EXPERIMENTAL STUDY OF THE pi+ p ---> K+ SIGMA+ REACTION AT 12-GeV/c

title: Proportional Chamber Readout System

title: A FIVE RAY OSCILLOSCOPE FOR MEASURING PI+ MESON LIFETIME

title: FOCUSING DOUBLE ARM SPECTROMETER

title: Experimental study of gluon and sea quark polarizations (The first stage of the POLEX program at UNK)

title: Search for parity-nonconservation effects in deep-inelastic μ-N interaction
abstract: The difference of the cross sections for deep inelastic scattering of muons with average momenta 21 GeV/ c with right and left helicity at large angles, i.e., with large momentum transfer, has been measured. No statistically-significant dependence of cross sections on the longitudinal polarization of muons has been found, i.e. no parity-nonconservation effects in deep inelastic μN interaction have been observed. The magnitude of the cross-section asymmetry R = [〈σ R 〉 − 〈σ L 〉] [〈σ R 〉+ + 〈σ L 〉] may be represented as R = β 〈 Q 2 〉 = (− 4 ± 6) × 10 −3 〈 Q 2 , (GeV/ c ) 2 〉. The limitations G o ( μ ) = (+ 6 ± 10) G have been obtained for the constant G o ( μ ) of vector-axial interaction ( G o (μ) 2 ) [ μ γα(1 + γ 5 )μ] J α o (hadron, V-A).

title: Coherent mixing in three and four quark generations
abstract: New dynamical mechanism of quark mass generations and mixing is demonstrated in the examples of three and four generations. In the framework of the new mixing pattern, called the coherent mixing, the CKM elements are predicted compatible with experimental data for three generations, and are strongly constrained for four generations.

title: Dynamical regimes of the QCD string with quarks
abstract: SummaryThis a short report on the first paper (A. Dubin, A. Kaidalov and Yu.  (1993)) of a series devoted to quantum dynamics of the quark-antiquark system at large distances. Starting from the QCD Lagrangian, we derive the effective action for a massive quark and antiquark at large distances, corresponding to the minimal-area law of the Wilson loop. The path integral method is used to quantize the system and the spectrum is obtained with asymptotically linear Regge trajectories. Two dynamical regimes distinguished by the string energy-momentum distribution are found: at large orbital excitations (l≫1) the system behaves as a string and yields the Regge slope of 1/2πσ, while at smalll one obtains a potential-like regime for the relativistic or non-relativistic system. The problem of relative time is clarified. It is shown that in the valence-quark approximation one can reduce the initial four-dimensional dynamics to three dimensions.

title: Magnetic susceptibility in QCD
abstract: Magnetic susceptibility in the deconfined phase of QCD is calculated in a closed form using a recent general expression for the quark gas pressure in magnetic field. Quark selfenergies are entering the result via Polyakov line factors and ensure the total paramagnetic effect, increasing with temperature. A generalized form of magnetic susceptibility in nonzero magnetic field suitable for experimental and lattice measurements is derived, showing a good agreement with available lattice data.

title: Nucleon matrix elements and baryon masses in the Dirac orbital model
abstract: Using the expansion of the baryon wave function in a series of products of single-quark bispinors (Dirac orbitals), the nonsinglet axial and tensor charges of a nucleon are calculated. The leading term yields gA = 1.27 in good agreement with experiment. Calculation is essentially parameter-free and depends only on the strong coupling constant value αs. The importance of lower Dirac bispinor component, yielding 18% to the wave-function normalization is stressed. As a check, the baryon decupletmasses in the formalism of this model are also computed using standard values of the string tension σ and the strangequark mass ms; the results being in a good agreement with experiment.

title: Microscopic study of the string breaking in QCD
abstract: Theory of strong decays defines in addition to decay widths also the channel coupling and the mass shifts of the levels above the decay thresholds. In the standard decay models of the 3P0 type the decay vertex is taken to be a phenomenological constant γ and such a choice leads to large mass shifts of all meson levels due to real and virtual decays, the latter giving a divergent contribution. Here we show that taking the microscopic details of decay vertex into account, one obtains new string width effect coefficient, which strongly suppresses virtual decay contribution. In addition for a realistic space structure of the decay vertex of highly excited states, the decay matrix elements appear to be strongly different from those, where the constant γ is used. From our analysis also follows that so-called flattening potential can imitate the effects of intermediate decay channels.