Critical Behavior of the Schwinger Model with Wilson Fermions

We present a detailed analysis, in the framework of the MFA approach, of the critical behaviour of the lattice Schwinger model with Wilson fermions on lattices up to $24^2$, through the study of the Lee-Yang zeros and the specific heat. We find compelling evidence for a critical line ending at $\kappa = 0.25$ at large $\beta$. Finite size scaling analysis on lattices $8^2,12^2,16^2, 20^2$ and $24^2$ indicates a continuous transition. The hyperscaling relation is verified in the explored $\beta$ region.Comment: 12 pages LaTeX file, 10 figures in one uuencoded compressed postscript file. Report LNF-95/049(P

An Analytic Variational Study of the Mass Spectrum in 2+1 Dimensional SU(3) Hamiltonian Lattice Gauge Theory

We calculate the masses of the lowest lying eigenstates of improved SU(2) and SU(3) lattice gauge theory in 2+1 dimensions using an analytic variational approach. The ground state is approximated by a one plaquette trial state and mass gaps are calculated in the symmetric and antisymmetric sectors by minimising over a suitable basis of rectangular states

Helicity of the W Boson in Lepton+Jets ttbar Events

We examine properties of ttbar candidates events in lepton+jets final states to establish the helicities of the W bosons in t->W+b decays. Our analysis is based on a direct calculation of a probability that each event corresponds to a ttbar final state, as a function of the helicity of the W boson. We use the 125 events/pb sample of data collected by the DO experiment during Run I of the Fermilab Tevatron collider at sqrt{s}=1.8 TeV, and obtain a longitudinal helicity fraction of F_0=0.56+/-0.31, which is consistent with the prediction of F_0=0.70 from the standard model

Hard Single Diffraction in pbarp Collisions at root-s = 630 and 1800 GeV

Using the D0 detector, we have studied events produced in proton-antiproton collisions that contain large forward regions with very little energy deposition (``rapidity gaps'') and concurrent jet production at center-of-mass energies of root-s = 630 and 1800 Gev. The fractions of forward and central jet events associated with such rapidity gaps are measured and compared to predictions from Monte Carlo models. For hard diffractive candidate events, we use the calorimeter to extract the fractional momentum loss of the scattered protons.Comment: 11 pages 4 figures. submitted to PR

Low-lying isomeric states in 169^{169}Ta

Two low-lying isomeric states in $^{169}$Ta have been identified via $^{159}$Tb($^{16}$O,6n$\gamma$)$^{169}$Ta reaction. Their half-lives are measured to be $28\pm 5$ ns for the 9/2$^{-}$ level and $17\pm 4$ ns for the 5/2$^{-}$ level by using the delayed $\gamma$-$\gamma$ coincidence method. These two isomeric states are considered to be the bandheads with 9/2$^{-}[514]$ and 1/2$^{-}[541]$ configurations respectively

Identification of Rotational Band in Doubly Odd 170^{170}Ta

High spin states in $^{170}$Ta have been studied via $^{159}$Tb($^{16}$O,5n$\gamma$)$^{170}$Ta reaction through excitation functions, K X-$\gamma$ and $\gamma$-$\gamma$-t coincidence measurements. Three rotational bands have been identified among which one coupled band and an unfavored $\Delta$I=2 E2 transition sequence are newly found in this work. The possible quasiparticle configurations of these bands are discussed