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Forward elastic scattering and Pomeron models
M. Broilo, E. G. S. Luna, and M. J. Menon
Phys. Rev. D 98, 074006 – Published 5 October 2018
Recent data from LHC13 by the TOTEM Collaboration indicate an unexpected decrease in the value of the ρ parameter and a σtot value in agreement with the trend of previous measurements at 7 and 8 TeV. These data at 13 TeV are not simultaneously described by the predictions from Pomeron models selected by the COMPETE Collaboration but show agreement with the maximal Odderon dominance, as recently demonstrated by Martynov and Nicolescu. Here, we present a detailed analysis on the applicability of Pomeron dominance by means of a general class of forward scattering amplitude, consisting of even-under-crossing leading contributions associated with single, double, and triple poles in the complex angular momentum plane and subleading even and odd Regge contributions. The analytic connection between σtot and ρ is obtained by means of singly subtracted dispersion relations, and we carry out fits to pp and ¯pp data in the interval 5 GeV–13 TeV. The data set comprises all the accelerator data below 7 TeV, and we consider two independent ensembles by adding either only the TOTEM data or the TOTEM and ATLAS data at the LHC energy region. In the data reductions to each ensemble, the uncertainty regions are evaluated with both one and two standard deviations (∼68%and ∼95% CL, respectively). Besides the general analytic model, we investigate four particular cases of interest, three of them typical of outstanding models in the literature. We conclude that, within the experimental and theoretical uncertainties and both ensembles, the general model and three particular cases are not able to describe the σtot and ρ data at 13 TeV simultaneously. However, if the discrepancies between the TOTEM and ATLAS data are not resolved, one Pomeron model, associated with double and triple poles and with only 7 free parameters, seems not to be excluded by the complete set of experimental information presently available.