Karim Benakli

French National Centre for Scientific Research, Lutetia Parisorum, Île-de-France, France

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Publications (68)206.78 Total impact

  • Source
    Karim Benakli · Shira Chapman · Luc Darmé · Yaron Oz
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    ABSTRACT: We use the method of characteristics to study superluminal graviton (thereof called swift graviton) propagation in theories of higher curvature gravity of the form $($Riemann$)^2$, $($Riemann$)^3$, $\nabla^2 ($Riemann$)^2$ and $($Riemann$)^4$. We consider a pp-wave background. When probed by gravitons with an appropriate polarisation, several of the gravitational theories under consideration exhibit characteristic hypersurfaces outside the flat space-time light-cone.
    Preview · Article · Dec 2015
  • Source
    Ignatios Antoniadis · Karim Benakli · Mariano Quiros
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    ABSTRACT: We present a novel mechanism of supersymmetry breaking embeddable in string theory and simultaneously sharing the main advantages of (sequestered) gravity and gauge mediation. It is driven by a Scherk-Schwarz deformation along a compact extra dimension, transverse to a D-brane stack supporting the supersymmetric extension of the Standard Model. This fixes the magnitude of the gravitino mass, together with that of the gauginos of a bulk gauge group, at a scale as high as $10^{10}$ GeV. Supersymmetry breaking is mediated to the observable sector dominantly by gauge interactions using massive messengers transforming non-trivially under the bulk and Standard Model gauge groups and leading to a neutralino LSP as dark matter candidate. The Higgsino mass $\mu$ and soft Higgs-bilinear B$\mu$-term could be generated at the same order of magnitude as the other soft terms by effective supergravity couplings as in the Giudice-Masiero mechanism.
    Preview · Article · Nov 2015
  • Karim Benakli · Luc Darmé
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    ABSTRACT: We present two distinct topics: I) We describe the propagation of a spin-3/2 state in a background which preserves invariance under space translations and rotations but not under Lorentz boost transformations. We start by building a generalisation of the Volkov-Akulov Lagrangian for a goldstino in a fluid. A super-Higgs mechanism leads to the modified Rarita-Schwinger Lagrangian describing a slow gravitino. We identify the physical propagating degrees of freedom and derive the corresponding equations of motion. This includes some new results. II) Fake Split Supersymmetry Models are proposed to alleviate some of the problems of the original Split SUSY. In particular it is no more necessary to restrict to a Mini-Split scenario as higher values of the supersymmetry breaking scale (Mega-Split) are now allowed. The FSSM relies on swapping the higgsinos for new states in identical gauge group representations but different Yukawa couplings.
    No preview · Article · Nov 2015
  • Karim Benakli · Luc Darmé · Mark D. Goodsell
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    ABSTRACT: We study two realisations of the Fake Split Supersymmetry Model (FSSM), the simplest model that can easily reproduce the experimental value of the Higgs mass for an arbitrarily high supersymmetry scale M S , as a consequence of swapping higgsinos for equivalent states, fake higgsinos, with suppressed Yukawa couplings. If the LSP is identified as the main Dark matter component, then a standard thermal history of the Universe implies upper bounds on M S , which we derive. On the other hand, we show that renormalisation group running of soft masses above M S barely constrains the model — in stark contrast to Split Supersymmetry — and hence we can have a “Mega Split” spectrum even with all of these assumptions and constraints, which include the requirements of a correct relic abundance, a gluino life-time compatible with Big Bang Nucleosynthesis and absence of signals in present direct detection experiments of inelastic dark matter. In an appendix we describe a related scenario, Fake Split Extended Supersymmetry, which enjoys similar properties.
    No preview · Article · Nov 2015 · Journal of High Energy Physics
  • Source
    Karim Benakli · Luc Darmé · Mark Goodsell
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    ABSTRACT: We study two realisations of the Fake Split Supersymmetry Model (FSSM), the simplest model that can easily reproduce the experimental value of the Higgs mass for an arbitrarily high supersymmetry scale, as a consequence of swapping higgsinos for equivalent states, fake higgsinos, with suppressed Yukawa couplings. If the LSP is identified as the main Dark matter component, then a standard thermal history of the Universe implies upper bounds on the supersymmetry scale, which we derive. On the other hand, we show that renormalisation group running of soft masses above the supersymmetry scale barely constrains the model - in stark contrast to Split Supersymmetry - and hence we can have a "Mega Split" spectrum even with all of these assumptions and constraints, which include the requirements of a correct relic abundance, a gluino life-time compatible with Big Bang Nucleosynthesis and absence of signals in present direct detection experiments of inelastic dark matter. In an appendix we describe a related scenario, Fake Split Extended Supersymmetry, which enjoys similar properties.
    Full-text · Article · Aug 2015
  • Ignatios Antoniadis · Karim Benakli

    No preview · Article · Apr 2015 · Modern Physics Letters A
  • Source
    Karim Benakli · Luc Darmé · Yaron Oz
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    ABSTRACT: When the supersymmetry breaking sector is a fluid background, Lorentz invariance is broken spontaneously. The super-Higgs mechanism leads to a gravitino Lagrangian with Lorentz symmetry violating terms. We analyse the resulting field equations and constraints. We identify the physical spin 3/2 and spin 1/2 helicity states, derive their equations of motion and construct the propagator. The violation of Lorentz symmetry implies that the longitudinal mode has a non-relativistic dispersion relation, whose speed is lower than the speed of light. We briefly comment on possible implications to gravitino cosmology and phenomenology.
    Full-text · Article · Jul 2014 · Journal of High Energy Physics
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    K. Benakli · M. Goodsell · F. Staub · W. Porod
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    ABSTRACT: We examine the possibilities for constructing models with Dirac gaugino masses and unification of gauge couplings. We identify one promising model, and discuss to what extent it can have a "natural SUSY" spectrum. We then determine the low-energy constraints upon it, and propose a constrained set of boundary conditions at the unification scale. We describe the implementation of these boundary conditions in the spectrum-generator generator \SARAH and we perform a first exploration of the parameter space, specifically searching for points where the spectrum is relatively light. It is shown that the pattern of the masses of SUSY states is very different compared to any expectations from the constrained MSSM.
    Full-text · Article · Mar 2014 · Physical Review D
  • Source
    Karim Benakli
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    ABSTRACT: We review the emergence and fate of goldstinos in different frameworks. First, we consider a super-Higgs mechanism when supersymmetry breaking is induced by neither an F-term nor a D-term but related to a more general stress energy-momentum tensor. This allows us to build a novel Lagrangian that describes the propagation of a spin-3/2 state in a fluid. Then we briefly review the ubiquitous pseudo-goldstinos when breaking supersymmetry in an extra dimension. We remind that the fermion (gravitino or gaugino) soft masses can be tuned to be of Dirac-type. Finally, we briefly connect the latter to the study of models with Dirac-type gaugino masses and stress the advantage of having both an F and a D-term sizable contributions for the hierarchies of soft-terms as well as for minimizing R-symmetry breaking.
    Preview · Article · Feb 2014 · The European Physical Journal Conferences
  • Source
    Karim Benakli · Luc Darmé · Mark D. Goodsell · Pietro Slavich
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    ABSTRACT: We consider a scenario where supersymmetry is broken at a high energy scale, out of reach of the LHC, but leaves a few fermionic states at the TeV scale. The particle content of the low-energy effective theory is similar to that of Split Supersymmetry. However, the gauginos and higgsinos are replaced by fermions carrying the same quantum numbers but having different couplings, which we call fake gauginos and fake higgsinos. We study the prediction for the light-Higgs mass in this Fake Split-SUSY Model (FSSM). We find that, in contrast to Split or High-Scale Supersymmetry, a 126 GeV Higgs boson is easily obtained even for arbitrarily high values of the supersymmetry scale M S . For M S ≳ 108 GeV, the Higgs mass is almost independent of the supersymmetry scale and the stop mixing parameter, while the observed value is achieved for tan β between 1.3 and 1.8 depending on the gluino mass.
    Full-text · Article · Dec 2013 · Journal of High Energy Physics
  • Source
    Karim Benakli · Yaron Oz · Giuseppe Policastro
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    ABSTRACT: Supersymmetry is spontaneously broken when the field theory stress-energy tensor has a non-zero vacuum expectation value. In local supersymmetric field theories the massless gravitino and goldstino combine via the super-Higgs mechanism to a massive gravitino. We study this mechanism in four-dimensional fluids, where the vacuum expectation value of the stress-energy tensor breaks spontaneously both supersymmetry and Lorentz symmetry. We consider both constant as well as space-time dependent ideal fluids. We derive a formula for the gravitino mass in terms of the fluid velocity, energy density and pressure. We discuss some of the phenomenological implications.
    Preview · Article · Oct 2013 · Journal of High Energy Physics
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    Karim Benakli · Mark D. Goodsell · Florian Staub
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    ABSTRACT: We investigate the mass, production and branching ratios of a 125 GeV Higgs in models with Dirac gaugino masses. We give a discussion of naturalness, and describe how deviations from the Standard Model in the key Higgs search channels can be simply obtained. We then perform parameter scans using a SARAH package upgrade, which produces SPheno code that calculates all relevant quantities, including electroweak precision and flavour constraint data, to a level of accuracy previously impossible for this class of models. We study three different variations on the minimal Dirac gaugino extension of the (N)MSSM.
    Full-text · Article · Nov 2012 · Journal of High Energy Physics
  • I.antoniadis · K.benakli
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    ABSTRACT: We review the status of low-scale string theories and large extra-dimensions. After an overview on different string realizations, we discuss some of the main important problems and we summarize present bounds on the size of possible extra-dimensions from collider experiments.
    No preview · Article · Jan 2012 · International Journal of Modern Physics A
  • Source
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    ABSTRACT: This proceeding is based on arXiv:1105.0591 [hep-th] where we consider breaking of supersymmetry in intersecting D-brane configurations by slight deviation of the angles from their supersymmetric values. We compute the masses generated by radiative corrections for the adjoint scalars on the brane world-volumes. In the open string channel, the string two-point function receives contributions only from the infrared limits of N~4 and N~2 supersymmetric configurations, via messengers and their Kaluza-Klein excitations, and leads at leading order to tachyonic directions.
    Full-text · Article · Jan 2012
  • Source
    Karim Benakli
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    ABSTRACT: The issue of a Majorana, Dirac or pseudo-Dirac mass for gauginos must not be reduced to a question of an extension of the Minimal Supersymmetric Standard Model by extra states, parameters and phenomenological implications. On the contrary, it is intimately related to the fundamental issue of the realization of new symmetries in nature, R-symmetries. We present here a very dense compilation of the main features of models with (pseudo-)Dirac gauginos.
    Preview · Article · Nov 2011 · Fortschritte der Physik
  • Karim Benakli · Mark D. Goodsell · Ann-Kathrin Maier
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    ABSTRACT: We consider the extension of the Minimal Supersymmetric Standard Model by Dirac masses for the gauginos. We study the possibility that the same singlet S that pairs up with the bino, to form a Dirac fermion, is used to generate μ and Bμ terms through its vacuum expectation value. For this purpose, we assume that, in the Higgs potential, the necessary R-symmetry breaking originates entirely from a superpotential term κ3S3 and discuss the implications for the spectrum of the model.
    No preview · Article · Oct 2011 · Nuclear Physics B
  • Source
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    ABSTRACT: We consider breaking of supersymmetry in intersecting D-brane configurations by slight deviation of the angles from their supersymmetric values. We compute the masses generated by radiative corrections for the adjoint scalars on the brane world-volumes. In the open string channel, the string two-point function receives contributions only from the infrared and the ultraviolet limits. The latter is due to tree-level closed string uncanceled NS-NS tadpoles, which we explicitly reproduce from the effective Born-Infeld action. On the other hand, the infrared region reproduces the one-loop mediation of supersymmetry breaking in the effective gauge theory, via messengers and their Kaluza-Klein excitations. In the toroidal set-up considered here, it receives contributions only from broken N=4 and N=2 supersymmetric configurations, and thus always leads at leading order to a tachyonic direction, in agreement with effective field theory expectations.
    Full-text · Article · May 2011 · Journal of High Energy Physics
  • Source
    Karim Benakli · Mark D. Goodsell · Ann-Kathrin Maier
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    ABSTRACT: We consider the extension of the Minimal Supersymmetric Standard Model by Dirac masses for the gauginos. We study the possibility that the same singlet that pairs up with the bino, to form a Dirac fermion, is used to generate mu and Bmu terms through its vacuum expectation value. For this purpose, we assume that, in the Higgs potential, the necessary R-symmetry breaking originates entirely from a superpotential term cubic in the singlet and discuss the implications for the spectrum of the model.
    Preview · Article · Apr 2011
  • Source
    K. Benakli · M.D. Goodsell
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    ABSTRACT: We investigate the building of models with Dirac gauginos and perturbative gauge coupling unification. Here, in contrast to the MSSM, additional fields are required for unification, and these can naturally play the role of the messengers of supersymmetry breaking. We present a framework within which such models can be constructed, including the constraints that the messenger sector must satisfy; and the renormalisation group equations for the soft parameters, which differ from those of the MSSM. For illustration, we provide the spectrum at the electroweak scale for explicit models whose gauge couplings unify at the scale predicted by heterotic strings.
    Preview · Article · Mar 2010 · Nuclear Physics B
  • Source
    Karim Benakli
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    ABSTRACT: A very large extra dimension may contain many localized branes. We discuss the possibility to formulate such models as a spin system where each spin indicates the supersymmetry direction preserved by the corresponding brane. In the evolution of the universe, the extra dimensions might have ended into a vacuum made of patches with different orientation of the spins, responsible for the observed breaking of supersymmetry. We discuss the limit where the separation of these patches is by very thin defects described as localization of gravitino masses. Comment: 15 pages, no figure. Typos corrected. References added. Version accepted for publication.
    Preview · Article · Feb 2010 · New Journal of Physics

Publication Stats

2k Citations
206.78 Total Impact Points

Institutions

  • 2008-2014
    • French National Centre for Scientific Research
      Lutetia Parisorum, Île-de-France, France
  • 2007-2009
    • Pierre and Marie Curie University - Paris 6
      Lutetia Parisorum, Île-de-France, France
  • 2002-2003
    • Université de Neuchâtel
      • Institut de physique (IPH)
      Neuenburg, Neuchâtel, Switzerland
  • 1998-2002
    • CERN
      • Physics Department (PH)
      Genève, Geneva, Switzerland
  • 1999
    • Texas A&M University
      College Station, Texas, United States
  • 1996
    • Abdus Salam International Centre for Theoretical Physics
      • Section of High Energy, Cosmology and Astroparticle Physics
      Trst, Friuli Venezia Giulia, Italy
  • 1992-1994
    • École Polytechnique
      • Centre de Physique Théorique
      Paliseau, Île-de-France, France