of the nucleon structure, tensor charge is also a bridge that relates nucleon EDMs to quark EDMs. With a combination of nucleon EDM measurements and tensor charge extractions, we investigate the experimental constraint on quark EDMs, and its sensitivity to $C P$ violation sources from new physics beyond the electroweak scale. We obtain the current limits on quark EDMs as $1.27 \times 1 0^{- 24} e \cdot cm$ for the up quark and $1.17 \times 1 0^{- 24} e \cdot cm$ for the down quark at the scale of $4 Ge V^{2}$ . We also study the impact of future nucleon EDM and tensor charge measurements, and show that upcoming new experiments will improve the constraint on quark EDMs by about three orders of magnitude leading to a much more sensitive probe of new physics models.
↳ hep-phhep-exnucl-exnucl-thPRD(2018)·42 citations
12
Excited states of the Wick-Cutkosky model with the Nakanishi representation in the Light-Front framework
R. Pimentel🇧🇷 · W. de Paula🇧🇷
The Wick-Cutkosky model is investigated using the framework of the Nakanishi Perturbative Integral Representation projected in the Light-Front hyperplane for an s-wave amplitude. We developed a new technique based on sucessive integration by parts of the Nakanishi Representation which enabled us to transform one of the integrations into a sum. With a set of boundary conditions it was possible to guess the format of the solution, which was in fact a distribution. The eigenequations obtained were the same as the originals of Cutkosky \cite{CutPR54}. Finally, a numerical check confirmed that the final equation reproduce the same eigenvalues as the initial Bethe-Salpeter equation.
↳ hep-phmath-phmath.MPnucl-thFew Body Syst.(2016)·7 citations
13
Quantum Numbers of Recently Discovered $Ω_{c}^{0}$ Baryons from Lattice QCD
M. Padmanath🇩🇪 · Nilmani Mathur🇮🇳
We present the ground and excited state spectra of $Ω_{c}^{0}$ baryons with spin up to 7/2 from lattice quantum chromodynamics with dynamical quark fields. Based on our lattice results, we predict the quantum numbers of five $Ω_{c}^{0}$ baryons, which have recently been observed by the LHCb Collaboration. Our results strongly indicate that the observed states $Ω_{c} (3000)^{0}$ and $Ω_{c} (3050)^{0}$ have spin-parity $J^{P} = 1/ 2^{-}$ , the states $Ω_{c} (3066)^{0}$ and $Ω_{c} (3090)^{0}$ have $J^{P} = 3/ 2^{-}$ , whereas $Ω_{c} (3119)^{0}$ is possibly a $5/ 2^{-}$ state.
↳ hep-phhep-exhep-latnucl-thPRL(2017)·115 citations
14
Effect of strong magnetic fields on the crust-core transition and inner crust of neutron stars
Jianjun Fang · Helena Pais · Sagar Pratapsi · Sidney Avancini · Jing Li · Constança Providência
The Vlasov equation is used to determine the dispersion relation for the eigenmodes of magnetized nuclear and neutral stellar matter, taking into account the anomalous magnetic moment of nucleons. The formalism is applied to the determination of the dynamical spinodal section, a quantity that gives a good estimation of the crust-core transition in neutron stars. We study the effect of strong magnetic fields, of the order of $1 0^{15} - 1 0^{17}$ G, on the extension of the crust of magnetized neutron stars. The dynamical instability region of neutron-proton-electron ( $n p e$ ) matter at subsaturation densities is determined within a relativistic mean field model. It is shown that a strong magnetic field has a large effect on the instability region, defining the crust-core transition as a succession of stable and unstable regions due to the opening of new Landau levels. The effect of the anomalous magnetic moment is non-negligible for fields larger than 10 $^{15}$ G. The complexity of the crust at the transition to the core and the increase of the crust thickness may have direct impact on the properties of neutrons stars related with the crust.
↳ astro-ph.HEnucl-thPRC(2017)·31 citations
15
Proton Cumulants and Correlation Functions in Au + Au Collisions at $s_{NN}$ =7.7-200 GeV from UrQMD Model
Shu He🇨🇳 · Xiaofeng Luo🇨🇳
We studied the acceptance dependence of proton cumulants (up to fourth order) and correlation functions in 0--5\% most central Au+Au collisions at $s_{NN}$ =7.7, 11.5, 19.6, 27, 39, 62.4 and 200 GeV from UrQMD model. We found that high order proton cumulants show suppressions at large acceptance. By decomposing the proton cumulants into linear combination of multi-proton correlation functions, we observed the two-proton correlation functions always show negative values due to the effects of baryon number conservations. The three and four-proton correlation functions are close to zero and show negligible acceptance dependence. We further observed that the proton cumulants and correlation functions follow similar trends and show a scaling behavior when plotting the results versus mean number of protons. The comparisons between experimental data and the UrQMD calculations show that the non-monotonic energy dependence of proton correlation functions measured by STAR experiment cannot be described by the UrQMD model. The UrQMD calculations can provide us baselines for the experimental studies of the proton cumulants and correlation functions. Finally, we propose to measure the rapidity dependence of the reduced proton correlation functions to search for the QCD critical point in heavy-ion collisions.
↳ nucl-exhep-exhep-phnucl-thPLB(2017)·38 citations

Affiliations

first authorsco-authorsvia INSPIRE