William B. Kilgore

Brookhaven National Laboratory, New York City, New York, United States

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Publications (45)63.42 Total impact

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    William B. Kilgore
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    ABSTRACT: 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 $\alpha_s$. The next-to-leading (NLO) and next-to-next-to-leading order (NNLO) terms are computed in closed form, in terms of $\Gamma$-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 $(\epsilon^{1})$. 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.
    12/2013; 89(7).
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    William B. Kilgore
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    ABSTRACT: 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.
    European Physical Journal C 08/2013; 73(10). · 5.25 Impact Factor
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    William B. Kilgore
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    ABSTRACT: 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.
    Physical review D: Particles and fields 05/2012; 86(1).
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    ABSTRACT: This is a summary of the activities of the Physics at the LHC working group in the XIth Workshop on High Energy Physics Phenomenology (WHEPP-XI) held at the Physical Research Laboratory, Ahmedabad, India in January 2010. We discuss the activities of each sub-working group on physics issues at colliders such as Tevatron and Large Hadron Collider (LHC). The main issues discussed involve (1) results on W mass measurement and associated QCD uncertainties, (2) an attempt to understand the asymmetry measured at Tevatron in the top quark production, and (3) phenomenology of warped space dimension model. Keywords.Large Hadron Collider; top quark; W-mass; QCD and EW radiative corrections; extra dimensions.
    WHEEP-XI; 04/2012 · 0.56 Impact Factor
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    William B. Kilgore, Christian Sturm
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    ABSTRACT: 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.
    Physical review D: Particles and fields 07/2011;
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    William B Kilgore
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    ABSTRACT: A basic introduction to the application of QCD at hadron colliders is presented. I briefly review the phenomenological and theoretical origins of QCD, and then discuss factorization and infrared safety, parton distributions, the computation of hard scattering amplitudes and applications of perturbative QCD.
    Pramana 04/2011; 76:757-766. · 0.56 Impact Factor
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    William B. Kilgore
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    ABSTRACT: 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.
    Physical review D: Particles and fields 02/2011; 83(11).
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    William B. Kilgore
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    ABSTRACT: 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.
    12/2007;
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    ABSTRACT: The experiments at Run 2 of the Tevatron have each accumulated over 1 inverse femtobarn of high-transverse momentum data. Such a dataset allows for the first precision (i.e. comparisons between theory and experiment at the few percent level) tests of QCD at a hadron collider. While the Large Hadron Collider has been designed as a discovery machine, basic QCD analyses will still need to be performed to understand the working environment. The Tevatron-for-LHC workshop was conceived as a communication link to pass on the expertise of the Tevatron and to test new analysis ideas coming from the LHC community. The TeV4LHC QCD Working Group focussed on important aspects of QCD at hadron colliders: jet definitions, extraction and use of Parton Distribution Functions, the underlying event, Monte Carlo tunes, and diffractive physics. This report summarizes some of the results achieved during this workshop.
    11/2006;
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    ABSTRACT: This Report summarises the activities of the "SM and Higgs" working group for the Workshop "Physics at TeV Colliders", Les Houches, France, 2-20 May, 2005. On the one hand, we performed a variety of experimental and theoretical studies on standard candles (such as W, Z, and ttbar production), treating them either as proper signals of known physics, or as backgrounds to unknown physics; we also addressed issues relevant to those non-perturbative or semi-perturbative ingredients, such as Parton Density Functions and Underlying Events, whose understanding will be crucial for a proper simulation of the actual events taking place in the detectors. On the other hand, several channels for the production of the Higgs, or involving the Higgs, have been considered in some detail. The report is structured into four main parts. The first one deals with Standard Model physics, except the Higgs. A variety of arguments are treated here, from full simulation of processes constituting a background to Higgs production, to studies of uncertainties due to PDFs and to extrapolations of models for underlying events, from small-$x$ issues to electroweak corrections which may play a role in vector boson physics. The second part of the report treats Higgs physics from the point of view of the signal. In the third part, reviews are presented on the current status of multi-leg, next-to-leading order and of next-to-next-to-leading order QCD computations. Finally, the fourth part deals with the use of Monte Carlos for simulation of LHC physics. Comment: 234 pages, 173 figures. Web page of the workshop (with links to the talks): http://lappweb.in2p3.fr/conferences/LesHouches/Houches2005/
    04/2006;
  • William B. Kilgore
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    ABSTRACT: There has been great progress in Higgs physics recently. Inclusive production channels have now been computed to next‐to‐next‐to‐leading order, and many associated production channels and their backgrounds have been computed to next‐to‐leading order. We are well positioned to discover the Higgs boson at the LHC and to make crucial first measurements of the Higgs boson couplings. © 2005 American Institute of Physics
    AIP Conference Proceedings. 03/2005; 753(1):309-322.
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    William B. Kilgore
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    ABSTRACT: 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. Comment: 4 pages
    Physical Review D 03/2004; · 4.69 Impact Factor
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    Robert Harlander, William Kilgore
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    ABSTRACT: New techniques developed in connection with the NNLO corrections to the Higgs production rate at hadron colliders and some recent applications are reviewed.
    06/2003;
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    Robert V. Harlander, William B. Kilgore
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    ABSTRACT: 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. Comment: 16 pages, 10 figures. Minor changes. References Added. Journal reference added
    Physical Review D 04/2003; · 4.69 Impact Factor
  • William Kilgore, Robert Harlander
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    ABSTRACT: The search for Higgs bosons at the LHC will rely primarily on inclusive production modes. It has recently become possible to calculate inclusive production rates at next-to-next-to-leading order in perturbative QCD. I will briefly discuss the methods developed to perform these calculations and present results for both scalar and pseudoscalar Higgs boson production at Hadron colliders.
    04/2003;
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    ABSTRACT: In this paper, we analyze the high-energy limits for Higgs boson + two jet production. We consider two high-energy limits, corresponding to two dierent kinematic regions: (a) the Higgs boson is centrally located in rapidity between the two jets, and very far from either jet; (b) the Higgs boson is close to one jet in rapidity, and both of these are very far from the other jet. In both cases the amplitudes factorize into impact factors or coecient functions connected by gluons exchanged in the t channel. Accordingly, we compute the coecient function for the production of a Higgs boson from two o-shell gluons, and the impact factors for the production of a Higgs boson in association with a gluon or a quark jet. We include the full top quark mass dependence and compare this with the result obtained in the large top-mass limit.
    02/2003;
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    ABSTRACT: In this paper, we analyze the high-energy limits for Higgs boson plus two jet production. We consider two high-energy limits, corresponding to two different kinematic regions: a) the Higgs boson is centrally located in rapidity between the two jets, and very far from either jet; b) the Higgs boson is close to one jet in rapidity, and both of these are very far from the other jet. In both cases the amplitudes factorize into impact factors or coefficient functions connected by gluons exchanged in the t channel. Accordingly, we compute the coefficient function for the production of a Higgs boson from two off-shell gluons, and the impact factors for the production of a Higgs boson in association with a gluon or a quark jet. We include the full top quark mass dependence and compare this with the result obtained in the large top-mass limit. Comment: 35 pages, 6 figures
    Physical Review D 01/2003; · 4.69 Impact Factor
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    Robert Harlander, William Kilgore
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    ABSTRACT: The evaluation of the NNLO QCD corrections to the production of a scalar and a pseudo-scalar Higgs boson is described. Comment: 5+2 pages, 4 figures (9 ps-files). Talk given at RADCOR/Loops and Legs 2002, September 8-13, 2002, Kloster Banz, Germany
    Nuclear Physics B - Proceedings Supplements 11/2002; · 0.88 Impact Factor
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    W.B. Kilgore
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    ABSTRACT: 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.
    Nuclear Physics B - Proceedings Supplements 08/2002; 117:282–284. · 0.88 Impact Factor
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    Robert V. Harlander, William B. Kilgore
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    ABSTRACT: 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.
    Journal of High Energy Physics 08/2002; 10(10). · 5.62 Impact Factor

Publication Stats

1k Citations
63.42 Total Impact Points

Institutions

  • 1999–2013
    • Brookhaven National Laboratory
      • Physics Department
      New York City, New York, United States
  • 2002
    • CERN
      Genève, Geneva, Switzerland
  • 2001
    • Michigan State University
      • Department of Physics and Astronomy
      East Lansing, MI, United States
  • 1996
    • Fermi National Accelerator Laboratory (Fermilab)
      Batavia, Illinois, United States