An analysis is presented of the rapidity and transverse momentum distributions and of the nuclear stopping power in collisions of % + and K + mesons with A! and Au nuclei at 250 GeV/c. The experimental results are compared to predictions of the additive quark model and the dual parton model. The AQM offers an overall consistent description of the data in this experiment. The DPM reproduces reasonably well the rapidity spectra in the central and projectile fragmentation regions, but fails to describe the nuclear stopping power.

The NA22 data on 7r" 7r” correlations are ana­ lyzed in terms of a number of twoand three-dimensional parametrizations (Gaussian space-time, Goldhaber, Bowler string-like, Bertsch hydrodynamical, Kopylov-Podgoretskii, etc.). Contrary to the results obtained for e+e” and pp col­ lisions, the Goldhaber parametrization, as well as string-like models, fail in describing the hadron-hadron data. Better fits are obtained in the framework of surface-emitting fireball­ like models, both when including and excluding hydrody­ namical expansion of nuclear matter. Our results indicate that pion radiation occurs at earlier stages of matter evolu­ tion than in nuclear collisions.

The correlation of negative particles at small momentum difference and its dependence on multiplicity and on kinematical cuts is studied in n +/?-interactions at 250 GeV/c. In terms of the Kopylov-Podgoretskir parametrization, an average radius of the pion emitting region of rK — 1.59 ± 0.14 fm and a life-time (or emission depth) t = 0.83 ± 0.25 fm are found. The Lorentz invariant parametrization of Goldhaber gives rG= 0.85 ± 0.04 fm. As­ suming two different sources of pions, their radii are es­ timated as /■, = 1.75 ± 0.25 fm and r 2 = 0.60 ± 0.08 fm. An angular and multiplicity dependence of the space-time size of the source is observed. The source is elongated along the collision axis and has larger size rK at higher multiplicities. The radius rK decreases with increasing pion pair momentum. The size of the emitting region appears to be larger for low rapidity pions than for pions from the fragmentation region. No evidence is found for a unique reference frame, where the pion source is mo­ tionless for each n +p collision, i.e. where the space-time size of the source is definitely smaller than in any other frame.

In the present work, we make use of simplified nonlinear models based on the compressibility factor (Peter et al., Phys. Plasmas, vol. 20 (12), 2013, 123104) to predict the gain of one-dimensional (1-D) free-electron lasers (FELs), considering space-charge and thermal effects. These models proved to be reasonable to estimate some aspects of 1-D FEL theory, such as the position $z$ of the onset of mixing, in the case of a initially cold electron beam, and the position $z$ of the breakdown of the laminar regime, in the case of an initially warm beam (Peter et al., Phys. Plasmas, vol. 21 (11), 2014, 113104). The results given by the models are compared to wave–particle simulations showing a reasonable agreement.

Cross-sections are obtained for coherent interac­ tions of 7r+ and K +-mesons with A1 and Au nuclei at 250 GeV/c, leading to three, five and seven charged mesons. The total coherent cross-section is (4.3 ± 0.5)% of the inelastic cross-section for each of the four meson-nucleus interac­ tions. In 85% of the coherent events, the charged meson pro­ duction is accompanied by neutral mesons. Effective mass distributions are presented for coherently produced particles, including charged mesons and photons, carrying total mea­ sured energy of more than 85% of the initial energy. Charged particle and 7 spectra are analysed. No charge asymmetry is observed within the coherently produced cluster.

Cross-sections are obtained for coherent interac­ tions of 7r+ and K +-mesons with A1 and Au nuclei at 250 GeV/c, leading to three, five and seven charged mesons. The total coherent cross-section is (4.3 ± 0.5)% of the inelastic cross-section for each of the four meson-nucleus interac­ tions. In 85% of the coherent events, the charged meson pro­ duction is accompanied by neutral mesons. Effective mass distributions are presented for coherently produced particles, including charged mesons and photons, carrying total mea­ sured energy of more than 85% of the initial energy. Charged particle and 7 spectra are analysed. No charge asymmetry is observed within the coherently produced cluster.

We investigate the occurrence of extreme and rare events, i.e., giant and rare light pulses, in a periodically modulated CO2 laser model. Due to nonlinear resonant processes, we show a scenario of interaction between chaotic bands of different orders, which may lead to the formation of extreme and rare events. We identify a crisis line in the modulation parameter space, and we show that, when the modulation amplitude increases, remaining in the vicinity of the crisis, some statistical properties of the laser pulses, such as the average and dispersion of amplitudes, do not change much, whereas the amplitude of extreme events grows enormously, giving rise to extreme events with much larger deviations than usually reported, with a significant probability of occurrence, i. e., with a long-tailed non-Gaussian distribution. We identify recurrent regular patterns, i. e., precursors, that anticipate the emergence of extreme and rare events, and we associate these regular patterns with unstable periodic orbits embedded in a chaotic attractor. We show that the precursors may or may not lead to the emergence of extreme events. Thus, we compute the probability of success or failure (false alarm) in the prediction of the extreme events, once a precursor is identified in the deterministic time series. We show that this probability depends on the accuracy with which the precursor is identified in the laser intensity time series.

In the present work, we describe the linear growth rate of the laser field for a one-dimensional theoretical single-pass free-electron laser, including space-charge and thermal effects, in the hydrodynamical regime. In a recent work (Peter, Endler & Rizzato, Phys. Plasmas, vol. 21, 2014, 113104), the thermal effects were already included for a water-bag initial distribution for the longitudinal velocities of the particles of the beam. Here, we extend the result for different and symmetrical initial distributions, considering that in the hydrodynamical regime, the beam can be thought of as a warm fluid composed of a sum of different fluids with different densities, where the initial distribution of each fluid is a water-bag distribution. The total pressure of the beam is related to the sum of the pressures of these fluids. This approach is much less complicated than the kinetic approach. We compare the results given by the linear set of equations and wave–particle simulations for water-bag and Gaussian initial distributions. The evolution of the particle distribution in the phase space is also shown in order to demonstrate that the assumption of the sum of different fluids reproduces the physics of the system in a reasonable fashion.

In the present work, we extend results of a previous paper [Peter et al., Phys. Plasmas 20, 12 3104 (2013)] and develop a semi-analytical model to account for thermal effects on the nonlinear dynamics of the electron beam in free-electron lasers. We relax the condition of a cold electron beam but still use the concept of compressibility, now associated with a warm beam model, to evaluate the time scale for saturation and the peak laser intensity in high-gain regimes. Although vanishing compressibilites and the associated divergent densities are absent in warm models, a series of discontinuities in the electron density precede the saturation process. We show that full wave-particle simulations agree well with the predictions of the model. (C) 2014 AIP Publishing LLC.

We investigate the effects of random perturbations on fully chaotic open systems. Perturbations can be applied to each trajectory independently (white noise) or simultaneously to all trajectories (random map). We compare these two scenarios by generalizing the theory of open chaotic systems and introducing a time-dependent conditionally-map-invariant measure. For the same perturbation strength we show that the escape rate of the random map is always larger than that of the noisy map. In random maps we show that the escape rate κ and dimensions D of the relevant fractal sets often depend nonmonotonically on the intensity of the random perturbation. We discuss the accuracy (bias) and precision (variance) of finite-size estimators of κ and D, and show that the improvement of the precision of the estimations with the number of trajectories N is extremely slow ([proportionality]1/lnN). We also argue that the finite-size D estimators are typically biased. General theoretical results are combined with analytical calculations and numerical simulations in area-preserving baker maps.

The present work revisits the subjects of mixing, saturation, and space-charge effects in free-electron lasers. Use is made of the compressibility factor, which proves to be a helpful tool in the related systems of charged beams confined by static magnetic fields. The compressibility allows to perform analytical estimates of the elapsed time until the onset of mixing, which in turn allows to estimate the saturated amplitude of the radiation field. In addition, the compressibility helps to pinpoint space-charge effects and the corresponding transition from Compton to Raman regimes.

A transition from Mandelbrot-like sets to Arnold tongues is characterized via a coupling of two non-identical quadratic maps proposed by us. A two-dimensional parameter-space considering the parameters of the individual quadratic maps was used to demonstrate numerically the event. The location of the parameter sets where Naimark-Sacker bifurcations occur, which is exactly the place where Arnold tongues of arbitrary periods are born, was computed analytically.

The present work explores the full role of relativistic effects in the transport of magnetically focused non-neutral cold beams. Not only relativistic effects along the transport axis are discussed, but relativistic effects associated with the transverse particle dynamics are also investigated. Transverse effects are directly connected with the amount of charge the beam transports and a proper discussion of relativistic features should include accurate analysis of all fields self-consistently created by space charge. We review and adapt the equilibrium analysis, and proceed to develop a convenient method to tackle dynamical situations. Simulations revealing how flattop initial conditions, the typical equilibrium profiles of non-relativistic beams, evolve toward highly nonlinear states in relativistic beams are then presented and discussed.

We investigate the role of the temperature in the onset of singularities and the consequent breakdown in a macroscopic fluid model for long-range interacting systems. In particular, we consider an adiabatic fluid description for the transport of intense inhomogeneous charged particle beams. We find that there exists a critical temperature below which the fluid model always develops a singularity and breaks down as the system evolves. As the critical temperature is approached, however, the time for the occurrence of the singularity diverges. Therefore, the critical temperature separates two distinct dynamical phases: a nonadiabatic transport at lower temperatures and a completely adiabatic evolution at higher temperatures. These findings are verified with the aid of self-consistent N-particle simulations.

We construct a Lagrangian warm-fluid model for describe the behavior of a inhomogeneous charged-particle beam, under the effects of a constant solenoidal focusing field. The equations of motion are derived for an adiabatic process, with a state equation originated from the ideal gas law. In the end, the model is compared with self-consistent simulation and is used to explain emittance growth and jets of particle even when the system is out of equilibrium.

We show that noise enhances the trapping of trajectories in scattering systems. In fully chaotic systems, the decay rate can decrease with increasing noise due to a generic mismatch between the noiseless escape rate and the value predicted by the Liouville measure of the exit set. In Hamiltonian systems with mixed phase space we show that noise leads to a slower algebraic decay due to trajectories performing a random walk inside Kolmogorov-Arnold-Moser islands. We argue that these noise-enhanced trapping mechanisms exist in most scattering systems and are likely to be dominant for small noise intensities, which is confirmed through a detailed investigation in the Hénon map. Our results can be tested in fluid experiments, affect the fractal Weyl's law of quantum systems, and modify the estimations of chemical reaction rates based on phase-space transition state theory.