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R. S. Willey

Publications and source records attributed to R. S. Willey.

12 recordsLinked to original sources
arXiv2001

Nonperturbative bound on high multiplicity cross sections in phi^4_3 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.

hep-ph↗
arXiv1999

Unstable Higgs Particle and the Equivalence Theorem

We consider the subtleties involved in the application of the Equivalence Theorem to the decay of an unstable Higgs particle. This is formally justified from consideration of unitarity and resonant elastic scattering of the stable decay products. By explicit perturbative calculation we find that the imaginary parts of the one-loop amplitudes for that decay are in agreement with the Equivlence Theorem only when one includes the imaginary parts generated by evaluatuing the tree-level amplitudes at the complex on-shell value of the four-momentum squared of the unstable particle.

hep-ph↗
arXiv1998

Electroweak Parameters in the $\bar{MS}$-Scheme

We study electroweak parameters sensitive to the radiative corrections, such as $ρ$-ratio and $\hff$ decay rates in the $\ms$-scheme in the heavy $t$-quark mass limit $m_{t} \gg m_{w}$. In $\ms$-scheme the two-loop electroweak corrections $\sim m_{t}^{4}$ dominate over the QCD corrections $\sim \as m_{t}^{2}$ in the $ρ$-ratio. The relation between the on-shell coupling constants and $\ms$-parameters is found to be rather sensitive to the Higgs boson mass.

hep-ph↗
arXiv1997

Gauge Invariant Higgs 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 RG. This construction allows us to extract a reliable, gauge invariant bound on the Higgs 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 ``error'' estimate is provided between the Landau gauge fixed and the gauge invariant results.

hep-ph↗
arXiv1997

Gauge Invariant Effective Potentials and Higgs 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 mass.

hep-ph↗
arXiv1997

Gauge Dependence of Lower Bounds on the Higgs Mass Derived from Electroweak Vacuum Stability Constraints

We examine the gauge dependence of lower bounds on the Higgs 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 gauge and demonstrate that the lower bounds on the Higgs 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.

hep-ph↗
arXiv1996

MS bar Perturbation Theory and the Higgs Boson Mass

We show that MS bar perturbation theory develops tachyonic singularities for some value of the dimensional regularization scale mu unless the physical Higgs mass exceeds some (cutoff dependent) minimum value.

hep-ph↗
arXiv1995

On the Lower Bound for the Higgs Boson Mass

We provide an alternative derivation of a lower bound on the mass of the Higgs boson which is somewhat simpler and more direct than the derivation based on the effective potential. For one TeV cutoff, the result is the same. For high scale cutoff, the lower bound is increased by slightly more than the expected uncertainty of the calculation.

hep-ph↗
arXiv1994

On the scheme dependence of the Electroweak radiative corrections

We study the scheme dependence of the two-loop expression for the $ρ$-parameter of the Standard Model in the heavy $t$-quark mass limit $m_{t} \gg m_{w}$. In the $\ms$-scheme the two-loop electroweak correction to the ${\cal O}(m_{t}^{2})$ term in $\dr$ is found greater than the QCD $\as$-correction.

hep-ph↗