arXiv subjects
Publications and source records attributed to William B. Kilgore.
I discuss the contributions of the one-loop single-real-emission amplitudes, $gg\to H g$, $qg\to H q$, etc. to inclusive Higgs boson production through next-to-next-to-next-to-leading order in the strong coupling.
I compute the contributions of the one-loop single-real-emission amplitudes, $gg\to H g$, $qg\to H q$, etc., to inclusive Higgs boson production through next-to-next-to-next-to-leading order (N^3LO) in the strong coupling $α_s$. The next-to-leading (NLO) and next-to-next-to-leading order (NNLO) terms are computed in closed form, in terms of $Γ$-functions and the hypergeometric functions ${}_{2}F_{1}$ and ${}_{3}F_{2}$. I compute the \nnnlo\ terms as Laurent expansions in the dimensional regularization parameter through order $(ε^{1})$. To obtain the \nnnlo\ terms, I perform an extended threshold expansion of the phase space integrals and map the resulting coefficients onto a basis of harmonic polylogarithms.
The infrared structure of (multi-loop) scattering amplitudes is determined entirely by the identities of the external particles participating in the scattering. The two-loop infrared structure of pure \qcd\ amplitudes has been known for some time. By computing the two-loop amplitudes for $\bar{f}\,f\longrightarrow X$ and $\bar{f}\,f\longrightarrow V_1\,V_2$ scattering in an $SU(N)\times SU(M)\times U(1)$ gauge theory, I determine the anomalous dimensions which govern the infrared structure for any massless two-loop amplitude.
I describe a procedure by which one can transform scattering amplitudes computed in the four dimensional helicity scheme into properly renormalized amplitudes in the 't Hooft-Veltman scheme. I describe a new renormalization program, based upon that of the dimensional reduction scheme and explain how to remove both finite and infrared-singular contributions of the evanescent degrees of freedom to the scattering amplitude.
I apply commonly used regularization schemes to a multi-loop calculation to examine the properties of the schemes at higher orders. I find complete consistency between the conventional dimensional regularization scheme and dimensional reduction, but I find that the four dimensional helicity scheme produces incorrect results at next-to-next-to-leading order and singular results at next-to-next-to-next-to-leading order. It is not, therefore, a unitary regularization scheme.
The Drell-Yan mechanism for the production of lepton pairs is one of the most basic processes for physics studies at hadron colliders. It is therefore important to have accurate theoretical predictions. In this work we compute the two-loop virtual mixed QCD x QED corrections to Drell-Yan production. We evaluate the Feynman diagrams by decomposing the amplitudes into a set of known master integrals and their coefficients, which allows us to derive an analytical result. We also perform a detailed study of the ultraviolet and infrared structure of the two-loop amplitude and the corresponding poles in epsilon.
I describe a method for determining the coefficients of scalar integrals for one-loop amplitudes in quantum field theory. The method is based upon generalized unitarity and the behavior of amplitudes when the free parameters of the cut momenta approach infinity. The method works for arbitrary masses of both external and internal legs of the amplitudes. It therefore applies not only to QCD but also to the Electroweak theory and to quantum field theory in general.
I describe a subtraction scheme for the next-to-next-to-leading order calculation of single inclusive production at hadron colliders. Such processes include Drell-Yan, W^{+/-}, Z and Higgs Boson production. The key to such a calculation is a treatment of initial state radiation which preserves the production characteristics, such as the rapidity distribution, of the process involved. The method builds upon the Dipole Formalism and, with proper modifications, could be applied to deep inelastic scattering and e^+ e^- annihilation to hadrons.
The total cross section for Higgs production in bottom-quark annihilation is evaluated at next-to-next-to-leading order (NNLO) in QCD. This is the first time that all terms at order alpha_s^2 are taken into account. We find a greatly reduced scale dependence with respect to lower order results, for both the factorization and the renormalization scales. The behavior of the result is consistent with earlier determinations of the appropriate factorization scale for this process of mu_F ~ M_H/4, and supports the validity of the bottom parton density approach for computing the total inclusive rate. We present precise predictions for the cross section at the Tevatron and the LHC.
The production cross section for pseudo-scalar Higgs bosons at hadron colliders is computed at next-to-next-to-leading order (NNLO) in QCD. The pseudo-scalar Higgs is assumed to couple only to top quarks. The NNLO effects are evaluated using an effective lagrangian where the top quarks are integrated out. The NNLO corrections are similar in size to those found for scalar Higgs boson production.
I report on a calculation of the inclusive Higgs boson production cross section at hadron colliders at next-to-next-to-leading order in QCD. The result is computed as an expansion about the threshold region. By continuing the expansion to very high order, we map the result onto basis functions and obtain the result in closed analytic form.
Inclusive production via gluon fusion will be the most important production channel for Higgs boson discovery at the LHC. I report on a calculation of the inclusive Higgs boson production cross section at $pp$ and $p\bar p$ colliders at next-to-next-to-leading order in QCD.
The Higgs boson production cross section at pp and p\bar{p} colliders is calculated in QCD at next-to-next-to-leading order (NNLO). We find that the perturbative expansion of the production cross section is well behaved and that scale dependence is reduced relative to the NLO result. These findings give us confidence in the reliability of the prediction. We also report an error in the NNLO correction to Drell-Yan production.
We describe the contributions of virtual corrections and soft gluon emission to the inclusive Higgs boson production cross section $pp\to H + X$ computed at next-to-next-to-leading order in the heavy top quark limit. We also discuss estimates of the leading non-soft corrections.
The contributions of virtual corrections and soft gluon emission to the inclusive Higgs production cross section pp -> H + X are computed at next-to-next-to-leading order in the heavy top quark limit. We show that this part of the total cross section is well behaved in the sense of perturbative convergence, with the NNLO corrections amounting to an enhancement of the NLO cross section by \sim 5% for LHC and 10-20% for the Tevatron. We compare our results with an existing estimate of the full NNLO effects and argue that an analytic evaluation of the hard scattering contributions is needed.
We present results of a next-to-leading order calculation of three jet production at hadron colliders. This calculation will have many applications. In addition to computing such three-jet observables as spectra, mass distributions, this calculation permits the first next-to-leading order studies at hadron colliders of jet and event shape variables.
I present results of a next-to-leading order calculation of three jet production at hadron colliders. This calculation will have many applications. In addition to computing three-jet observables (spectra, mass distributions), this calculation permits the first next-to-leading order studies (at hadron colliders) of jet and event shape variables.
We present the tree-level amplitudes involving one, two and three photons that are required for next-to-leading order QCD calculations of production rates of three final-state particles. We also present the required one-loop amplitudes in terms of previously published results.