arXiv subjects

I. M. Dremin

Publications and source records attributed to I. M. Dremin.

At least 109 records · Page 6Linked to original sources

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

Energy dependence of mean multiplicities in gluon and quark jets at the next-to-next-to-next-to-leading order

Analytic predictions for the energy dependence of the mean multiplicities in gluon and quark jets are presented at the next-to-next-to-next-to-leading order (3NLO) of perturbative QCD and are compared to experiment. The 3NLO correction to the gluon jet multiplicity is found to be small. The corresponding theoretical expression provides a good description of available gluon jet measurements. In contrast, the 3NLO correction to the quark jet multiplicity is large and the theoretical expression does not describe the data accurately. It is shown that the well known success of the next-to-leading order (NLO) approximation in describing the energy evolution of quark jet multiplicity can be attributed to the equivalence of the quark and gluon expressions at NLO to within a constant factor, and to almost constant contributions from higher order terms to the gluon jet result.

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↗

arXiv1998

Multiparticle Dynamics 1998: Summary talk

Contents: 1. Pomeron physics 2. Multiplicities 3. Single-particle distributions 4. Correlations and fluctuations 5. Special final states and interaction mechanisms 6. Cosmic rays and forward detectors

hep-ph↗

arXiv1998

Abelian Landau-Pomeranchuk-Migdal effects

It is shown that the high-energy expansion of the scattering amplitude calculated from Feynman diagrams factorizes in such a way that it can be reduced to the eikonalized form up to the terms of inverse power in energy in accordance with results obtained by solving the Klein-Gordon equation. Therefore the two approaches when applied to the suppression of the emission of soft photons by fast charged particles in dense matter should give rise to the same results. A particular limit of thin targets is briefly discussed.

hep-ph↗

arXiv1998

Energy dependence of ratios of multiplicities and their slopes for gluon and quark jets

The difference between the ratio of multiplicities and the ratio of their derivatives on energy for gluon and quark jets is calculated up to next-to-next-to leading order of perturbative QCD. Its non-zero value is uniquely defined by the running property of the QCD coupling constant. It is shown that this difference is rather small compared to values which can be obtained from experimental data. This disagreement can be ascribed either to strong non-perturbative terms or to experimental problems with a scale choice, jets separation and inadequate assignement of soft particles to jets.

hep-ph↗

arXiv1998

Schroedinger cats, quantum slings and azimuthal effects in nucleus-nucleus collisions

Confinement of a chromodynamical string can result in specific effects in scattering processes and multiparticle production. In particular, due to its rotation secondary fragments of the splitting apart string can move like stones thrown from a sling. That would be detected as the azimuthal asymmetry of particle distributions in individual events. Thus we propose to explain the elliptic flow observed in AA-collisions as a sling-effect. It can provide information about confinement of quarks inside particles or binding forces in nuclei. Nonclassical states of the created particles like the Schroedinger cats are produced. Some classical and quantum-mechanical estimates of possible effects are given. Experimental facts which can be used for their verification are discussed.

hep-ph↗

arXiv1997

Particles and Nuclei as Quantum Slings

Rotation of such objects as an atomic nucleus or a chromodynamical string can result in specific effects in scattering processes and multiparticle production. Secondary fragments of the rotating nucleus or of the decaying string can move like stones thrown from a sling. That would be detected as the azimuthal asymmetry of particle distributions in individual events. Non-classical states of the created particles like the Schr"\{o}dinger cats are produced. Some classical and quantum-mechanical estimates of possible effects are given. Experimental facts which can be used for their verification are discussed.

hep-ph↗

arXiv1997

Sudakov Form Factors in Leptoproduction of Vector Mesons

It is shown that Sudakov form factors for a colour dipole in a QCD-inspired model of leptoproduction of vector mesons reduce the value of the cross section of the process by an order of magnitude. They suppress the large size quark- antiquark pairs and unequal sharing of energy among the components of the dipole. Some freedom in the choice of the model parameters is also discussed.

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arXiv1997

Pattern Recognition in High Multiplicity Events

In very high energy collisions, many particles are produced and distributed in the available phase space volume in various ways. With advent of new accelerator facilities (especially, for nucleus-nucleus collisions), the problem of pattern recognition in high multiplicity events becomes very actual in order to classify such events and to separate those of them with some special features (e.g. ring-like events, jets and other regular patterns). This paper presents the first attempt to use wavelet technique for pattern recognition in nucleus-nucleus collisions. After describing the method in general, we demonstrate its power by applying it to a single event of Pb-Pb collision at 158A GeV with 1072 charged particles produced and discuss results obtained for some other events. Further extension of the method is proposed.

hep-ex↗

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

Density and Charge Fluctuations in Multiple Production

Oscillations of cumulant moments of multiplicity distributions at high ranks, evolution of factorial moments with bin sizes (intermittency, fractality), zeros of the truncated generating functions of multiplicity distributions, and charge fluctuations in multiparticle production processes are discussed.

hep-ph↗

arXiv1996

Multiplicity Moments in QCD and Experiment

QCD predictions for moments of parton multiplicity distributions are discussed. The next-to-leading terms and conservation law give rise to the peculiar oscillating shape of some ratio of the moments. The similar shape has been found by moment analysis of hadron multiplicities. Experimental data, theoretical Monte Carlo models and phenomenological fits have been used for ee, hh, hA, AA reactions at high energies.

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

High E$_T$ jets and double scattering

The recently found excess of high E$_T$ jets over current QCD predictions is attributed to gluon radiation at double scattering process inside a nucleon. The order of magnitude estimate of the cross section fits experimental findings rather well. The specific features of the process are discussed. Various similar hadronic effects related to the short radiation length are described.

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 and experiment on multiplicity distributions

The solution of QCD equations for generating functions of {\it parton} multiplicity distributions reveals new peculiar features of cumulant moments oscillating as functions of their rank. It happens that experimental data on {\it hadron} multiplicity distributions in $e^{+}e^{-}, hh, AA$ collisions possess the similar features. However, the "more regular" models like $λϕ^3$ behave in a different way. Evolution of the moments at smaller phase space bins and zeros of the truncated generating functions are briefly discussed.

hep-ph↗

arXiv1995

Multiplicity Distributions of Squeezed Isospin States

Multiplicity distributions of neutral and charged particles arising from squeezed coherent states are investigated. Projections onto global isospin states are considered. We show how a small amount of squeezing can significantly change the multiplicity distributions. The formalism is proposed to describe the phenomenological properties of neutral and charged particles anomalously produced in hadronic and nuclear collisions at very high energies.

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