Instantons, diquarks and non-leptonic weak decays of hyperons

This work is devoted to the study of the non-perturbative contributions in non-leptonic hyperon decays. We show that the instanton-induced 't Hooft interaction can naturally explain the Delta I=1/2 rule, by generating quark-diquark clustering inside octet baryons. We compute P-wave and S-wave amplitudes in the Instanton Liquid Model (ILM), and find good agreement with experiment. We propose a model-independent procedure to test on the lattice if the leading quark-quark attraction in the 0^+ anti-triplet channel responsible for diquark structures in hadrons is originated by the interaction generated by quasi-classical fields or it is predominantly due to other perturbative and/or confining forces.Comment: Final version to appear on PR

Parton distributions in a constituent quark scenario

A simple picture of the constituent quark as a composite system of point-like partons is used to construct the unpolarized and polarized parton distributions by a convolution between constituent quark momentum distributions and constituent quark structure functions. We achieve good agreement with experiments in the unpolarized, as well as, in the polarized case. When our results are compared with similar calculations using non-composite constituent quarks, the accord with the experiments of the present scheme is impressive. We conclude that DIS data are consistent with a low energy scenario dominated by composite constituents of the nucleon.Comment: 4 pages; latex using espcrc1.sty; 4 postscript figures; Invited talk at the Workshop ``Nucleon '99'', Frascati; Italy 7-9 June 1999. Submitted to Nuc. Phys.

Instantons, Chiral Dynamics and Hadronic Resonances

We use the Interacting Instanton Liquid Model (IILM) as a tool to study the role played by the chiral interactions in the lowest-lying vector and axial vector meson resonances. We find that narrow a1 and rho meson resonances can be generated by instanton-induced chiral forces, even in the absence of confinement. In the IILM, these hadrons are found to have masses only about 30% larger than the experimental value and small width <10-50 MeV. This result suggests that chiral interactions are very important in these systems and provide most of their mass. We explore the decaying patterns of the rho meson, in the absence of confinement. We argue that, in our model where only chiral forces are switched on, this meson decays dissociating into its quark anti-quark constituents

Generalized parton distributions of the nucleon in constituent quark models

Generalized parton distributions (GPDs) are studied at the hadronic (nonperturbative) scale within different assumptions based on a relativistic constituent quark model. In particular, by means of a meson-cloud model we investigate the role of nonperturbative antiquark degrees of freedom and the valence quark contribution. A QCD evolution of the obtained GPDs is used to add perturbative effects and to investigate the GPDs' sensitivity to the nonperturbative ingredients of the calculation at larger (experimental) scale.Comment: 4 pages, 1 figure, presented at the Baryon-04 Conference, Palaiseau (France), October 25-29, 2004. Nuclear Physics A, to be publishe

Spin force dependence of the parton distributions: the ratio F_2^n(x,Q^2)\/F_2^p(x,Q^2)

Light-front Hamiltonian dynamics is used to relate low-energy constituent quark models to deep inelastic unpolarized structure functions of the nucleon. The approach incorporates the correct Pauli principle prescription consistently and it allows a transparent investigation of the effects due to the spin-dependent SU(6)-breaking terms in the quark model Hamiltonian. Both Goldstone-boson-exchange interaction and hyperfine-potential models are discussed in a unified scheme and a detailed comparison, between the two(apparently) different potential prescriptions, is presented

Are There Diquarks in the Nucleon?

This work is devoted to the study of diquark correlations inside the nucleon. We analyze some matrix elements which encode information about the non-perturbative forces, in different color anti-triplet diquark channels. We suggest a lattice calculation to check the quark-diquark picture and clarify the role of instanton-mediated interactions. We study in detail the physical properties of the 0+ diquark, using the Random Instanton Liquid Model. We find that instanton forces are sufficiently strong to form a diquark bound-state, with a mass of ~500 MeV, which is compatible with earlier estimates. We also compute its electro-magnetic form factor and find that the diquark is a broad object, with a size comparable with that of the proton.Comment: Final version, accepted for publication on Phys. Rev.

Comparison of albuterol sulphate and base dry powder particulate deposition using the Calu-3 lung epithelial model

To effectively predict the fate of formulated inhalation compounds delivered to the lung, a model of the airway epithelium should reflect drug permeability and transport characteristics in vivo. Most cell-based system established for this purpose, study drug transport using wet models and thus do not necessarily represent in vivo conditions. Recently, air-interface models have been established that increase the relevance of in vitro transport studies to the in vivo state. The aim of our study was to elucidate the dissolution and diffusion process of deposited dry drug particulates (albuterol) after aerosolization onto the epithelial surface and compare these to conventional in vitro `glass models. Two forms of albuterol were investigated (albuterol base and albuterol sulphate), to evaluate the effects of lipophilicity and aqueous solubility on the mechanism of transport

Light Hadron Spectrum in the Instanton Liquid Model

We review our recent study of the role played by the chiral interactions induced by instantons, in the lowest-lying sector of the light hadron spectrum. We discuss how the ordering of the lowest meson and baryon excitations is explained by the structure of the instanton-induced quark-quark and gluon-gluon interaction. We focus on the pion, nucleon, vector- and axial-vector mesons, and on the scalar glueball. We find that all these hadrons are bound in this model and have realistic masses.Comment: 8 pages, talk given at "Hadron 07", XII International Conference on Hadron Spectroscopy, Frascati, October 8-13, 200