Nuclear Theory Publications (50)

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Nuclear Theory Publications

Transverse densities describe the distribution of charge and current at fixed light-front time and provide a frame-independent spatial representation of hadrons as relativistic systems. We calculate the transverse densities of the octet baryons at peripheral distances b = O(M_pi^{-1}) in an approach combining chiral effective field theory (ChEFT) and dispersion analysis. The densities are represented as dispersive integrals of the imaginary parts of the baryon electromagnetic form factors in the timelike region (spectral functions). Read More


Theoretical models of the (d,p) reaction are exploited for both nuclear astrophysics and spectroscopic studies in nuclear physics. Usually, these reaction models use local optical model potentials to describe the nucleon- and deuteron-target interactions. Within such a framework the importance of the deuteron D-state in low-energy reactions is normally associated with spin observables and tensor polarization effects - with very minimal influence on differential cross sections. Read More


We develop a new formalism to describe the inclusive production of small radius jets in heavy-ion collisions, which is consistent with jet calculations in the simpler proton-proton system. Only at next-to-leading order (NLO) and beyond, the jet radius parameter $R$ and the jet algorithm dependence of the jet cross section can be studied and a meaningful comparison to experimental measurements is possible. We are able to consistently achieve NLO accuracy by making use of the recently developed semi-inclusive jet functions within Soft Collinear Effective Theory (SCET). Read More


The death of the massive stars due to supernova explosion is a key ingredient in stellar evolution, stellar population synthesis. The electron capture (EC) plays a vital role in supernovae explosions. According to the Shell-Model Monte Carlo (SMMC) method, basing onthe Random Phase Approximation (RPA) and Linear Response Theory Model (LRTM), we study the strongly screening EC rates of nuclides $^{52, 53, 59, 60}$Fe in presupernova. Read More


The $p\bar{p}$ invariant mass spectra of the processes $J/\psi\to p\bar{p}\omega$, $J/\psi\to p\bar{p}\rho$, and $J/\psi\to p\bar{p}\gamma$ close to the $p\bar{p}$ threshold are calculated by means of the $N\bar{N}$ optical potential. The potential model for $N\bar{N}$ interaction in the $^{1}S_{0}$ state is proposed. The parameters of the model are obtained by fitting the cross section of $N\bar{N}$ scattering together with the $p\bar{p}$ invariant mass spectra of the $J/\psi$ decays. Read More


In order to systematically examine the possible maximum mass of neutron stars, which is one of the important properties characterizing the physics in high-density region, I construct neutron star models by adopting phenomenological equations of state with various values of nuclear saturation parameters for low-density region, which are connected to the equation of state for high-density region characterized by the possible maximum sound velocity in medium. I derive an empirical formula for the possible maximum mass of neutron star. If massive neutron stars are observed, it could be possible to get a constraint on the possible maximum sound velocity for high-density region. Read More


We relate the forward two-photon exchange (TPE) amplitudes to integrals of the inclusive cross sections. These relations yield an alternative way for the evaluation of the TPE correction to hyperfine-splitting (HFS) in the hydrogen-like atoms. Our result is equivalent to the standard approach (Iddings, Drell and Sullivan) implying the Burkhardt-Cottingham sum rule. Read More


The nuclear $\alpha$ decay of heavy nuclei is investigated based on the nuclear energy density functional, which leads to the $\alpha$ potential inside the parent nucleus in terms of the proton and neutron density profiles of the daughter nucleus. We use the Skyrme force model, Gogny force model, and relativistic mean field model to get the nucleon density profiles inside heavy nuclei. Once the nucleon density profiles are determined, the parameters of the nuclear $\alpha$ potential are fitted to the observed $\alpha$ decay half-lives of heavy nuclei. Read More


We provide a parametrization of a new phenomenological scaling function obtained from a chi-square fit to a selected set of (e,e') cross section data expanding a band centered around the quasielastic peak. We start from a re-analysis of quasielastic electron scattering from nuclear matter within the relativistic mean field model. The cross section depends on the relativistic effective mass of the nucleon, $m_N^*$, and it scales with respect to a new scaling variable, $\psi^*$. Read More


Contemporary data are analyzed concerning the half-lives of the $^{229m}$Th isomer in neutral atoms and various ions. It is explicitly shown that the isomer lifetime may strongly depend on the plain environmental physical conditions like pressure and temperature. Calculation is performed on the united platform of interplay of traditional and subthreshold resonance conversion. Read More


In this paper, we have applied a three-dimensional approach for calculation of the relativistic nucleon-nucleon potential. The quadratic operator relation between the non-relativistic and the relativistic nucleon-nucleon interactions is formulated as a function of relative two-nucleon momentum vectors, which leads to a three-dimensional integral equation. The integral equation is solved by the iteration method, and the matrix elements of the relativistic potential are calculated from non-relativistic ones. Read More


We have studied the scaling properties of the electromagnetic response functions of $^4$He and $^{12}$C nuclei computed by the Green's Function Monte Carlo approach, retaining only the one-body current contribution. Longitudinal and transverse scaling functions have been obtained in the relativistic and non relativistic cases and compared to experiment for various kinematics. The characteristic asymmetric shape of the scaling function exhibited by data emerges in the calculations in spite of the non relativistic nature of the model. Read More


Heavy quark $R_{AA}$ and $v_2$ have been calculated at RHIC energy considering initial conditions with and without pre-equilibrium phase to highlight the impact of the latter on heavy quark observables. The momentum evolution of the heavy quark has been studied by means of the Boltzmann transport equation. To model the pre-equilibrium phase we have used the KLN initial condition. Read More


Recent classical-statistical numerical simulations have established the "bottom-up" thermalization scenario of Baier et al. as the correct weak coupling effective theory for thermalization in ultrarelativistic heavy-ion collisions. We perform a parametric study of photon production in the various stages of this bottom-up framework to ascertain the relative contribution of the off-equilibrium "Glasma" relative to that of a thermalized Quark-Gluon Plasma. Read More


Amorphous solids or glasses are known to exhibit stretched-exponential decay over broad time intervals in several of their macroscopic observables: intermediate scattering function, dielectric relaxation modulus, time-elastic modulus etc. This behaviour is prominent especially near the glass transition. In this Letter we show, on the example of dielectric relaxation, that stretched-exponential relaxation is intimately related to the peculiar lattice dynamics of glasses. Read More


The structures, point defects and impacts of fission products for U3Si (\b{eta}-U3Si and {\gamma}-U3Si) and USi2 ({\alpha}-USi2 and \b{eta}-USi2) are studied by first-principles calculations. The lattice parameters of U3Si and USi2 are calculated and the stability of different types of point defects is predicted by their formation energies. The results show that silicon vacancies are more prone to be produced than uranium vacancies in \b{eta}-USi2 matrix, while uranium vacancies are the most stable defects of other three types of crystallographic structures. Read More


A recent analysis of data on the two photon production of the $\eta_c$ and its decay to $K(K\pi)$ has determined the $K\pi$ $S$-wave amplitude in a "model-independent" way assuming primarily that the additional kaon is a spectator in this decay. The purpose of this paper is to fit these results, together with classic $K\pi$ production data from LASS, within a formalism that implements unitarity for the di-meson interaction. This fixes the $I=1/2$ $K\pi\to K\pi$ $S$-wave amplitude up to 2. Read More


A new convenient method to diagonalize the non-relativistic many-body Schroedinger equation with two-body central potentials is derived. It combines kinematic rotations (democracy transformations) and exact calculation of overlap integrals between bases with different sets of mass-scaled Jacobi coordinates, thereby allowing for a great simplification of this formidable problem. We validate our method by obtaining a perfect correspondence with the exactly solvable three-body ($N=3$) Calogero model in 1D. Read More


Effects of the isospin-symmetry breaking due to the strong interaction are systematically studied for nuclear masses near the $N=Z$ line, using extended Skyrme energy density functionals (EDFs) with proton-neutron-mixed densities and new terms breaking the isospin symmetry. Two parameters associated with the new terms are determined by fitting mirror and triplet displacement energies (MDEs and TDEs) of isospin multiplets. The new EDFs reproduce the MDEs for $T=\frac12$ doublets and $T=1$ triplets, as well as the staggering of TDE for $T=1$ triplets. Read More


The influence of pairing correlations on the neutron root mean square (rms) radius of nuclei is investigated in the framework of self-consistent Skyrme Hartree-Fock-Bogoliubov calculations. The continuum is treated appropriately by the Green's function techniques. As an example the nucleus $^{124}$Zr is treated for a varying strength of pairing correlations. Read More


With a newly improved isospin- and momentum-dependent interaction and an isospin-dependent Boltzmann-Uehling-Uhlenbeck transport model, we have investigated the effects of the slope parameter $L$ of the nuclear symmetry energy and the isospin splitting of the nucleon effective mass $m_{n-p}^*=(m_n^*-m_p^*)/m$ on the centroid energy of the isovector giant dipole resonance and the electric dipole polarizability in $^{208}$Pb. With the isoscalar nucleon effective mass $m_s^*=0.7m$ constrained by the empirical optical potential, we obtain a constraint of $L=67. Read More


Light-by-light scattering sumrules based on general field theory principles relate cross-sections with different helicities. In this paper the simplest sumrule is tested for the $I=0$ and $2$ channels for "real" photon-photon collisions. Important contributions come from the long-lived pseudoscalar mesons and from di-meson intermediate states. Read More


A two-phase description of the quark-nuclear matter hybrid equation of state that takes into account the effect of excluded volume in both the hadronic and the quark-matter phases is introduced. The nuclear phase manifests a reduction of the available volume as density increases, leading to a stiffening of the matter. The quark-matter phase displays a reduction of the effective string-tension in the confining density-functional from available volume contributions. Read More


The exclusive vector meson production cross section is one of the most promising observables to probe the high energy regime of the QCD dynamics. In particular, the squared momentum transfer ($t$) distributions are an important source of information about the spatial distribution of the gluons in the hadron and about fluctuations of the color fields. In this paper we complement previous studies on exclusive vector meson photoproduction in hadronic collisions presenting a comprehensive analysis of the $t$ - spectrum measured in exclusive $\rho$, $\phi$ and $J/\Psi$ photoproduction in $pp$ and $PbPb$ collisions at the LHC. Read More


By applying chiral-perturbation-theory methods to the QCD sector of the Lorentz-violating Standard-Model Extension, we investigate Lorentz violation in the strong interactions. In particular, we consider the CPT-even pure-gluon operator of the minimal Standard-Model Extension. We construct the lowest-order chiral effective Lagrangian for three as well as two light quark flavors. Read More


We calculated the QCD equation of state using Taylor expansions that include contributions from up to sixth order in the baryon, strangeness and electric charge chemical potentials. Calculations have been performed with the Highly Improved Staggered Quark action in the temperature range $T\in [135~{\rm MeV}, 330~{\rm MeV}]$ using up to four different sets of lattice cut-offs corresponding to lattices of size $N_\sigma^3\times N_\tau$ with aspect ratio $N_\sigma/N_\tau=4$ and $N_\tau =6-16$. The strange quark mass is tuned to its physical value and we use two strange to light quark mass ratios $m_s/m_l=20$ and $27$, which in the continuum limit correspond to a pion mass of about $160$ MeV and $140$ MeV espectively. Read More


Production of $\rho^{0}$ meson at high $p_T$ in high-energy nuclear collisions is investigated for the first time at the next-leading-order in the QCD improved parton model. The $\rho^0$ fragmentation functions (FFs) in vacuum at any scale $Q$ are obtained by evolving through NLO DGLAP equations a newly developed initial parametrization of $\rho^0$ FFs at a scale $\rm Q_{0}^2=1.5\ GeV^2$ from a broken SU(3) model. Read More


Classical symmetries broken at the quantum level are called anomalies. Since the discovery of this surprising phenomenon, it has become a very active field of research in physics. A remarkable class of anomalies occurs when the continuous scale symmetry (CS) of a scale free quantum system is broken into a discrete scale symmetry (DS) for a critical value of a control parameter. Read More


The scattering amplitude of polarized nucleons has been found within the framework of the Klein Gordon with the spin phenomenological interaction potential. It has the Glauber type representation. The differential cross sections of polarized nucleon are considered and discussed. Read More


The nonmesonic weak decay of $\Lambda$ hypernuclei is studied within a microscopic diagrammatic approach which is extended to include the three--nucleon induced mechanism. We adopt a nuclear matter formalism which, through the local density approximation, allows us to model finite hypernuclei, a one--meson--exchange weak transition potential and a Bonn nucleon--nucleon strong potential. One--, two-- and three--nucleon induced weak decay rates are predicted for $^{12}_\Lambda$C by including ground state correlations up to second order in the nucleon--nucleon potential and the recoil of the residual nucleus. Read More


2017Jan
Affiliations: 1Egyptian Ctr. Theor. Phys., Cairo, WLCAPP, Cairo, 2Ain Shams U., Cairo, 3Ain Shams U., Cairo

Generic axiomatic-nonextensive statistics characterized by two asymptotic properties, to each of them a scaling function is assigned, characterized by c and d for first and second scaling property, respectively, is formulated in a grand-canonical ensemble with finite volume in the thermodynamic limit. The thermodynamic properties of a relativistic ideal gas of hadron resonances are studied. It is found that this generic statistics satisfies the requirements of the equilibrium thermodynamics. Read More


The high quality data provided by helioseismology, solar neutrino flux measurements, spectral determination of solar abundances, nuclear reactions rates coefficients among other experimental data, leads to the highly accurate prediction of the internal structure of the present Sun - the standard solar model. In this talk, I have discussed how the standard solar model, the best representation of the real Sun, can be used to study the properties of dark matter, for which two complementary approaches have been developed: - to limit the number of theoretical candidates proposed as the dark matter particles, this analysis complements the experimental search of dark matter, and - as a template for the study of the impact of dark matter in the evolution of stars, which possibly occurs for stellar populations formed in regions of high density of dark matter, such as stars formed in the centre of galaxies and the first generations of stars. Read More


Hadronic form factors for semileptonic decay of the $\Lambda_c$ are calculated in a nonrelativistic quark model. The full quark model wave functions are employed to numerically calculate the form factors to all relevant orders in ($1/m_c$, $1/m_s$). The form factors obtained satisfy relationships expected from the heavy quark effective theory (HQET). Read More


Multi-particle azimuthal cumulants, often used to study collective flow in high-energy heavy-ion collisions, have recently been applied in small collision systems such as pp and p+A to extract the second-order azimuthal harmonic flow v2. Recent observation of four-, six- and eight-particle cumulants with "correct sign" c_2{4}<0, c_2{6}>0, c_2{8}<0 and approximate equality of the inferred single-particle harmonic flow, $v_2\{4\}\approx v_2{6} \approx v_2\{8\}$, have been used as strong evidence for a collective emission of the all soft particles produced in the collisions. We show that these relations are violated due to the non-gaussianity in the event-by-event fluctuation of flow and/or non-flow. Read More


A principal goal of gravitational-wave astronomy is to constrain the neutron star equation of state (EOS) by measuring the tidal deformability of neutron stars. The tidally induced departure of the waveform from that of point-particle (or spinless binary black hole (BBH)) increases with the stiffness of the EOS. We show that causality (the requirement that the speed of sound is less than the speed of light for a perfect fluid satisfying a one-parameter equation of state) places an upper bound on tidal deformability as a function of mass. Read More


In this work, we investigate the possibility to interpret two nucleon resonances, the $N(1875)$ and the $N(2100)$ as hadronic molecular states from the $\Sigma^*K$ and $\Sigma K^*$ interactions, respectively. With the help of the effective Lagrangians where the coupling constants are determined by the SU(3) symmetry, the $\Sigma^*K$ and $\Sigma K^*$ interactions are described by the vector-meson and pseudoscalar-meson exchanges. With the one-boson-exchange potential obtained, the bound states from the $\Sigma^*K$ and $\Sigma K^*$ interactions are searched in a quasipotential Bethe-Saltpeter equation approach. Read More


Mesonic and nucleon fluctuation effects are investigated in medium. We couple the nucleon field to the $2+1$ flavor meson model and investigate the finite temperature and density behavior of the system. Somewhat contrary to earlier expectations we find that the axial anomaly tends to strengthen at finite density. Read More


The deformation parameters beta and gamma together with the two-quasiparticle excitations are taken into account, for the first time, as coordinates within a symmetry conserving (angular momentum and particle number) generator coordinate method. The simultaneous consideration of collective as well as single particle degrees of freedom allows us to describe soft and rigid nuclei as well as the transition region in between. We apply the new theory to the study of the spectra and transition probabilities of the 156-172Er isotopes with a Pairing plus Quadrupole residual interaction. Read More


In a well-established many-body framework, successful in modeling a great variety of nuclear processes, we analyze the role of the spectral functions (SFs) accounting for the modifications of the dispersion relation of nucleons embedded in a nuclear medium. We concentrate in processes mostly governed by one-body mechanisms, and study possible approximations to evaluate the particle-hole propagator using SFs. We also investigate how to include together SFs and long-range RPA-correlation corrections in the evaluation of nuclear response functions, discussing the existing interplay between both type of nuclear effects. Read More


A review is given of our present knowledge of different parametrization of experimental results in inelastic scattering process with polarized proton beams. Spin observables in inelastic proton scattering for a set of lightweight nuclei are studied at intermediate energies in the region of 100-500 MeV. Two important types of DWIA calculations are used in the analysis of experiments. Read More


Some recent progress and open questions in extracting and understanding the new physics underlying the density dependence of nuclear symmetry energy from laboratory experiments are discussed. Read More


Both fast and slow configurations of rotating neutron stars (NSs) are studied with the recently-constructed unified NS EoSs. The calculations for pure quark stars (QSs) and hybrid stars (HSs) are also done, using several updated quark matter EoSs and Gibbs construction for obtaining hadron-quark mixed phase. All three types of EoSs fulfill the recent 2-solar-mass constrain. Read More


We investigate the phase structure of QCD with 3 degenerate quark flavors as function of the degenerate quark masses at vanishing baryon number density. We use the Highly Improved Staggered Quarks on lattices with temporal extent $N_{t}=6$ and perform calculations for six values of quark masses, which in the continuum limit correspond to pion masses in the range $80~{\rm MeV} \lesssim m_{\pi} \lesssim 230~$MeV. By analyzing the volume and temperature dependence of the chiral condensate and chiral susceptibility we find no direct evidence for a first order phase transition in this range of pion mass values. Read More


We study the tensor-optimized antisymmetrized molecular dynamics (TOAMD) as a successive variational method in many-body systems with strong interaction for nuclei. In TOAMD, the correlation functions for the tensor force and the short-range repulsion and their multiples are operated to the AMD state as the variational wave function. The total wave function is expressed as the sum of all the components and the variational space can be increased successively with the multiple correlation functions to achieve convergence. Read More


A general theory of pseudomagnetic effects for the propagation of polarized neutrons through polarized target in multi resonance approach is presented. Some applications related to the proposed search for time reversal invariance violation in neutron scattering are considered. Read More


The recent fast growth of a population of millisecond pulsars with precisely measured mass provides an excellent opportunity to characterize these compact stars at an unprecedented level. This is because the stellar parameter values can be accurately computed for known mass and spin rate and an assumed equation of state (EoS) model. For each of the 16 such pulsars and for a set of EoS models from nucleonic, hyperonic, strange quark matter and hybrid classes, we numerically compute fast spinning stable stellar parameter values considering the full effect of general relativity. Read More


We outline a novel chiral kinetic theory framework for systematic computations of the Chiral Magnetic Effect (CME) in ultrarelativistic heavy-ion collisions. The real part of the fermion determinant in the QCD effective action is expressed as a supersymmetric world-line action of spinning, colored, Grassmanian point particles in background gauge fields, with equations of motion that are covariant generalizations of the Bargmann-Michel-Telegdi and Wong equations. Berry's phase is obtained in a consistent non-relativistic adiabatic limit. Read More


HfF$^+$ cation is a very promising system to search for the electron electric dipole moment (EDM), and corresponding experiment is carried out by E. Cornell group. Here we theoretically investigate the cation to search for another T,P-odd effect -- the nuclear magnetic quadrpole moment (MQM) interaction with electrons. Read More


The ratio of (pseudo)rapidity density of transverse energy and the (pseudo)rapidity density of charged particles, which is a measure of the mean transverse energy per particle, is an important observable in high energy heavy-ion collisions, which reveals about the mechanism of particle production and the freeze-out criteria. Its collision energy and centrality dependence is exactly like the chemical freeze-out temperature till top RHIC energy. The LHC measurement at $\sqrt{s_{NN}}$ = 2. Read More


In this work we show how the emergence of a new degree of freedom in the nuclear bulk not only softens the EoS but reduces the radii of stars with high central density. If an enough repulsive channel, as the strange vector $\phi$ meson, is added to the scheme, we are able to simulate very massive and compact stars. Indeed we are able to construct an equation of state (EoS) that predicts a 2. Read More