CP-violating effects inZ decays to τ leptons

We calculate CP-odd correlations inZ decays to leptons, . These correlations are sensitive to the weak dipole moment of the . With 10⁷ producedZ particles and with observation of the decay channels and v we estimate that can be determined with an accuracy of about (1 s.d.).     

Ellipsoidal bag model for heavy quark system

The ellipsoidal bag model is used to describe heavy quark systems such asQ ,Q g andQ ² . Instead of two step model, these states are described by an uniform picture. The potential derived from the ellipsoidal bag forQ is almost equivalent to the Cornell potential. For aQ ² system with large quark pair separation, an improvement of 70 MeV is obtained comparing with the spherical bag.     

Entropy functionals of Kolmogorov-Sinai type and their limit theorems

Two functionals and are introduced forC ^*-dynamical systems with invariant states and stationary channels. It is shown that the Kolmogorov-Sinai-type theorems hold for these functionals and . Our functionals and are set within the framework of quantum information theory and generalize a quantum KS entropy by CNT and the mutual entropy by Ohya.     

Chargino-neutralino production inp\bar p-collisions for the left-right supersymmetric model

An extension of the Supersymmetric Standard Model to the supersymmetricSU(2) _L×SU(2) _R×U(1) _B–L model is considered. The gauge group contains a bidoublet and triplet Higgs field. We investigate the possibility of detecting chargino and neutralino production in -collisions atCDF, namely . A numerical analysis is performed for , tan 1 and a lower bound on the lightest supersymmetric particle (LSP) mass, GeV. Using conservative assumptions ofM _WR300 GeV andgg _Lg _R, we find the cross sections are: , and pb, and thus _L 24 _L at TeV. Cross sections are also given for larger values of the center of mass energy up to those available at the SSC. The results are compared with the prompt-lepton background of theW _{L, R} ^– decays from . Both decays for bosons show Jacobian peaks for (p _T150 GeV forM _WR) at =90°. Furthermore the chargino signature unlike the promptlepton background is symmetric under the Jacobian peak. We also exhibit the dependence of the angular distribution of the chargino on the c.m. angle forp _T40 GeV, 150 GeV at TeV.     

Four-quark states and nucleon-antinucleon annihilation within the quark model with QCD vacuum-induced interaction

The spectrum of , J^p=0⁺, 2⁺ mesons is discussed. We have shown that due to instanton-induced forces the physical states are strong mixtures of theSU _f (3) group basis states. The cross-sections for annihilation of the system into mesons are obtained. Thea ₀(980) meson is considered as meson consisting of 9 _f and 36 _f plets. The branchings are also predicted for the cross-sections for production of thea ₀(980) and tensor mesons in annihilation.     

On the purification of factor states

Let be aC*-algebra and be an opposite algebra. Notions of exact andj-positive states of are introduced. It is shown, that any factor state of can be extended to a pure exactj-positive state of . The correspondence generalizes the notion of the purifications map introduced by Powers and Størmer. The factor states ₁ and ₂ are quasi-equivalent if and only if their purifications and are equivalent.     

On the support of the Ashtekar-Lewandowski measure

We show that the Ashtekar-Isham extension of the configuration space of Yang-Mills theories is (topologically and measure-theoretically) the projective limit of a family of finite dimensional spaces associated with arbitrary finite lattices.These results are then used to prove that is contained in a zero measure subset of with respect to the diffeomorphism invariant Ashtekar-Lewandowski measure on . Much as in scalar field theory, this implies that states in the quantum theory associated with this measure can be realized as functions on the extended configuration space .     

Conformal field theories,representations and lattice constructions

An account is given of the structure and representations of chiral bosonic meromorphic conformal field theories (CFT's), and, in particular, the conditions under which such a CFT may be extended by a representation to form a new theory. This general approach is illustrated by considering the untwisted andZ ₂-twisted theories, () and respectively, which may be constructed from a suitable even Euclidean lattice . Similarly, one may construct lattices and by analogous constructions from a doubly-even binary code . In the case when is self-dual, the corresponding lattices are also. Similarly, () and are self-dual if and only if is. We show that has a natural triality structure, which induces an isomorphism and also a triality structure on . For the Golay code, is the Leech lattice, and the triality on is the symmetry which extends the natural action of (an extension of) Conway's group on this theory to the Monster, so setting triality and Frenkel, Lepowsky and Meurman's construction of the natural Monster module in a more general context. The results also serve to shed some light on the classification of self-dual CFT's. We find that of the 48 theories () and with central charge 24 that there are 39 distinct ones, and further that all 9 coincidences are accounted for by the isomorphism detailed above, induced by the existence of a doubly-even self-dual binary code.     

Fast neutrino decay and solar neutrino detectors

The neutrino decay solution of the solar neutrino problem is revisited in the context of majoron models. It is shown that for a definite range of parameters this scenario reconciles both the Homestake and the Kamiokande data. The prediction for Gallium detectors is also given. Attention is devoted to the analysis of the signal, which is the crucial prediction of this scenario. It is shown that the sensitivity of Borexino is sufficient to observe this signal and to distinguish it from the alternative signal provided by hybrid models of neutrino oscillation and magnetic moment transitions. Other sources of solar production are also reviewed (matter induced decay, MSW catalized decay or the decay of solar 17 keV neutrinos).     

Covariance algebras in field theory and statistical mechanics

Starting from aC*-algebra and a locally compact groupT of automorphisms of we construct a covariance algebra with the property that the corresponding *-representations are in one-to-one correspondence with covariant representations of i.e. *-representations of in which the automorphisms are continuously unitarily implemented. We further construct for relativistic field theory an algebra yielding the *-representations of in which the space time translations have their spectrum contained inV. The problem of denumerable occurence of superselection sectors is formulated as a condition on the spectrum of . Finally we consider the covariance algebra built with space translations alone and show its relevance for the discussion of equilibrium states in statistical mechanics, namely we restore in this framework the equivalence of uniqueness of the vacuum, irreducibility and a weak clustering property.On leave of absence from Istituto di Fisica G. Marconi — Roma.     

Precise calculation of the dynamical exponent of two-dimensional percolation

We report numerical data obtained on the special-purpose computer PERCOLA for the exponent of the electrical conductivity of 2D percolation. The extrapolation yields and a correction to the scaling exponent=1.2±0.2.     

Binary reactions in $$\bar pp$$ collisions at intermediate energies

We discuss here the binary reactions of strange and charmed particle production in collisions at intermediate energies. In the case of baryon production with only one strange or charmed quark the cross section is determined by planar diagrams withK ^*,K ^** orD ^*,D ^**-meson poles in thet-channel. We calculated these diagrams in the frame of quark-gluon string model (QGSM) proposed earlier. We obtained also the cross-sections for reactions with baryon exchange in thet-channel with and pair in the final state. Predicted cross-sections for the reactions of production are of the order of hundred nanobarns. Using reggeon calculus we estimated cross-sections of binary reactions with two or three strange quarks in the final state: and . We discuss also the possible manifestation of color transparency effects in reactions with antiprotons on nuclei where all antiproton quarks annihilate.     

Recursion method for the density of states and spectral dimension of percolation networks

We use the recursion method to calculate the vibrational density of states of site percolation clusters slightly above the percolation threshold. It is found that is proportional to at long wavelengths. At shorter length scales, is proportional to , with the fraction dimension . The cross-over from phonon to fraction regime is characterized by a rapid rise in in agreement with effective medium calculations.     

Quantum principal commutative subalgebra in the nilpotent part ofU_q \widehat{sl}_2 and lattice KdV variables

We propose a quantum lattice version of B. Feigin and E. Frenkel's constructions, identifying the KdV differential polynomials with functions on a homogeneous space under the nilpotent part of . We construct an action of the nilpotent part of on their lattice counterparts, and embed the lattice variables in a , coinduced from a quantum version of the principal commutative subalgebra, which is defined using the identification of with its dual algebra.     

B c and $$b\bar bc\bar c$$ at theZ 0-boson pole

The cross-section for the production of quarks ine ⁺ e ^– annihilation, that proves to be at a level of for is calculated within the frames of the QCD perturbation theory. The cross sections for the associated production of 1S-and 2S-wave states ofB _c-meson in the reaction were calculated in the nonrelativistic model of a heavy quarkonium. The number of _bc -hyperons to be expected at LEP is estimated on the basis of the assumption on quark-hadron duality.     

On the purification map

The investigation of purifications of factor states has been carried on. It is shown, that any factor state of aC*-algebra admits at most one purification , so one can introduce the purification map . It turns out, that the Powers and Størmer inequality is valid in this general situation.     

Mass dependent αs evolution and the light gluino existence

There is an intriguing discrepancy between values measured directly at the CERNZ ₀-factory and low-energy (at few GeV) measurements transformed toQ=M _z0 by a massless QCD evolution relation. There exists and attempt to reconcile this discrepancy by introducing a light gluinog in the MSSM. We study in detail the influence of heavy thresholds on evolution. First, we construct the exact explicit solution to the mass-dependent two-loop RG equation for the running . This solution describes heavy thresholds smoothly. Second, we use this solution to recalculate a new values corresponding to low-energy input data. Our analysis demonstrates that usingmass-dependent RG procedure generally produces corrections of two types: Asymptotic correction due to effective shift of threshold position; Local threshold correction only for the case when input experiment lies in the close vicinity of heavy particle threshold:Q _expt -M _h . Both effects result in the effective shift of the values of the order of 10^–3. However, the second one could be enhanced when the gluino mass is close to a heavy quark mass. For such a case the sum effect could be important for the discussion of the light gluino existence as it further changes theg mass.Work supported in part by INTAS-93-1180     

The microstructure of electrodeposited amorphous or microcrystalline Fe-P alloys

Dependent on is produced through electrodeposition in three modifications: microcrystalline if , amorphous if and in a mixed state containing both components if . The interpretation of results of large and small angle X-ray scattering, of measurements of the coercivity and of the mechanical density shows that the three modifications consist of two phases. The structure of the grain boundary phase in the microcrystalline alloys differs considerably from that of the amorphous phase. This arises from the dependence of the atomic volume on the average phosphorus content . The volume fraction of the crystalline component decreases with increasing up to . But even in alloys revealing X-ray patterns without any peaks coming from crystalline particles small angle X-ray scattering indicates the existence of metal-rich inclusions occupying some percent of the total volume.     

Comparative study of damage spreading in the Ising model using heat-bath,glauber, and metropolis dynamics

We study the time evolution of two configurations of the Ising model submitted to heat-bath (HB), Glauber (G), and two types of Metropolis (M and ) dynamics, analyzing the damage spreading on a square lattice. We find that the damages produced by the dynamics G and M are greater than those resulting from HB and dynamics. We also observe that, only for zero magnetic field, the damages of the dynamics G and M seem to be numerically equivalent.