Reviews of topical problems

Unexpected interaction properties between high energy protons

Lebedev Physical Institute, Russian Academy of Sciences, Leninsky prosp. 53, Moscow, 119991, Russian Federation

Experimental data on proton-proton interactions in high energy collisions show that the elastic-to-inelastic scattering ratio varies in an unexpected way with collision energy, the decrease at comparatively low energies being followed by a factor of over 1.5 (!) increase in the energy range from 11—60 GeV at the Intersecting Storage Rings (ISR) to 7—13 TeV at the Large Hadron Collider (LHC). Intuitive expectations would be that, classically, proton break-up processes will continue increasing in number compared to proton survivals. It can be assumed that this surprising effect is either due to the asymptotic freedom property or to the collision time being extremely short at such high energies. The unquestionable unitarity principle is combined with the available elastic scattering data to gain new insight into the spatial shape of the interaction region of colliding protons. How this region evolves at energies currently used is considered and some predictions on its behavior at still higher energies are made for different assumptions concerning the relative roles of elastic scattering and inelastic processes. The shape can transform rather drastically if elastic processes keep rising in proportion. There is an unexpected corollary to this unexpected property. The possible origins of the effect and its relation to strong interaction dynamics are discussed.

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Keywords: proton, elastic and inelastic processes, interaction region, impact parameter, torus, black disk
PACS: 11.80.−m, 13.85.−t, 14.20.Dh (all)
DOI: 10.3367/UFNe.2016.11.037977
Citation: Dremin I M "Unexpected interaction properties between high energy protons" Phys. Usp. 60 333–344 (2017)
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Received: 16th, September 2016, revised: 14th, October 2016, 30th, November 2016

Оригинал: Дрёмин И М «Неожиданные свойства взаимодействия протонов при высоких энергиях» УФН 187 353–366 (2017); DOI: 10.3367/UFNr.2016.11.037977

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