689 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
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
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
Determination of quark-antiquark component of the photon wave function for u, d, s quarks
Based on the data for the transitions pi0, eta, eta' -> gamma gamma^*(Q^2)
and reactions of the e^+ e^- -annihilations, e^+ e^- -> rho0, omega, phi and
e^+ e^--> hadrons at 1<E_{e^+e^-}<3.7 GeV, we determine the light-quark
components of the photon wave function gamma^*(Q^2) -> q anti-q (q= u, d, s)
for the region 0< Q^2 <1 (GeV/c)^2.Comment: 17 pages, some typos correcte
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
Systematics of quark-antiquark states: where are the lightest glueballs?
The analysis of the experimental data of Crystal Barrel Collaboration on the
p anti-p annihilation in flight with the production of mesons in the final
state resulted in a discovery of a large number of mesons over the region
1900-2400 MeV, thus allowing us to systematize quark-antiquark states in the
(n,M^2) and (J,M^2) planes, where n and J are radial quantum number and spin of
the meson with the mass M. The data point to meson trajectories in these planes
being approximately linear, with a universal slope. Basing on these data and
results of the recent K-matrix analysis a nonet classification is performed. In
the scalar-isoscalar sector, the broad resonance state f0(1200-1600) is
superfluous for the q anti-q classification, i.e. it is an exotic state. The
ratios of coupling constants for the transitions f0-> pi pi, K anti-K, eta eta,
eta eta' point to the gluonium nature of the broad state f0(1200-1600). The
problem of the location of the lightest pseudoscalar glueball is also
discussed.Comment: 10 pages, Latex, Talk given at HADRON-2003, 31 August - 5 September
2003, Aschaffensburg, German
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