Mostrando recursos 1 - 20 de 429

  1. 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...

  2. 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...

  3. 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...

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

    Kris Heyde; Peter Von Neumann-cosel
    ar

  5. 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.

  6. 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.

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

    Margueron, J.
    International audience

  8. 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...

  9. 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...

  10. Mesonic Decay of Charm Hypernuclei Λc+

    Ghosh Sabyasachi; Fontoura Carlos E.; Krein Gastão
    Λc+ hypernuclei are expected to have binding energies and other properties similar to those of strange hypernuclei in view of the similarity between the quark structures of the strange and charmed hyperons, namely Λ(uds) and Λc+(udc). One striking difference however occurs in their mesonic decays, as there is almost no Pauli blocking in the nucleonic decay of a charm hypernucleus because the final-state nucleons leave the nucleus at high energies. The nuclear medium nevertheless affects the mesonic decays of charm hypernucleus because the nuclear mean fields modify the masses of the charm hyperon. In the present communication we present results...

  11. General Description of Fission Observables: GEF Model Code

    Schmidt, Karl-Heinz; Jurado, Beatriz; Amouroux, Charlotte; Schmitt, C.
    The GEF (" GEneral description of Fission observables ") model code is documented. It describes the observables for spontaneous fission, neutron-induced fission and, more generally, for fission of a compound nucleus from any other entrance channel, with given excitation energy and angular momentum. The GEF model is applicable for a wide range of isotopes from Z = 80 to Z = 112 and beyond, up to excitation energies of about 100 MeV. The results of the GEF model are compared with fission barriers, fission probabilities, fission-fragment mass-and nuclide distributions, isomeric ratios, total kinetic energies, and prompt-neutron and prompt-gamma yields and...

  12. Microwold 20. “Spontaneous ” Nuclear Disintegration

    N. N. Leonov
    “Spontaneous ” nuclear disintegration results from increase in the density of ether in the contemporary Universe. Red shift is indicative of increase in the density of ether in the peripheral regions of the Universe. The observable phenomenon of “spontaneous ” nuclear disintegration provides experimental evidence of the fact that increase in the density of ether in the contemporary Universe takes place in the entire Universe rather in its peripheral layers. It is common knowledge that atomic nuclei of a number of chemical elements are capable of being disintegrated by external influence into various fragments from single nucleons to different nucleonic...

  13. Real time processing of neutron monitor data using the edge editor algorithm

    Mavromichalaki Helen; Paschalis Pavlos
    The nucleonic component of the secondary cosmic rays is measured by the worldwide network of neutron monitors (NMs). In most cases, a NM station publishes the measured data in a real time basis in order to be available for instant use from the scientific community. The space weather centers and the online applications such as the ground level enhancement (GLE) alert make use of the online data and are highly dependent on their quality. However, the primary data in some cases are distorted due to unpredictable instrument variations. For this reason, the real time primary data processing of the measured...

  14. Dense nucleonic matter and the renormalization group

    Drews Matthias; Hell Thomas; Klein Bertram; Weise Wolfram
    Fluctuations are included in a chiral nucleon-meson model within the framework of the functional renormalization group. The model, with parameters fitted to reproduce the nuclear liquid-gas phase transition, is used to study the phase diagram of QCD. We find good agreement with results from chiral effective field theory. Moreover, the results show a separation of the chemical freeze-out line and chiral symmetry restoration at large baryon chemical potentials.

  15. The detection of solar proton produced 14CO

    P. Jöckel; C. A. M. Brenninkmeijer; M. G. Lawrence; P. Siegmund
    Major solar eruptions (coronal mass ejections) are accompanied by massive ejections of protons. When these charged particles head for the Earth through the interplanetary magnetic field with high flux and energy, a solar proton event (SPE) is recorded. Strong SPEs, in which energetic protons penetrate the atmosphere in large numbers are rare, but do have chemical effects (Crutzen, 1975; Jackman et al., 1990, 2001).  They also have nucleonic effects by which they can almost instantaneously increase the atmospheric production of radio-nuclides, including 14C (radiocarbon), but this has never been demonstrated. We show, using satellite observations and modeling, that the 2nd...

  16. From crystalline to exotic arrangements of matter in neutron star crusts

    Figerou S.; Sébille F.; de la Mota V.; Eudes Ph.
    We investigate the occurrence of exotic structures in the outermost layers of neutron stars within the framework of a microscopic model describing the nucleonic dynamics through a time-dependent mean field approach at around zero temperature. In this model starting from an initial crystalline lattice of nuclei at subnuclear densities the system evolves and self-organizes in various low-lying energy structures without assumption of final shapes. These structures are studied in terms of a density phase diagram. We investigate their sensitivity to the isotopic composition and to the symmetries of the lattice.

  17. Atmospheric electric field effects of cosmic rays detected in Mexico City

    J. F. Valdés-Galicia; L. X. González
    We studied the possible effects of atmospheric electric fields, generated in thunderstorms, on the cosmic ray intensity detected at the Earth’s surface by investigating the variations of the counting rates of the cosmic-ray nucleonic component, obtained from the neutron monitor installed in Mexico City, for thunderstorms during 1996 and 1997. These were years of minimum solar activity. We compare our experimental results with the general theory of cosmic ray meteorological effects by Dorman (1995).The observed intensity variation is about 0.2%. According to Dorman (1995), the effect should be between 0.27% and 0.81% on the counting rate of the neutron monitor...

  18. Electroweak reactions with light nuclei

    Bacca S.
    The investigation of light nuclei with ab-initio methods provides an optimal setting to probe our knowledge on nuclear forces, because the few-nucleon problem can be solved accurately. Nucleons interact not only in pairs but also via many-body forces. Theoretical efforts need to be taken towards the identification of nuclear observables sensitive to the less known many-nucleon forces. Electromagnetic reactions can potentially provide useful information on this. We present results on photo-absorption and electron scattering off light nuclei, emphasizing the role of three-body forces and the comparison with experimental data. On the other hand, reactions induced by weak probes, like neutrino...

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

    Lopez O.; Lehaut G.; Durand D.; Aouadi M.
    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 (nucleonnucleon collisions) dissipation. For this latter, a connection to in-medium transport properties of nuclear matter is proposed and comprehensive values of the nucleon mean free path and nucleon-nucleon cross section are extracted.

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

    Lopez O.; Lehaut G.; Durand D.; Aouadi M.
    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 (nucleonnucleon collisions) dissipation. For this latter, a connection to in-medium transport properties of nuclear matter is proposed and comprehensive values of the nucleon mean free path and nucleon-nucleon cross section are extracted.

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