414 research outputs found
New analyticity constraints on the high energy behavior of hadron-hadron cross sections
We here comment on a series of recent papers by Igi and Ishida[K. Igi and M.
Ishida, Phys. Lett B 622, 286 (2005)] and Block and Halzen[M. M. Block and F.
Halzen, Phys. Rev D 72, 036006 (2005)] that fit high energy and
cross section and -value data, where is the ratio of the real to
the imaginary portion of the forward scattering amplitude. These authors used
Finite Energy Sum Rules and analyticity consistency conditions, respectively,
to constrain the asymptotic behavior of hadron cross sections by anchoring
their high energy asymptotic amplitudes--even under crossing--to low energy
experimental data. Using analyticity, we here show that i) the two apparently
very different approaches are in fact equivalent, ii) that these analyticity
constraints can be extended to give new constraints, and iii) that these
constraints can be extended to crossing odd amplitudes. We also apply these
extensions to photoproduction. A new interpretation of duality is given.Comment: 9 pages, 1 postscript figure; redone for clarity, removal of typos,
changing reference; figure replace
Analyticity as a Robust Constraint on the LHC Cross Section
It is well known that high energy data alone do not discriminate between
asymptotic and behavior of and cross sections.
By exploiting high quality low energy data, analyticity resolves this ambiguity
in favor of cross sections that grow asymptotically as . We here show
that two methods for incorporating the low energy data into the high energy
fits give numerically identical results and yield essentially identical tightly
constrained values for the LHC cross section. The agreement can be understood
as a new analyticity constraint derived as an extension of a Finite Energy Sum
Rule.Comment: 8 pages, Latex2e, 2 postscript figures; major changes made; accepted
for publication in Phys Rev
Hadron pair photoproduction within the Veneziano model
We first suppose that low-energy hadron pair photoproduction reactions
gamma(*) gamma(*) -> h h-bar are dominated by s-channel resonance
contributions. Their normalization is then calculated by their correspondence
with the Reggeon term in the Regge parametrization of the gamma h total cross
sections. For the case of p p-bar, we make use of the measured gamma p total
cross section, and for the case of K+K-, we make use of the corresponding total
cross section that is estimated using Regge factorization. For hadrons that
have no such data, we can only provide rough estimation based on the additive
quark rule. As an effective approach that is convenient and parameter-free, we
adopt the Veneziano model in the simplest form. The model is only applicable to
the region of low centre-of-mass energy. When the transverse momentum is large,
perturbative QCD takes over, whereas in the Regge region, it is known that the
Regge pole picture fails in photoproduction. Despite the shortcomings of the
model, we find that the parameter-free amplitudes offer a sound description of
the data at hand.Comment: 24 pages, 11 figure
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