On Participants Number Fluctuations for Given Centrality AA-Interactions in the Classical Glauber Approach

In the framework of the classical Glauber approach the exact analytical expression for the variance of the number of participants (wounded nucleons) for given centrality AA interactions is presented. It's shown, that in the case of nucleus-nucleus collisions along with the optical approximation term the additional "contact" term appears. The numerical calculations for PbPb collisions at SPS energies show that at intermediate values of the impact parameter the "optical" and "contact" terms contributions to the variance of the participants number are of the same order and their sum is in a good agreement with the results of independent MC simulations of this process. The correlation between the numbers of participants in colliding nuclei is taken into account. In particular it's demonstrated that in PbPb collisions at SPS energies the variance of the total number of participants approximately three times exceeds the Poisson one in the impact parameter region 10-12 Fm. The fluctuations of the number of collisions are also discussed.Comment: a short version to be published in the Proceedings of Baldin ISHEPP XVII

On description of the correlation between multiplicities in windows separated in azimuth and rapidity

The forward-backward (FB) multiplicity correlations in two windows separated in rapidity and azimuth are analyzed in the framework of the model with independent identical emitters (strings). Along with the short-range contribution, originating from the correlation between particles produced by a single string, the long-range contribution, originating from the fluctuation in the number of strings, is taken into account. The connection of the FB multiplicity correlation coefficient with the two-particle correlation function and the di-hadron correlation analysis is traced. It's also shown that the direct azimuthal flow leads to the forward ridge structure in the resulting two-particle correlation function.Comment: 8 pages, reported at HEPQFT-2013(The XXI International Workshop High Energy Physics and Quantum Field Theory, 23-30 June 2013, Saint Petersburg Area, Russia

Space-time picture of the string fragmentation and the fusion of colour strings

It is shown that naive two stage scenario of the soft multiparticle production in hadronic and nuclear collisions at high energy, when at first stage the colour strings are formed and at the second stage these strings, or some other (higher colour) strings formed due to fusion of primary strings, are decaying, emitting observed particles, encounters some difficulties at the attempt to analyse the space-time picture of the process. Simple analysis shows the dominant is the process when the formation and the decay of a string occur in parallel - a string breaks into two parts already at rather small length (about 1-2 fm in its c.m. system), then the process repeats in the pieces and so on. Nevertheless it is proved to be possible to agree the string fusion idea with the space-time picture of a string decay. In the framework of the Artru-Mennessier model of a string fragmentation the simple interpretation of the homogeneity of the rapidity distribution for hadrons produced from the decay of a single string at high energy is presented and the analytical estimate for the density of this rapidity distribution is obtained.Comment: 6 pages, 5 figures, to be published in the Proceedings of Baldin ISHEPP XI

The dependence of the number of pomerons on the impact parameter and the long-range rapidity correlations in pp collisions

The simple model which enables to take into account the effects of a colour string fusion in pp interactions is suggested. The parameters of the model are connected with the parameters of the pomeron trajectory and its couplings to hadrons. On the base of the model the MC algorithm which enables to calculate the long-range correlation functions between multiplicities and between the average transverse momentum and the multiplicity in pp collisions is developed.Comment: 12 pages, 3 figures, reported at the Baldin ISHEPP XX

Cumulative Phenomena through the Quark-Parton Diagram Summation at Thresholds

A microscopic treatment of cumulative phenomena based on perturbative QCD calculations of the corresponding quark diagrams near the threshold is presented. To sum all diagrams like these the special technique based on the recurrence relations was developed. The x-behaviour of the nuclear structure function $F_{2}(x)$ in the cumulative region x>1 was found to be roughly exponential, governed by an effective coupling constant, which depends on the QCD coupling constant and quark mass. Two mechanisms for cumulative particle production, direct and spectator ones, were analysed. It was shown that due to final state interactions the leading terms of the direct mechanism contribution are cancelled and the spectator mechanism is the dominant one. It leads to a smaller slope of the particle production rates compared to the slope of the nuclear structure function in the cumulative region, in agreement with the recent experimental data. The slope difference is due to additional multiple interactions between nuclear and projectile partons which enter the spectator mechanism for the cumulative production. The different versions of hadronization mechanisms of the produced cumulative quarks into hadrons are also discussed.Comment: 13 pages, LaTeX, one PostScript figur

Transverse Momentum Dependence of Cumulative Pions

In the framework of the recently proposed QCD based parton model for the cumulative phenomena in the interactions with nuclei the dependence of the cumulative pion production rates on the transverse momentum is studied. The mean value of the transverse momentum is found to grow with x in the cumulative region. The obtained results are in agreement with the available experimental data.Comment: 9 pages, LaTeX, two PostScript figures, psfig.sty and epsf.st

Multiplicity and Pt Correlations in AA-interactions at High Energies

The theoretical description of the correlations between observables in two separated rapidity intervals in relativistic nuclear collisions is presented. It is shown, that the event-by-event pt-pt correlation defined as the correlation between event mean values of transverse momenta of all particles emitted in two different rapidity intervals does not decrease to zero with the increase of the number of strings in contrast with two particle pt-pt correlation - the correlation between the transverse momenta of single particles produced in these two rapidity windows. In the idealized case with the homogeneous string distribution in the transverse plane in the framework of the cellular analog of string fusion model (SFM) the asymptotic of pt-pt correlation coefficient is analytically calculated and compared with the results of the Monte-Carlo (MC) calculations fulfilled both in the framework of the original SFM and in the framework of its cellular analog, which enables to control the MC algorithms. In the case with the realistic nucleon distribution density of colliding nuclei the results of the MC calculations of the pt-pt correlation function for minimum bias nuclear collisions at SPS, RHIC and LHC energies are presented and analysed.Comment: 7 pages, LaTeX, 3 figures in PostScript, to be published in the XVIIIth QFTHEP Workshop proceeding

Cellular Approach to Long-Range ptp_t and Multiplicity Correlations in the String Fusion Model

The long-range $p_t$ and multiplicity($n$) correlations in high-energy nuclear collisions are studied in the framework of a simple cellular analog of the string fusion model. Two cases with local and global string fusion is considered. The $p_t$--$n$ and $n$--$n$ correlation functions and correlation coefficients are calculated analytically in some asymptotic cases using suggested Gauss approximation. It's shown that at large string density the $p_t$--$n$ and $n$--$n$ correlation coefficients are connected and the scaling takes place. The behavior of the correlations at small string density is also studied. The asymptotic results are compared with results of the numerical calculations in the framework of proposed cellular approach.Comment: 21 pages, LaTeX, 7 figures in PostScript, Russian version will appear in the journal "Vestnik SPbU

Deuteron Disintegration in Quark-Parton Model

The deuteron disintegration process with the emission of fast proton in the vicinity of the kinematical boundary of the reaction, when Feynman variable $x\to 2$, is studied. The consideration is fulfilled in the framework of the quark-parton model of cumulative phenomena based on perturbative QCD calculations of the corresponding quark diagrams near the thresholds, at which some quarks ("donors") in the nuclear flucton transfer all their longitudinal momenta to the distinguished active quarks and become soft. The presence of the multi-quark $6q$-configuration in a deuteron is essentially exploited in the consideration. The different versions of hadronization mechanisms of the produced cumulative quarks into cumulative particles are analyzed. It is shown that in the case of the production of cumulative protons from deuteron the hadronization through the coalescence of three cumulative quarks is favorable and leads to the $(2-x)^5$ cross section threshold behavior whereas the usual hadronization through one cumulative quark fragmentation into proton the same as the calculations predicts for the deuteron structure function $F^d_2(x)$ at $x\to 2$ in DIS processes. The results of the calculations are compared with the available experimental data.Comment: 8 pages, LaTe

Simple Cellular Model of Long-Range Multiplicity and ptp_t Correlations in High-Energy Nuclear Collisions

A simple cellular model for the description of the long-range multiplicity and $p_t$ correlations in high-energy nuclear collisions originating from the string fusion model is proposed. Three versions of the model: without fusion, with local and with global string fusion are formulated. A Gauss approximation which enables explicit analytical calculations of the correlation functions in some asymptotic cases in the framework of the model is developed. The assumptions of the model and the validity of a Gauss approximation are checked up in the simplest (no fusion) case when the explicit solution of the model can be found. The role of a size of cells is analysed. The modification of the results in the case of non-Poissonian distributions is also discussed.Comment: 15 pages, LaTeX, 5 figures in PostScript, Russian version will appear in the journal "Vestnik SPbU