Mostrando recursos 1 - 20 de 440

  1. Quantum Monte Carlo methods for nuclear physics

    Stefano Gandolfi; Francesco Pederiva; J. Carlson; S. Gandolfi; F. Pederiva; Steven C. Pieper; R. Schiavilla; K. E. Schmidt; R. B. Wiringa
    Quantum Monte Carlo methods have proved very valuable to study the structure and reactions of light nuclei and nucleonic matter starting from realistic nuclear interactions and currents. These ab-initio calculations reproduce many low-lying states and transi-tion moments in light nuclei, and simultaneously predict many properties of light nuclei and neutron matter over a rather wide range of energy and momenta. We review the nuclear interactions and currents, and describe the continuum Quantum Monte Carlo methods used in nuclear physics. These methods are similar to those used in condensed matter and electronic structure but naturally include spin-isospin, tensor, spin-orbit, and three-body...

  2. On the Nucleonic Components producing Large Cosmic-Ray Bursts under Thick Shield

    Tadashi Kameda; Masami Wada
    By analysing the size-frequenq, distributions of large cosmic ray bursts obtained at three stations by SRI ion chambers, it is concluded that: a) about 40 % of the total bursts at sea level are those induced by N-rays, and the portion of them decreases with increasing size, b) apsorption mean free path of burst-producing N-rays is 120 g/cm2 in air, and decreases with increasing size, approaching to collision mean free path of air. Moreover, from the comparison of our results with others, it is shown that the absorption mean free path of burst-producing N-rays near sea level is not same...

  3. Progress of Theoretical Physics Supplement No. 112, 1993 Chapter III Characteristic Aspects of Pion-Condensed Phases

    Tatsuyuki Takatsuka; Ryozo Tamagaki; Toshitaka Tatsumi
    Characteristic aspects of pion-condensed phases are described in a simple model, for the system involving only nucleons and pions which interact through the TC- N P-wave interac-tion. We consider one typical version in each of three kinds of pion condensation; the one of neutral pions (TC0), the one of charged pions (TCc) and the combined one in which both the TC 0 and TCc condensations are coexistent. Emphasis is put on the description to clarify the novel structures of the nucleon system which are realized in the pion-condensed phases. At first, it is shown that the TC0 condensation is equivalent...

  4. Nucleonic and Electromagnetic Reaction Cross Sections of Medium and High Energy llLi Projectiles

    Michio Honma; Hiroyuki Saga Wa
    We study the reaction cross sections of "Li projectile on various targets at high projectile energy E1ab/A=800 MeV. The cross section due to the nucleonic interaction is calculated by using a simple Glauber model, while that due to the electromagnetic interaction is obtained by assuming the break-up process through the giant dipole resonance of the projectile. The small separation energy of two neutrons outside 9Li core enhances significantly both the cross sections of "Li projectile, especially on heavy targets. The calculated cross sections reproduce fairly well the experimental data except Pb case. The calculations are also perlormed in a medium...

  5. c World Scientic Publishing Company NUCLEAR POINT-GROUP SYMMETRIES AND NEW IDEAS ABOUT NUCLEAR STABILITY: AN OVERVIEW

    J. Dudek; See Profile; A. Gozdz; Available From J. Dudek; J. Dudek; D. Curien; K. Mazurek
    The nuclear mean-eld theory and the group representation theory can be used to op-timise the search for strong nuclear shell eects. The two theories allow to correlate the symmetry aspects with the presence of large gaps in the single-particle spectra, facilitate in this way the conditions of search for strong nucleonic- and nuclear-binding and thus for an increased nuclear stability. In this article we give a short overview of the related on-going research, focussing on the results of the TetraNuc Collaboration. 1.

  6. The Second Class Current and Structure of Elementary...

    Hirofumi Senju; T Akeo Ma Tsushima
    We examine what is required for the structure of elementary particles by the second class nucleonic currents which was recently discovered by Sugimoto et al. The experiment strongly suggests that the quark has a radius of a few tenth of fermi and the partons are constituents of quarks. We discuss briefly a possible internal structure of the quark. § 1. Important experiment Recently Sugimoto, Tanihata and Goring performed a very important experi-ment on 11-decays of nuclei. 1l The data show that the /3 ray angular distribution in the 11 decays of polarized 12B and 12N(JP=1 +) into 12C(JP=O+) cannot be...

  7. Nuclear stopping for heavy-ion induced reactions in the Fermi energy range: from 1-Body to 2-Body dissipation

    O. Lopez; G. Lehaut; D. Dur; M. Aouadi(indra Collaboration
    Abstract. We study the stopping in heavy-ion induced reactions around the Fermi energy in central collisions. The stopping is minimal around the Fermi energy and corresponds to the crossover between the Mean-Field and the nucleonic regimes. This is attributed to the change in the energy dissipation going from 1-body (Mean-Field) to 2-body (nucleon-nucleon collisions) dissipation. For this latter, a connection to in-medium transport prop-erties of nuclear matter is proposed and comprehensive values of the nucleon mean free path and nucleon-nucleon cross section are extracted. 1

  8. Elementary Excitations in a Solid Nuclear Matter

    Koichi Takahashi
    The effects of elementary excitations to the nature of dense solid nuclear matter are investigated using the Pandharipande·Smith (PS) potentials. A trial wave function embodying a simple cubic structure of nucleonic lattice leads to the Hamiltonian describing the dynamics of lattice vibrations (or phonons) spin·waves (or magnons) and isospin·waves (or 'isomagnons'). Magnons and isomagnons are treated as the Holstein·Primakoff bosons. In the density range from around 0.3 to 1 nucleons/fm3, the dynamics of phonons approximately reproduces the equations of state for PS's potentials 2 and 3. At the lowest order of perturbations, due to the tensor interaction, magnon has an...

  9. X-ray Hotspot Flares and Implications for Cosmic Ray Acceleration and magnetic field amplification in Supernova Remnants

    Boaz Katz; Eli Waxman
    For more than fifty years, it has been believed that cosmic ray (CR) nuclei are accelerated to high energies in the rapidly expanding shockwaves created by powerful supernova explosions. Yet observational proof of this conjecture is still lacking. Recently, Uchiyama and collaborators reported the detection of small-scale X-ray flares in one such supernova remnant, dubbed “RX J1713-3946 ” (a.k.a. G347.3-0.5), which also emits very energetic, TeV (1012 eV) range, gamma-rays. They contend that the variability of these X-ray “hotspots ” implies that the magnetic field in the remnant is about a hundred times larger than normally assumed; and this, they...

  10. On the Structure of A=3 Nuclei

    Syed Afsar Abbas; Shakeb Ahmad
    Abstract A=3 is the lightest genuine “nucleus ” with an “inside ” with a centre and an outside/surface. As A=2 nucleus does not have an “inside ” what transpires in A=3 to make this happen? The hole in the charge distribution of 3He is a major problem in the A=3 nuclei. The canonical wave function of A=3 nuclei which does well fo r the electromagnetic p roperties of A=3 nuclei fails to produce the hole in A=3 nuclei. We show that this wave function does give the surface while the “inside ” is completely missed by it. The reproduction of...

  11. Seoul, Korea


    Computational fluid dynamics (CFD) is an important f ield in mechanical engineering, and also gives physicians interests especially for vascular practices recently. Since the 1950s, CFD is widely utilized in various fields not only in mechanical engineering but also in aeromechanics, marine engineering, civil engineering, meteorological dynamics, environmental engineering, nucleonic and medical engineering. Navier-Stokes ’ (NS) equation is usually used for analysis of viscous and compressible fluid such as blood [1]. With the advance of computational science, a non-linear NS equation is easy put into practice in CFD analysis instead of the linear NS equation, which converts the variable boundary...

  12. Final-state interactions in deep-inelastic scattering from a tensor polarized deuteron target.

    Wim Cosyn; Misak Sargsian
    Abstract. Deep-inelastic scattering (DIS) from a tensor polarized deuteron is sensitive to possible non-nucleonic components of the deuteron wave function. To accurately estimate the size of the nucleonic contribution, final-state interactions (FSIs) need to be accounted for in calculations. We outline a model that, based on the diffractive nature of the effective hadron–nucleon interaction, uses the generalized eikonal approximation to model the FSIs in the resonance region, taking into account the proton-neutron component of the deuteron. The calculation uses a factorized model with a basis of three resonances with mass W < 2 GeV as the relevant set of effective...

  13. EMC Effect, Short-Range Correlations in Nuclei and Neutron Stars

    Mark Strikman
    The recent x> 1 (e,e’) and correlation experiments at momentum transfer Q2 ≥ 2 GeV2 confirm presence of short-range correlations (SRC) in nuclei mostly build of nucleons. Recently we evaluated in a model independent way the dominant photon contribution to the nuclear structure. Taking into account this effect and using defini-tion of x consistent with the exact kinematics of eA scattering (with exact sum rules) results in the significant reduction of RA(x,Q 2) = F2A(x,Q 2)/F2N (x,Q 2) ratio which explains ∼ 50 % of the EMC effect for x ≤ 0.55 where Fermi motion effects are small. The remaining...

  14. Imprinting Quantum Fluctuations on Hydrodynamic Initial Conditions

    J. S. Morel; Z. Qiua; U. Heinza
    We have developed an algorithm to imprint quantum fluctuations onto the initial transverse en-ergy density profile according to a given two-point covariance function. Using as an example MC-KLN initial conditions with added fluctuations satisfying the covariance function derived in [1], we find that effects from sub-nucleonic gluon field fluctuations on the eccentricity harmonics n vary strongly with the gluonic correlation length controlled by the saturation momentum Qs. Varying Qs over the range probed in Au+Au collisions at RHIC, we find gluon fluctuation in-duced enhancements of the eccentricity coefficients ranging from 10 to 20 % in central collisions. 1. Event-by-event fluctuations...

  15. Magnetic dipole excitations in nuclei: Elementary modes of nucleonic motion

    Kris Heyde; Peter Von Neumann-cosel
    ar

  16. Coupled-cluster computations of atomic nuclei G. Hagen1,2, T. Papenbrock2,1, M. Hjorth-Jensen3,4, and

    D. J. Dean
    Abstract. In the past decade, coupled-cluster theory has seen a renaissance in nuclear physics, with computations of neutron-rich and medium-mass nuclei. The method is efficient for nuclei with product-state references, and it describes many aspects of weakly bound and unbound nuclei. This report reviews the technical and conceptual developments of this method in nuclear physics, and the results of coupled-cluster calculations for nucleonic matter, and for exotic isotopes of helium, oxygen, calcium, and some of their neighbors.

  17. Contents

    R. J. Furnstahl; K. Hebeler
    Abstract. We review recent developments in the use of renormalization group (RG) methods in low-energy nuclear physics. These advances include enhanced RG technology, particularly for three-nucleon forces, which greatly extends the reach and accuracy of microscopic calculations. We discuss new results for the nucleonic equation of state with applications to astrophysical systems such as neutron stars, new calculations of the structure and reactions of finite nuclei, and new explorations of correlations in nuclear systems.

  18. An empirical approach combining nuclear physics and dense nucleonic matter

    Margueron, J.
    International audience

  19. Magnetic Hexadecapole γ Transitions and Neutrino-Nuclear Responses in Medium-Heavy Nuclei

    Lotta Jokiniemi; Jouni Suhonen; Hiroyasu Ejiri
    Neutrino-nuclear responses in the form of squares of nuclear matrix elements, NMEs, are crucial for studies of neutrino-induced processes in nuclei. In this work we investigate magnetic hexadecapole (M4) NMEs in medium-heavy nuclei. The experimentally derived NMEs, MEXP(M4), deduced from observed M4 γ transition half-lives are compared with the single-quasiparticle (QP) NMEs, MQP(M4), and the microscopic quasiparticle-phonon model (MQPM) NMEs MMQPM(M4). The experimentally derived M4 NMEs are found to be reduced by a coefficient k≈0.29 with respect to MQP(M4) and by k≈0.33 with respect to MMQPM(M4). The M4 NMEs are reduced a little by the quasiparticle-phonon correlations of the MQPM...

  20. An Optimized Gamma-ray Densitometry Tool for Oil Products Determination

    Amirmohammad Beigzadeh; Hossein Afarideh; Eskandar Asadi Amirabadi; Zahra Soltani; Gholam Reza Etaati
    Gamma-ray densitometry or nucleonic gauges have been widely used in industries to improve the quality of products, optimize processes and save energy and materials. Compared with common time-consuming and expensive chemical analyses, the proposed method is relatively fast and more reliable. Density measurement is normally based on the absorption of gamma radiation as it passes through the process material. The absorption which is proportional to the changes in material density indicates product density as the measuring path is held constant. In this study, a number of Monte Carlo simulations have been performed using the MCNP-4C code to optimize the arrangement...

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