Unitarisation dependence of diffractive scattering in light of high-energy collider data

Atri Bhattacharya,Jean-René Cudell,Rami Oueslati,Arno Vanthieghem

doi:10.1007/jhep09(2021)005

Atri Bhattacharya, Jean-René Cudell + Show 2 more

Open Access

https://doi.org/10.1007/jhep09(2021)005

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Abstract

We study the consequences of high-energy collider data on the best fits to total, elastic, inelastic, and single-diffractive cross sections for pp and poverline{p} scattering using different unitarisation schemes. We find that the data are well fitted both by eikonal and U-matrix schemes, but that diffractive data prefer the U-matrix. Both schemes may be generalised by means of an additional parameter; however, this yields only marginal improvements to the fits. We provide estimates for ρ, the ratio of the real part to the imaginary part of the elastic amplitude, for the different fits. We comment on the effect of the different schemes on present and future cosmic ray data.

Highlights

IceTop [32], an investigation of the dependence of cross sections on different unitarisation schemes assumes paramount importance
We study the consequences of high-energy collider data on the best fits to total, elastic, inelastic, and single-diffractive cross sections for pp and ppscattering using different unitarisation schemes
The implementation of diffraction within a unitarisation scheme at high energy has to confront two questions: how does one describe the diffractive amplitude at the Born level, and how does one embed that amplitude within a unitarisation scheme?

Summary

Brief survey of unitarisation schemes and fit to non-diffractive forward data

The differential cross section for elastic scattering may be expressed in terms of the elastic amplitude A(s, t) as dσel dt. The most common scheme is the eikonal scheme, and it has been derived for structureless bodies, in optics, in potential scattering and in QED Another proposed scheme is the U matrix scheme, which can be motivated by a form of Bethe-Salpeter equation [37]. Direct measurements of inelastic cross sections, i.e. not derived from total and elastic measurements, from UA5 at SppS [20], ATLAS [9, 10], LHCb [12], ALICE [6], and TOTEM [18]. This gives a total of 37 data points. The resulting fit leads to the following parameters of table 1

Unitarisation and diffraction

Fit parameters and data

Results

Conclusions