Chaos in dynamical systems potentially provides many different dynamical states arising from a single attractor. We call this the reservoir property and give here a precise meaning to two aspects of such property. In both cases, the high... more
Chaos in dynamical systems potentially provides many different dynamical states arising from a single attractor. We call this the reservoir property and give here a precise meaning to two aspects of such property. In both cases, the high flexibility of chaos comes into play, as compared to more regular regimes. In this article, we especially focus on the fact that
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Abstract We review a neural network model based on chaotic dynamics [Babloyantz & Louren co , 1994, 1996] and provide a detailed discussion of its biological and computational relevance. Chaos can be viewed as a \reservoir"... more
Abstract We review a neural network model based on chaotic dynamics [Babloyantz & Louren co , 1994, 1996] and provide a detailed discussion of its biological and computational relevance. Chaos can be viewed as a \reservoir" containing an innite,number of unstable periodic orbits. In our approach, the periodic orbits are used as coding devices. By considering a large enough number of them, one can in principle expand the information processing capacity of small or moderate-size networks. The system is most of the time in an undetermined state characterized by a chaotic attractor. Depending on the type of an external stimulus, the dynamics is stabilized into one of the available periodic orbits, and the system is then ready to process information. This corresponds to the system being driven into an \attentive" state. We show that, apart from static pattern processing, the model is capable of dealing with moving stimuli. We especially consider in this paper the case of transient visual stimuli, which has a clear biological relevance. The advantages of chaos over more regular regimes are discussed. Keywords: Chaos; Computation; Attention; Spatiotemporal Dynamics; Neural Networks; Cortical Layers; Processing of Changing Visual Stimuli 2
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Page 1. PHYSICAL REVIEW E VOLUME 52, NUMBER 2 AUGUST 1995 Control of low-dimensional spatiotemporal chaos in Fourier space Carlos Lourenqo, Mare Hougardy, and Agnessa Babloyantz Service de Chimie-Physique ...
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Chaos in dynamical systems potentially provides many different dynamical states arising from a single attractor. We call this the reservoir property and give here a precise meaning to two aspects of such property. In both cases, the high... more
Chaos in dynamical systems potentially provides many different dynamical states arising from a single attractor. We call this the reservoir property and give here a precise meaning to two aspects of such property. In both cases, the high flexibility of chaos comes into play, as compared to more regular regimes. In this article, we especially focus on the fact that
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Data from J/ψ and ψ′ production in p - A collisions are used to determine the cross section for absorption of pre-resonance charmonium in nuclear matter. The J/ψ suppression in O - Cu, O - U and S - U collisions is fully reproduced by the... more
Data from J/ψ and ψ′ production in p - A collisions are used to determine the cross section for absorption of pre-resonance charmonium in nuclear matter. The J/ψ suppression in O - Cu, O - U and S - U collisions is fully reproduced by the corresponding nuclear absorption, while Pb - Pb collisions show an additional suppression increasing with centrality. We study the onset of this change in terms of hadronic comover interactions and conclude that so far no conventional hadronic description can consistently account for all data. Deconfinement, starting at a critical point determined by central S - U collisions, is in accord with the observed suppression pattern.
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The ratio of cross-sections for muon pair production through the Drell-Yan process in p − p and p − d reactions has been measured at y ≈ 0, with 450 GeVc incident protons. The asymmetry amounts to −0.09 ± 0.02 ± 0.025. The ratio of the... more
The ratio of cross-sections for muon pair production through the Drell-Yan process in p − p and p − d reactions has been measured at y ≈ 0, with 450 GeVc incident protons. The asymmetry amounts to −0.09 ± 0.02 ± 0.025. The ratio of the nucleon sea structure functions derived from this measurement amounts to 0.51 ± 0.04 ± 0.05 at x = 0.18 and suggests that isospin symmetry is broken in the light quark sea of the nucleon.
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The study of oxygen-uranium reactions at 200 GeV/nucleon shows a significant transverse energy dependence of the yield of 's relative to muon pairs produced in the mass continuum. This feature, observed for the first time, is in agreement... more
The study of oxygen-uranium reactions at 200 GeV/nucleon shows a significant transverse energy dependence of the yield of 's relative to muon pairs produced in the mass continuum. This feature, observed for the first time, is in agreement with predictions from quark-gluon plasma formation, although alternative explanations by hadronic effects cannot be ruled out at this stage.
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This report is the result of the collaboration and research effort of the Quarkonium Working Group over the last three years. It provides a comprehensive overview of the state of the art in heavy-quarkonium theory and experiment, covering... more
This report is the result of the collaboration and research effort of the Quarkonium Working Group over the last three years. It provides a comprehensive overview of the state of the art in heavy-quarkonium theory and experiment, covering quarkonium spectroscopy, decay, and production, the determination of QCD parameters from quarkonium observables, quarkonia in media, and the effects on quarkonia of physics beyond the Standard Model. An introduction to common theoretical and experimental tools is included. Future opportunities for research in quarkonium physics are also discussed.
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We report on a precision measurement of low-mass muon pairs in 158 AGeV indium-indium collisions at the CERN SPS. A significant excess of pairs is observed above the yield expected from neutral meson decays. The unprecedented sample size... more
We report on a precision measurement of low-mass muon pairs in 158 AGeV indium-indium collisions at the CERN SPS. A significant excess of pairs is observed above the yield expected from neutral meson decays. The unprecedented sample size of 360 000 dimuons and the good mass resolution of about 2% allow us to isolate the excess by subtraction of the decay sources. The shape of the resulting mass spectrum is consistent with a dominant contribution from pi+pi-->rho-->mu+mu- annihilation. The associated space-time averaged rho spectral function shows a strong broadening, but essentially no shift in mass. This may rule out theoretical models linking hadron masses
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Alessandro, B.; Alexa, C.; Arnaldi, R.; Atayan, M.; Beolè, S.; Boldea, V.; Bordalo, P.; Borges, G.; Castanier, C.; Castor, J.; Chaurand, B.; Cheynis, B.; Chiavassa, E.; Cicalò, C.; Comets, MP; Constantinescu, S.; Cortese, P.; de Falco,... more
Alessandro, B.; Alexa, C.; Arnaldi, R.; Atayan, M.; Beolè, S.; Boldea, V.; Bordalo, P.; Borges, G.; Castanier, C.; Castor, J.; Chaurand, B.; Cheynis, B.; Chiavassa, E.; Cicalò, C.; Comets, MP; Constantinescu, S.; Cortese, P.; de Falco, A.; de Marco, N.; Dellacasa, G.; Devaux, A.; ...
We highlight issues which are often underestimated in the experimental analyses on quarkonium polarization: the relation between the parameters of the angular distributions and the angular momentum composition of the quarkonium, the... more
We highlight issues which are often underestimated in the experimental analyses on quarkonium polarization: the relation between the parameters of the angular distributions and the angular momentum composition of the quarkonium, the importance of the choice of the reference frame, the interplay between observed decay and production kinematics, and the consequent influence of the experimental acceptance on the comparison between experimental measurements and theoretical calculations. Given the puzzles raised by the available experimental results, new measurements must provide more detailed information, such that physical conclusions can be derived without relying on model-dependent assumptions. We describe a frame-invariant formalism which minimizes the dependence of the measurements on the experimental acceptance, facilitates the comparison with theoretical calculations, and probes systematic effects due to experimental biases. This formalism is a direct and generic consequence of the rotational invariance of the dilepton decay distribution and is independent of any assumptions specific to particular models of quarkonium production. The use of this improved approach, which exploits the intrinsic multidimensionality of the problem, will significantly contribute to a faster progress in our understanding of quarkonium production, especially if adopted as a common analysis framework by the LHC experiments, which will soon perform analyses of quarkonium polarization in proton-proton collisions.
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The rotational properties of angular momentum eigenstates imply the existence of a frame-independent relation among the parameters of the decay distribution of vector mesons into fermions. This relation is a generalization of the Lam-Tung... more
The rotational properties of angular momentum eigenstates imply the existence of a frame-independent relation among the parameters of the decay distribution of vector mesons into fermions. This relation is a generalization of the Lam-Tung identity, a result specific to Drell-Yan production in perturbative QCD, here shown to be equivalent to the dynamical condition that the dilepton always originates from a transversely polarized photon.
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The analysis of the data collected by the NA50 experiment in 1998, reported in this paper, extends and clarifies the pattern of the previously observed J/ψ anomalous suppression. This new measurement, besides providing a deeper... more
The analysis of the data collected by the NA50 experiment in 1998, reported in this paper, extends and clarifies the pattern of the previously observed J/ψ anomalous suppression. This new measurement, besides providing a deeper understanding of the previous observations, reveals a steady significative decrease in the J/ψ production rate up to the most central Pb-Pb collisions. It clearly rules out the presently available conventional (hadronic) models of J/ψ suppression, which unanimously predict a saturation of the J/ψ rate for central Pb-Pb collisions. On the contrary and together with the sharp onset of the anomalous suppression previously reported, the new observation leads to a global production rate pattern which finds its natural explanation in the framework of the formation of a deconfined state of quarks and gluons.
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The Drell-Yan and cross-sections measured in PbPb collisions are compared with the values extrapolated from the results obtained in proton and light ion induced reactions. While the Drell-Yan production exhibits the normal expected... more
The Drell-Yan and cross-sections measured in PbPb collisions are compared with the values extrapolated from the results obtained in proton and light ion induced reactions. While the Drell-Yan production exhibits the normal expected behaviour, the yield of in PbPb interactions is abnormally low, as it lies 9 standard deviations below the expected value. Moreover, the departure from the expected behaviour increases significantly from peripheral to central collisions.
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... Authors: Arnaldi, R.; Averbeck, R.; Banicz, K.; Castor, J.; Chaurand, B.; Cicalò, C.; Colla, A.; Cortese, P.; Damjanovic, S.; David, A.; de Falco, A.; Devaux, A.; Drees, A.; Ducroux, L.; En'yo, H.; Ferretti, A.;... more
... Authors: Arnaldi, R.; Averbeck, R.; Banicz, K.; Castor, J.; Chaurand, B.; Cicalò, C.; Colla, A.; Cortese, P.; Damjanovic, S.; David, A.; de Falco, A.; Devaux, A.; Drees, A.; Ducroux, L.; En'yo, H.; Ferretti, A.; Floris, M.; Force, P.; Guettet, N.; Guichard, A.; Gulkanian, H.; Heuser, J.; Keil, M ...
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Measurements of inclusive charged-hadron transverse-momentum and pseudorapidity distributions are presented for proton-proton collisions at sqrt(s) = 0.9 and 2.36 TeV. The data were collected with the CMS detector during the LHC... more
Measurements of inclusive charged-hadron transverse-momentum and pseudorapidity distributions are presented for proton-proton collisions at sqrt(s) = 0.9 and 2.36 TeV. The data were collected with the CMS detector during the LHC commissioning in December 2009. For non-single-diffractive interactions, the average charged-hadron transverse momentum is measured to be 0.46 +/- 0.01 (stat.) +/- 0.01 (syst.) GeV/c at 0.9 TeV and 0.50 +/- 0.01 (stat.) +/- 0.01 (syst.) GeV/c at 2.36 TeV, for pseudorapidities between -2.4 and +2.4. At these energies, the measured pseudorapidity densities in the central region, dN(charged)/d(eta) for |eta| < 0.5, are 3.48 +/- 0.02 (stat.) +/- 0.13 (syst.) and 4.47 +/- 0.04 (stat.) +/- 0.16 (syst.), respectively. The results at 0.9 TeV are in agreement with previous measurements and confirm the expectation of near equal hadron production in p-pbar and pp collisions. The results at 2.36 TeV represent the highest-energy measurements at a particle collider to date.
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The dimuon production in 200 GeV/nucleon oxygen-uranium interactions is studied by the NA 38 Collaboration. The production ofJ/ψ, correlated with the transverse energyET, is investigated and compared to the continuum, as a function of the... more
The dimuon production in 200 GeV/nucleon oxygen-uranium interactions is studied by the NA 38 Collaboration. The production ofJ/ψ, correlated with the transverse energyET, is investigated and compared to the continuum, as a function of the dimuon massM and transverse momentumPT. A value of 0.64±0.06 is found for the ratio (ψ/Continuum at highET)/(ψ/Continuum at lowET), from which theJ/ψ relative suppression can be extracted. This suppression is enhanced at lowPT.
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Data from J/ψ and ψ′ production in p - A collisions are used to determine the cross section for absorption of pre-resonance charmonium in nuclear matter. The J/ψ suppression in O - Cu, O - U and S - U collisions is fully reproduced by the... more
Data from J/ψ and ψ′ production in p - A collisions are used to determine the cross section for absorption of pre-resonance charmonium in nuclear matter. The J/ψ suppression in O - Cu, O - U and S - U collisions is fully reproduced by the corresponding nuclear absorption, while Pb - Pb collisions show an additional suppression increasing with centrality. We study the onset of this change in terms of hadronic comover interactions and conclude that so far no conventional hadronic description can consistently account for all data. Deconfinement, starting at a critical point determined by central S - U collisions, is in accord with the observed suppression pattern.
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First results are reported on and Drell-Yan cross-sections in PbPb reactions at 158 GeV/c per nucleon. The ratio of cross-sections σJ/ψ/σDY is studied as a function of the impact parameter of the collision estimated from the measured... more
First results are reported on and Drell-Yan cross-sections in PbPb reactions at 158 GeV/c per nucleon. The ratio of cross-sections σJ/ψ/σDY is studied as a function of the impact parameter of the collision estimated from the measured transverse energy.