814 research outputs found
Non-resonant kaon pair production and medium effects in proton-nucleus collisions
We study the non-resonant (non-) production of pairs by
protons of 2.83 GeV kinetic energy on C, Cu, Ag, and Au targets within the
collision model, based on the nuclear spectral function, for incoherent primary
proton--nucleon and secondary pion--nucleon creation processes. The model takes
into account the initial proton and final kaon absorption, target nucleon
binding and Fermi motion as well as nuclear mean-field potential effects on
these processes. We calculate the antikaon momentum dependences of the
exclusive absolute and relative pair yields in the acceptance window
of the ANKE magnetic spectrometer, used in a recent experiment performed at
COSY, within the different scenarios for the antikaon-nucleus optical
potential. We demonstrate that the above observables are strongly sensitive to
this potential. Therefore, they can be useful to help determine the
optical potential from the direct comparison of the results of our calculations
with the data from the respective ANKE-at-COSY experiment. We also show that
the pion--nucleon production channels dominate in the low-momentum ,
production in the considered kinematics and, hence, they have to be accounted
for in the analysis of these data.Comment: 19 page
Medium effects in pair production by 2.83 GeV protons on nuclei
We study pair production in the interaction of protons of 2.83
GeV kinetic energy with C, Cu, Ag, and Au target nuclei in the framework of the
nuclear spectral function approach for incoherent primary proton--nucleon and
secondary pion--nucleon production processes, and processes associated with the
creation of intermediate pairs. The approach accounts for the
initial proton and final hyperon absorption, final meson
distortion in nuclei, target nucleon binding, and Fermi motion, as well as
nuclear mean-field potential effects on these processes. We calculate the
momentum dependence of the absolute yield from the
target nuclei considered, in the kinematical conditions of the ANKE experiment,
performed at COSY, within the different scenarios for the -nucleus
effective scalar potential. We show that the above observable is appreciably
sensitive to this potential in the low-momentum region. Therefore, direct
comparison of the results of our calculations with the data from the
ANKE-at-COSY experiment can help to determine the above potential at finite
momenta. We also demonstrate that the two-step pion--nucleon production
channels dominate in the low-momentum production in the chosen
kinematics and, therefore, they have to be taken into account in the analysis
of these data.Comment: 29 page
Light scattering by optically anisotropic scatterers II: T--matrix computations for radially and uniformly anisotropic droplets
This is the second paper in a series on light scattering from optically
anisotropic scatterers embedded in an isotropic medium. The apparently complex
T-matrix theory involving mixing of angular momentum components turns out to be
an efficient approach to calculating scattering in these systems. We present
preliminary results of numerical calculations of the scattering by spherical
droplets in some simple cases. The droplets contain optically anisotropic
material with local radial or uniform anisotropy. We concentrate on cases in
which the scattering is due only to the local optical anisotropy within the
scatterer. For radial anisotropy we find non-monotonic dependence of the
scattering cross-section on the degree of anisotropy can occur in a regime for
which both the Rayleigh and semi-classical theories are inapplicable. For
uniform anisotropy the cross-section is strongly dependent on the angle between
the incident light and the optical axis, and for larger droplets this
dependence is non-monotonic.Comment: 14 pages, 6 figures, uses RevTex
Subthreshold and near-threshold kaon and antikaon production in proton-nucleus reactions
The differential production cross sections of K^+ and K^- mesons have been
measured at the ITEP proton synchrotron in p+Be, p+Cu collisions under lab
angle of 10.5^0, respectively, at 1.7 and 2.25, 2.4 GeV beam energies. A
detailed comparison of these data with the results of calculations within an
appropriate folding model for incoherent primary proton-nucleon, secondary
pion-nucleon kaon and antikaon production processes and processes associated
with the creation of antikaons via the decay of intermediate phi mesons is
given. We show that the strangeness exchange process YN->NNK^- gives a small
contribution to the antikaon yield in the kinematics of the performed
experiment. We argue that in the case when antikaon production processes are
dominated by the channels with KK^- in the final state, the cross sections of
the corresponding reactions are weakly influenced by the in-medium kaon and
antikaon mean fields.Comment: 24 pages. accepted for publication at J.Phys.
Two-particle decays of B_c meson into charmonium states
The factorization of hard and soft contributions into the hadronic decays of
B_c meson at large recoils is explored in order to evaluate the decay rates
into the S, P and D-wave charmonia associated with rho and pi. The constraints
of approach applicability and uncertainties of numerical estimates are
discussed. The mode with the J/psi in the final state is evaluated taking into
account the cascade radiative electromagnetic decays of excited P-wave states,
that enlarges the branching ratio by 20-25%.Comment: 13 pages, LaTeX axodraw-style, 1 figure, 2 table
Variational Lie algebroids and homological evolutionary vector fields
We define Lie algebroids over infinite jet spaces and establish their
equivalent representation through homological evolutionary vector fields.Comment: Int. Workshop "Nonlinear Physics: Theory and Experiment VI"
(Gallipoli, Italy; June-July 2010). Published v3 = v2 minus typos, to appear
in: Theoret. and Mathem. Phys. (2011) Vol.167:3 (168:1), 18 page
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