3 research outputs found
The Missing Odderon
In contrast to theoretical expectations, experimental results at sqrt(s)=200
GeV for the reaction gamma p --> pi0 X show no evidence for odderon exchange.
The upper limit on the cross section is an order of magnitude smaller than the
theoretical estimate. It is argued that chiral symmetry leads to a large
suppression, taking the thoeretical estimates well below the data. Two
additional arguments are presented which may decrease the theoretical estimate
further. The calculations are more sensitive to the assumptions made in
evaluating the hadronic scattering amplitude than in the processes considered
previously and lattice gauge calculations indicate that the odderon intercept
may be appreciably lower than usually assumed. These two latter effects are
particularly relevant for the reactions gamma p --> f2(1270)X and gamma p -->
a2(1320)X for which the data upper limits are also below the theoretical
predictions, but not so dramatically as for gamma p --> pi0 X.Comment: 12 pages, 3 figure
and Polarizabilities from {} Data on the Base of S-Matrix Approach
We suggest the most model-independent and simple description of the
process near threshold in framework of S-matrix
approach. The amplitudes contain the pion polarizabilities and rather
restricted information about interaction. Application of these
formulae for description of MARK-II \cite{M2} and Crystal Ball \cite{CB} data
gives: ,
(in units system ) at the experimental values of scattering lengths. Both
values are compartible with current algebra predictions.Comment: LaTeX, 14 pages plus 6 figures (not included, available upon request)
, ISU-IAP.Th93-03, Irkuts