A. S. Cornell

Institute for Theoretical and Experimental Physics, Moskva, Moscow, Russia

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Publications (70)233.16 Total impact

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    ABSTRACT: The measurement of the triple Higgs boson coupling is one of the most important goals of the Higgs physics program in present and future collider experiments. This would provide the first direct information on the Higgs potential, which is responsible for electroweak symmetry breaking mechanism. We present a double Higgs production scenario at the Large Hadron-Electron Collider (LHeC) and Future Circular Hadron-Electron Collider (FCC- he) through e -p collisions, which will provide information about trilinear coupling and the possibility of probing new physics, if there is any. The LHeC will provide e - beams to collide head-on with proton beams of 7 TeV from the Large Hadron Collider (LHC). The prospect of replacing the LHC with the high energy FCC, with proton beams of 50 TeV, is used for FCC-he studies. Energy of the e - is taken to be 60 GeV for both LHeC and FCC-he. Effects of non-standard CP-even and CP-odd couplings for hhh, hWW and hhWW have been studied and constrained at a 95% C.L.
    Journal of Physics Conference Series 06/2015; 623(1). DOI:10.1088/1742-6596/623/1/012017
  • Ammar Abdalgabar, A. S. Cornell
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    ABSTRACT: The evolution equations of the gauge and Yukawa couplings are derived for the two-loop renormalisation group equations in a five-dimensional SM compactified on a $S^1/Z_2$ to yield standard four space-time dimensions. Different possibilities can be discussed, however, we shall consider the limiting case in which all matter fields are localised on the brane. We will compare our two-loop results to the results found at one-loop level, and investigate the evolution of $\sin^2 \theta_W$ in this scenario also.
    Discovery Physics at the LHC, Kruger National Park- South Africa; 06/2015
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    Ammar Abdalgabar, Alan S. Cornell
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    ABSTRACT: The possibility of generating a large trilinear $A_t$ soft supersymmetry breaking coupling at low energies through renormalisation group evolution in the 5D MSSM is investigated. Using the power law running in five dimensions and a compactification scale in the 10-$10^3$ TeV range, to show that gluino mass may drive a large enough $A_t$ to reproduce the measured Higgs mass and have a light stop superpartner below $\sim 1$ TeV as preferred by the fine tuning argument for the Higgs mass.
    High Energy Particle Physics Workshop, Johannesburg; 06/2015
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    ABSTRACT: We attempt a simultaneous fit of the excess in Higgs boson transverse momentum distributions in the $\gamma\gamma$ and $ZZ^*$ decay channels as well as certain excesses in the search for di-Higgs boson resonances observed with Run I data at the Large Hadron Collider. An answer is found in a scenario with a heavy scalar with mass in the range $275-285$~GeV, together with a scalar dark matter candidate with mass around $55-60$~GeV. This is consistent with all cosmological and direct dark matter search constraints, as well as the limit on the invisible decay width of the observed Higgs boson. In this scenario the producion of the heavy scalar in association with single top quark is not suppressed, compared to that of the Higgs boson. It is also important to look out for Higgs boson production in association with intermediate missing transverse energy. Another consequence is the possible decay of the heavy scalar into $VV$, where $V=Z$ and $W^{\pm}$.
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    ABSTRACT: We explore unification and natural supersymmetry in a five dimensional extension of the standard model in which the extra dimension may be large, of the order of 1-10 TeV. Power law running generates a TeV scale A_ term allowing for the observed 125 GeV Higgs and allowing for stop masses below 2 TeV, compatible with a natural SUSY spectrum. We supply the full one-loop RGEs for various models and use metastability to give a prediction that the gluino mass should be lighter than 3.5 TeV for A_t <= 2.5 TeV, for such a compactification scale, with brane localised 3rd generation matter. We discuss why models in which the 1st and 2nd generation of matter fields are located in the bulk are likely to be ruled out. We also look at electroweak symmetry breaking in these models.
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    ABSTRACT: The analysis of gravitino fields in curved spacetimes is usually carried out using the Newman-Penrose formalism. In this paper we consider a more direct approach with eigenspinor-vectors on spheres, to separate out the angular parts of the fields in a Schwarzschild background. The radial equations of the corresponding gauge invariant variable obtained are shown to be the same as in the Newman-Penrose formalism. These equations are then applied to the evaluation of the quasinormal mode frequencies, as well as the absorption probabilities of the gravitino field scattering in this background.
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    ABSTRACT: The study of Higgs production in e + e − collisions presents us with an avenue for studying Higgs to W W coupling in the t-channel. Our understanding of the tensor structure of the Higgs boson is furthered by learning the phenomenology of how it couples to the W W pair in these reactions. This can be done by applying effective coupling strength constants to an effective Lagrangian as beyond standard model (BSM) terms and performing Monte Carlo studies with these terms present. The investigation includes a two dimensional analysis of the polar angle and the Higgs boson momentum, such that the correlation between these variables can lead to enhanced sensitivity to new dynamics. We also present an energy scan of cross sections for the processes. A likelihood analysis is performed to show that an electron positron collider operating with an integrated luminosity of 5fb −1 would be enough to fully realise an admixture of BSM effects. 1. Introduction With the July 2012 discovery of what appears to be the Higgs boson [1, 2], we now have a great opportunity to further our knowledge of the particle. We do know that the particle which was discovered resembles the Higgs boson described by the standard model (SM), but a large amount of research is being conducted with the goal of searching for signatures associated with it which can only be described by physics beyond the standard model (BSM). The Large Hadron Collider (LHC) is the only active provider of data and information pertaining to Higgs production, but we cannot expect it to provide an answer to all of the questions which the scientific community can pose about the Higgs boson. This is why a thorough study of e + e − collisions is vital if we wish to find BSM physics intrinsic to Higgs production. Since e + e − collisions are seldom used to study Higgs production in general, it is necessary to first try and evaluate what BSM effects such a collider can produce. In this study, we do this by computationally modelling the channels in e + e − which are involved in Higgs production, namely the t-channel and s-channel, incorporated with BSM parameters. Once the hypotheses are created, a likelihood analysis is used to determine the luminosity which an e + e − collider should have in order to comfortably detect BSM effects experimentally.
    The 59th Annual Conference of the South African Institute of Physics, Johannesburg, South Africa; 01/2015
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    ABSTRACT: The signature produced by the Standard Model Higgs boson in the Vector Boson Fusion (VBF) mechanism is usually pinpointed by requiring two well separated hadronic jets, one of which (at least) of them tends to be in the forward direction. With the increase of instantaneous luminosity at the LHC, the isolation of the Higgs boson produced with the VBF mechanism is rendered more challenging. In this paper the feasibility of single jet tagging is explored in a high-luminosity scenario. It is demonstrated that the separation in rapidity between the tagging jet and the Higgs boson can be effectively used to isolate the VBF signal. This variable is robust from the experimental and QCD stand points. Single jet tagging allows us to probe the spin-CP quantum numbers of the Higgs boson.
    Physical Review D 12/2014; 91(5). DOI:10.1103/PhysRevD.91.053009 · 4.86 Impact Factor
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    Ammar. Abdalgabar, A. S. Cornell
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    ABSTRACT: The evolution equations of the Yukawa couplings and quark mixings are performed for the one-loop renormalisation group equations in six-dimensional models compactified in different possible ways to yield standard four space-time dimensions. Different possibilities for the matter fields are discussed, that is where they are in the bulk or localised to the brane. These two possibilities give rise to quite similar behaviours when studying the evolution of the Yukawa couplings and mass ratios. We find that for both scenarios, valid up to the unification scale, significant corrections are observed.
    arXiv; 10/2014
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    ABSTRACT: Even if the unification and supersymmetry breaking scales are around $10^6$ to $10^{9}$ TeV, a large $A_t$ coupling may be entirely generated at low energies through RGE evolution in the 5D MSSM. Independent of the precise details of supersymmetry breaking, we take advantage of power law running in five dimensions and a compactification scale in the $10-10^3$ TeV range to show how the gluino mass may drive a large enough $A_t$ to achieve the required $125.5$ GeV Higgs mass. This also allows for sub-TeV stops, possibly observable at the LHC, and preserving GUT unification, thereby resulting in improved naturalness properties with respect to the four dimensional MSSM. The results apply also to models of "split families" in which the first and second generation matter fields are in the bulk and the third is on the boundary, which may assist in the generation of light stops whilst satisfying collider constraints on the first two generations of squarks.
    Journal of High Energy Physics 08/2014; 2014(7):1-8. DOI:10.1007/JHEP07(2014)158 · 6.22 Impact Factor
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    ABSTRACT: Even if the unification and supersymmetry breaking scales are around $10^6$ to $10^{9}$ TeV, a large $A_t$ coupling may be entirely generated at low energies through RGE evolution in the 5D MSSM. Independent of the precise details of supersymmetry breaking, we take advantage of power law running in five dimensions and a compactification scale in the $10-10^3$ TeV range to show how the gluino mass may drive a large enough $A_t$ to achieve the required $125.5$ GeV Higgs mass. This also allows for sub-TeV stops, possibly observable at the LHC, and preserving GUT unification, thereby resulting in improved naturalness properties with respect to the four dimensional MSSM. The results apply also to models of "split families" in which the first and second generation matter fields are in the bulk and the third is on the boundary, which may assist in the generation of light stops whilst satisfying collider constraints on the first two generations of squarks.
    Journal of High Energy Physics 08/2014; 1407(2015):158. · 6.22 Impact Factor
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    ABSTRACT: Two compact universal extra dimensional models are an interesting class of models for different theoretical and phenomenological issues, such as the justification of having three standard model fermion families, suppression of proton decay rate, dark matter parity from relics of the 6-dimensional Lorentz symmetry, origin of masses and mixings in the standard model. However, these theories are merely effective ones, with typically a reduced range of validity in their energy scale. We explore two limiting cases of the three standard model generations all propagating in the bulk or all localised to a brane, from the point of view of renormalisation group equation evolutions for the Higgs sector and for the neutrino sector of these models. The recent experimental results of the Higgs boson from the LHC allow, in some scenarios, stronger constraints on the cut-off scale to be placed, from the requirement of the stability of the Higgs potential.
    European Physical Journal C 05/2014; 74(2014):2893. DOI:10.1140/epjc/s10052-014-2893-4 · 5.44 Impact Factor
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    ABSTRACT: The exploration of the tensor structure of the Higgs boson interaction with pairs of weak bosons may turn out to be a useful probe into physics beyond the Standard Model. Two formulations have been used here to explore the tensor structure in an electron-positron collider. This includes the study of both the processes $e^+ e^- \to \nu\bar{\nu}H$ and $e^+ e^- \to ZH$. The investigation includes a two-dimensional analysis of the polar angle and the Higgs boson momentum, such that the correlation between these variables can lead to enhanced sensitivity to new dynamics. Since the `anomalous' couplings affect the total Higgs production rate rather significantly, a scan of the total cross section can reveal the presence of higher-dimensional operators having coefficients with substantial strength. Moreover, we emphasize that some of the gauge invariant operators also affect the triple gauge boson vertices, thus leading to variation in the $W$-pair production rate.
    Journal of High Energy Physics 05/2014; 2015(2). DOI:10.1007/JHEP02(2015)128 · 6.22 Impact Factor
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    ABSTRACT: The evolution equations of the Yukawa couplings and quark mixings are derived for the one-loop renormalization group equations in six-dimensional models, compactified in different possible ways to yield standard four space-time dimensions. Different possibilities for the matter fields are also discussed, such as the case of bulk propagating or brane localized fields. We discuss in both cases the evolution of the Yukawa couplings, the Jarlskog parameter and the Cabibbo-Kobayashi-Maskawa matrix element, and find that for both scenarios, as we run up to the unification scale, significant renormalization group corrections are present. We also discuss the results of different observables of the five-dimensional universal extra dimension model in comparison with these six-dimensional models and the model dependence of the results.
    Physical Review D 09/2013; 88(5):056006. DOI:10.1103/PhysRevD.88.056006 · 4.86 Impact Factor
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    Ammar Abdalgabar, A. S. Cornell
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    ABSTRACT: The evolution equations of the Yukawa couplings and quark mixings are derived for the one-loop renormalization group equations in the 5D Minimal Supersymmetric Standard Model on an {$S^1 / Z_2$} orbifold. Different possibilities for the matter fields are discussed such as the cases of bulk propagating or brane localised fields. We discuss in both cases the evolution of the mass ratios and the implications for the mixing angles.
    Journal of Physics Conference Series; 05/2013
  • T. M. Aliev, A. S. Cornell, Naveen Gaur
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    ABSTRACT: In the present work we study the effects of an unparticle U as the possible source of missing energy in the decay B → K(K ∗)+missing energy. We find that the dependence of the differential branching ratio on the K(K ∗)-meson’s energy in the presence of the vector unparticle operators is very distinctive from that of the SM. Moreover, in using the existing upper bound on B → K(K ∗ ) + missing energy decays, we have been able to put more stringent constraints on the parameters of unparticle stuff.
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    ABSTRACT: We review the Universal Extra-Dimensional Model compactified on a S1/Z2 orbifold, and the renormalisation group evolution of quark and lepton masses, mixing angles and phases both in the UED extension of the Standard Model and of the Minimal Supersymmetric Standard Model. We consider two typical scenarios: all matter fields propagating in the bulk, and matter fields constrained to the brane. The resulting renormalisation group evolution equations in these scenarios are compared with the existing results in the literature, together with their implications.
    Modern Physics Letters A 09/2012; 28(11). DOI:10.1142/S0217732313300073 · 1.34 Impact Factor
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    Lu-Xin Liu, A. S. Cornell
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    ABSTRACT: In this paper we study the renormalization effects of the quark flavor mixings and the Higgs self-coupling in a five-dimensional model where the boson fields are propagating in the bulk while the matter fields are localized to the brane. We first explore the evolution behaviors for the Cabibbo-Kobayashi-Maskawa matrix in this scenario. Then, in light of the recent LHC bounds on the Higgs mass, we find that the Higgs self-coupling evolution has an improved vacuum stability condition, which is in contrast with that of Standard Model and the Universal Extra Dimension scenario, where the theory has a much lower ultraviolet cutoff.
    Physical review D: Particles and fields 09/2012; 86(5). DOI:10.1103/PhysRevD.86.056002 · 4.86 Impact Factor
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    ABSTRACT: We consider a five-dimensional Minimal Supersymmetric Standard Model compactified on a S1/Z2 orbifold, and study the evolution of neutrino masses, mixing angles and phases for different values of tan beta and different radii of compactification. We consider the usual four dimensional Minimal Supersymmetric Standard Model limit plus two extra-dimensional scenarios: where all matter superfields can propagate in the bulk, and where they are constrained to the brane. We discuss in both cases the evolution of the mass spectrum, the implications for the mixing angles and the phases. We find that a large variation for the Dirac phase is possible, which makes models predicting maximal leptonic CP violation especially appealing.
    European Physical Journal Plus 06/2012; 128(1). DOI:10.1140/epjp/i2013-13006-4 · 1.48 Impact Factor
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    ABSTRACT: Leptonic decays of B-mesons are theoretically very clean probes for testing the Standard Model (SM) and possible physics beyond it. Amongst the various leptonic decays of the B-meson, the pure dileptonic decay B → ℓ+ ℓ- is very important, as this mode is helicity suppressed in the SM but can be substantially enhanced in some of the models beyond the SM, such as supersymmetric (SUSY) theories and the two Higgs doublet model (2HDM). Although the purely dileptonic decay mode is helicity suppressed in the SM its associated mode B → ℓ+ ℓ-γ does not have the same suppression, due to the presence of γ in the final state. In this paper we will also analyze the effects of enhanced Z-penguins on these two decay modes.
    International Journal of Modern Physics A 01/2012; 21(12). DOI:10.1142/S0217751X06029491 · 1.09 Impact Factor

Publication Stats

568 Citations
233.16 Total Impact Points

Institutions

  • 2014
    • Institute for Theoretical and Experimental Physics
      Moskva, Moscow, Russia
  • 2009–2014
    • University of the Witwatersrand
      • School of Physics
      Johannesburg, Gauteng, South Africa
  • 2005–2012
    • Kyoto University
      • Yukawa Institute for Theoretical Physics
      Kioto, Kyōto, Japan
  • 2003–2011
    • Korea Institute for Advanced Study
      Sŏul, Seoul, South Korea
  • 2007–2008
    • Institut de Physique Nucléaire de Lyon
      Lyons, Rhône-Alpes, France
    • University of Lyon
      Lyons, Rhône-Alpes, France
    • Claude Bernard University Lyon 1
      • Institut de physique nucléaire de Lyon (IPNL)
      Villeurbanne, Rhone-Alpes, France
  • 2000–2008
    • University of Melbourne
      • School of Physics
      Melbourne, Victoria, Australia