19587032
Properties of the a1 meson from lattice QCD.
We determine the mass and decay constant of the $a_1$ meson using Monte Carlo simulation of lattice QCD. We find $M_{a_1} = 1250 \pm 80$ MeV and $f_{a_1} = 0.30 \pm 0.03 ~({\rm GeV})^2$, in good agreement with experiment.
119548610
Biased Metropolis-heat-bath algorithm for fundamental-adjoint SU(2) lattice gauge theory
For SU(2) lattice gauge theory with the fundamental-adjoint action an efficient heat-bath algorithm is not known so that one had to rely on Metropolis simulations supplemented by overrelaxation. Implementing a novel biased Metropolis-heat-bath algorithm for this model, we find improvement factors in the range 1.45 to 2.06 over conventionally optimized Metropolis simulations. If one optimizes further with respect to additional overrelaxation sweeps, the improvement factors are found in the range 1.3 to 1.8.
121063312
Search for symmetry restoration in the fundamental SU(2) Higgs model
Abstract The phase structure of the fundamental SU(2) Higgs model at finite temperature is investigated close to the zero-temperature Higgs transition by Monte Carlo methods. In the confined phase at zero temperature we find a crossover from a confined to a deconfined region that remains quite sharp on lattices of temporal extent NT = 4 even close to the Higgs transition. On asymmetric lattices the Higgs transition shifts slightly compared to the zero-temperature, symmetric lattice, giving indirect evidence for symmetry restoration at high temperature.
15338965
Infrared and ultraviolet properties of the Landau gauge quark propagator
Abstract We present a current summary of a program to study the quark propagator using lattice QCD. We use the Overlap and “Asqtad” quark actions on a number of lattice ensembles. to assess systematic errors. We comment on the place of this work amongst studies of QCD Green's functions in other formulations. A preliminary calculation of the running quark mass is presented.
14897456
Divergent chiral condensate in the quenched Schwinger model
We calculate numerically the eigenvalue distribution of the overlap Dirac operator in the quenched Schwinger model on a lattice. The distribution does not fit any of the three universality classes of spontaneous chiral-symmetry breaking, and its strong volume dependence indicates that the chiral condensate in the quenched theory is an ill-defined and divergent quantity. When we reweight configurations with the Dirac determinant to study the theory with N{sub f}=1, we obtain a distribution of eigenvalues that is well-behaved and consistent with the theory of explicit symmetry breaking due to the anomaly.
119542063
Study of chiral symmetry in quenched QCD using the overlap Dirac operator
We compute fermionic observables relevant to the study of chiral symmetry in quenched QCD using the overlap Dirac operator for a wide range of fermion mass. We use analytical results to disentangle the contribution from exact zero modes and simplify our numerical computations. Details concerning the numerical implementation of the overlap Dirac operator are presented. {copyright} {ital 1999} {ital The American Physical Society}
19721612
Evidence for muon production by particles from Cygnus X-3.
We have observed underground cosmic-ray muons, corresponding to a secondary flux of approx.7 x 10/sup -11/ cm/sup -2/ s/sup -1/, at a depth of 1800-m water equivalent, which appear to be initiated by Cygnus X-3. This identification is based on both direction and phase coherence. The existence of such secondary muons conflicts with the current understanding of photon cascades and/or the nature and location of Cygnus X-3.
45078944
Measurements of production polarization and decay asymmetry for Xi - hyperons.
42810293
Comparison of exclusive reactions at large t.
Cross sections or upper limits are reported for 12 meson-baryon and two baryon-baryon reactions for an incident momentum of 9.9 GeVc, near 90/sup 0/ c.m.: ..pi../sup +- /p..-->..p..pi../sup +- /,pp/sup +- /,..pi../sup +0//sup +- /,K/sup +/)Sigma)/sup +- /, (..lambda../sup 0/)Sigma)/sup 0/)K/sup 0/;K/sup +- /p..-->..pK/sup +- /;p/sup +- /p..-->..pp. By studying the flavor dependence of the different reactions, we have been able to isolate the quark-interchange mechanism as dominant over gluon exchange and quark-antiquark annihilation
37501749
Search for direct CP violation in nonleptonic decays of charged Xi and lambda hyperons
A search for direct CP violation in the nonleptonic decays of hyperons has been performed. In comparing the product of the decay parameters, alpha(Xi)alpha(Lambda), in terms of an asymmetry parameter, A(XiLambda), between hyperons and antihyperons in the charged Xi-->Lambdapi and Lambda-->ppi decay sequence, we found no evidence of direct CP violation. The parameter A(XiLambda) was measured to be 0.012+/-0.014.
32857126
Polarization of Xi - and Omega - hyperons produced from neutral beams.