Hadronic form factors and the J/ψJ/\psi secondary production cross section: an update

Improving previous calculations, we compute the $D + \bar{D} \to J/\psi + \pi$ cross section using the most complete effective lagrangians available. The new crucial ingredients are the form factors on the charm meson vertices, which are determined from QCD sum rules calculations. Some of them became available only very recently and the last one, needed for our present purpose, is calculated in this work.Comment: 12 pages, 9 eps figure

Does the D−/D+D^-/D^+ production asymmetry decrease at large xFx_F?

We have applied the meson cloud model (MCM) to calculate the asymmetries in $D$ and $D_s$ meson production in high energy $\Sigma^-$-nucleus and $\pi^-$-nucleus collisions. We find a good agreement with recent data. Our results suggest that the asymmetries may decrease at large $x_F$.Comment: revised version with new figures and added references to appear in Phys. Rev. Let

Meson Cloud and SU(3) Symmetry Breaking in Parton Distributions

We apply the Meson Cloud Model to the calculation of nonsinglet parton distributions in the nucleon sea, including the octet and the decuplet cloud baryon contributions. We give special attention to the differences between nonstrange and strange sea quarks, trying to identify possible sources of SU(3) flavor breaking. A analysis in terms of the $\kappa$ parameter is presented, and we find that the existing SU(3) flavor asymmetry in the nucleon sea can be quantitatively explained by the meson cloud. We also consider the $\Sigma^+$ baryon, finding similar conclusions.Comment: 17 pages, LaTeX, 8 figures in .ps file

Charm and longitudinal structure functions with the Kharzeev-Levin-Nardi model

We use the Kharzeev-Levin-Nardi model of the low $x$ gluon distributions to fit recent HERA data on charm and longitudinal structure functions. Having checked that this model gives a good description of the data, we use it to predict $F^c_2$ and $F_L$ to be measured in a future electron-ion collider. The results interpolate between those obtained with the de Florian-Sassot and Eskola-Paukkunen-Salgado nuclear gluon distributions. The conclusion of this exercise is that the KLN model, simple as it is, may still be used as an auxiliary tool to make estimates both for heavy ion and electron-ion collisions.Comment: 6 pages, 7 figure

Systematics of Leading Particle Production

Using a QCD inspired model developed by our group for particle production, the Interacting Gluon Model (IGM), we have made a systematic analysis of all available data on leading particle spectra. These data include diffractive collisions and photoproduction at HERA. With a small number of parameters (essentially only the non-perturbative gluon-gluon cross section and the fraction of diffractive events) good agreement with data is found. We show that the difference between pion and proton leading spectra is due to their different gluon distributions. We predict a universality in the diffractive leading particle spectra in the large momentum region, which turns out to be independent of the incident energy and of the projectile type.Comment: 13 pages, Latex, 4 ps figures. To appear in Phys. Rev.

Gluon saturation and the Froissart bound: a simple approach

At very high energies we expect that the hadronic cross sections satisfy the Froissart bound, which is a well-established property of the strong interactions. In this energy regime we also expect the formation of the Color Glass Condensate, characterized by gluon saturation and a typical momentum scale: the saturation scale $Q_s$. In this paper we show that if a saturation window exists between the nonperturbative and perturbative regimes of Quantum Chromodynamics (QCD), the total cross sections satisfy the Froissart bound. Furthermore, we show that our approach allows us to describe the high energy experimental data on $pp/p\bar{p}$ total cross sections.Comment: 6 pages, 5 figures. Includes additional figures, discussion and reference

Diffractive Dissociation In The Interacting Gluon Model

We have extended the Interacting Gluon Model (IGM) to calculate diffractive mass spectra generated in hadronic collisions. We show that it is possible to treat both diffractive and non-diffractive events on the same footing, in terms of gluon-gluon collisions. A systematic analysis of available data is performed. The energy dependence of diffractive mass spectra is addressed. They show a moderate narrowing at increasing energies. Predictions for LHC energies are presented.Comment: 12 pages, latex, 14 figures (PostScript Files included); accepted for publication in Phys. Rev. D (Feb.97

Medicinal Chemistry Updates on Bacterial Efflux Pump Modulators

Antibiotic resistance is one of the most pressing health issues of our days. It can arise due to a multiplicity of factors, such as target modification, decrease in the drug uptake, changes in the metabolic pathways and activation of efflux pumps. The overexpression of efflux pumps is responsible for the extrusion of drugs, making antibiotic therapy fail, as the quantity of intracellular antibiotic is not enough to provide the desired therapeutic effect. Efflux pumps can be included in five families according to their composition, nature of substrates, energy source, and number of transmembrane spanning regions. The ABC superfamily is mainly found in Gram-positive bacteria, use ATP as an energy source, and only a limited number of ABC pumps confer multidrug resistance (MDR). On the other hand, the MFS family, most present in Gram-positive bacteria, and the RND family, characteristic of Gram-negative bacteria, are most associated with antibiotic resistance. A wide variety of inhibitors have been disclosed for both families, from either natural or synthetic sources, or even drugs that are currently in therapy for other diseases. The other two families are the SMR, which are the smallest drug efflux proteins known, and the MATE family, whose pumps can also resort to the sodium gradient as an energy source. In this review, it is intended to present a comprehensive review of the classes of efflux pump inhibitors from the various sources, highlighting their structure-activity relationships, which can be useful for medicinal chemists in the pursuit of novel efflux pump inhibitors. Copyright© Bentham Science Publishers; For any queries, please email at [email protected].[Not available

Virtual Meson Cloud of the Nucleon and Intrinsic Strangeness and Charm

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.Comment: 9 pages RevTex, 4 figure