Jorge Dias de Deus

Multiplicity in pp and AA collisions: the same power law from energy–momentum constraints in string production

Abstract We show that the dependence of the charged particle multiplicity on the centre-of-mass energy of the collision is, in the String Percolation Model, driven by the same power law behavior in both proton–proton and nucleus–nucleus collisions. The observed different growths are a result of energy–momentum constraints that limit the number of formed strings at low energy. Based on the very good description of the existing data, we provide predictions for future high energy LHC runs.

Rapidity dependence of particle densities in pp and AA collisions

We use multiple scattering and energy conservation arguments to describe dn=d jNANA as a function of dn=d jpp in the framework of string percolation. We discuss the pseudo-rapidity and beam rapidity Y dependence of particle densities. We present our results for pp, AuAu, and Pb-Pb collisions at RHIC and LHC.

Multiparticle production and long range correlations in e+e− annihilations and pp high energy collisions

Abstract It is argued that long range correlation effects will become increasingly important not only in hard processes (e + e − ), as predicted by perturbative QCD, but as well in high energy soft collisions. A comparison is made, in the framework of Dual Unitarization, between recent PETRA results on the energy dependence of 〈 n 〉 and 〈 p T 〉 and ISR data (as well as indications from cosmic ray data) and a consistent description is obtained. A simple quantitative explanation is given for the observed rise of forward-backward correlations at ISR as a result of the presence of intrinsic long range correlations.

Fragmentation functions in nuclei

Abstract Changes of parton fragmentation functions in nuclear matter can be quantitatively understood using rescaling ideas and perturbative QCD evolution equations starting from the physical hadronization threshold.

The black disk and the dip in the differential elastic cross section at asymptotic energy

Abstract We test the validity of the black disk limit in elastic scattering by studying the evolution of the dip in the scaling variable τ = − t D σ tot , where t D is the transverse momentum squared at the dip and σ tot the total cross section. As s → ∞ and − t D → 0 , τ may consistently be approaching the black disc value, τ → s → ∞ τ BD = 35.92 GeV 2 mb .

The search of asymptopia in soft physics at high energy

Abstract We show, with a simple, conventional, soft physics model with Reggeon+Pomeron terms, that, without odderon or/and minijet QCD contributions, existing data on total cross sections, ϱ parameter and elastic scattering are well understood in the energy region from √s⋍5 GeV up to cosmic rays, √s⋍20 TeV .

What can be learned from charged and negative particle distributions in limited rapidity intervals

Abstract Recent data at √s=22 GeV on cut rapidity gap distributions confirm, in a model independent manner, that independent clusters are responsible for particle production. These clusters have an extent in rapidity of the order of 1.8. Strong correlations between charged and negative particles, within a cluster, imply that the ratio of the respective negative binomial distribution constants, K K_ , remains constant over a wide central rapidity gap. Asymptotically it is predicted that K K_ →1 .

Intermittency and scaling in rapidity particle distributions

Abstract We use the one-dimensional Ising model as a toy model to simulate intermittency and scaling in rapidity particle distributions. Many results agree with what is observed in multiparticle production, thus suggesting that rapidity distrubutions do not reveal critical behaviour but rather show the relevance of short distance positive correlations, the statistical effect of many sources emitting particles and the role of finite size kinematical constraints. Comparisons with p p data are presented.

Fractal behaviour and correlations in rapidity particle distributions at high energies

Abstract Recent arguments of Sarcevic and Satz for multifractal behaviour in rapidity particle distributions are shown to have a simple explanation in terms of multisource production in hadron collisions as it happens in the negative binomial approximation. The arguments for strict fractal behaviour may, however, still be justified if use is made of the correlation Mueller moments instead of the factorial moments.

Quantum number flow in diffraction dissociation of mesons

Abstract The flow of quantum numbers and forward-backward asymmetries in pomeron-meson interactions are discussed in the framework of the parton model. By assuming that the pomeron interacts with one parton of the meson, one arrives at: (1) forward-backward charge asymmetry even in π dissociation, (2) an excess of strangeness in the backward hemisphere in K dissociation, (3) more particles produced backwards. These results do not seem to be shared by more conventional models of diffraction dissociation.