Centrality in hadron collisions

In hadron interactions at the LHC energies, the reflective scattering mode starts to play a noticeable role which is expected to be even a more significant beyond the energies of the LHC. This new but still arguable phenomenon implies a peripheral dependence of the inelastic probability distribution in the impact parameter space and asymptotically evolving to the black ring. As a consequence, the straightforward extension to hadrons of the centrality definition adopted for nuclei needs to be modified.

Cul-De-Sac of the Spatial Image of Proton Interactions

The unitarity condition in the impact parameter space is used to obtain some information about the shape of the interaction region of colliding protons. It is shown that, strictly speaking, a reliable conclusion can be gained only if the behavior of the elastic scattering amplitude (especially, its imaginary part) at all transferred momenta is known. This information is currently impossible to obtain from experimentation. In practice, several assumptions and models are used. They lead to different results as shown below.

Some Recent Results on High-Energy Proton Interactions

Recent experimental results about the energy behavior of the total cross sections, the share of elastic and inelastic contributions to them, the peculiar shape of the differential cross section and our guesses about the behavior of real and imaginary parts of the elastic scattering amplitude are discussed. The unitarity condition relates elastic and inelastic processes. Therefore it is used in the impact-parameter space to get some information about the shape of the interaction region of colliding protons by exploiting new experimental data. The obtained results are described.

Is There a Hollow Inside the Proton?

We discuss a recently proposed interpretation of some model descriptions of the proton-proton elastic scattering data as a manifestation of alleged relative transparency of the central part of the interaction region in the impact parameter space. We argue that the presence of nonzero real part of the elastic scattering amplitude in the unitarity condition enables to conserve the traditional interpretation.

Gribov universality of hadron cross sections at ultrahigh energies

The current status of ultrahigh energy diffractive collisions is given. Profile function and K-matrix function techniques in the impact parameter space are presented, and the Gribov universality of the hadron total cross sections is discussed.

Asymptotic regimes for hadron diffractive scatterings and Coulomb interaction: Arguments for the black disk mode

Comparative analysis of the interplay of hadron and Coulomb interactions in [Formula: see text] scattering amplitudes is performed in a broad energy interval, [Formula: see text], for two extreme cases: for the asymptotic interactions of hadrons in black disk and resonant disk modes. The interactions are discussed in terms of the [Formula: see text]-matrix function technique. In the asymptotic regime, the real part of the hadronic amplitude is concentrated in both cases on the boundary of the disks in the impact parameter space but the LHC energy region is not asymptotic for the resonant disk mode that lead to a specific interplay of hadronic and Coulombic amplitudes. For the [Formula: see text] scattering at [Formula: see text] an interplay of the hadron and Coulomb interactions in the resonant disk modes is realized in a shoulder in [Formula: see text] at [Formula: see text]. The absence of such a shoulder in the data at 8 TeV can be considered as an argument against the resonant disk mode.

Hadron diffractive scattering at ultrahigh energies and Coulomb interaction

We study the interplay of hadronic and Coulomb interactions for pp scattering at LHC energies on the basis of the previous determination of the real part of the amplitude [V. V. Anisovich, V. A. Nikonov and J. Nyiri, Int. J. Mod. Phys. A 30, 1550188 (2015)]. The interference of hadron and Coulomb interactions is discussed in terms of the K-matrix function technique. Supposing the black disk mode for the asymptotic interaction of hadrons, we calculate interference effects for the energies right up to [Formula: see text] TeV. It turns out that the real part of the amplitude is concentrated in the impact parameter space at the border of the black disk that results in a growth of interplay effects with the energy increase.