319 research outputs found
Masses and Internal Structure of Mesons in the String Quark Model
The relativistic quantum string quark model, proposed earlier, is applied to
all mesons, from pion to , lying on the leading Regge trajectories
(i.e., to the lowest radial excitations in terms of the potential quark
models). The model describes the meson mass spectrum, and comparison with
measured meson masses allows one to determine the parameters of the model:
current quark masses, universal string tension, and phenomenological constants
describing nonstring short-range interaction. The meson Regge trajectories are
in general nonlinear; practically linear are only trajectories for light-quark
mesons with non-zero lowest spins. The model predicts masses of many new
higher-spin mesons. A new meson is predicted with mass 1910 Mev. In
some cases the masses of new low-spin mesons are predicted by extrapolation of
the phenomenological short-range parameters in the quark masses. In this way
the model predicts the mass of to be MeV, and
the mass of to be MeV (the potential model predictions
are 100 Mev lower). The relativistic wave functions of the composite mesons
allow one to calculate the energy and spin structure of mesons. The average
quark-spin projections in polarized -meson are twice as small as the
nonrelativistic quark model predictions. The spin structure of reveals an
80% violation of the flavour SU(3). These results may be relevant to
understanding the ``spin crises'' for nucleons.Comment: 30 pages, REVTEX, 6 table
Proposed Search for Mixing in Polarization Phenomena
The and meson mass difference induces the mixing of the
and resonances, the amplitude of which, between the
and thresholds, is large in magnitude, of the order of , and possesses the
phase sharply varying by about 90. We suggest performing the polarized
target experiments on the reaction at high energy in
which the fact of the existence of mixing can be
unambiguously and very easily established through the presence of a strong jump
in the azimuthal asymmetry of the wave production cross section
near the thresholds. The presented estimates of the polarization
effect to be expected in experiment are to a great extent model independent.Comment: RevTeX, 9 pages, 1 figure. A number of typographical and grammatical
errors correcte
Charmonium Composition and Nuclear Suppression
We study charmonium production in hadron-nucleus collisions through the
intermediate next-to-leading Fock space component , formed by
a colour octet pair and a gluon. We estimate the size of this state
and show that its interaction with nucleons accounts for the observed
charmonium suppression in nuclear interactions.Comment: Plain TeX, 8 pages, 5 figures available upon reques
Meson model for f_0(980) production in peripheral pion-nucleon reactions
The Juelich model for pion-pion-scattering, based on an effective meson-meson
Lagrangian is applied to the analysis of the S-wave production amplitudes
derived from the BNL E852 experiment pi^- p -> pi^0 pi^0 n for a pion momentum
of 18.3 GeV. The unexpected strong dependence of the S-wave partial wave
amplitude on the momentum transfer between the proton and neutron in the
vicinity of the f_0(980) resonance is explained in our analysis as interference
effect between the correlated and uncorrelated pi^0 pi^0 pairs.Comment: 6 pages, 7 figures, formulas added, typos removed, new figure
The two-pion spectra for the reaction \pi^- p -> \pi^0\pi^0 n at 38 GeV/c pion momentum and combined analysis of the GAMS, Crystal Barrel and BNL data
We perform the K-matrix analysis of meson partial waves with IJ^{PC}
=00^{++}, 10^{++}, 02^{++}, 12^{++} basing on GAMS data on \pi^-p -> \pi^0\pi^0
n, \eta\eta n, \eta\eta' n together with BNL data on \pi^-p -> K\bar K n and
Crystal Barrel data on p\bar p (at rest) -> \pi^0\pi^0\pi^0, \pi^0\eta\eta,
\pi^0\pi^0\eta. The positions of the amplitude poles (physical resonances) are
determined as well as the positions of the K-matrix poles (bare states) and the
values of bare state couplings to two-meson channels. Nonet classification of
the determined bare states is discussed.Comment: LaTex, 15 pages and 10 figure
Nuclear dependence coefficient for the Drell-Yan and J/ production
Define the nuclear dependence coefficient in terms of ratio
of transverse momentum spectrum in hadron-nucleus and in hadron-nucleon
collisions: . We argue that in small region, the
for the Drell-Yan and J/ production is given by a universal function:\
, where parameters a and b are completely determined by either
calculable quantities or independently measurable physical observables. We
demonstrate that this universal function is insensitive to the
A for normal nuclear targets. For a color deconfined nuclear medium, the
becomes strongly dependent on the A. We also show that our
for the Drell-Yan process is naturally linked to perturbatively
calculated at large without any free parameters, and the
is consistent with E772 data for all .Comment: latex, 28 pages, 10 figures, updated two figures, and add more
discussion
DGLAP analyses of nPDF: constraints from data
We explain how the constraints from present experimental data can be used to
obtain the nPDF in the framework of LO DGLAP evolution. We will also compare
the only two available sets of this type and comment on the important
information that neutrino factories could provide.Comment: 1 pages, 1 postscript figure. Invited talk at the NuFact'02 workshop
(Neutrino Factories based on Muon Storage Rings), London, July 200
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