Mechanism of single-spin asymmetries generation in the inclusive hadron processes

We discuss a nonperturbative mechanism for generation of the single-spin asymmetries in hadron interactions. It is based on the chiral quark model combined with unitarity and impact parameter picture and provides explanation for the experimental regularities observed under the measurements of the spin asymmetries.     

Thermodynamics of constituent quarks

We investigate the thermal behavior of quarks and antiquarks interacting via a temperature-dependent linear potential. The quarks are constituent quarks with dynamically generated masses from the background linear σ model.     

The spin structure of constituent quarks

We review the theory and present status of the proton spin problem and discuss how the spin structure of constituent quarks is manifest in polarised deep inelastic scattering.     

Distributions and correlations of constituent quarks in jets

In the frame of the quark recombination model, we study the momentum distributions and correlations of constituent quarks in jets by analyzing the final state hadrons generated by PYTHIA for the hard parton fragmentation processes in vacuum. Parameterizations for the distributions are tabulated.     

Distributions and correlations of constituent quarks in jets

In the frame of the quark recombination model, we study the momentum distributions and cor- relations of constituent quarks in jets by analyzing the final state hadrons generated by PYTHIA for the hard parton fragmentation processes in vacuum. Parameterizations for the distributions are tabulated.     

Distribution of charmed constituent quarks in hadrons

By using a statistical approach within noncovariant perturbation theory, the distributions of light and charmed quarks in hadrons are derived with allowance for the charmed-quark mass. The parameters of the model are extracted from a comparison with NA3 data on the hadroproduction of J/ψ particles. A reanalysis of EMC data on charm production in muon-nucleon scattering is performed. In relation to the conventional source of charmed quarks from photon-gluon fusion, the EMC data are found to suggest the presence of an additional contribution from deep-inelastic scattering on charmed quarks at large x. The resulting admixture of Fock states that contain charmed quarks in the decomposition of the proton wave function is about 1%. The approach presented for the excitation of Fock states involving charmed quarks can also be applied to states featuring beauty quarks, as well as to the hadronic component of the virtual photon (resolved photon component).     

Spin asymmetries for large-pt jet production in two-photon processes

Relying on the hard scattering formalism we estimate cross sections and spin asymmetries for large-p_t jet production from two-photon processes in collisions of electrons and positrons of definite helicity states. We use distribution functions of polarized partons in polarized electrons obtained in a modified leading logarithmic approximation as well as spin-dependent parton cross sections according to lowest-order QCD calculations. Detecting at least one forward or backward hadronic jet, topologies of jets can be observed different from the 2 large p_t production.     

Spin-spin asymmetries in inclusive muon proton charm production

Spin-spin asymmetries have been calculated in the inclusive process \(\mu ^ + p \to \mu c\bar cX\) with reference to photon gluon events only. The resulting asymmetries are small and relatively insensitive to the exact form of the structure functions used.     

Model of a hybrid chiral bag involving constituent quarks

A three-phase modification of the hybrid quark-bag model is considered. In addition to the asymptotic-freedom and the hadronization phase, it includes the intermediate phase of constituent quarks. In the (1+1)-dimensional version of this model, a self-consistent solution is found with allowance for fermion-vacuum-polarization effects. Within this solution, the total bag energy, including the one-loop contribution from the Dirac sea, is investigated as a function of parameters that characterize bag geometry, the condition of a nonvanishing boson-condensate density in the internal region being imposed. It is shown that the ground-state bag configuration that is constructed on the basis of the solution found here, which minimizes the total energy, and which includes all three phases exists and is unique.     

The spin structure of the constituent quarks and of the nucleon

We define a constituent quark within QCD. It is shown that the spin of such a quark and hence also the spin of the nucleon is a complex phenomenon. We discuss it in view of the experimental data.Received: 31 March 2005, Revised: 13 May 2005, Published online: 28 July 2005     

From current to constituent quarks and the spin of the proton

We show in the context of an effective Lagrangian for baryons and pseudoscalar mesons how derivative couplings to Goldstone bosons modify the axial charges. Applying these considerations to constituent quarks we relate a modification of their axialU(1) charges to their internal structure which is represented here in term of a flavour singletφ ⁰ field attached to quarks. We end up with aSU (6)-type constituent quark model which describes the experimental results very well.     

Proton–proton interaction in constituent quarks model at LHC energies

In this paper we consider soft processes at LHC energies in the framework of the constituent quark model. We show that this rather naive model is able to describe all available soft process data at lower energies and to predict the behavior of the total cross section, the elastic and diffractive cross sections at LHC energy. It turns out that the “input” pomeron that has been used in this approach has parameters that are close to the so called “hard” pomeron with rather large intercept Δ≈0.12 and small value of the slope α^′ _P≈0.08 GeV^-2. We show that the elastic amplitude has a minimum at impact parameter b=0 and a maximum at b≈2 GeV^-1. Such a behavior is the result of overlapping of the parton clouds that belong to the different quarks in the hadron.     

CP asymmetries in (semi-)inclusive B^0 decays

It was recently pointed out that inclusive decays could show mixing-induced CP violation. The totally inclusive asymmetry is expected to be tiny [] because of large cancellations among the asymmetries in the charmless, single charm and double charm final states. Enriching particular final state configurations could significantly increase the CP-asymmetry and observability. Such studies can extract fundamental CKM (Cabibbo-Kobayashi-Maskawa) parameters, and (perhaps) even . A superb vertex detector could see CP violation with flavor-tagged mesons within the CKM model. Because the effects could be significantly larger due to new physics, they should be searched for in existing or soon available data samples. Received: 3 July 1998 / Published online: 22 October 1998     

Pionic transitions as tests of the connection between current and constituent quarks

A proposed connection between current and constituent quarks is discussed and tested through comparison with the magnitudes and signs of amplitudes for pionic transitions between hadrons.     

Spin forces in mesons made up of quarks of different mass

With the help of a variational method we apply the standard Coulomb + Linear potential to the analysis of mesons constructed from quarks of different mass. Fine and hyperfine splittings are discussed, with particular emphasis on their asymptotic behaviour. Striking differences in this behaviour are predicted to occur compared with the case of mesons built up from equal mass quarks, with the spin-orbit mixing force playing here a fundamental role. Such predictions may be tested within the bottom \((b\bar u)\) meson family. Our considerations are also extended to the strange and charmed mesons. Our model favours ak(O⁺) below theK ^* (1.430), and predicts a partial inversion in the ordering of theP-wave states of the charmed mesons \((c\bar u)\) .     

Size of polarization in inclusive processes

We study polarization in inclusive processes in the beam fragmentation region in the framework of a simple Regge-cut model. We obtain predictions for the dependence on the kinematic variables, and we estimate the magnitude of polarization.