2,616 research outputs found
Evidence that the Pomeron transforms as a non-conserved vector current
The detailed dependences of central meson production on the azimuthal angle
phi, t and the meson J^P are shown to be consistent with the hypothesis that
the soft Pomeron transforms as a non-conserved vector current. Further tests
are proposed. This opens the way for a quantitative description of q-qbar and
glueball production in p p -> p M p.Comment: 12 pages, latex, 4 figure
Scalar Glueball-qqbar Mixing above 1 GeV and implications for Lattice QCD
Lattice QCD predictions have motivated several recent studies of the mixing
between the predicted JPC = 0++ glueball and a qqbar nonet in the 1.3 to 1.7
GeV region. We show that results from apparently different approaches have some
common features, explain why this is so and abstract general conclusions. We
place particular emphasis on the flavour dependent constraints imposed by
decays of the f0(1370), f0(1500) and f0(1700) to all pairs of pseudoscalar
mesons. From these results we identify a systematic correlation between
glueball mass, mixing, and flavour symmetry breaking and conclude that the
glueball may be rather lighter than some quenched lattice QCD computations have
suggested. We identify experimental tests that can determine the dynamics of a
glueball in this mass region and discuss quantitatively the feasibility of
decoding glueball-qqbar mixing.Comment: 33 pages, Latex, 4 Figure
Light Hadron Spectroscopy: Theory and Experiment
Rapporteur talk at the Lepton-Photon Conference, Rome, July 2001: reviewing
the evidence and strategies for understanding scalar mesons, glueballs and
hybrids, the gluonic Pomeron and the interplay of heavy flavours and light
hadron dynamics. Dedicated to the memory of Nathan Isgur, long-time
collaborator and friend, whose original ideas in hadron spectroscopy formed the
basis for much of the talk.Comment: to be published in "Lepton Photon 2001 Conference Proceedings" (World
Scientific Publishing), 19 pages with 6 figure
Scalar mesons above and below 1 GeV
We show that two nonets and a glueball provide a consistent description of
data on scalar mesons below 1.7 GeV. Above 1 GeV the states form a conventional
(q bar q) nonet mixed with the glueball of lattice QCD. Below 1 GeV the states
also form a nonet, as implied by the attractive forces of QCD, but of more
complicated nature. Near the center they are 4 quark states of the Jaffe type
in S-wave, with some (q bar q) in P-wave, but further out they rearrange in
colour to two colourless (q bar q) pairs and finally as meson-meson states. A
simple effective chiral model for such a system with two scalar nonets can be
made involving two coupled linear sigma models. One of these could be looked
upon as the Higgs sector of nonpertubative QCD.Comment: 34 pages in Latex, minor improvements in sec
Central production of mesons: Exotic states versus Pomeron structure
We demonstrate that the azimuthal dependence of central meson production in
hadronic collisions, when suitably binned, provides unambiguous tests of
whether the Pomeron couples like a conserved vector-current to protons. We
discuss the possibility of discriminating between q-qbar and glueball
production in such processes. Our predictions apply also to meson production in
tagged two-photon events at electron--positron colliders and to vector-meson
production in ep collisions at HERA.Comment: 15 pages, latex, no figur
Looking for a gift of Nature: Hadron loops and hybrid mixing
We investigate how coupling of valence q qbar to meson pairs can modify the
properties of conventional q qbar and hybrid mesons. In a symmetry limit the
mixing between hybrids and conventional q qbar with the same J^PC is shown to
vanish. Flavor mixing between heavy and light q qbar due to meson loops is
shown to be dual to the results of gluon mediated pQCD, and qualitatively
different from mixing involving light flavors alone. The validity of the OZI
rule for conventional q qbar and hybrid mesons is discussed.Comment: v2: added important references and discussion of previous literature;
results and conclusions unchanged. 8 pages, 2 figure
Dynamics and Decay of Heavy-Light Hadrons
Recent signals for narrow hadrons containing heavy and light flavours are
compared with quark model predictions for spectroscopy, strong decays, and
radiative transitions. In particular, the production and identification of
excited charmed and cs states are examined with emphasis on elucidating the
nature of and states. Roughly 200 strong decay amplitudes of
and states up to 3.3 GeV are presented. Applications include determining
flavour content in mesons and the mixing angle in and wave
states and probes of putative molecular states. We advocate searching for
radially excited states in B decays.Comment: 19 pages, 7 figures, revtex. A numerical error is corrected. Some
strong decay rates have change
Spin of ground state baryons
We calculate the quark spin contribution to the total angular momentum of
flavor octet and flavor decuplet ground state baryons using a spin-flavor
symmetry based parametrization method of quantum chromodynamics. We find that
third order SU(6) symmetry breaking three-quark operators are necessary to
explain the experimental result Sigma_1=0.32(10). For spin 3/2 decuplet baryons
we predict that the quark spin contribution is Sigma_3=3.93(22), i.e.
considerably larger than their total angular momentum.Comment: 8 page
Nature of the light scalar mesons
Despite the apparent simplicity of meson spectroscopy, light scalar mesons
cannot be accommodated in the usual structure. We study the
description of the scalar mesons below 2 GeV in terms of the mixing of a chiral
nonet of tetraquarks with conventional states. A strong
diquark-antidiquark component is found for several states. The consideration of
a glueball as dictated by quenched lattice QCD drives a coherent picture of the
isoscalar mesons.Comment: 14 pages, 1 figure, accepted for publication in Phys. Rev.
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