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D. Sousa

Publications and source records attributed to D. Sousa.

17 recordsLinked to original sources
arXiv2026

Scalable topological quantum computing based on Sine-Cosine chain models

This work proposes a scalable framework for topological quantum computing using Matryoshka-type Sine-Cosine chains. These chains support high-dimensional qudit encoding within single systems, reducing the physical resource overhead compared to conventional qubit arrays. We describe how these chains can be used in Y-junction braiding protocols for gate operations and in extended memory architectures capable of storing multiple qubits simultaneously. Fidelity analysis shows partial topological protection against disorder, suggesting this approach is a possible pathway toward low-overhead quantum hardware.

quant-ph↗
arXiv2004

Anomalous suppression of $π^0$ production at large transverse momentum in Au + Au and d + Au collisions at $\sqrt{{\bf s}_{\bf NN}} =$ 200 GeV

We propose a model of suppression of large $p_T$-pions in heavy ion collisions based on the interaction of the large $p_T$ pion with the dense medium created in the collision. The model is practically the same as the one previously introduced to describe $J/ψ$ suppression. Both the $p_T$ and the centrality dependence of the data are reproduced. In deuteron-gold collisions, the effect of the final state interaction with the dense medium turns out to be negligibly small. Here the main features of the data are also reproduced both at mid and at forward rapidities.

hep-ph↗
arXiv2004

Large transverse momentum suppression of $π^0$'s in Au+Au and d+Au collisions at $\sqrt{s}=200$ GeV

We propose a model of suppression of $π^0$'s based on two different effects: at low $p_T$ we take into account the shadowing corrections, while at large $p_T$ the suppression is produced due to the interaction of the large $p_T$ pion with the dense medium created in the collision. The main features of the data on $AuAu$ and $dAu$ collisions are reproduced both at mid and at forward rapidities.

nucl-th↗
arXiv2003

New J/$ψ$ suppression data and the comovers interaction model

New data on the $J/ψ$ suppression both in proton-nucleus and in lead-lead interactions have been presented recently by the NA50 collaboration. We show that these data, together with the final ones on sulfur-uranium interactions, can be described in the framework of the comovers interaction model with a unique set of three parameters : the nuclear absorption cross-section, the comovers interaction cross-section and a single (rescaled) absolute normalization. Expectations for $J/ψ$ suppression at RHIC are also discussed.

nucl-th↗
arXiv2002

J/$ψ$ suppression as a function of the energy of the zero degree calorimeter : can it discriminate between deconfining and comovers interaction models ?

The ratio of $J/ψ$ over Drell-Yan cross-sections as a function of the energy of the zero degree calorimeter in $Pb$ $Pb$ collisions has been computed in a comovers interaction model and compared with the results of a deconfining model. The predictions of the two models are different both for peripheral events and for very central ones. These differences are analyzed and the results of the models confronted with available data -- not only for $Pb$ $Pb$ but also for $pA$ and $SU$ collisions.

nucl-th↗
arXiv2002

Strange particle production at RHIC in the Dual Parton Model

We compute the mid-rapidity densities of pions, kaons, baryons and antibaryons in $Au$-$Au$ collisions at $\sqrt{s} =$ 130 GeV in the Dual Parton Model supplemented with final state interaction (comovers interaction). The ratios $B/n_{part}$ ($\bar{B}/n_{part}$) increase between peripheral ($n_{part} = 18$) and central ($n_{part} = 350)$ collisions by a factor 2.4 (2.0) for $Λ$'s, 4.8 (4.1) for $Ξ$'s and 16.5 (13.5) for $Ω$'s. The ratio $K^-/π^-$ increases by a factor 1.3 in the same centrality range. A comparison with available data is presented.

nucl-th↗
arXiv2002

Analysis of the first RHIC results in the String Fusion Model

First results from RHIC on charged multiplicities, evolution of multiplicities with centrality, particle ratios and transverse momentum distributions in central and minimum bias collisions, are analyzed in a string model which includes hard collisions, collectivity in the initial state considered as string fusion, and rescattering of the produced secondaries. Multiplicities and their evolution with centrality are successfully reproduced. Transverse momentum distributions in the model show a larger $p_T$-tail than experimental data, disagreement which grows with increasing centrality. Discrepancies with particle ratios appear and are examined comparing with previous features of the model at SPS.

hep-ph↗
arXiv2001

Why is the J/$ψ$ suppression enhanced at large transverse energy ?

We study the ratio of $J/ψ$ over minimum bias in $Pb$ $Pb$ collisions at SPS energy. The NA50 data exhibit a sharp turn-over at $E_T \sim 100$ GeV (close to the knee of the $E_T$ distribution) followed by a steady, steep decrease at larger $E_T$. We show that this behaviour can be explained by the combined effects of a small decrease of the hadronic $E_T$ in the $J/ψ$ event sample (due to the $E_T$ taken by the $J/ψ$ trigger), together with the sharp decrease of the $E_T$ distributions in this $E_T$ region (tail). This phenomenon does not affect the (true) ratio $J/ψ$ over $DY$ (obtained by the NA50 standard analysis), but does affect the one obtained by the so-called minimum bias analysis. A good agreement is obtained with the data coming from both analysis -- as well as with the ratios of $J/ψ$ and $DY$ over minimum bias -- in the whole $E_{T}$ region.

nucl-th↗
arXiv2001

Charged multiplicities and $J/ψ$ suppression at SPS and RHIC energies

Charged multiplicities in nucleus--nucleus collisions are calculated in the Dual Parton Model taking into account shadowing corrections. Its dependence on the number of collisions and participants is analyzed and found in agreement with experiment at SPS and RHIC energies. Using these results, we compute the $J/ψ$ suppression at SPS as a function of the transverse energy and of the energy of the zero degree calorimeter. Predictions for RHIC are presented.

nucl-th↗
arXiv2001

Charged Multiplicities at SPS and RHIC and consequences for $J/ψ$ suppression

Hadron multiplicities in nucleus--nucleus interactions are calculated in the Dual Parton Model and its dependence on the number of collisions and the number of participants is analyzed. Shadowing corrections are calculated as a function of impact parameter and the multiplicity per participant as a funtion of centrality is found to be in agreement with experiment at SPS and RHIC energies. The obtained results are used to compute the $J/ψ$ suppression in a comover approach.

nucl-th↗
arXiv2001

Centrality Dependence of Hadron Multiplicities in Nuclear Collisions in the Dual Parton Model

We show that, even in purely soft processes, the hadronic multiplicity in nucleus-nucleus interactions contains a term that scales with the number of binary collisions. In the absence of shadowing corrections, this term dominates at mid rapidities and high energies. Shadowing corrections are calculated as a function of impact parameter and the centrality dependence of mid-rapidity multiplicities is determined. The multiplicity per participant increases with centrality with a rate that increases between SPS and RHIC energies, in agreement with experiment.

nucl-th↗
arXiv2001

J/psi suppression at SPS and RHIC in the comovers approach

The NA50 collaboration data on the $J/ψ$ suppression are compared with the results obtained in a comovers approach based on the Dual Parton Model (DPM). Predictions for the $J/ψ$ suppression versus the charged multiplicity - measured in the rapidity region of the dimuon trigger - are given for SPS and RHIC energies.

nucl-th↗
arXiv2001

Monte Carlo model for nuclear collisions from SPS to LHC energies

A Monte Carlo model to simulate nuclear collisions in the energy range going from SPS to LHC, is presented. The model includes in its initial stage both soft and semihard components, which lead to the formation of color strings. Collectivity is taken into account considering the possibility of strings in color representations higher than triplet or antitriplet, by means of string fusion. String breaking leads to the production of secondaries. At this point, the model can be used as initial condition for further evolution by a transport model. In order to tune the parameters and see the results in nucleus-nucleus collisions, a naif model for rescattering of secondaries is introduced. Results of the model are compared with experimental data, and predictions for RHIC and LHC are shown.

hep-ph↗
arXiv2000

Baryon and strangeness enhancement at SPS, RHIC and LHC energies in the String Fusion Model

Strangeness and baryon enhancement in heavy ion collisions are discussed in the framework of the String Fusion Model. The Monte Carlo version of this model is shown to reasonably reproduce three of the features that have been pointed out as evidences of the finding of the Quark Gluon Plasma. Namely hyperon/antihyperon enhancement, dependence of the slope of the $p_{T}$ distributions on the mass of the produced particles and on the centrality of the collision, are described. Predictions for RHIC and LHC energies are presented.

hep-ph↗
arXiv2000

Consequences of parton's saturation and string's percolation on the developments of cosmic ray showers

At high gluon or string densities, gluons' saturation or the strong interaction among strings, either forming colour ropes or giving rise to string's percolation, induces a strong suppression in the particle multiplicities produced at high energy. This suppression implies important modifications on cosmic ray shower development. In particular, it is shown that it affects the depth of maximum, the elongation rate, and the behaviour of the number of muons at energies around 10^{17}-10^{18} eV. The existing cosmic ray data point out in the same direction.

astro-ph↗
arXiv1998

Signals of phase transition in atmospheric showers

We discuss collective effects like percolation, quark gluon plasma, or string fusion and their effect on the longitudinal development of high energy showers in air. It is shown that iron-air showers could develop more slowly than expected and produce the observed change in the slope of $X_max$ at the highest energies.

hep-ph↗