Transverse momentum of charged hadrons observed in deep inelastic muon scattering

The transverse momenta of charged hadrons produced in high energy muon-proton scattering have been studied. The average squared transverse momentum 〈p²_⊥〉 shows a strong dependence on z = E_h/v characteristic of intrinsic momentum effects and a significant rise as a function of s = W². The W², q², x and z dependences of the data are compared with the predictions of a perturbative QCD model.     

The case for a quartet model of hadrons

A model of hadrons based on an underlying quartet leads to a more satisfactory picture of weak interactions than one based on a triplet. Hadrons containing the fourth type of quark may be as low as 700 MeV above their uncharmed counterparts. It is argued that charmed hadrons should be searched for in photoproduction and (under certain circumstances) in hadronic formation experiments.     

A Markoffian model for hadrons

The hadron is considered as a system consisting of other bound hadrons, the configuration state of which changes with the time. Its time development is described as a Markov process by Kolmogorov's equations. The stationary solution of Kolmogorov's equations for the Markoffian hadronic system makes it possible to calculate certain physical parameters for stable hadrons. The calculation of the magnetic moments of the proton and neutron in this model yields values which are in good agreement with the experimental data.     

A non-Abelian vortex-bond model of hadrons

It is argued for a general class of models by analyzing the internal holonomy group of the cylindrically symmetric solutions that the most general vortex-like configurations of minimal energy can always be transformed to Abelian form. The corresponding “magnetic” fluxes are defined gauge invariantly. In the case of the SU(3) local gauge group, Nambu's valency-model is recovered. The stability problem in the case of small-amplitude oscillations reduces to the analogue investigation for “truly” Abelian vortices.     

Gluon condensation and the bag model of hadrons

Migdal's scheme for gluon condensation is applied to a model where gluons are dynamically confined by coloured Higgs fields and are also subjected to ac-number colour field due to external “semiclassical” quarks. We show that, no matter how strong the external field becomes, stabilization of the gluonic ground state is guaranteed by the formation of an inhomogeneous gluon condensate. The contribution to the total energy from the condensate is computed semiclassically using a variational approximation. A physical interpretation of the results obtained is given in terms of a renormalization of the MIT bag model input parameters in particular the zero point energy coefficientZ and the bag constantB.

     

The nuclear force and a magnetic monopole model of hadrons

The two-pion exchange potential of the nuclear force is constructed from the phase shifts of the low energy πN and ππ scattering. The large difference between the potentials thus constructed from the phenomenological potentials of Hamada-Johnston and of Bryan is pointed out. It is found that this difference has the form of the attractive Van der Waals potential plus an inner repulsive core. The existence of the Van der Waals force is discussed in connection with the magnetic monopole model of hadrons.     

A new quark model for hadrons

It is suggested that quarks and leptons are composites of still more fundamental PRE-entities.     

Beyond the quark model of hadrons from lattice QCD

Lattice QCD can give direct information on OZI-violating contributions to mesons. Here we explore the contributions that split flavour singlet and non-singlet meson masses. I discuss in detail the spectrum and decays for scalar mesons (i.e. including glueball effects). I also review the status of hybrid mesons and their decays.Received: 30 September 2002, Published online: 22 October 2003PACS: 12.38.Gc Lattice QCD calculations - 12.39.Mk Glueball and nonstandard multi-quark/gluon states     

Rapidity distributions of hadrons in the HydHSD hybrid model

A multistage hybrid model intended for describing heavy-ion interactions in the energy region of the NICA collider under construction in Dubna is proposed. The model combines the initial, fast, interaction stage described by the model of hadron string dynamics (HSD) and the subsequent evolution that the expanding system formed at the first stage experiences at the second stage and which one treats on the basis of ideal hydrodynamics; after the completion of the second stage, the particles involved may still undergo rescattering (third interaction stage). The model admits three freeze-out scenarios: isochronous, isothermal, and isoenergetic. Generally, the HydHSD hybrid model developed in the present study provides fairly good agreement with available experimental data on proton rapidity spectra. It is shown that, within this hybrid model, the two-humped structure of proton rapidity distributions can be obtained either by increasing the freeze-out temperature and energy density or by more lately going over to the hydrodynamic stage. Although the proposed hybrid model reproduces rapidity spectra of protons, it is unable to describe rapidity distributions of pions, systematically underestimating their yield. It is necessary to refine the model by including viscosity effects at the hydrodynamic stage of evolution of the system and by considering in more detail the third interaction stage.     

QCD and a holographic model of hadrons

We propose a five-dimensional framework for modeling low-energy properties of QCD. In the simplest three parameter model we compute masses, decay rates and couplings of the lightest mesons. The model fits experimental data to within 10%. The framework is a holographic version of the QCD sum rules, motivated by the anti-de Sitter/conformal field theory correspondence. The model naturally incorporates properties of QCD dictated by chiral symmetry, which we demonstrate by deriving the Gell-Mann-Oakes-Renner relationship for the pion mass.     

Bag model of hadrons with massive quarks

We generalize the bag model of hadrons to include massive quarks and investigate in particular the properties of the l = 0 octet and decimet baryons with m_p = m_n = 0, m_λ = 270 MeV (obtained by fitting the decimet). The magnetic moments and weak axial vector/vector transition moments are calculated and compared with experimental data for cases in which data exists. We also speculate on the mechanism by which the remaining degeneracies in the baryons are lifted and on modifications which are necessary to construct a bag model of mesons.     

Hydrodynamical model of electron-positron annihilation into hadrons

Landau's hydrodynamical model of multiparticle production is formulated for e⁺e^? → hadrons at center-of-momentum energies 10 GeV and higher. An analytical solution to the problem of spherical expansion of a relativistic fluid is presented. When hadrons condense out at the last stage of expansion, fluid thermal motion is taken into account. We derive predictions for multiplicities, average secondary energies and inclusive single particle distributions for various secondary hadrons; these results are then compared to other models. Finally, we investigate the internal consistency of the model.     

Low-energy properties of hadrons in the relativistic quark model

The properties of light and heavy mesons, baryons and tetraquarks are discussed within a QCD-motivated relativistic quark model. The results for the mass spectra, electroweak properties and Regge trajectories of hadrons are presented.     

The mass of the muon

It is shown that a classical relativistic charged particle has an anomalous magnetic moment g=4α/3. If such a “dressed” particle with its mass m, charge e, and anomalous magnetic moment g is quantized by a generalized Dirac equation, then the wave equation predicts a second mass m_μ=m_e(3/2α+1). It is suggested that a magnetic portion of the self-energy is quantized.     

A kinematical model for quarks and hadrons

Starting from simple topological arguments due to Dirac on the classical rotational properties of extended rigid bodies, we abstract the concept of a finite-size spinor (FSS). The FSS is a concept distinct from both point spinors (e.g., electrons) and composite spinors (e.g., nuclei), and suggests a new model for baryons. The FSS offers a natural explanation of threeness for the quarks, excludes the existence of free quarks, denies the operational definition of quark spin statistics, and, moreover, leads to the dual model of hadronic interactions.Research supported in part by the National Science Foundation, the Army Research Office (Durham), and the U.S. Atomic Energy Commission.