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A. Giovannini

Publications and source records attributed to A. Giovannini.

At least 19 recordsLinked to original sources
arXiv2007

On Statistical Mechanics Developments of Clan Concept in Multiparticle Production

Clan concept has been introduced in multiparticle dynamics in order to interpret the wide occurrence of negative binomial (NB) regularity in n-charged particle multiplicity distributions (MDs) in various high energy collisions. The centrality of clan concept led to the attempt to justify its occurrence within a statistical model of clan formation and evolution. In this framework all thermodynamical potentials have been explicitly calculated in terms of NB parameters. Interestingly it was found that NB parameter k corresponds to the one particle canonical partition function. The goal of this paper is to explore a possible temperature and volume dependence of parameter k in various classes of events in high energy hadron-hadron collisions. It is shown that the existence of a phase transition at parton level from the ideal clan gas associated to the semihard component with k>1 to the ideal clan gas of the hard component with k<1 implies a discontinuity in the average number of particles at hadron level.

hep-ph↗
arXiv2006

Maps of zeroes of the grand canonical partition function in a statistical model of high energy collisions

Theorems on zeroes of the truncated generating function in the complex plane are reviewed. When examined in the framework of a statistical model of high energy collisions based on the negative binomial (Pascal) multiplicity distribution, these results lead to maps of zeroes of the grand canonical partition function which allow to interpret in a novel way different classes of events in pp collisions at LHC c.m. energies.

hep-ph↗
arXiv2004

Clan structure analysis and QCD parton showers in multiparticle dynamics. An intriguing dialog between theory and experiment

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.

hep-ph↗
arXiv2003

Signals of new physics in global event properties in pp collisions in the TeV energy domain: rapidity intervals

The study of possible new physics signals in global event properties in pp collisions in the TeV energy domain is extended from full phase-space to rapidity intervals experimentally accessible at LHC. The elbow structure in the total multiplicity distribution predicted in full phase-space is clearly present also in restricted rapidity intervals, leading to very strong charged particle correlations. It is also found that energy densities comparable to those reached in heavy ion collisions at RHIC could be attained in pp collisions at LHC.

hep-ph↗
arXiv2003

On signals of new physics in global event properties in pp collisions in the TeV energy domain

In the framework of the weighted superposition mechanism of different classes of minimum bias events (or substructures), described by the negative binomial multiplicity distribution, in possible scenarios for pp collisions in the TeV energy domain, we explore global properties of an eventual new class of events, characterised by high hadron and clan densities, to be added to the soft (without minijets) and semihard (with minijets) ones. It turns out that the main signal of the mentioned new physical expectations at 14 TeV c.m. energy would be an ``elbow structure'' in the tail of the total charged particle multiplicity distribution in complete disagreement with the second shoulder structure predicted by Pythia Monte Carlo calculations: a challenging problem for new experimental work.

hep-ph↗
arXiv2003

Open problems in forward-backward multiplicity correlations in hadron-hadron collisions in the TeV region

Continuing previous work on forward-backward multiplicity correlation properties in proton-proton collisions in the framework of the weighted superposition model of two components (each one described by a negative binomial multiplicity distribution) with the addition of the leakage parameter which controls clan spreading from one hemisphere to the opposite one, we examine E735 data on the c.m. energy dependence of the total correlation strength and of the forward variance at fixed total multiplicity. A comparison with the Chou-Yang approach to the problem is presented and extrapolations of the mentioned variables at LHC c.m. energy in possible scenarios in the new energy domain are discussed.

hep-ph↗
arXiv2002

Heavy flavours production in deeply inelastic scattering and gluon density in the proton

Heavy flavours production in e-p DIS is studied at intermediate values of the transferred four-momentum square, under the assumption of boson-gluon-fusion mechanism dominance (no intrinsic heavy flavours contributions). In this framework different expressions for the splitting functions in the gluon density evolution equation, with respect to the standard (DGLAP) ones, are explicitly derived.

hep-ph↗
arXiv2002

Inelastic J/psi electroproduction in e-p collisions

Following HERA experiments our interest is focused, in the present paper, on charmonium production in lepton-proton collisions. Inelastic J/ψelectroproduction is quite difficult to be measured due to the low rates of events; almost all experimental studies are indeed performed in photoproduction regime. J/ψresonance is considered as the product of the hadronization of a c \bar{c} pair generated via boson-gluon fusion. The leading order contribution to the differential cross section, with respect to virtual photon-proton center of mass energy W and transferred four-momentum squared Q^2, is written as the sum of two terms related to a colour singlet and a colour octet c \bar{c} pair production respectively. This expression contains two-gluons contributions and depends on three parameters; two of them are related to the hadronization fractions in charmonium states for the c \bar{c} pair (colour singlet and colour octet), while the third parameter takes into accout possible ``hot-spot'' effects. The values of these parameters are estimated by mean of a fit to the experimental data collected by H1 collaboration at HERA. By using different gluon densities, different sets of parameters are obtained, always with good fits.

hep-ph↗
arXiv2002

Forward-backward multiplicity correlations in e+e- annihilation and pp collisions and the weighted superposition mechanism

Forward-backward multiplicity correlations in symmetric collisions are calculated independently of the detailed form of the corresponding multiplicity distribution. Applications of these calculations to e+e- annihilation and ppbar collisions confirm the existence of the weighted superposition mechanism of different classes of substructures or components. When applied to ppbar collisions in particular, clan concept and its particle leakage from one hemisphere to the opposite one become of fundamental importance. The increase with c.m. energy of the correlation strength as well as the behaviour of the average number of backward particles vs. the number of forward particles are correctly reproduced.

hep-ph↗
arXiv2002

Forward-backward multiplicity correlations and leakage parameter behaviour in asymmetric high energy collisions

Continuing previous work, forward-backward multiplicity correlations are studied in asymmetric collisions in the framework of the weighted superposition mechanism of different classes of events. New parameters for the asymmetric clan distribution and for the particle leakage from clans in one hemisphere to the opposite one are introduced to effectively classify different classes of collisions. This tool should be used to explore forward-backward multiplicity correlations in AB and pA collisions in present and future experiments at RHIC and LHC.

hep-ph↗
arXiv2002

Superposition effect and clan structure in forward-backward multiplicity correlations

The main purpose of this paper is to discuss the link between forward-backward multiplicity correlations properties and the shape of the corresponding final charged particle multiplicity distribution in various classes of events in different collisions. It is shown that the same mechanism which explains the shoulder effect and the H_n vs. n oscillations in charged particle multiplicity distributions, i.e., the weighted superposition of different classes of events with negative binomial properties, reproduces within experimental errors also the forward-backward multiplicity correlation strength in e+e- annihilation at LEP energy and allows interesting predictions for pp collisions in the TeV energy region, to be tested at LHC, for instance with the ALICE detector. We limit ourselves at present to study substructures properties in hadron-hadron collisions and e+e- annihilation; they are examined as ancillary examples in the conviction that their understanding might be relevant also in other more complex cases.

hep-ph↗
arXiv1999

Possible scenarios for soft and semi-hard components structure in central hadron-hadron collisions in the TeV region: pseudo-rapidity intervals

Continuing previous work on collective variables properties in full phase space in hadron-hadron collisions in the TeV region our investigation is extended to multiplicity distributions and clan structure analysis in pseudo-rapidity intervals. Total multiplicity distributions (MDs) are considered also here as the weighted superposition of soft and semi-hard components, and described by Pascal(NB)MD. The soft component is characterised by KNO and Feynman scaling behaviour in all scenarios which differ in the semi-hard component properties only. In fact, the semi-hard component has been supposed to satisfy, in scenario 1, KNO and Feynman scaling behaviour and to violate it strongly in scenario 2. A third possibility has been explored: it is a QCD inspired scenario and leads to expectations intermediate between the just mentioned two. The semi-hard component structure becomes dominant in the TeV energy domain, a huge mini-jet production is indeed the main phenomenon in this region. In addition a new species of clans is generated suggesting a phase transition in the clan production in scenarios 2 and 3. Our results can be compared with Tevatron and LHC experimental data when available.

hep-ph↗
arXiv1997

Soft and Semi-Hard Components Structure in Multiparticle Production in High Energy Collisions

Superposition of jets of different flavors as well as superposition of jets of different topologies describe well observed structures (shoulder, H_q oscillations) in e+e- annihilation. The analysis of similar effects seen in experimental data in hadron-hadron collision is performed successfully by superimposing soft and semi-hard contributions at various energies. Negative Binomial multiplicity distributions are chosen in all examined classes of collisions as elementary substructures, i.e., as QCD inspired genuine self-similar fractal processes. Predictions on final particle multiplicity distributions in hadron-hadron collisions at 14 TeV are discussed.

hep-ph↗
arXiv1997

Oscillations of Moments and Structure of Multiplicity Distributions in e+e- Annihilation

Starting from the recognized fact that oscillations of moments with rank and shoulder structure in the multiplicity distribution have the same origin in the full sample of events in e+e- annihilation, we push our investigation to the 2-jet sample level, and argue in favor of the use of the negative binomial multiplicity distribution as the building block of multiparticle production in e+e- annihilation events. It will be shown that this approach leads to definite predictions for the correlation structure, e.g., that correlations are flavour independent.

hep-ph↗
arXiv1995

Clan Structure in Rapidity Intervals

We present a cascading model for a single jet, inspired to QCD and to the phenomenological analysis of multiplicity distributions. The model, describing as it does a two dimensional evolution in virtuality and rapidity, allows analytical predictions for clan analysis parameters to be made.

hep-ph↗