61.
The influence of negative-energy states on proton-proton bremsstrahlung
- de Jong, F.; Nakayama, K.
We investigate the effect of negative-energy states on proton-proton
bremsstrahlung using a manifestly covariant amplitude based on a T-matrix
constructed in a spectator model. We show that there is a large cancellation
among the zeroth-order, single- and double-scattering diagrams involving
negative-energy nucleonic currents. We thus conclude that it is essential to
include all these diagrams when studying effects of negative-energy states.
62.
On the macroscopic limit of nuclear collective motion and its relation
to chaotic behavior
- Hofmann, H.
In this note we concentrate on slow collective motion of isoscalar type at
small but finite excitations, as given in nuclear fission, for instance. We
report on microscopic results of transport coefficients, review how they depend
on temperature and address the interplay of one and two body viscosity. We
examine how transport properties might be influenced by chaotic behavior of
nucleonic dynamics.
63.
eta' meson production in proton-proton collisions
- Nakayama, K.; Arellano, H. F.; Durso, J. W.; Speth, J.
The pp -> pp eta' reaction is investigated within a relativistic
meson-exchange model of hadronic interactions. We explore the role of nucleonic
and mesonic, as well as the N* resonance currents, in producing eta' mesons. In
order to learn more about the production mechanisms, new measurements in the
energy region far from the threshold are required.
64.
Neutrino scattering as a probe for the strange content of the nucleon
- Alberico, W. M.
We consider different methods and observables which can be obtained by the
measurement of neutrino scattering off nucleons and nuclei with the purpose of
finding evidence for the strange form factors of the nucleon, which enter into
structure of the nucleonic weak neutral current.
65.
Quantum Monte Carlo calculations of symmetric nuclear matter
- Gandolfi, Stefano; Pederiva, Francesco; Fantoni, Stefano; Schmidt, Kevin E.
We present an accurate numerical study of the equation of state of nuclear
matter based on realistic nucleon--nucleon interactions by means of Auxiliary
Field Diffusion Monte Carlo (AFDMC) calculations. The AFDMC method samples the
spin and isospin degrees of freedom allowing for quantum simulations of large
nucleonic systems and can provide quantitative understanding of problems in
nuclear structure and astrophysics.
66.
Proceedings of ICRC 2001: 2447 c
- E. Van Der Swaluw
The Galactic (nucleonic) cosmic-ray spectrum up
to the knee (E
eV) is believed to originate from acceleration
processes occurring at supernova remnant shocks.
This idea is confirmed by theoretical predictions, which give
a similar estimate for the maximum particle energy, which
can be reached at these shocks.
67.
The influence of co-rotating interaction regions on relativistic cosmic rays and geomagnetic activity
- Duggal, S. P.; Pomerantz, M. A.; Tsao, C. H.; Tsurutani, B. T.; Smith, E. J.
It is established that the nucleonic intensity recorded at the polar stations Thule and McMurdo decreases as the streams associated with co-rotating interaction regions (CIR) overtake the earth. The modulation, however, is limited to only those CIR-streams in which a neutral sheet is imbedded. In contrast to this, all CIR-streams produce geomagnetic storms.
68.
Proceedings of ICRC 2001: 2447 c
- Copernicus Gesellschaft Icrc; E. Van Der Swaluw; Bram Achterberg
The Galactic (nucleonic) cosmic-ray spectrum up to the knee (E eV) is believed to originate from acceleration processes occurring at supernova remnant shocks. This idea is confirmed by theoretical predictions, which give a similar estimate for the maximum particle energy, which can be reached at these shocks.
69.
Quark Model Study of The eta Photoproduction: Evidence for a New S11
Resonance?
- Saghai, B.; Li, Z.
An extensive and systematic study of the recent eta photoproduction data up
to 1.2 GeV is presented within a chiral constituent quark model. A model
embodying all known nucleonic resonances shows clear need for a yet
undiscovered third S11 resonance in the second resonance region, for which we
determine the mass (1.729 GeV) and the total width (183 MeV). Furthermore, we
extract the configuration mixing angles, an important property of the
quark-quark interaction in the quark model, for the resonances S11(1535) and
S11(1650), as well as for the resonances D13(1520) and D13(1700). Our results
agree well with the quark model predictions. In addition, the partial eta N
decay widths...
70.
Trinucleon photonuclear reactions with $\Delta$-isobar excitation:
Processes below pion-production threshold
- Deltuva, A.; Yuan, L. P.; Adam Jr., J.; Fonseca, A. C.; Sauer, P. U.
Radiative nucleon-deuteron capture and two- and three-body photo
disintegration of the three-nucleon bound state are described. The description
uses the purely nucleonic charge-dependent CD-Bonn potential and its
coupled-channel extension CD Bonn + $\Delta$. The $\Delta$-isobar excitation
yields an effective three-nucleon force and effective two- and three-nucleon
currents besides other $\Delta$-isobar effects; they are mutually consistent.
Exact solutions of three-particle equations are employed for the initial and
final states of the reactions. The current has one-baryon and two-baryon
contributions and couples nucleonic with $\Delta$-isobar channels.
$\Delta$-isobar effects on the observables are isolated. Shortcomings of the
theoretical description are discussed and their consequence for the calculation
of observables is estimated.
71.
Production of $\omega$-mesons in proton-proton collisions
- Nakayama, K.; Szczurek, A.; Hanhart, C.; Haidenbauer, J.; Speth, J.
The production of $\omega$-mesons in proton-proton collisions for proton
incident energies up to 2.2 GeV is investigated within a meson-exchange model
of hadronic interactions.
We find a large cancellation between the dominant $\pi\rho\omega$
meson-exchange current and nucleonic current contributions. A comparison with
preliminary data from SATURNE calls for the inclusion of off-shell form factors
at the $NN\omega$ and $\pi\rho\omega$ production vertices. Due to the present
lack of knowledge of these form factors, together with the destructive
interference mentioned above, the relative magnitude of the nucleonic and
meson-exchange current contributions cannot be determined from existing total
cross section data. However, it is shown that the angular distribution of the
produced $\omega$-mesons...
72.
Regularity and chaos in the nuclear masses
- Leboeuf, P.
Shell effects in atomic nuclei are a quantum mechanical manifestation of the
single--particle motion of the nucleons. They are directly related to the
structure and fluctuations of the single--particle spectrum. Our understanding
of these fluctuations and of their connections with the regular or chaotic
nature of the nucleonic motion has greatly increased in the last decades. In
the first part of these lectures these advances, based on random matrix
theories and semiclassical methods, are briefly reviewed. Their consequences on
the thermodynamic properties of Fermi gases and, in particular, on the masses
of atomic nuclei are then presented. The structure and importance of shell
effects in the nuclear masses with...
73.
The Dynamical Structure of the
- G. Kortemeyer,P. U. Sauer,A. Stadler
The pion-nucleon interaction in the P 33 partial wave is assumed to proceed
simultaneously through the excitation of the Delta-isobar and through a phenomenologically
introduced non-resonant background potential. The introduction
of the background potential allows a more realistic parameterization
of the pion-nucleon-Delta vertex compared with the previously used one without
background. It also modifies the propagation of the Delta-isobar in the nuclear
medium and gives rise to novel effective nucleon-Delta interactions. Their consequences
on predictions for observables in the two-nucleon system at intermediate
energies and in the three-nucleon bound state are studied.
Typeset using REVT
E
X
I. INTRODUCTION
Internal nucleonic degrees of freedom can get excited when nucleons interact. The lowest
state of...
74.
Primordial Nucleosynthesis And Dark Matter
- Subir Sarkar
Introduction
The focus of this Workshop is the problem of dark matter. It is well established
that the dynamics of galaxies and clusters is dominated by unseen matter
which contributes ¸ 10 Gamma 20% of the critical density.
2
In contrast, the luminous
(nucleonic) matter in such structures has a density parameter of only
3
Omega
N ' 2:2 Theta 10
Gamma3
+ 6:1 Theta 10
Gamma4
h
Gamma1:3
; (1)
where the first term accounts for the stars and the second for the X-ray emitting
gas. Here, h j H 0 /100kmsec
Gamma1
Mpc
Gamma1
is the present Hubble parameter. The
obvious question is whether the dark matter might also be nucleonic but in
the form of
75.
Primordial Nucleosynthesis And Dark Matter
- Subir Sarkar
Introduction The focus of this Workshop is the problem of dark matter. It is well established that the dynamics of galaxies and clusters is dominated by unseen matter which contributes ¸ 10 \Gamma 20% of the critical density. 2 In contrast, the luminous (nucleonic) matter in such structures has a density parameter of only 3 \Omega N ' 2:2 \Theta 10 \Gamma3 + 6:1 \Theta 10 \Gamma4 h \Gamma1:3 ; (1) where the first term accounts for the stars and the second for the X-ray emitting gas. Here, h j H 0 /100kmsec \Gamma1 Mpc \Gamma1 is the present Hubble...
76.
Improving Stochastic Estimator Techniques for Disconnected Diagrams
- Viehoff, J.; Eicker, N.; Guesken, S.; Hoeber, H.; Lacock, P.; Lippert, Th.; Ritzenhoefer, G.; Schilling, K.; Spitz, A.; Ueberholz, P.
Disconnected diagrams are expected to be sensitive to the inclusion of
dynamical fermions. We present a feasibility study for the observation of such
effects on the nucleonic matrix elements of the axial vector current, using
SESAM full QCD vacuum configurations with Wilson fermions on $16^3\times 32$
lattices, at $\beta =5.6$. Starting from the standard methods developed by the
Kentucky and Tsukuba groups, we investigate the improvement from various
refinements thereof.
77.
Probing the deuteron structure at small N-N distances by cumulative pion
production
- Illarionov, Alexei Yu.; Litvinenko, Anatoli G.; Lykasov, Gennady I.
The fragmentation of deuterons into pions emitted forward in the kinematic
region forbidden for free nucleon-nucleon collisions is analyzed. It is shown
that the inclusion of the non-nucleonic degrees of freedom in a deuteron
results in a satisfactory description of the data for the inclusive pion
spectrum and improves the description of the data about $T_{20}$. According to
the data, $T_{20}$ has very small positive values, less than 0.2, which
contradicts the theoretical calculations ignoring these degrees of freedom.
78.
Conditions for Confinement and Freeze-Out
- Magas, V.; Satz, H.
Matter implies the existence of a large-scale connected cluster of a uniform
nature. The appearance of such clusters as function of hadron density is
specified by percolation theory. We can therefore formulate the freeze-out of
interacting hadronic matter in terms of the percolation of hadronic clusters.
The resulting freeze-out condition as function of temperature and
baryo-chemical potential interpolates between resonance gas behaviour at low
baryon density and repulsive nucleonic matter at low temperature, and it agrees
well with data.
79.
Tensor Structure Function b$_1$(x) For Spin-One Hadrons
- Kumano, S.
High-energy spin physics became a popular topic recently after the EMC
finding for the proton's spin content. There exist unmeasured spin-dependent
structure functions ($b_1$, $b_2$, $b_3$, and $b_4$) for spin-one hadrons such
as the deuteron. The tensor structure function $b_1(x)$ could be measured by
the proposed 15 GeV European Electron Facility. The measurement provides
important clues to physics of non-nucleonic components in spin-one nuclei and
to tensor structures on the quark-parton level.
80.
Leading nucleon and the hadronic flux in the atmosphere
- Bellandi, J.; Fleitas, J. R.; de Deus, J. Dias
We present in this paper a calculation of the hadronic flux in the
atmosphere. Using an iterative leading particle model and the Glauber model, we
relate the moment of the leading particle distribution in nucleon-air
collisions with the respective one in nucleon-proton collisions. In this way,
we obtain a description of the nucleonic and hadronic fluxes in the atmosphere.
Contribution to the 26th International Cosmic Ray Conference, Salt Lake City -
Utah, August 1999 (HE 1.2.20).
