50,304 research outputs found
The Phillips - Barger model for the elastic cross section and the Odderon
Inspired by the recent TOTEM data for the elastic proton -- proton ()
scattering at 8 and 13 TeV, we update previous studies of the
differential cross sections using the Phillips -- Barger (PB) model, which
parametrizes the amplitude in terms of a small number of free parameters. We
demonstrate that this model is able to describe the recent data on a
statistically acceptable way. Additionally, we perform separate fits of the
data for each center - of - mass energy and propose a parametrization for
the energy dependence of the parameters present in the PB model. As a
consequence, we are able to present the PB predictions for the elastic proton -
proton cross section at GeV and TeV, which are compared
with the existing antiproton -- proton () data. We show that the PB
predictions, constrained by the data, are not able to describe the
data. In particular, the PB model predicts a dip in the differential
cross section that is not present in the data. Such result suggests
the contribution of the Odderon exchange at high energies.Comment: 6 pages, 4 tables, 2 figures, results updated, matches published
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Quantum Electro and Chromodynamics treated by Thompson's heuristic approach
In this work we apply Thompson's method (of the dimensions and scales) to
study some features of the Quantum Electro and Chromodynamics. This heuristic
method can be considered as a simple and alternative way to the Renormalisation
Group (R.G.) approach and when applied to QED-lagrangian is able to obtain in a
first approximation both the running coupling constant behavior of alpha(mu)
and the mass m(mu).The calculations are evaluated just at d_c=4, where d_c is
the upper critical dimension of the problem, so that we obtain the logarithmic
behavior both for the coupling alpha and the excess of mass Delta m on the
energy scale mu. Although our results are well-known in the vast literature of
field theories,it seems that one of the advantages of Thompson's method, beyond
its simplicity is that it is able to extract directly from QED-lagrangian the
physical (finite) behavior of alpha(mu) and m(mu), bypassing hard problems of
divergences which normally appear in the conventional renormalisation schemes
applied to field theories like QED. Quantum Chromodynamics (QCD) is also
treated by the present method in order to obtain the quark condensate value.
Besides this, the method is also able to evaluate the vacuum pressure at the
boundary of the nucleon. This is done by assumming a step function behavior for
the running coupling constant of the QCD, which fits nicely to some quantities
related to the strong interaction evaluated through the MIT-bag model.Comment: RevTex, 25 pages, no figure
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