We have applied the Meson Cloud Model (MCM) to calculate the charm and strange antiquark distribution in the nucleon. The resulting distribution, in the case of charm, is very similar to the intrinsic charm momentum distribution in the nucleon. This seems to corroborate the hypothesis that the intrinsic charm is in the cloud and, at the same time, explains why other calculations with the MCM involving strange quark distributions fail in reproducing the low x region data. From the intrinsic strange distribution in the nucleon we have extracted the strangeness radius of the nucleon, which is in agreement with other meson cloud calculations. Many years ago, it has been suggested by Sullivan [1] that some fraction of the nucleon's anti-quark sea distribution may be associated with non-perturbative processes like the pion * 1 cloud of the nucleon. The generalization of this process to other mesons is depicted in figs. 1a and b, and was used in refs. [2,3] to calculate the strange and anti-strange sea quark distributions in the nucleon.Recent analysis of deep inelastic neutrino-hadron scattering data [4] renewed the interest on the meson cloud picture of the nucleon. It is well known that, in this picture there is an asymmetry between sea quark and anti-quark momentum distributions [2]. This happens because the quark and the anti-quark are in different hadronic bound states. On the other hand, in extracting sea distributions from hard processes, it is usually assumed that the quark and antiquark sea contributions are equal. From the point of view of QCD, no definite statement on this subject can be made. Based on charge conjugation symmetry it is only possible to say that the quark sea distribution in the nucleon is equal to the antiquark sea distribution in the antinucleon. In ref. [4] it is shown that, in contrast to the meson cloud approach expectation, the sea strange and anti-strange quark distributions are quite similar. At first sight this would be a very strong argument against the relevance of the meson cloud [5]. The attempt to explain experimental data with the meson cloud model performed in refs. [2,3] has shown not only that the asymmetry present in this model seems to be in conflict with data but also that the calculated distributions are far below data for x < 0.3. However, in ref.[6], these data were reconsidered and combined with the CTEQ collaboration analysis [7]. The conclusion of the authors was that, considering the error bars, existing data do not exclude some asymmetry between the strange and anti-strange momentum distributions, which is significant only for x > 0.2 − 0.3.In the present work we apply the meson cloud model (MCM) to study strangeness and charm in the nucleon. In the case of strangeness, we shall try to extract some estimates on the strangeness radius of the nucleon. This is a very interesting quantity from both theoretical and phenomenological point of view. Indeed, approved parity-violating lepton scattering experiments at MIT-Bates [8] and CEBAF [9] will provide information on ...
We have studied the fluctuation effects in proton-proton collisions through the analysis of their observables. To investigate the role of fluctuations in the initial conditions, we have used the interacting gluon model, modified by the inclusion of the impact parameter, and have applied the one-dimensional Landau's Hydrodynamical Model to the fireballs thus generated. The rapidity and pseudorapidity distributions were calculated using two distinct procedures, one taking the fluctuations into account and the other the usual method considering only one fireball with the average initial conditions. The results show indeed the importance of fluctuations. ͓S0556-2813͑97͒02902-6͔
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