744 research outputs found
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
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
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
Radiative decays of basic scalar, vector and tensor mesons and the determination of the P-wave q\bar q multiplet
We perform simultaneous calculations of the radiative decays of scalar mesons
f_0(980)-> \gamma\gamma, a_0(980)-> \gamma\gamma, vector meson \phi(1020)->
\gamma f_0(980), \gamma a_0(980), \gamma \pi^0, \gamma \eta, \gamma \eta' and
tensor mesons a_2(1320)-> \gamma\gamma, f_2(1270)-> \gamma\gamma, f_2(1525)->
\gamma\gamma assuming all these states to be dominantly the q\bar q ones. A
good description of the considered radiative decays is reached by using almost
the same radial wave functions for scalar and tensor mesons that supports the
idea for the f_0(980), a_0(980) and a_2(1320), f_2(1270), f_2(1525) to belong
to the same P -wave q\bar q multiplet.Comment: 28 pages, LaTeX, 9 PostScript figures, epsfig.st
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
The rho -> gamma pi and omega -> gamma pi decays in quark-model approach and estimation of coupling for pion emission by quark
In the framework of the relativistic and gauge invariant spectral integral
technique, we calculate radiative decays rho(770)-> gamma pi(140) and
omega(780)-> gamma pi(140) supposing all mesons (pi, rho and omega) to be
quark-antiquark states. The q anti-q wave functions found for mesons and photon
lead to a reasonably good description of data ( keV,
keV,
keV) that makes it possible
to estimate the coupling for the bremsstrahlung emission of pion by quarks
. We have found two values for the pion
bremsstrahlung coupling: (Solution I) and
(Solution II). Within SU(6)-symmetry for
nucleons, Solution I gives us for pi NN coupling the value that is in qualitative agreement with the pi N
scattering data, . For excited states, we have
estimated the partial widths in Solution I as follows: keV, keV, keV. The large uncertainties emphasise the necessity to carry out
measurements of the meson radiative processes in the region of large masses.Comment: 23 pages in IOP forma
Quark--antiquark states and their radiative transitions in terms of the spectral integral equation. {\Huge III.} Light mesons
We continue the investigation of mesons in terms of the spectral integral
equation initiated before [hep-ph/0510410, hep-ph/0511005] for the
and systems: in this paper we consider the light-quark ()
mesons with masses GeV. The calculations have been performed for the
mesons lying on linear trajectories in the -planes, where is the
radial quantum number. Our consideration relates to the states with
one component in the flavor space, with the quark and antiquark masses equal to
each other, such as , , ,
, , , , ,
, , , ,
, at . We obtained the wave functions
and mass values of mesons lying on these trajectories. The corresponding
trajectories are linear, in agreement with data. We have calculated the
two-photon decays , ,
, , and radiative transitions ,
, that agree qualitatively with the experiment. On this
basis, we extract the singular part of the interaction amplitude, which
corresponds to the so-called "confinement interaction". The description of the
data requires the presence of the strong -channel singularities for both
scalar and vector exchanges.Comment: 48 pages, 24 figure
Three-body dispersion-relation N/D equations for the coupled decay channels ppbar (J^{PC}=0^{-+}) --> pi^0 pi^0 pi^0, eta pi^0 pi^0, eta eta pi^0, K Kbar pi^0
During several years the data on different channels ppbar (J^{PC}=0^{-+}) -->
3 mesons presented by Crystal Barrel Collaboration were successfully analyzed
by extracting the leading amplitude singularities - pole singularities - with
the aim to obtain information about two-meson resonances. But these analyses do
not take into account three-body final state interactions (FSI) in an
explicitly correct way. This paper is devoted to the consideration of this
problem.Comment: 16 pages, no figure
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