339 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
Amplitude analysis of reactions pi(-)p->etapi(-)p and pi(-)p->etapi(0)n on polarized target and the exotic 1-+ meson
Recently several experimental groups analysed data on and reactions with exotic -wave and
found a conflicting evidence for an exotic meson . High
statistics data on these reactions are presently analysed by BNL E852
Collaboration. All these analyses are based on the crucial assumption that the
production amplitudes do not depend on nucleon spin. This assumption is in
sharp conflict with the results of measurements of ,
and on polarized targets at
CERN which find a strong dependence of production amplitudes on nucleon spin.
To ascertain the existence of exotic meson , it is necessary to
perform a model-independent amplitude analysis of reactions and . We demonstrate that measurements of
these reactions on transversely polarized targets enable the required model
independent amplitude analysis without the assumption that production
amplitudes are independent on nucleon spin. We suggest that high statistics
measurements of reactions and be made on polarized targets at BNL and at Protvino IHEP, and that
model-independent amplitude analyses of this polarized data be performed to
advance hadron spectroscopy on the level of spin dependent production
amplitudes.Comment: 23 page
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
scattering S wave from the data on the reaction
The results of the recent experiments on the reaction
performed at KEK, BNL, IHEP, and CERN are analyzed in detail. For the I=0
S wave phase shift and inelasticity a new set
of data is obtained. Difficulties emerging when using the physical solutions
for the S and D wave amplitudes extracted with the partial wave
analyses are discussed. Attention is drawn to the fact that, for the
invariant mass, m, above 1 GeV, the other solutions, in principle,
are found to be more preferred. For clarifying the situation and further
studying the resonance thorough experimental investigations of the
reaction in the m region near the threshold
are required.Comment: 17 pages, 5 figure
Energy loss of fast quarks in nuclei
We report an analysis of the nuclear dependence of the yield of Drell-Yan
dimuons from the 800 GeV/c proton bombardment of , C, Ca, Fe, and W
targets. Employing a new formulation of the Drell-Yan process in the rest frame
of the nucleus, this analysis examines the effect of initial-state energy loss
and shadowing on the nuclear-dependence ratios versus the incident proton's
momentum fraction and dimuon effective mass. The resulting energy loss per unit
path length is GeV/fm. This is the first
observation of a nonzero energy loss of partons traveling in nuclear
environment.Comment: 5 pages, including 4 figure
Systematization of tensor mesons and the determination of the glueball
It is shown that new data on the -resonances in the mass
range MeV support the linearity of the -trajectories,
where is the radial quantum number of quark--antiquark state. In this way
all vacancies for the isoscalar tensor -mesons in the range up to 2450
MeV are filled in. This allows one to fix the broad -state with
MeV and MeV as the lowest tensor glueball. PACS
numbers: 14.40.-n, 12.38.-t, 12.39.-MkComment: 10 pages, 1 figur
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
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
Charmonium suppression in p-A collisions
The new high precision data on charmonium production in proton-nucleus
collisions by the E866/NuSea collaboration at Fermilab allow - together with
older data at lower energies - to fix a unique set of parameters for the
standard production and absorption scenario of charmonium in a proton-nucleus
reaction. In this scenario the c-cbar pair is formed in an octet state, emits a
gluon and continues its radial expansion in a singlet state until it has
reached the charmonium radius. In all three phases it can interact with the
nuclear environment. We find that the lifetime of the octet state is much
shorter than acceptable on physical grounds. This challenges the physical
reality of the first phase in the standard scenario.Comment: 8 pages, 10 figure
Nuclear parton distributions at next to leading order
We perform a next to leading order QCD global analysis of nuclear deep
inelastic scattering and Drell-Yan data using the convolution approach to
parameterize nuclear parton densities. We find both a significant improvement
in the agreement with data compared to previous extractions, and substantial
differences in the scale dependence of nuclear effects compared to leading
order analyses.Comment: 9 pages, 10 figure
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