The Charm of the Proton and the Λc+\Lambda _c^{+} Production

We propose a two component model for charmed baryon production in $pp$ collisions consisting of the conventional parton fusion mechanism and fragmentation plus quarks recombination in which a $ud$ valence diquark from the proton recombines with a $c$-sea quark to produce a $\Lambda_c^+$. Our two-component model is compared with the intrinsic charm two-component model and experimental data.Comment: 6 pages, LaTex, 2 figures included, aipproc.sty included. Talk presented at Simposio Latino Americano de Fisica de Altas Energias, Merida, Mexico, November 199

The Λ0\Lambda_0 Polarization and the Recombination Mechanism

We use the recombination and the Thomas Precession Model to obtain a prediction for the $\Lambda _0$ polarization in the $p+p \to \Lambda_0+X$ reaction. We study the effect of the recombination function on the $\Lambda_0$ polarization.Comment: 4 pages, LaTex, 1 figures included, aipproc.sty included. Talk presented at Simposio Latino Americano de Fisica de Altas Energias, Merida, Mexico, November 199

On the intrinsic charm and the recombination mechanisms in charm hadron production

We study $\Lambda_c^\pm$ production in $pN$ and $\pi^-N$ interactions. Recent experimental data from the SELEX and E791 Collaborations at FNAL provide important information on the production mechanism of charm hadrons. In particular, the production of the $\Lambda_c$ baryon provides a good test of the intrinsic charm and the recombination mechanisms, which have been proposed to explain the so called leading particle effects.Comment: 11 pages, two figures (postscript), late

Three and two-hadron correlations in \sqrt{s_{NN}}=200 GeV proton-proton and nucleus-nucleus collisions

We compare the azimuthal correlations arising from three and two hadron production in high energy proton-proton and nucleus-nucleus collisions at \sqrt{s_{NN}}=200 GeV, using the leading order matrix elements for two-to-three and two-to-two parton-processes in perturbative QCD. We first compute the two and three hadron production cross sections in mid-rapidity proton-proton collisions. Then we consider Au + Au collisions including parton energy loss using the modified fragmentation function approach. By examining the geometrical paths the hard partons follow through the medium, we show that the two away-side partons produced in two-to-three processes have in average a smaller and a greater path length than the average path length of the away-side parton in two-to-two processes. Therefore there is a large probability that in the former processes one of the particles escapes while the other gets absorbed. This effect leads to an enhancement in the azimuthal correlations of the two-to-three with respect to the two-to-two parton-processes when comparing to the same processes in proton-proton collisions since in average the particle with the shortest path length looses less energy with respect to the away side particle in two-to-two processes. We argue that this phenomenon may be responsible for the shape of the away-side in azimuthal correlations observed in mid-rapidity Au + Au collisions at RHIC.Comment: 4 pages, 2 figure

The broad away side of azimuthal correlations: 3 vs 2 final state particles in high energy nuclear collisions

In high energy heavy ion collisions at RHIC there are important aspects of the medium induced dynamics, that are still not well understood. In particular, there is a broadening and even a double hump structure of the away-side peak appearing in azimuthal correlation studies in Au+Au collisions which is absent in p+p collisions at the same energies. These features are already present but suppressed in p+p collisions: 2 to 3 parton processes produce such structures but are suppressed with respect to 2 to 2 processes. We argue that in A+A collisions the different geometry for the trajectories of 3 as opposed to 2 particles in the final state, together with the medium induced energy loss effects on the different cross sections, create a scenario that enhances processes with 3 particles in the final state, which gives on average this double hump structure.Comment: Prepared for the 5th International Workshop on High-pT Physics at LHC, ICN-UNAM, 27 Sep.-1 Oct, 201