A two-component geometrical model for rho production in heavy ion collisions
This paper has been withdrawn by the authors, due to issues concerning the use of unpublished experimental data.
hep-ph↗
arXiv subjects
J. Dias de Deus
Publications and source records attributed to J. Dias de Deus.
Percolation and high energy cosmic rays above $10^{17}$ eV
In this work we argue that, in the interpretation of the energy dependence of the depth of the shower maximum and of the muon content in high energy cosmic ray showers ($E > 10^{17}$ eV), other variables besides the composition may play an important role, in particular those characterising the first (high energy) hadronic collisions. The role of the inelasticity, of the nature of the leading particle, and of the particle multiplicity are discussed. A consistent interpretation of existing data within a string percolation model implemented in a hybrid, one dimensional simulation method is given.
hep-ph↗
Fluctuations and Correlations in hadron-hadron and nucleus-nucleus collisions and String Percolation
This paper has been withdrawn due to an error in figure 5.
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Percolation of color sources and critical temperature
We argue that clustering of color sources, leading to the percolation transition, may be the way to achieve deconfinement in heavy ion collisions. The critical density for percolation is related to the effective critical temperature of the thermal bath asociated to the presence of strong color fields inside the percolating cluster. We find that the temperature is rapidity, centrality and energy dependent. We emphasize the similarities of percolation of strings with color glass condensate.
hep-ph↗
Limiting fragmentation in heavy-ion collisions and percolation of strings
The observed limiting fragmentation of charged particle distributions in heavy ion collisions is difficult to explain as it does not apply to the proton spectrum itself. On the other hand, string percolation provides a mechanism to regenerate fast particles, eventually compensating the rapidity shift (energy loss) of the nucleons. However a delicate energy-momentum compensation is required, and in our framework we see no reason for limiting fragmentation to be exact. A prediction, based on percolation arguments, is given for the charged particle density in the full rapidity interval at LHC energy $(\sqrt s =5500 GeV)$.
hep-ph↗
Percolation and cosmic ray physics above $10^{17}$eV
We argue that the energy dependence of the average position of the shower maximum, $\bar X_{max}$, and of the number of produced muons, $N_μ$, can be explained by a change, around $10^{17}$eV, in the energy dependence of the inelasticity $K$, which decreases with the energy above the string percolation threshold.
hep-ph↗
Percolation Effects in Very High Energy Cosmic Rays
Most QCD models of high energy collisions predict that the inelasticity $K$ is an increasing function of the energy. We argue that, due to percolation of strings, this behaviour will change and, at $\sqrt{s} \simeq 10^4$ GeV, the inelasticity will start to decrease with the energy. This has straightforward consequences in high energy cosmic ray physics: 1) the relative depth of the shower maximum $\bar{X}$ grows faster with energy above the knee; 2) the energy measurements of ground array experiments at GZK energies could be overestimated.
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Associated multiplicity to high $p_T$ events and percolation of colour sources
We show that the multiplicity distribution associated to high $p_T$ events is given in terms of the total multiplicity distribution in an universal way due to the fact that these events are self-shadowed. In particular, the mean associated multiplicity is related to the fluctuations on the multiplicity distribution. In the framework of percolation of strings these fluctuations are related to clustering and as a result the associated multiplicity presents a peculiar dependence on centrality which can be experimentally tested.
hep-ph↗
Universality of the transverse momentum distributions in the framework of percolation of strings
In the framework of percolation of color sources, the transverse momentum distribution in heavy ion and $p+p$ collisions at all centralities and energies are shown to follow a universal behaviour. The width of the distribution depends on the fluctuations of the number of color sources per cluster. At low densities, there are only independent single color sources, no fluctuations occurs and the distribution is described by a single exponential. At very high densities, only one cluster of many color sources appears and therefore there are not fluctuations either and the hardness of the distribution is suppressed. The Cronin effect in this framework is due to a maximum of the fluctuations which decreases as the density increases. We obtain a good agreement with experimental data including the low $p_T$ behaviour and the spectra for different particles. We show that the transverse momentum and multiplicity distributions are related to each other in a defined way. This point is satisfied by the experimental data on $p+p$ collisions at different energies.
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Density saturation and the decrease of the normalised width of the multiplicity distribution in high energy pp collisions
It is experimentally observed that the width of the KNO multiplicity distribution --or the negative binomial parameter 1/k-- for pp collisions, in the energy region 10 to 1800 GeV, is an increasing function of the energy. We argue that in models with parton or string saturation such trend will necessary change: at some energy the distribution will start to become narrower. In the framework of percolating strings, we have estimated the change to occur at an energy of the order of 5--10 TeV.
hep-ph↗
Transverse Momentum Fluctuations from Clustering and Percolation of Strings
Transverse momentum fluctuations can be understood as resulting from clustering of strings or partons. Data allows to distinguish clustering without percolation, from clustering with percolation. Percolation is clearly favored by data.
hep-ph↗
Schwinger Model and String Percolation in Hadron-Hadron and Heavy Ion Collisions
In the framework of the Schwinger Model for percolating strings we establish a general relation between multiplicity and transverse momentum square distributions in hadron-hadron and heavy ion collisions. Some of our results agree with the Colour Glass Condensate model.
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An Estimate of the Percolation Parameter in Heavy Ion Collisions
From existing hadron and heavy ion collisions data on \bar{p}/p central production we estimate the value of the percolation parameter at RHIC energies.
hep-ph↗
Percolation approach to quark gluon plasma in high energy pp collisions
We apply continuum percolation to proton-proton collisions and look for the possible threshold to phase transition from confined nuclear matter to quark gluon plasma. Making the assumption that J/Psi suppression is a good signal to the transition, we discuss this phenomenon for pp collisions, in the framework of a dual model with strings.
hep-ph↗
Inclusive density of secondaries in heavy ion collisions
The inclusive density of charged secondaries produced in high energy heavy ion collisions are calculated in the framework of multiple scattering theory and quark-gluon string model. The obtained results are in agreement with the data only assuming rather large inelastic screening/percolation effects. We predict the total saturation of relative inclusive densities in dependence on the number of interacting nucleon. Predictions for LHC are also given.
hep-ph↗
Cross Sections, Probabilities, Multiplicities and Spectra of Secondaries in High Energy Heavy Ion Interactions
We present a short review of theoretical results (mainly for experimentalists) published in many different papers. The formulae are presented for the different integrated cross sections, the number of interacting nucleons, multiplicities of secondaries, the dispersions of multiplicity distributions. Two possible tests for the search of Quark-Gluon Plasma formation are discussed. CERN SPS data for production of secondaries in central Pb+Pb collisions are compared with Quark-Gluon String Model predictions.
hep-ph↗
Particle rapidity density and collective phenomena in heavy ion collisions
We analyse recent results on charged particle pseudo-rapidity densities from RHIC in the framework of the Dual String Model, in particular when including string fusion. The model, in a simple way, agrees with all the existing data and is consistent with the presence of the percolation transition to the Quark-Gluon Plasma already at the CERN-SPS. It leads to strict saturation of the particle (pseudo-)rapidity density, normalised to the number of participant nucleons, as that number increases. A comparison with recent WA98 data is presented.
hep-ph↗
Multiplicity distributions associated to subthreshold events in heavy-ion collisions
Subthreshold events (pion production, for instance) at energies $E< m_π$ are treated as rare events. The associated multiplicity distribution $P_c (n)$ and the unconstrained distribution P(n), when there is no rare event-trigger, are related by the model independent relation $P_c (n) = {n^2 \over \average{n^2}} P(n)$. This relation, and in particular its improved version inspired in clustering of nucleons, is in fair agreement with data. Moreover, it allows to extract from the multiplicity data information on the number of nucleons involved in meson production processes, occuring at energies below the production threshold in free nucleon collisions.
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