arXiv subjects

V. A. Nechitailo

Publications and source records attributed to V. A. Nechitailo.

At least 19 recordsLinked to original sources

arXiv2017

Central and peripheral interactions of hadrons

Surprisingly enough, the ratio of elastic to inelastic cross sections of proton interactions increases with energy in the interval correspond- ing to ISR - LHC (i.e. from 10 GeV to 10 TeV). That leads to special features of their spatial interaction region at these and higher ener- gies. Within the framework of some phenomenological models, we show how the particular ranges of the transferred momenta measured in elastic scattering experiments expose the spatial features of the in- elastic interaction region according to the unitarity condition. The difference between their predictions at higher energies is discussed. The notion of central and peripheral collisions of hadrons is treated in terms of the impact parameters description. It is shown that the shape of the differential cross section in the diffraction cone is mostly determined by collisions with intermediate impact parameters. Elastic scattering at very small transferred momenta is sensitive to peripheral processes with large impact parameters. The role of central collisions in formation of the diffraction cone is less significant.

hep-ph↗

arXiv2016

Asymmetric vector mesons produced in nuclear collisions

It is argued that the experimentally observed phenomenon of asymmetric shapes of vector mesons produced in nuclear media during high energy nucleus-nucleus collisions can be explained as Fano-Feshbach resonances. It has been observed that the mass distributions of lepton pairs created at meson decays decline from the traditional Breit-Wigner shape with some excess in the low-mass wing of the resonance. It is clear that the whole phenomenon is related to some interaction with the nuclear medium. Moreover, it can be further detalized in quantum mechanics as the interference of direct and continuum states in Fano-Feshbach effect. To reveal the nature of the interaction it is proposed to use a phenomenological model of the additional contribution due to Cherenkov gluons. They can be created because of the excess of the refractivity index over 1 just in the low-mass wing as required by the classical Cherenkov treatment. In quantum mechanics, this requirement is related to the positive real part of the interaction amplitude in this wing. The corresponding parameters are found from the comparison with $ρ$-meson data and admit reasonable explanation.

hep-ph↗

arXiv2013

Proton periphery activated by multiparticle dynamics

It is shown that protons become more active at the periphery with increase of their collision energy. By computing the impact parameter distribution of the proton-proton overlap function at LHC energies and comparing it with ISR (and S$p\bar p$S for $p\bar p$) data, we conclude that the peripheral region of protons plays an increasing role in the rise of total cross sections through multiparticle dynamics. The size of the proton as well as its blackness increase with energy. The protons become more black both in the central region and, especially, at the periphery. This effect can be related to the ridge phenomenon and to the inelastic diffraction processes at LHC energies.

hep-ph↗

arXiv2012

Testing scaling laws for the elastic scattering of protons

Theoretical proposals of scaling laws for the differential elastic scattering cross sections of protons are confronted with experimental data over a wide energy range. Different combinations of the transferred momentum and energy resulting from the solution of the definite partial differential equation are attempted as scaling variables. Reasonable scaling of the differential cross sections in the diffraction cone has been shown for one of these variables. The violation of the geometrical scaling is ascribed to the increase of the proton blackness with energy. The origin of high-t region violations of scaling laws is discussed.

hep-ph↗

arXiv2012

Elastic pp-scattering at \sqrt s=7 TeV with the genuine Orear regime and the dip

The unitarity condition unambigously requires the Orear region to appear in between the diffraction cone at low transferred momenta and hard parton scattering regime at high transferred momenta in hadron elastic scattering. It originates from rescattering of the diffraction cone processes. It is shown that such region has been observed in the differential cross section of the elastic pp-scattering at \sqrt s=7 TeV. The Orear region is described by exponential decrease with the scattering angle and imposed on it damped oscillations. They explain the steepening at the end of the diffraction cone as well as the dip and the subsequent maximum observed in TOTEM data. The failure of several models to describe the data in this region can be understood as improper account of the unitarity condition. It is shown that the real part of the amplitude can be as large as the imaginary part in this region. The overlap function is calculated and shown to be small outside the diffraction peak. Its negative sign there indicates the important role of phases in the amplitudes of inelastic processes.

hep-ph↗

arXiv2011

Soft multiple parton interactions as seen in multiplicity distributions at Tevatron and LHC

We analyse the multiplicity distributions of charged particles at Tevatron (p\bar p) and LHC (pp) energies in the framework of the independent pair parton interactions (IPPI) model. It is shown that the number of soft pair parton interactions (and therefore the density of the partonic medium) is large and increases with energy. The mean multiplicity at each parton interaction grows also with energy. This growth depends on the width of the rapidity window. The similar conclusions are obtained in the multiladder exchange model (QGSM).

hep-ph↗

arXiv2007

Asymmetry of in-medium rho-mesons as a signature of Cherenkov effects

Cherenkov gluons may be responsible for the asymmetry of dilepton mass spectra near rho-meson observed in experiment. They can be produced only in the low-mass wing of the resonance. Therefore the dilepton mass spectra are flattened there and their peak is slightly shifted to lower masses compared with the in-vacuum rho-meson mass. This feature must be common for all resonances.

hep-ph↗

arXiv2004

Independent pair parton interactions-model of hadron interactions

A model of independent pair parton interactions is proposed, according to which, hadron interactions are represented by a set of independent binary parton collisions. The final multiplicity distribution is described by a convolution of the negative binomial distributions in each of the partonic collisions. As a result, it is given by a weighted sum of negative binomial distributions with parameters multiplied by the number of active pairs. Its shape and moments are considered. Experimental data on multiplicity distributions in high energy $p\bar p$ processes are well fitted by these distributions. Predictions for the CERN Large Hadron Collider and higher energies are presented. The difference between $e^+e^-$ and $p\bar p$ processes is discussed.

hep-ph↗

arXiv2002

Moments of the truncated multiplicity distributions

In experiment, the multiplicity distributions of inelastic processes are truncated due to finite energy, insufficient statistics or special choice of events. It is shown that the moments of such truncated multiplicity distributions possess some typical features.In particular, the oscillations of cumulant moments at high ranks and their negative values at the second rank can be considered as ones most indicative on specifics of these distributions. They allow to distinguish between distributions of different type.

hep-ph↗

arXiv2001

Wavelets and their use

This review paper is intended to give a useful guide for those who want to apply discrete wavelets in their practice. The notion of wavelets and their use in practical computing and various applications are briefly described, but rigorous proofs of mathematical statements are omitted, and the reader is just referred to corresponding literature. The multiresolution analysis and fast wavelet transform became a standard procedure for dealing with discrete wavelets. The proper choice of a wavelet and use of nonstandard matrix multiplication are often crucial for achievement of a goal. Analysis of various functions with the help of wavelets allows to reveal fractal structures, singularities etc. Wavelet transform of operator expressions helps solve some equations. In practical applications one deals often with the discretized functions, and the problem of stability of wavelet transform and corresponding numerical algorithms becomes important. After discussing all these topics we turn to practical applications of the wavelet machinery. They are so numerous that we have to limit ourselves by some examples only. The authors would be grateful for any comments which improve this review paper and move us closer to the goal proclaimed in the first phrase of the abstract.

hep-ph↗

arXiv2000

Wavelet-patterns in nucleus-nucleus collisions at 158A GeV

We propose to use {\it multidimensional} \w \an for pattern recognition in high multiplicity events and consider some examples. Wavelet analysis reveals clustering phenomena in multiparticle production processes. Results of event-by-event studies of some nucleus-nucleus collisions at 158A GeV are reported. The clusterization topology is found to be different in different events. Typical patterns include jets and ring-like structures. They are demonstrated here for five high multiplicity events.

hep-ph↗

arXiv1999

Evolution of average multiplicities of quark and gluon jets

The energy evolution of average multiplicities of quark and gluon jets is studied in perturbative QCD. Higher order (3NLO) terms in the perturbative expansion of equations for the generating functions are found. First and second derivatives of average multiplicities are calculated. The mean multiplicity of gluon jets is larger than that of quark jets and evolves more rapidly with energy. It is shown which quantities are most sensitive to higher order perturbative and nonperturbative corrections. We define the energy regions where the corrections to different quantities are important. The latest experimental data are discussed.

hep-ph↗

arXiv1999

High Order Perturbative QCD Approach to Multiplicity Distributions of Quark and Gluon Jets

The second and third factorial moments of the multiplicity distributions of gluon and quark jets are calculated up to the next-to-next-to-next-to leading order in perturbative QCD, using the equations for generating functions. The results are confronted with experimental data. A general discussion on high order corrections revealed by such an approach is given. Other possible corrections and approaches are discussed as well.

hep-ph↗

arXiv1997

Comparative Analysis of Multiplicity Distributions in Inelastic Processes for Different Colliding Particles and Nuclei

Theoretical prediction of oscillations of cumulant moments of parton multiplicity distributions inside a jet supported by experimental data in some multiple production processes asks for analysis of the phenomenon for the whole set of available reactions. We have found out that the oscillations persist in any kind of processes and increase for particles with more complicated structure i.e. in the order of ee, eh, hh, hA, AA. The effect is not strongly dependent on the available phase space. Theoretical values of moments for quark and gluon jets up to 5th rank are shown. Zeros of the truncated generating function and singularities of the total generating function are discussed.

hep-ph↗

arXiv1996

Charge Distribution in Soft Chiral Pion Bremsstrahlung

Bremsstrahlung of soft chiral pions in high-energy processes is considered. The distribution over number of neutral and charged pions is shown to obey the inverse square root law. This law is argued to be generic for multiple coherent production of soft chiral pions.

hep-ph↗

arXiv1996

Moment Analysis of Multiplicity Distributions

Moment analysis of global multiplicity distribution previously done for $e^{+}e^{-}$ and $hh$ processes is applied to $hA$ and $AA$ collisions. The oscillations of cumulants as functions of their rank are found in all the cases. Some phenomenological approaches and quark-gluon string models are confronted to experimental data. It has been shown that the analysis is a powerful tool for revealing the tiny features of the distributions, and its qualitative results in various processes are rather stable for different multiplicity cut-offs determined by experimental (or Monte-Carlo) statistics.

hep-ph↗

arXiv1996

Multiplicity Distributions in QCD and $λφ^3_6$-model

It is shown that QCD with vector gluons predicts drastically different multiplicity distributions compared to the scalar $λφ^3$-model (in 6 dimensions). In particular, the QCD predicted minimum of cumulant moments of the distributions at ranks about $5\div7$ does not reveal itself in the scalar model. The oscillations at higher ranks survive only. Thus, the experimental fact of that minimum at ranks about $5\div7$ supports the vector nature of gluons and singular kernels in QCD and gluodynamics.

hep-ph↗

arXiv1995

QCD Heat Kernel in Covariant Gauge

We report the calculation of the fourth coefficient in an expansion of the heat kernel of a non-minimal, non-abelian kinetic operator in an arbitrary background gauge in arbitrary space-time dimension. The fourth coefficient is shown to bring a nontrivial gauge dependence due to the contribution of the lowest order off-shell gauge invariant structure.

hep-th↗