1,248 research outputs found
Systematics of q anti-q states in the (n,M^2) and (J,M^2) planes
In the mass region up to M < 2400 MeV we systematise mesons on the plots
(n,M^2) and (J,M^2), thus setting their classification in terms of n^{2S+1}L_J
q anti-q states. The trajectories on the (n,M^2)-plots are drawn for the
following (IJ^{PC})-states: a_0(10^{++}), a_1(11^{++}), a_2(12^{++}),
a_3(13^{++}), a_4(14^{++}), pi(10^{-+}), pi_2(12^{-+}), eta(00^{-+}),
eta_2(02^{-+})$, rho(11^{--}), f_0(00^{++}), f_2(02^{++}). All trajectories are
linear, with nearly the same slopes. At the (J,M^2)-plot we set out meson
states for leading and daughter trajectories: for pi, rho, a_1, a_2 and P'.Comment: 6 pages, LaTeX, 16 EPS figures, epsfig.st
Colour effective particles and confinement
Here I present a brief review of papers where the idea is pushed forward that
colour confinement is realized by singular interaction at large distances
between colour effective particles (constituent quarks, diquarks, massive
effective gluons).Comment: Talk at Workshop ''Hadron Structure and QCD'' Gatchina, Russia, July
5 - July 9, 201
Partial decay widths of baryons in the spin-momentum operator expansion method
The cross sections for photo- and pion-induced production of baryon
resonances and their partial decay widths to the two--body and multi--body
final states are calculated in the framework of the operator expansion method.
The approach is fully relativistic invariant, and it allows us to perform
combined analyses of different reactions imposing directly the analyticity and
unitarity constraints. All formulae are given explicitly in the form used by
the Crystal Barrel collaboration in the partial wave analysis.Comment: 15 pages, 6 figure
Resonance : Is it a scalar glueball ?
The ratios of partial widths for the decay of a glueball into two
pseudoscalar mesons are calculated under the assumption that the production of
light quark pairs () in soft gluon-\-induced reactions
goes on within universal symmetry breaking. Parameter of the violation of
flavour symmetry is fixed by the central hadron production data in high energy
hadron collisions and/or by the ratios of radiative decay amplitudes and . The ratios of coupling constants which are calculated with this parameter coincide
reasonably with those of , supporting an idea about glueball nature
of .Comment: LaTex, 8 pages, 2 .eps figures in one uuencoded file, uses epsfi
Radiative decays of quarkonium states, momentum operator expansion and nilpotent operators
We present the method of calculation of radiative decays of composite
quark-antiquark systems with different J^{PC}: (Q\bar Q)_{in} -> gamma (Q\bar
Q)_{out}. The method is relativistic invariant, it is based on the double
dispersion relation integrals over the masses of composite mesons, it can be
used for the high spin particles and provides us with the gauge invariant
transition amplitudes. We apply this method to the case when the photon is
emitted by a constituent in the intermediate state (additive quark model). We
perform the momentum operator expansion of the spin amplitudes for the decay
processes. The problem of nilpotent spin operators is discussed.Comment: 21 pages, 1 figur
Mechanisms of the production in the reaction
The model of the pure one-pion exchange mechanism, which gives a good
description of the GAMS results on the alteration of the -wave
mass spectrum in the region in the reaction
with increasing , is compared with the recent detailed data on the and
distributions of the events obtained by the BNL-E852
Collaboration. It is shown that the predictions of this model are not confirmed
by the BNL data. Therefore the observed phenomenon should be explained by the
different exchange mechanism. It is most likely to be the exchange
mechanism.Comment: 11 pages including 3 figure
Chiral multiplets of excited mesons
It is shown that experimental meson states with spins J=0,1,2,3 in the energy
range 1.9 - 2.4 GeV obtained in recent partial wave analysis of
proton-antiproton annihilation at LEAR remarkably confirm all predictions of
chiral symmetry restoration. Classification of excited mesons
according to the representations of chiral group is
performed. There are two important predictions of chiral symmetry restoration
in highly excited mesons: (i) physical states must fill out approximately
degenerate parity-chiral multiplets; (ii) some of the physical states with the
given are members of one parity-chiral multiplet, while the other
states with the same are members of the other parity-chiral
multiplet. For example, while some of the excited states are
systematically degenerate with states forming (0,1)+(1,0)
chiral multiplets, the other excited states are degenerate
with states ((1/2,1/2) chiral multiplets). Hence, one of the
predictions of chiral symmetry restoration is that the combined amount of
and states must coincide with the amount of
states in the chirally restored regime. It is shown that the
same rule applies (and experimentally confirmed) to many other meson states.Comment: 14 pages, discussion and conclusion section is largely extende
Chiral symmetry restoration in hadron spectra
The evidence and the theoretical justification of chiral symmetry restoration
in high-lying hadrons is presented.Comment: Invited talk given at Int. School on Nuclear Physics "Quarks in
Hadrons and Nuclei", September 2002, Erice/Sicily/Italy; to appear in Progr.
Part. Nucl. Phys., vol. 50; 10 page
Quark-gluonium content of the scalar-isoscalar states f_0(980), f_0(1300), f_0(1500), f_0(1750), f_0(1420 ^{+150}_{- 70}) from hadronic decays
On the basis of the decay couplings f_0 -> \pi\pi, K\bar K, \eta\eta,
\eta\eta', which had been found before, in the study of analytical
(IJ^{PC}=00^{++})-amplitude in the mass range 450-1900 MeV, we analyse the
quark-gluonium content of resonances f_0(980), f_0(1300), f_0(1500), f_0(1750)
and the broad state f_0(1420 ^{+ 150}_{-70}). The K-matrix technique used in
the analysis makes it possible to evaluate the quark-gluonium content both for
the states with switched-off decay channels (bare states, f^{bare}_0) and the
real resonances. We observe significant change of the quark-gluonium
composition in the evolution from bare states to real resonances, that is due
to the mixing of states in the transitions f_0(m_1)-> real mesons-> f_0(m_2)
responsible for the decay processes as well. For the f_0(980), the analysis
confirmed the dominance of q\bar q component thus proving the n\bar n/s\bar s
composition found in the study of the radiative decays. For the mesons
f_0(1300), f_0(1500) and f_0(1750), the hadronic decays do not allow one to
determine uniquely the n\bar n, s\bar s and gluonium components providing
relative pecentage only. The analysis shows that the broad state f_0(1420 ^{+
150}_{-70}) can mix with the flavour singlet q\bar q component only, that is
consistent with gluonium origin of the broad resonance.Comment: 20 pages, LaTeX, 10 PostScript figures, epsfig.st
Parity doubling of highly excited mesons
Glozman has proposed that highly excited mesons and baryons fall into parity
doublets, and that the f4(2050) on the leading Regge trajectory should have a
nearly degenerate J^{PC} = 4^{-+} partner. A re-analysis of Crystal Barrel data
does not support this idea. A likely explanation is that centrifugal barriers
on the leading trajectory allow formation of the L=J-1 states, but are too
strong to allow L=J states. Two new polarisation experiments have the potential
for major progress in meson spectroscopy.Comment: 7 pages, 2 figures, 1 table. Further experimental detail added and
additional algebra. Conclusions unchanged. To be published in Physics Letters
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