259 research outputs found
On nature of the scalar-isoscalar mesons in the uniformizing-variable method based on analyticity and unitarity
The experimental data on the processes
in the
channel have been jointly analyzed to study the status
and nature of the . The method of analysis is based on analyticity and
unitarity and uses an uniformization procedure. Some spectroscopic implications
from results of the analysis are discussed.Comment: 18 pages, 5 figures, 9 table
Parameters of scalar resonances from the combined analysis of data on processes and decays
A combined analysis of data on isoscalar S-wave processes
and on decays
from the DM2, Mark III and BESIII
collaborations is performed to study mesons. The method of analysis is
based on analyticity and unitarity and uses an uniformization procedure. In the
analysis limited only to the multi-channel -scattering data, two
possible sets of parameters of the were found: in both cases the
mass was about 700 MeV but the total width was either about 600 or 930 MeV. The
extension of the analysis using only the DM2 and Mark III data on the
decays does not allow to choose between these sets. However, the data from
BESIII on the di-pion mass distribution in the decay
clearly prefers the wider state. Spectroscopic implications from
results of the analysis are also discussed.Comment: the formalism is also described (text overlap) in arXiv:1108.3725;
new extended analysis of data; revised PRD versio
Some indication for a missing chiral partner eta_4 around 2 GeV
The high-lying mesons in the light quark sector previously obtained from the
partial wave analysis of the proton-antiproton annihilation in flight at 1.9 -
2.4 GeV region at CERN reveal a very high degree of degeneracy. This degeneracy
can be explained as due to an effective restoration of both SU(2)_L * SU(2)_R
and U(1)_A symmetries combined with a principal quantum number n + J. In this
case there must be chiral partners for the highest spin states in the 2 and 2.3
GeV bands presently missing in the data. Here we reanalyze the Crystal Barrel
data and show an indication for existence of the missing state around
2 GeV. This result calls for further experimental search of the missing states
both in the proton-antiproton annihilation and in the production reactions.Comment: 4 pp. A fit with the energy-dependent width has been added that
agrees with the previous analysis. Accepted by PR
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
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
Unquenching the scalar glueball
Computations in the quenched approximation on the lattice predict the
lightest glueball to be a scalar in the 1.5-1.8 GeV region. Here we calculate
the dynamical effect the coupling to two pseudoscalars has on the mass, width
and decay pattern of such a scalar glueball. These hadronic interactions allow
mixing with the scalar nonet, which is largely fixed by the
well-established K_0^*(1430). This non-perturbative mixing means that, if the
pure gluestate has a width to two pseudoscalar channels of ~100 MeV as
predicted on the lattice, the resulting hadron has a width to these channels of
only ~30 MeV with a large eta-eta component. Experimental results need to be
reanalyzed in the light of these predictions to decide if either the f_0(1500)
or an f_0(1710) coincides with this dressed glueball.Comment: 12 pages, LaTex, 3 Postscript figure
Colorless States in Perturbative QCD: Charmonium and Rapidity Gaps
We point out that an unorthodox way to describe the production of rapidity
gaps in deep inelastic scattering, recently proposed by Buchm\"uller and
Hebecker, suggests a description of the production of heavy quark bound states
which is in agreement with data. The approach questions the conventional
treatment of the color quantum number in perturbative QCD.Comment: 14 pages, plain Latex, 9 postscript figures included. Uses epsf.sty.
Postscript file of paper with figures also available at
http://phenom.physics.wisc.edu/pub/preprints/1995/madph-95-919.ps.Z or at
ftp://phenom.physics.wisc.edu/pub/preprints/1995/madph-95-919.ps.
Study of the system in the mass range up to 1200 MeV
The reaction has been studied with GAMS-2000
spectrometer in the secondary 38 GeV/c -beam of the IHEP U-70
accelerator. Partial wave analysis of the reaction has been performed in the
mass range up to 1200 MeV. The -meson is seen as a sharp
peak in S-wave. The -dependence of production cross section has
been studied. Dominant production of the at a small transfer
momentum confirms the hypothesis of Achasov and Shestakov about significant
contribution of the exchange () in the mechanism
of meson production in -channel of the reaction.Comment: 4 pages, 3 figures, talk given at HADRON'9
Process pi p -> pi pi N at high energies and moderate momenta transferred to the nucleon and the determination of parameters of the f_0(980) and f_0(1300)
We present the results of simultaneous analysis of the S-wave pi pi-spectra
in the reactions pi^- p -> (pi^0 pi^0)_S n at p_{lab}=38 GeV/c (GAMS) and pi^-
p -> (pi^+ pi^-)_S n at p_{lab}=18 GeV/c (E852 Collaboration) at moderate
momenta transferred to the nucleon, |t| < 1.5 (GeV/c)^2. The t-distributions
are described by the reggeized pi- and a_1-exchanges provided by the leading
and daughter trajectories, while the M_{pi pi}-spectra are determined by a set
of scalar-isoscalar resonances. With M_{pi pi}-distributions averaged over
t-intervals, we have found several solutions given by different t-channel
exchange mechanisms at |t| ~ (0.5-1.5) (GeV/c)^2, with resonance parameters
close to each other. We conclude that despite a poor knowledge of the structure
of the t-exchange, the characteristics of resonances such as masses and widths
can be reliably determined using the processes under discussion. As to pole
positions, we have found (1031 +/- 10) - i(35 +/- 6) MeV for f_0(980) and (1315
+/- 20) - i(150 +/- 30) MeV for f_0(1300).Comment: 17 pages, RevTeX, 10 EPS figures, misprints correcte
The lightest scalar glueball
Recently performed investigations of meson spectra allow us to determine the
resonance structure for the waves , , ,
= in the mass region up to 1900 MeV, thus
establishing the meson multiplets and .
Experimental data demonstrate that there are five scalar/isoscalar states in
this mass region. Four of them are states, that is, members of the
and nonets, while the fifth state is an extra
one not accomodated by systematics; it has the properties of the
lightest scalar glueball. Analysis of the -wave performed within the
framework of the dispersion relation technique allows us to reconstruct the
mixing of a pure gluonium with neighbouring scalar states belonging
to and nonets: three scalar mesons share the
gluonium state between each other -- those are two comparatively narrow
resonances and and a broad resonance
. The broad state is a descendant of the gluonium,
keeping about 40-50% of its component.Comment: 48 pages, LaTeX, 25 PostScript figures, epsfig.sty. Submitted to
Russian Journal Uspekhi Fiz. Nauk (Phys-Uspekhi
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