J. Smith

Stony Brook University, Stony Brook, New York, United States

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Publications (76)156.45 Total impact

  • V. Ravindran, J. Smith
    01/2012;
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    ABSTRACT: We review recent theoretical progress in evaluating higher order QCD corrections to Higgs boson differential distributions at hadron–hadron colliders.
    Modern Physics Letters A 11/2011; 18(25). · 1.11 Impact Factor
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    ABSTRACT: We present the gluon-gluon and photon-gluon helicity amplitudes for color singlet and octet charmonium production in polarized and unpolarized hadron-hadron and photon-hadron collisions.
    Physical review D: Particles and fields 11/2007;
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    V. Ravindran, J. Smith
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    ABSTRACT: Threshold enhanced perturbative QCD corrections to rapidity distributions of Z and W± bosons at hadron colliders are presented using the Sudakov resummed cross sections at N3LO level. We have used renormalization group invariance and the mass factorization theorem that these hard scattering cross sections satisfy to construct the QCD amplitudes. We show that these higher order threshold QCD corrections stabilize the theoretical predictions for vector boson production at the LHC under variations of both renormalization and factorization scales.
    Physical review D: Particles and fields 01/2007; 76(11).
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    ABSTRACT: We present threshold enhanced QCD corrections to rapidity distributions of di-leptons in the Drell–Yan process and of Higgs particles in both gluon fusion and bottom quark annihilation processes using Sudakov resummed cross sections. We have used renormalisation group invariance and the mass factorisation theorem that these hard scattering cross sections satisfy as well as Sudakov resummation of QCD amplitudes. We find that these higher order threshold QCD corrections stabilise the theoretical predictions under scale variations.
    Nuclear Physics B. 09/2006;
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    ABSTRACT: We present a detailed study of the total pp cross section for scalar Higgs production to next-to-next-to-leading order in αs at LHC energies, and of the pp̄ cross section at the Tevatron, combining an implementation of the solutions of the parton evolution equations at the three-loop order with the corresponding hard scatterings, evaluated at the same perturbative order. Our solutions of the DGLAP equations are implemented directly in x-space and allow for the study of the dependence of the results on the factorization (μF) and renormalization scales (μR) typical of a given process, together with the stability of the perturbative expansion. The input sets for the parton evolutions are those given by Martin, Roberts, Stirling and Thorne and by Alekhin. Results for K-factors are also presented. The NNLO corrections can be quite sizeable at typical collider energies. The stability region of the perturbative expansion is found when μR>mH∼μF.
    European Physical Journal C 08/2006; 47(3):703-721. · 5.25 Impact Factor
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    Gouranga C. Nayak, J. Smith
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    ABSTRACT: If the fundamental Planck scale is near a TeV, then TeV scale black holes should be produced in proton-proton collisions at the LHC where \sqrt{s} = 14 TeV. As the temperature of the black holes can be ~ 1 TeV we also expect production of Higgs bosons from them via Hawking radiation. This is a different production mode for the Higgs boson, which would normally be produced via direct pQCD parton fusion processes. In this paper we compare total cross sections and transverse momentum distributions d\sigma/dp_T for Higgs production from black holes at the LHC with those from direct parton fusion processes at next-to-next-to-leading order and next-to-leading order respectively. We find that the Higgs production from black holes can be larger or smaller than the direct pQCD production depending upon the Planck mass and black hole mass. We also find that d\sigma/dp_T of Higgs production from black holes increases as a function of p_T which is in sharp contrast with the pQCD predictions where d\sigma/dp_T decreases so we suggest that the measurement of an increase in d\sigma/dp_T as p_T increases for Higgs (or any other heavy particle) production can be a useful signature for black holes at the LHC.
    Physical Review D 03/2006; · 4.69 Impact Factor
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    Gouranga C. Nayak, J. Smith
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    ABSTRACT: We study inclusive heavy quarkonium production with definite polarizations in polarized proton-proton collisions using the nonrelativistic QCD color-octet mechanism. We present results for rapidity distributions of cross sections and spin asymmetries for the production of J/Ï and Ï{sup '} with specific polarizations in polarized p-p collisions at â(s)=200 GeV and 500 GeV at the RHIC within the PHENIX detector acceptance range.
    Physical review D: Particles and fields 01/2006; 73(1):014007-014007.
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    J. Smith, W.L. van Neerven
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    ABSTRACT: In the framework of the gluon–gluon fusion process for Higgs boson production there are two different prescriptions. They are given by the exact process where the gluons couple via top-quark loops to the Higgs boson and by the approximation where the top-quark mass mt is taken to infinity. In the latter case the coupling of the gluons to the Higgs boson is described by an effective Lagrangian. Both prescriptions have been used for the 2→2 body reactions to make predictions for Higgs boson production at hadron colliders. In next-to-leading order only the effective Lagrangian approach has been used to compute the single particle inclusive distributions. The exact computation of the latter has not been done yet because the n-dimensional extensions of 2→3 processes are not calculated and the two-loop virtual corrections are still missing. To remedy this we replace wherever possible the Born cross sections in the asymptotic top-quark mass limit by their exact analogues. These cross sections appear in the soft and virtual gluon contributions to the next-to-leading order distributions. This approximation is inspired by the fact that soft-plus-virtual gluons constitute the bulk of the higher order correction. Deviations from the asymptotic top-quark mass limit are discussed.
    Nuclear Physics B 01/2005; · 4.33 Impact Factor
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    ABSTRACT: We discuss the difference between n-dimensional regularization and n-dimensional reduction for processes in QCD which have an additional mass scale. Examples are heavy flavour production in hadron-hadron collisions or on-shell photon-hadron collisions where the scale is represented by the mass $m$. Another example is electroproduction of heavy flavours where we have two mass scales given by $m$ and the virtuality of the photon $Q=\sqrt{-q^2}$. Finally we study the Drell-Yan process where the additional scale is represented by the virtuality $Q=\sqrt{q^2}$ of the vector boson ($\gamma^*, W, Z$). The difference between the two schemes is not accounted for by the usual oversubtractions. There are extra counter terms which multiply the mass scale dependent parts of the Born cross sections. In the case of the Drell-Yan process it turns out that the off-shell mass regularization agrees with n-dimensional regularization. Comment: 12 pages Latex
    European Physical Journal C 11/2004; · 5.25 Impact Factor
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    ABSTRACT: In this paper we present the complete two-loop vertex corrections to scalar and pseudo-scalar Higgs boson production for general colour factors for the gauge group SU(N) in the limit where the top quark mass gets infinite. We derive a general formula for the vertex correction which holds for conserved and non-conserved operators. For the conserved operator we take the electromagnetic vertex correction as an example whereas for the non-conserved operators we take the two vertex corrections above. Our observations for the structure of the pole terms 1/ɛ4, 1/ɛ3 and 1/ɛ2 in two loop order are the same as made earlier in the literature for electromagnetism. However, we also elucidate the origin of the second order single pole term which is equal to the second order singular part of the anomalous dimension plus a universal function which is the same for the quark and the gluon.
    Nuclear Physics B 08/2004; · 4.33 Impact Factor
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    ABSTRACT: We discuss the next-to-next-to-leading order (NNLO) corrections to the total cross section for (pseudo-) scalar Higgs boson production. The computation is carried out in the effective Lagrangian approach which emerges from the standard model by taking the limit $m_t \to \infty$ where $m_t$ denotes the mass of the top quark. Comment: 6 pages, 5 figures, 7th DESY Workshop on Elementary Particle Theory, Loop and Legs in Quantum Field Theory,Zinnowitz, Germany, April 25-30, 2004
    Nuclear Physics B - Proceedings Supplements 05/2004; · 0.88 Impact Factor
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    ABSTRACT: We present the full next-to-next-to-leading order (NNLO) corrections to the coefficient function for the polarized cross section $d \Delta\sigma/d Q$ of the Drell-Yan process. We study the effect of these corrections on the process $p+p\to l^+l^-+`X'$ at an C.M. energy $\sqrt{S}=200 GeV$. All QCD partonic subprocesses have been included provided the lepton pair is created by a virtual photon, which is a valid approximation for a lepton pair invariant mass $Q<50 GeV$. For this reaction the dominant subprocess is given by $q+\bar q\to \gamma^*+`X'$ and its higher order corrections so that it provides us with an excellent tool to measure the polarized sea-quark densities. Comment: 5 pages, 5 figures, 7th DESY Workshop on Elementary Particle Theory, Loops and Legs in Quantum Field Theory, Zinnowitz, Germany, April 25-30, 2004
    Nuclear Physics B - Proceedings Supplements 05/2004; · 0.88 Impact Factor
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    ABSTRACT: We describe the calculation of inclusive Higgs boson production at hadronic colliders at next-to-next-to-leading order (NNLO) in perturbative quantum chromodynamics. We have used the technique developed in ref. [4]. Our results agree with those published earlier in the literature.
    Pramana 03/2004; 62(3):683-686. · 0.56 Impact Factor
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    B. Field, S. Dawson, J. Smith
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    ABSTRACT: The production of the standard model Higgs boson (H) plus one jet is compared with that of the lightest scalar Higgs boson (h0) plus one jet and that of the pseudoscalar Higgs boson (A0) plus one jet. The latter particles belong to the minimal supersymmetric model. We include both top and bottom quark loops to lowest order in QCD and investigate the limits of small quark mass and infinite quark mass. We give results for both the CERN Large Hadron Collider and the Fermilab Tevatron.
    Physical review D: Particles and fields 01/2004; 69(7).
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    ABSTRACT: We present the full next-to-next-to-leading order (NNLO) coefficient functions for the polarized cross section dΔσ/dQ for the Drell–Yan process p+p→l+l−+′X′. Here ′X′ denotes any inclusive hadronic state and Q represents the invariant mass of the lepton pair. All QCD partonic subprocesses have been included provided the lepton pair is created by a virtual photon, which is a valid approximation for Q<50 GeV. Unlike the differential distribution w.r.t. transverse momentum the dominant subprocess for the integrated cross section is given by and its higher order corrections so that massive lepton pair production provides us with an excellent tool to measure the polarized anti-quark densities. Our calculations are carried out using the method of n-dimensional regularization by making a special choice for the γ5 matrix. We give predictions for double longitudinal spin asymmetry measurements at the RHIC.
    Nuclear Physics B 11/2003; · 4.33 Impact Factor
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    ABSTRACT: We review recent theoretical progress in evaluating higher order QCD corrections to Higgs boson differential distributions at hadron-hadron colliders.
    Modern Physics Letters A 07/2003; · 1.11 Impact Factor
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    ABSTRACT: We present the next-to-next-to-leading order (NNLO) corrections to the total cross section for (pseudo-) scalar Higgs boson production using an alternative method than those used in previous calculations. All QCD partonic subprocesses have been included and the computation is carried out in the effective Lagrangian approach which emerges from the standard model by taking the limit $m_t \to \infty$ where $m_t$ denotes the mass of the top quark. Our results agree with those published earlier in the literature. We estimate the theoretical uncertainties by comparing the $K$-factors and the variation with respect to the mass factorization/renormalization scales with the results obtained by lower order calculations. We also investigate the dependence of the cross section on several parton density sets provided by different groups. Further we study which part of the coefficient functions dominates the cross section. This is of interest for the resummation of large corrections which occur near the boundary of phase space. It turns out that depending on the definition of the total cross section the latter is dominated by the the soft-plus-virtual gluon corrections represented by $\delta(1-x)$ and $(\ln^i(1-x)/(1-x))_+$ terms. PACS numbers: 12.38.-t, 12.38.Bx, 13.85.-t, 14.80.Gt.
    Nuclear Physics B 02/2003; 665. · 4.33 Impact Factor
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    ABSTRACT: We have computed the full next-to-leading (NLO) QCD corrections to the differential distributions for pseudo-scalar Higgs (A) production at large hadron colliders. This calculation has been carried out using the effective Lagrangian approach which is valid as long as the mass of the pseudo-scalar Higgs boson mA and its transverse momentum pT do not exceed the top-quark mass mt. The shape of the distributions hardly differ from those obtained for scalar Higgs (H) production because, apart from the overall coupling constant and mass, there are only small differences between the partonic differential distributions for scalar and pseudo-scalar production. Therefore, there are only differences in the magnitudes of the hadronic differential distributions which can be mainly attributed to the unknown mixing angle β describing the pseudo-scalar Higgs coupling to the top quarks.
    Physics Letters B 10/2002; · 4.57 Impact Factor
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    ABSTRACT: We present the full next-to-leading order (NLO) corrected inclusive cross section $d^3\Delta \sigma/dQ^2/dy/dp_T$ for massive lepton pair production in longitudinally polarized proton-proton collisions $p + p\to l^+l^- + 'X'$. Here $'X'$ denotes any inclusive hadronic state and Q represents the invariant mass of the lepton pair which has transverse momentum p_T and rapidity y. All QCD partonic subprocesses have been included provided the lepton pair is created by a virtual photon, which is a valid approximation for $Q<50{\rm GeV}$. Like in unpolarized proton-proton scattering the dominant subprocess is given by $q(\bar q) + g \to \gamma^* + 'X'$ so that massive lepton pair production provides us with an excellent method to measure the spin density of the gluon. Our calculations are carried out using the method of n-dimensional regularization by making a special choice for the $\gamma_5$-matrix. Like in the case of many other prescriptions evanescent counter terms appear. They are determined by computing the NLO coefficient functions for $d\Delta\sigma/dQ^2$ and the polarized cross section for Higgs production using both n-dimensional regularization and a four dimensional regularization technique in which the $\gamma_5$-matrix is uniquely defined. Our calculations reveal that the non-singlet polarized coefficient function equals the unpolarized one up to a minus sign. We give predictions for double longitudinal spin asymmetry measurements at the RHIC. Comment: 56 pages, LaTeX, 20 postscript figures. We have changed the discussion of the various regularization schemes in the penultimate paragraph of section 1 and in the text between Eq. (2.17) and Eq. (2.18). Furthermore a more careful comparison between our results and those in refs. [13],[14] for the quark-anti-quark channel reveals that we have full agreement. Further some misprints like the ones occuring in Eq. (2.61) and table 1 in section 4 are corrected
    Nuclear Physics B 07/2002; · 4.33 Impact Factor

Publication Stats

3k Citations
156.45 Total Impact Points

Institutions

  • 1986–2007
    • Stony Brook University
      • Institute for Theoretical Physics (C.N. Yang)
      Stony Brook, New York, United States
  • 1990–2005
    • Leiden University
      Leyden, South Holland, Netherlands
  • 2004
    • State University of New York
      New York City, New York, United States
  • 2002–2004
    • Harish-Chandra Research Institute
      Prayāg, Uttar Pradesh, India
  • 1996
    • Deutsches Elektronen-Synchrotron
      Hamburg, Hamburg, Germany
  • 1994
    • Southern Methodist University
      • Department of Physics
      Dallas, Texas, United States
  • 1993
    • Utrecht University
      Utrecht, Utrecht, Netherlands