Clan Structure Analysis and QCD Parton Showers in Multiparticle Dynamics: An Intriguing Dialog Between Theory and Experiment

Abstract

This paper contains a review of the main results of a search of regularities in collective variables properties in multiparticle dynamics, regularities which can be considered as manifestations of the original simplicity suggested by QCD. The method is based on a continuous dialog between experiment and theory. The paper follows the development of this research line, from its beginnings in the seventies to the current state of the art, discussing how it produced both sound interpretations of the most relevant experimental facts and intriguing perspectives for new physics signals in the TeV energy domain.

On statistical mechanics developments of clan concept in multiparticle production

“…Volume V is here the space volume occupied byN clans of the ideal clan gas satisfying Boltzmann equation of state (9). Notice that here we consider clans and not particles (or partons) as in Eq.(5).…”

“…by assuming on phenomenological grounds that k p = k h and n h = σn p with σ ≃ 2 (see Ref. [9] and related bibliography). The existence of the first two classes of events in e + e − annihilation (class I: 2-jet events; class II: 3-or more-jet events) as well as in pp collisions (class I: events without minijets; class II: events with minijets) was motivated by the discovery in both reactions of three relevant facts extensively discussed in Ref.s [10] and [11] and mentioned in the introduction of the present paper: a. the shoulder structure in n-particle multiplicity distribution of the total sample of events P n when plotted vs. n; b. H q vs. q oscillations, with H q the ratio of q-factorial cumulants, K q , and the q-factorial moments, F q , of the corresponding MD; c. the lack of forward (F) to backward (B) n-particle multiplicity correlation in e + e − annihilation and its strong enhancement in pp collisions.…”

Topological cross sections in proton-proton interactions at 50 GeV

“…At the present time, only several phenomenological models predict multiplicity distributions of charged particles in the region of high multiplicities [11][12][13][14]. The gluon-dominance model (GDM) is one of them [12].…”

“…Experimental topological cross sections along with the predictions of the gluon dominance model [11], IHEP model [13], and negative-binomial-distribution (NBD) model [14].…”

Clan structure analysis and new physics signals inppcollisions at LHC

“…and n F , n B the numbers of charged particles lying respectively in the forward and backward hemispheres, andn F andn B their corresponding average charged multiplicities [1,7,8,9]. It should be pointed out that the qualifying assumption of the WSM is that P n is described for each class of events in terms of the Pascal, i.e., negative binomial (NB), MD with the average charged particle multiplicity,n, and k (linked to the variance D 2 ≡ n 2 −n 2 by the relation k =n 2 /(D 2 −n)) as characteristic parameters, and this fact leads to a sound description of the experimental data [1,10,11].…”