33 research outputs found
A Second Look at String-Inspired Models for Proton-Proton Scattering via Pomeron Exchange
We re-examine a string dual model for elastic proton-proton scattering via
Pomeron exchange. We argue that the method of "Reggeizing" a propagator to take
into account an entire trajectory of exchanged particles can be generalized, in
particular by modifying the value of the mass-shell parameter in the model. We
then fit the generalized model to scattering data at large s and small t. The
fitting results are inconclusive, but suggest that a better fit might be
obtained by allowing the mass-shell to vary. The model fits the data equally
well (roughly) for a wide range of values of the mass-shell parameter, but the
other fitting parameters (the slope and intercept of the Regge trajectory, and
the coupling constant and dipole mass from the proton-proton-glueball coupling)
are then inconsistent with what we expect. On the other hand, using the
traditional method of Reggeization generates a weaker fit, but the other
parameters obtain more physically reasonable values. In analyzing the fitting
results, we also found that our model is more consistent with the sqrt(s) =
1800 GeV coming from the E710 experiment than that coming from the CDF
experiment, and that our model has the greatest discrepancy with the data in
the range 0.5 GeV^2 < |t| < 0.6 GeV^2, suggesting that the transition from soft
Pomeron to hard Pomeron may occur closer to t = -0.5 GeV^2 rather than t = -0.6
GeV^2 as previously thought.Comment: 16 pages, 7 figures, 2 table
Bethe Ansatz for a Quantum Supercoset Sigma Model
We study an integrable conformal OSp(2m + 2|2m) supercoset model as an analog
to the AdS_5 X S^5 superstring world-sheet theory. Using the known S-matrix for
this system, we obtain integral equations for states of large particle density
in an SU(2) sector, which are exact in the sigma model coupling constant. As a
check, we derive as a limit the general classical Bethe equation of Kazakov,
Marshakov, Minahan, and Zarembo. There are two distinct quantum expansions
around the well-studied classical limit, the lambda^{-1/2} effects and the 1/J
effects. Our approach captures the first type, but not the second.Comment: 30 pages, 1 figure, v2: references adde
Setting the scale of the p p and p bar p total cross sections using AdS/QCD
This paper is an addendum to our earlier paper \cite{pom} where we computed
the Pomeron contribution to and scattering in AdS/QCD. The
model of \cite{pom} depends on four parameters: the slope and intercept of the
Pomeron trajectory , a mass scale which
determines a form factor entering into matrix elements of the energy-momentum
tensor, and a coupling between the lightest spin
glueball and the proton which sets the overall scale of the total cross
section. Here we perform a more detailed computation of in
the Sakai-Sugimoto model using the construction of nucleons as instantons of
the dual 5d gauge theory and an effective 5d fermion description of these
nucleons which has been successfully used to compute a variety of nucleon-meson
couplings. We find
which is in reasonable agreement with the value determined by fitting single Pomeron exchange to data.Comment: 8 page