328 research outputs found
The role of secondary Reggeons in central meson production
We estimate the contribution of f_2 trajectory exchange to the central \eta
and \eta^\prime production. It is shown that secondary Reggeons may give a
large contribution to processes of double diffractive meson production at high
energy.Comment: 7 pages, Latex, 5 figure
Puzzles in Cabibbo-Suppressed Charm Decays
We identify two Cabibbo suppressed decay modes with anomalously high
branching ratios which are not simply explained by any model. All standard
model diagrams that can contribute to these decays are related by symmetries to
diagrams for other decays that do not show any such enhancement. If these high
branching ratios are confirmed by more precise experiments, they may require
new physics to explain them. Anomalies in decays and tests for possible
violation of G-parity are discussed.Comment: 12 pages, additional clarification at eq. (13), correction of error
in eq. (18) and subsequent discussio
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
Radiative decays: a new flavour filter
Radiative decays of the orbital excitations of the ,
and to the scalars , and are shown to
provide a flavour filter, clarifying the extent of glueball mixing in the
scalar states. A complementary approach to the latter is provided by the
radiative decays of the scalar mesons to the ground-state vectors ,
and . Discrimination among different mixing scenarios is strong.Comment: 12 pages, 1 table, 0 figure
Spin-dependent Parton Distributions from Polarized Structure Function Data
In the past year, polarized deep inelastic scattering experiments at CERN and
SLAC have obtained structure function measurements off proton, neutron and
deuteron targets at a level of precision never before achieved. The
measurements can be used to test the Bjorken and Ellis-Jaffe sum rules, and
also to obtain information on the parton distributions in polarized nucleons.
We perform a global leading-order QCD fit to the proton deep inelastic data in
order to extract the spin-dependent parton distributions. By using parametric
forms which are consistent with theoretical expectations at large and small
, we find that the quark distributions are now rather well constrained. We
assume that there is no significant intrinsic polarization of the strange quark
sea. The data are then consistent with a modest amount of the proton's spin
carried by the gluon, although the shape of the gluon distribution is not well
constrained, and several qualitatively different shapes are suggested. The
spin-dependent distributions we obtain can be used as input to phenomenological
studies for future polarized hadron-hadron and lepton-hadron colliders.Comment: 23 pages, DTP/94/3
Asymptotic Freedom for Non-Relativistic Confinement
Some aspects of asymptotic freedom are discussed in the context of a simple
two-particle non-relativisitic confining potential model. In this model
asymptotic freedom follows from the similarity of the free-particle and bound
state radial wave functions at small distances and for the same angular
momentum and the same large energy. This similarity, which can be understood
using simple quantum mechanical arguments, can be used to show that the exact
response function approaches that obtained when final state interactions are
ignored. A method of calculating corrections to this limit is given and
explicit examples are given for the case of the harmonic oscillator.Comment: 16 pages, 5 figures, RevTex
Charmonium Hybrid Production in Exclusive B Meson Decays
Recent data on charmonium production in B-meson decays suggest that
charmonium hybrid mesons with mass ~4 GeV may be produced in B-decay via
c\bar{c} colour octet operators. Some of these states are likely to be narrow
with clean signatures to J/\psi pi^+ pi^- final states. Experimental signatures
and search strategies for existing B-factories are described.Comment: references added and some of the text rewritten so it is cleare
Universality of Leading Relativistic Corrections to Bound State Gyromagnetic Ratios
We discuss the leading relativistic (nonrecoil and recoil) corrections to
bound state -factors of particles with arbitrary spin. These corrections are
universal for any spin and depend only on the free particle gyromagnetic
ratios. We explain the physical reasons behind this universality.Comment: 10 pp., based on talks given at the Gribov-80 Memorial Workshop,
ICTP, Trieste, Italy, May 2010 and at PSAS 2010 workshop, Les Houches, June
2010. To be published in the Gribov-80 Proceedings and in Can. J. Phy
Radiative Scalar Meson Decays in the Light-Front Quark Model
We construct a relativistic wavefunction for scalar mesons within the
framework of light-front quark model(LFQM). This scalar wavefunction is used to
perform relativistic calculations of absolute widths for the radiative decay
processes, and
which incorporate the effects of glueball-
mixing. The mixed physical states are assumed to be ,and
for which the flavor-glue content is taken from the mixing
calculations of other works. Since experimental data for these processes are
poor, our results are compared with those of a recent non-relativistic model
calculation. We find that while the relativistic corrections introduced by the
LFQM reduce the magnitudes of the decay widths by 50-70%, the relative
strengths between different decay processes are fairly well preserved. We also
calculate decay widths for the processes and
(0^{++})\to\gamma\gamm involving the light scalars and
to test the simple model of these mesons. Our results of
model for these processes are not quite consistent with well-established data,
further supporting the idea that and are not conventional
states.Comment: 10 pages, 4 figure
Canonical Interpretation of the D_{sJ}(2860) and D_{sJ}(2690)
The spectrum and decay properties of radially excited states are
examined in a new model. Good agreement is obtained with the properties of two
recently announced mesons identified as and
as a possible mixture of and
. Searching for these mesons in B decays is advocated due to
large predicted branching ratios.Comment: 6 pages, 2 ps figures, revte
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