R. S. Willey

Gauge dependence of lower bounds on the Higgs boson mass derived from electroweak vacuum stability constraints

We examine the gauge dependence of lower bounds on the Higgs boson mass obtained from the requirement that the electroweak vacuum be the global minimum of the effective potential. We study a simple model, the spontaneously broken Abelian Higgs model coupled to a chiral quark doublet in a two-parameter R{sub {xi},u} gauge, and demonstrate that the lower bounds on the Higgs boson mass obtained in this model are dependent on the choice of gauge parameters. We discuss the significance of this result for calculations in the standard model. {copyright} {ital 1997} {ital The American Physical Society}

Monte Carlo Simulation Calculation of Critical Coupling Constant for Continuum \phi^4_2

We perform a Monte Carlo simulation calculation of the critical coupling constant for the continuum {\lambda \over 4} \phi^4_2 theory. The critical coupling constant we obtain is [{\lambda \over \mu^2}]_crit=10.24(3).

Monte Carlo simulation calculation of critical coupling constant for continuum phi**4 in two-dimensions

We perform a Monte Carlo simulation calculation of the critical coupling constant for the continuum {\lambda \over 4} \phi^4_2 theory. The critical coupling constant we obtain is [{\lambda \over \mu^2}]_crit=10.24(3).

Gauge-invariant Higgs boson mass bounds from the physical effective potential

We study a simplified version of the standard electroweak model and introduce the concept of the physical gauge-invariant effective potential in terms of matrix elements of the Hamiltonian in physical states. This procedure allows an unambiguous identification of the symmetry breaking order parameter and the resulting effective potential as the energy in a constrained state. We explicitly compute the physical effective potential at one loop order and improve it using the renormalization group. This construction allows us to extract a reliable, gauge-invariant bound on the scalar mass by unambiguously obtaining the scale at which new physics should emerge to preclude vacuum instability. Comparison is made with popular gauge-fixing procedures and an {open_quotes}error{close_quotes} estimate is provided between the Landau gauge-fixed and the gauge-invariant results. {copyright} {ital 1997} {ital The American Physical Society}

Non-QCD contributions to heavy quark masses and sensitivity to the Higgs boson mass

We find that if the Higgs mass is close to its present experimental lower limit (100 GeV),Yukawa interactions in the quark-Higgs sector can make substantial contributions to the heavy quark MS masses.

Gauge-invariant effective potentials and Higgs boson mass bounds

The problem of defining a gauge-invariant effective potential with a strict energetic interpretation is examined in the context of spontaneously broken gauge theories. It is shown that such a potential can be defined in terms of a composite gauge-invariant order parameter in physical gauges. This effective potential is computed through one-loop order in a model with scalars and fermions coupled to an Abelian gauge theory, which serves as a simple model of the situation in electroweak theory, where vacuum stability arguments based on the scalar effective potential have been used to place lower bounds on the Higgs boson mass.

Nonperturbative bound on high multiplicity cross sections in φ 4 theory in three dimensions from lattice simulation

We have looked for evidence of large cross sections at large multiplicities in weakly coupled scalar field theory in three dimensions. We use spectral function sum rules to derive bounds on total cross sections where the sum can be expresed in terms of a quantity which can be measured by Monte Carlo simulation in Euclidean space. We find that high multiplicity cross sections remain small for energies and multiplicities for which large effects had been suggested.

Monte Carlo simulation calculation of the critical coupling constant for two-dimensional continuum {phi}{sup 4} theory

We perform a Monte Carlo simulation calculation of the critical coupling constant for the continuum {\lambda \over 4} \phi^4_2 theory. The critical coupling constant we obtain is [{\lambda \over \mu^2}]_crit=10.24(3).

Single spin asymmetries in muon pair production

Theoretical analyses of polarized leptoproduction data suggest that the polarized gluon structure function might be large, but there has been no independent measurement of this quantity. Measurements of single spin asymmetries in the production of muon pairs from the scattering of two protons, one of which is longitudinally polarized, can be interpreted in terms of polarized gluon and polarized quark structure functions. Here we compute the asymmetries for the parton subprocesses that contribute to the measured muon pair production.

On the axial vector current and PCAC in the σ-model

Abstract An explicit operator construction of the axial vector current in the boson σ model is given in perturbation theory. This current is finite and satisfies the PCAC condition with the renormalized pion field. It also (at least formally) satisfies the SU 2 × SU 2 equal-time time-component current algebra.