Investigation of high pt_{t} events in Nucleus-Nucleus collisions using the Hijing event generator

In recent years lot of interest has been observed in the nucleus-nucleus collisions at RHIC energies in phenomena related to high $p_{t}$ physics \cite{ref1}. The suppression of high $p_{t}$ particles and disappearance of back-to-back jets compared to the scaling with number of binary nucleon-nucleon collisions indicates that a nearly perfect liquid is produced in these collisions. Results on self shadowing of high $p_{t}$ events are presented using hadron multiplicity associated to high $p_{t}$ and unbiased events in nucleus-nucleus collisions \cite{ref2} obtained from the hijing event generator.Comment: 4 pages, 3 figures, Proceedings of the poster presented at Quark Matter 200

Rapidity long range correlations, parton percolation and color glass condensate

The similarities between string percolation and Glasma results are emphasized, special attention being paid to rapidity long range correlations, ridge structure and elliptic flow. As the string density of high multiplicity pp collisions at LHC energies has similar value as the corresponding to Au-Au semi-central collisions at RHIC we also expect in pp collisions long rapidity correlations and ridge structure, extended more than 8 units in rapidity.Comment: 3 pages, 3 figures, conference Quark Confinement and the hadron spectrum I

Elliptic flow at RHIC and LHC in the string percolation approach

The percolation of strings gives a good description of the RHIC experimental data on the elliptic flow, v2 and predicted a rise on the integrated v2 of the order of 25% at LHC such as it has been experimentally obtained. We show that the dependence of v2 on pT for RHIC and LHC energies is approximately the same as it has been observed, for all the centralities. We show the results for different particles and the dependence of v2 on the centralities and rapidity. Our results are compatible with an small value of the ratio eta/s in the whole energy range such as it was expected in the percolation framework.Comment: 20 pages, 12 figure

Mejora del olmo para su resistencia contra los escolítidos

Dutch Elm Disease (DED) forms a complex system of three elements closely interacting: a host, a pathogen and an insect vector. Elm breeding programmes for resistance to DED have been exclusively based on selecting or obtaining pathogen-resistant trees, thus stressing only the host–pathogen side of the interaction and missing the vector component. Resistance against the bark beetle vectors would involve mechanisms other than those implicated in fungus resistance. As a consequence the search for resistance to the vectors would offer more than just a different way of obtaining resistant elms as it would allow incorporation of a new type of resistance into pathogen-resistant trees. Suppressing twig crotch feeding by elm bark beetles would greatly reduce infection on healthy elms. Evidence of preferences by elm bark beetles among different elm species has been documented in the field and in controlled experiments, demonstrating that U. minor is preferred over U. laevis and U. glabra, whereas intraspecific preferences among individual elms or clones remain largely unexplored. The selection of an individual plant by an insect is a two-step process that involves finding and accepting the host. Plant chemicals can play a key role in both of these steps, acting either as long-range stimuli, such as attractants or repellents, or as close-range contact cues, such as feeding stimulants and deterrents, operating after landing on the plant surface. Research on the chemical aspects of elm selection by bark beetles is here reviewed, and prospects for the future are discussed.La enfermedad de la grafiosis de los olmos constituye un sistema formado por tres elementos estrechamente relacionados: un hospedante, un patógeno y un insecto vector. Los programas de mejora de olmos frente a la grafiosis se han basado en seleccionar u obtener árboles resistentes al patógeno, poniendo el énfasis sólo en la parte patógenohospedante de la interacción y olvidándose del componente vector. La resistencia frente a los escolítidos vectores supondría mecanismos distintos de aquéllos implicados en la resistencia frente al hongo. Como consecuencia, la búsqueda de resistencia frente a los vectores ofrecería no sólo una via diferente de obtener olmos resistentes, sino además la posibilidad de incorporar un nuevo tipo de resistencia a los árboles resistentes al patógeno. La supresión de la alimentación en las ramillas por los escolítidos del olmo reduciría notablemente la infección en los olmos sanos. La evidencia de preferencias en los escolítidos del olmo entre especies diferentes de olmos ha sido documentada en el campo y en experimentos controlados, demostrándose que U. minor es más preferido que U. laevis o que U. glabra, si bien, la existencia de preferencias intraespecíficas entre árboles o clones permanece inexplorada. La selección de una determinada planta por un insecto es un proceso doble que supone encontrar y aceptar al hospedante. Los compuestos químicos vegetales pueden representar un papel clave en ambas fases, actuando bien como estímulos a larga distancia, tales como atrayentes o repelentes, o bien como señales a corta distancia, tales como fagoestimulantes o fagodisuasores, que operan después del aterrizaje sobre la superficie vegetal. Se revisa aquí la investigación sobre los aspectos químicos en la selección de los olmos por los escolítidos y se discuten las perspectivas futuras

Production Associated to Rare Events in High Energy Hadron-Hadron Collisions

At very high energy the same universal relation between the multiparticle or the transverse energy distribution associated to a rare event $C$, $P_C$ and the corresponding minimum bias distribution P, $P_C(\nu)\equiv \nu/ P(\nu)$, $\nu\equiv n$ or $E_T$ works for nucleus-nucleus collisions as well as for hadron-hadron collisions. This suggests that asymptotically, all hadronic processes are similar.Comment: 9 pages, 4 Postscript figure

Fusion of strings vs. percolation and the transition to the quark-gluon plasma

In most of the models of hadronic collisions the number of exchanged colour strings grows with energy and atomic numbers of the projectile and target. At high string densities interaction between them should melt them into the quark-gluon plasma state. It is shown that under certain assumptions about the the string interaction, a phase transition to the quark gluon plasma indeed takes place in the system of many colour strings. It may be of the first or second order (percolation), depending on the particular mechanism of the interaction. The critical string density is about unity in both cases. The critical density may have been already reached in central Pb-Pb collisions at 158 A GeV.Comment: 16 pages, 3 Postscript figure