413 research outputs found
UNDERSTANDING THE SCALAR MESON NONET
It is shown that one can fit the available data on the a0(980), f0(980),
f0(1300) and K*0(1430) mesons as a distorted 0++ qq bar nonet using very few
(5-6) parameters and an improved version of the unitarized quark model. This
includes all light two-pseudoscalar thresholds, constraints from Adler zeroes,
flavour symmetric couplings, unitarity and physically acceptable analyticity.
The parameters include a bare uu bar or dd bar mass, an over-all coupling
constant, a cutoff and a strange quark mass of 100 MeV, which is in accord with
expectations from the quark model.
It is found that in particular for the a0(980) and f0(980) the KK bar
component in the wave function is large, i.e., for a large fraction of the time
the qq bar state is transformed into a virtual KK bar pair. This KK bar
component, together with a similar component of eta' pi for the a0(980) , and
eta eta, eta eta' and eta' eta' components for the f0(980), causes the
substantial shift to a lower mass than what is naively expected from the qq bar
component alone.
Mass, width and mixing parameters, including sheet and pole positions, of the
four resonances are given, with a detailed pedagogical discussion of their
meaning.Comment: 35 pages in plain latex (ZPC in press), 10 figures obtainable from
the author ([email protected]) with regular mail or as a large PS
fil
Production and detection of doubly charmed tetraquarks
The feasibility of tetraquark detection is studied. For the cc\bar{u}\bar{d}
tetraquark we show that in present (SELEX, Tevatron, RHIC) and future
facilities (LHCb, ALICE) the production rate is promising and we propose some
detectable decay channels.Comment: 6 pages, 5 figure
On Deusons or Deuteronlike Meson-Meson Bound States
The systematics of deuteronlike two-meson bound states, {\it deusons}, is
discussed. Previous arguments that many of the present non- states are
such states are elaborated including, in particular, the tensor potential. For
pseudoscalar states the important observation is made that the centrifugal
barrier from the P-wave can be overcome by the and terms of the
tensor potential. In the heavy meson sector one-pion exchange alone is strong
enough to form at least deuteron-like and composites
bound by approximately 50 MeV, while and states are
expected near the threshold.Comment: Invited talk at the Hadron93 International Conf. on Hadron
Spectroscopy, Como, Italy 22.-25.6. 1993. 5 pages in LATEX HU-SEFT R 1993-13
Scalar meson properties from D-meson decays
Decay amplitudes of D(D_s)->f0(980)X, X=pi, K, are compared to experimental
branching ratios with the aim of singling out the poorly known D->f0(980)
transition form factor in these amplitudes. Since the other elements of the
amplitudes are either calculable in an effective QCD theory using operator
product expansion or are known from experiment (e.g. the pion and kaon decay
constants), we can take advantage of these reactions to constrain the
transition form factors obtained in relativistic quark models. In these models,
the f0(980) wavefunction requires an unknown size parameter for both its
non-strange ubar u(dbar d) and strange sbar s components, which we fit to the
D(D_s) decay data.Comment: Talk given at the Few Body 18 conference in Santos, Brazil. 4 pages,
to be published in Nuclear Physics
Chiral Approach to Weak Radiative Hyperon Decays and the Asymmetry
We reanalyse the recent version of the chiral model of weak radiative hyperon
decays, proposed by Borasoy and Holstein. It is shown that predictions of the
analysed model are significantly changed when one accepts the usual
classification of as an SU(3)-singlet. In particular, for the
decay large negative asymmetry is obtained. This
is contrasted with the Hara's-theorem-violating approaches where this asymmetry
is large and positive.Comment: 15 LaTeX pages, 1 ps figur
Three channel model of meson-meson scattering and scalar meson spectroscopy
New solutions on the scalar -- isoscalar phase shifts are analysed
together with previous results using a separable potential model of
three coupled channels (, and an effective
system). Model parameters are fitted to two sets of solutions obtained in a
recent analysis of the CERN-Cracow-Munich measurements of the reaction on a polarized target. A relatively
narrow (90 -- 180 MeV) scalar resonance is found, in contrast
to a much broader ( MeV) state emerging from the analysis
of previous unpolarized target data.Comment: 10 Latex pages + 6 postscript figure
Another look at scattering in the scalar channel
We set up a general framework to describe scattering below 1 GeV
based on chiral low-energy expansion with possible spin-0 and 1 resonances.
Partial wave amplitudes are obtained with the method, which satisfy
unitarity, analyticity and approximate crossing symmetry. Comparison with the
phase shift data in the J=0 channel favors a scalar resonance near the
mass.Comment: 17 pages, 5 figures, REVTe
Stationary phase corrections in the process of bosonization of multi-quark interactions
The functional integration over the auxiliary bosonic variables of cubic
order related with the effective action of the Nambu -- Jona-Lasinio model with
't Hooft term has recently been obtained in the form of a loop expansion. Even
numbers of loops contribute to the action, while odd numbers of loops are
assigned to the measure. We consider the two-loop corrections and analyse their
effect on the low-lying pseudoscalar and scalar mass spectra, quark condensates
and weak decay constants. The results are compared to the leading order
calculations and other approaches.Comment: 22 pages, LaTeX, to appear in European Physics Journal
-to-Glueball form factor and Glueball production in decays
We investigate transition form factors of meson decays into a scalar
glueball in the light-cone formalism. Compared with form factors of to
ordinary scalar mesons, the -to-glueball form factors have the same power in
the expansion of . Taking into account the leading twist light-cone
distribution amplitude, we find that they are numerically smaller than those
form factors of to ordinary scalar mesons. Semileptonic ,
and decays are subsequently investigated. We
also analyze the production rates of scalar mesons in semileptonic decays
in the presence of mixing between scalar and glueball states. The
glueball production in meson decays is also investigated and the LHCb
experiment may discover this channel. The sizable branching fraction in , or could be a clear signal for a scalar glueball
state.Comment: 17 pages, 3 figure, revtex
Weak Hyperon Decays: Quark Sea and SU(3) Symmetry Breaking
An explanation of the difference in the values of the apparent ratios
for the S- and P- wave amplitudes of nonleptonic hyperon decays is proposed.
The argument is formulated in the framework of the standard pole model with
ground-state and excited baryons as intermediate
states for the P- and S- waves respectively. Under the assumption that the
dominant part of the deviation of from is due to large
quark sea effects, symmetry breaking in energy denominators is shown to
lead to a prediction for which is in excellent agreement with
experiment. This corroborates our previous unitarity calculations which
indicated that the matrix elements of the parity
conserving weak Hamiltonian between the ground-state baryons are characterized
by or more. A brief discussion of the problem of the
relative size of S- and P- wave amplitudes is given. Finally, implications for
weak radiative hyperon decays are also discussed.Comment: 26 pages, LATEX, 1647/PH IFJ Krako
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