1,205 research outputs found
Production of -mesons in proton-proton and proton-nucleus interactions at various energies
The experimental data on the production of -mesons in pp-collisions are
analyzed and a method of the unified description of these data in a broad
energy range for primary protons is proposed. The -mesons production in
pA-collisions is considered. The simple formulas for inclusive cross sections
of the production in these collisions are given. The results of the
calculations by these formulas are compared with the available experimental
data.Comment: 14 pages, LaTeX, uses ws-art.sty. Figures can be requested from
[email protected] or looked up in the article abov
Subthreshold Production on Nuclei by Mesons
The inclusive mesons production in --nucleus reactions in the
subthreshold energy regime is analyzed with respect to the one--step
() and the two--step () incoherent production processes on the basis of an appropriate
folding model, which allows one to take into account the various forms of an
internal nucleon momentum distribution as well as on-- and off--shell
propagation of the struck target nucleon. Contrary to proton--nucleus reactions
primary reaction channel is found to be significant practically at all
considered energies. Detailed predictions for the total and invariant
differential cross sections from \piC-- and \piPb--collisions at subthreshold
energies are provided.Comment: 18 pages, LaTeX, uses ws-art.sty, gzip+uuencoded postscript. Figures
are available by request from [email protected]
Subthreshold K+ Meson Production in Proton-Nucleus Reactions
The inclusive K+ mesons production in proton-nucleus collisions in the near
threshold and subthreshold energy regimes is analyzed with respect to the
one-step (pN->K+YN, Y=Lambda,Sigma) and the two-step (pN->NNpi, NN2pi;
piN->K+Y) incoherent production processes on the basis of an appropriate new
folding model, which takes properly into account the struck target nucleon
removal energy and momentum distribution (nucleon spectral function), extracted
from recent quasielastic electron scattering experiments and from many-body
calculations with realistic models of the NN interaction. Comparison of the
model calculations of the K+ double differential cross sections for the
reaction p+C at 1.2, 1.5 and 2.5 GeV beam energies with the existing
experimental data from the SATURNE experiment is given, illustrating both the
relative role of the primary and secondary production channels at considered
incident energies and those features of the cross sections which are sensitive
to the high momentum and high removal energy part of the nucleon spectral
function that is governed by nucleon-nucleon short-range and tensor
correlations. In--medium modifications of the available for pion and hyperon
production invariant energies squared due to the respective optical potentials
are needed to account for the experimental data on K+ production in the energy
region under consideration.Comment: 6 pages, LaTeX, uses revtex.st
Old and new parton distribution and fragmentation functions
A short review of problems with parton distribution functions in nucleons,
non-polarized and polarized, is given. The main part is devoted to the
transversity distribution its possible measurement and its first experimental
probe via spin asymmetry in semi-inclusive DIS. It is argued that the proton
transversity distribution could be successfully measured in future DIS
experiments with {\it longitudinally} polarized target.Comment: 9 pages, latex, czjphys2.sty, 4 eps figures. Submitted at 35-th
Rancontre de Moriond, March 2000 and at Praha-SPIN-2000, July 2000. To be
published in Czechoslovak J. Phys. (Suppl) 51 (2001
Anisotropically high entanglement of biphotons generated in spontaneous parametric down conversion
We show that the wave packet of a biphoton generated via spontaneous
parametric down conversion is strongly anisotropic. Its anisotropic features
manifest themselves very clearly in comparison of measurements performed in two
different schemes: when the detector scanning plane is perpendicular or
parallel to the plane containing the crystal optical axis and the laser axis.
The first of these two schemes is traditional whereas the second one gives rise
to such unexpected new results as anomalously strong narrowing of the biphoton
wave packet measured in the coincidence scheme and very high degree of
entanglement. The results are predicted theoretically and confirmed
experimentally
Beam Single-Spin Asymmetry in Semi-Inclusive Deep Inelastic Scattering
We calculate, in a model, the beam spin asymmetry in semi-inclusive jet
production in deep inelastic scattering. This twist-3, -odd observable is
non-zero due to final state strong interactions. With reasonable choices for
the parameters, one finds an asymmetry of several percent, about the size seen
experimentally. We present the result both as an explicit asymmetry calculation
and as a model calculation of the new transverse-momentum dependent
distribution function .Comment: 10 pages, 6 figures; minor changes made in the discussion; version
accepted for publicatio
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