946 research outputs found
Charm production at HERA
The ZEUS data on the charm structure function F_2^c at small x fit well to a
single power of x, corresponding to the exchange of a hard pomeron that is
flavour-blind. When combined with the contribution from the exchange of a soft
pomeron, the hard pomeron gives a good description of elastic
photoproduction.Comment: 6 pages, plain tex, with 3 figures embedded using epsf. Typos
corrected in equations (10) and (11
Exclusive Vector Photoproduction: Confirmation of Regge Theory
Recent small-t ZEUS data for exclusive rho photoproduction are in excellent
agreement with exchange of the classical soft pomeron with slope alpha'=0.25
GeV^{-2}. Adding in a flavour-blind hard-pomeron contribution, whose magnitude
is calculated from the data for exclusive J/psi photoproduction, gives a good
fit also to the ZEUS data for rho photoproduction at larger values of t, and to
phi photoproduction.Comment: 6 pages, plain tex, with 5 figures embedded using eps
Does the hard pomeron obey Regge factorisation?
While data for the proton structure function demand the presence of a
hard-pomeron contribution even at quite small Q^2, previous fits to the pp and
p\bar p total cross sections have found that in these there is little or no
room for such a contribution. We re-analyse the data and show that itmay indeed
be present and that, further, it probably obeys Regge factorisation:
sigma^{gamma p}(s,Q_1^2)sigma^{gamma p}(s,Q_2^2)= sigma^{pp}(s)sigma^{gamma
gamma}(s,Q_1^2,Q_2^2) for all values of Q_1^2 and Q_2^2.Comment: 11 pages, 10 figure
Light Vector Meson Spectroscopy
The current situation for vector meson spectroscopy is outlined, and it is
shown that the data are inconsistent with the generally-accepted model for
meson decay. A possible resolution in terms of exotic (hybrid) mesons is given.
Although this hypothesis resolves some of the issues, fresh theoretical
questions are raised. It is argued that high-precision annihilation
data provide an excellent laboratory for studying many aspects of
nonperturbative QCD.Comment: Paper T05 presented at the Workshop on e+e- Physics at Intermediate
Energies, SLAC, May 200
Unusual high-pT jet events at HERA
We calculate the cross-section for events at HERA where the proton loses only
a minute fraction of its initial energy, all of which goes into producing a
single pair of transverse jets.Comment: 4 pages plus figure
The Interest of Large-t Elastic Scattering
Existing data for large- elastic-scattering differential
cross-sections are energy-independent and behave as . This has been
explained in terms of triple-gluon exchange, or alternatively through
triple-singlet exchange. A discussion is given of the problems raised by each
of these explanations, and of the possibility that at RHIC or LHC energies the
exchange of three BFKL pomerons might result in a rapid rise with energy.Comment: 6 pages, plain tex, 3 figures embedded with eps
Perturbative Evolution and Regge Behaviour
The known analytic properties of the Compton amplitude at small place
significant constraints on its behaviour at large . This calls for a
re-evaluation of the role of perturbative evolution in past fits to data.Comment: Revised figures 4 and
Systematic Regge theory analysis of omega photoproduction
Systematic analysis of available data for -meson photoproduction is
given in frame of Regge theory. At photon energies above 20 GeV the
reaction is entirely dominated by Pomeron exchange.
However, it was found that Pomeron exchange model can not reproduce the
and data at high energies
simultaneously with the same set of parameters. The comparison between
and data indicates a large room for meson exchange contribution to
-meson photoproduction at low energies. It was found that at low
energies the dominant contribution comes from and -meson exchanges.
There is smooth transition between the meson exchange model at low energies and
Regge theory at high energies.Comment: 7 pages, 8 figures, revtex
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