Publications (68)206.78 Total impact

Article: On Swift Gravitons
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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 ppwave background. When probed by gravitons with an appropriate polarisation, several of the gravitational theories under consideration exhibit characteristic hypersurfaces outside the flat spacetime lightcone.  [Show abstract] [Hide abstract]
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 ScherkSchwarz deformation along a compact extra dimension, transverse to a Dbrane 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 nontrivially under the bulk and Standard Model gauge groups and leading to a neutralino LSP as dark matter candidate. The Higgsino mass $\mu$ and soft Higgsbilinear B$\mu$term could be generated at the same order of magnitude as the other soft terms by effective supergravity couplings as in the GiudiceMasiero mechanism. 
Article: Offtrail SUSY
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ABSTRACT: We present two distinct topics: I) We describe the propagation of a spin3/2 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 VolkovAkulov Lagrangian for a goldstino in a fluid. A superHiggs mechanism leads to the modified RaritaSchwinger 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 MiniSplit scenario as higher values of the supersymmetry breaking scale (MegaSplit) are now allowed. The FSSM relies on swapping the higgsinos for new states in identical gauge group representations but different Yukawa couplings. 
Article: (O)Mega split
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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 lifetime 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.  [Show abstract] [Hide abstract]
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 lifetime 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. 
Article: Extra dimensions at LHC

Article: The Slow Gravitino
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ABSTRACT: When the supersymmetry breaking sector is a fluid background, Lorentz invariance is broken spontaneously. The superHiggs 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 nonrelativistic dispersion relation, whose speed is lower than the speed of light. We briefly comment on possible implications to gravitino cosmology and phenomenology.  [Show abstract] [Hide abstract]
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 lowenergy 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 spectrumgenerator 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.  [Show abstract] [Hide abstract]
ABSTRACT: We review the emergence and fate of goldstinos in different frameworks. First, we consider a superHiggs mechanism when supersymmetry breaking is induced by neither an Fterm nor a Dterm but related to a more general stress energymomentum tensor. This allows us to build a novel Lagrangian that describes the propagation of a spin3/2 state in a fluid. Then we briefly review the ubiquitous pseudogoldstinos when breaking supersymmetry in an extra dimension. We remind that the fermion (gravitino or gaugino) soft masses can be tuned to be of Diractype. Finally, we briefly connect the latter to the study of models with Diractype gaugino masses and stress the advantage of having both an F and a Dterm sizable contributions for the hierarchies of softterms as well as for minimizing Rsymmetry breaking.  [Show abstract] [Hide abstract]
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 lowenergy 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 lightHiggs mass in this Fake SplitSUSY Model (FSSM). We find that, in contrast to Split or HighScale 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. 
Article: The SuperHiggs Mechanism in Fluids
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ABSTRACT: Supersymmetry is spontaneously broken when the field theory stressenergy tensor has a nonzero vacuum expectation value. In local supersymmetric field theories the massless gravitino and goldstino combine via the superHiggs mechanism to a massive gravitino. We study this mechanism in fourdimensional fluids, where the vacuum expectation value of the stressenergy tensor breaks spontaneously both supersymmetry and Lorentz symmetry. We consider both constant as well as spacetime 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. 
Article: Dirac Gauginos and the 125 GeV Higgs
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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.  [Show abstract] [Hide abstract]
ABSTRACT: We review the status of lowscale string theories and large extradimensions. 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 extradimensions from collider experiments.  [Show abstract] [Hide abstract]
ABSTRACT: This proceeding is based on arXiv:1105.0591 [hepth] where we consider breaking of supersymmetry in intersecting Dbrane 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 worldvolumes. In the open string channel, the string twopoint function receives contributions only from the infrared limits of N~4 and N~2 supersymmetric configurations, via messengers and their KaluzaKlein excitations, and leads at leading order to tachyonic directions. 
Article: Dirac Gauginos: A User Manual
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ABSTRACT: The issue of a Majorana, Dirac or pseudoDirac 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, Rsymmetries. We present here a very dense compilation of the main features of models with (pseudo)Dirac gauginos.  [Show abstract] [Hide abstract]
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 Rsymmetry breaking originates entirely from a superpotential term κ3S3 and discuss the implications for the spectrum of the model.  [Show abstract] [Hide abstract]
ABSTRACT: We consider breaking of supersymmetry in intersecting Dbrane 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 worldvolumes. In the open string channel, the string twopoint function receives contributions only from the infrared and the ultraviolet limits. The latter is due to treelevel closed string uncanceled NSNS tadpoles, which we explicitly reproduce from the effective BornInfeld action. On the other hand, the infrared region reproduces the oneloop mediation of supersymmetry breaking in the effective gauge theory, via messengers and their KaluzaKlein excitations. In the toroidal setup 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.  [Show abstract] [Hide abstract]
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 Rsymmetry breaking originates entirely from a superpotential term cubic in the singlet and discuss the implications for the spectrum of the model.  [Show abstract] [Hide abstract]
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. 
Article: Disordered Extra Dimensions
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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.
Publication Stats
2k  Citations  
206.78  Total Impact Points  
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Institutions

20082014

French National Centre for Scientific Research
Lutetia Parisorum, ÎledeFrance, France


20072009

Pierre and Marie Curie University  Paris 6
Lutetia Parisorum, ÎledeFrance, France


20022003

Université de Neuchâtel
 Institut de physique (IPH)
Neuenburg, Neuchâtel, Switzerland


19982002

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


19921994

École Polytechnique
 Centre de Physique Théorique
Paliseau, ÎledeFrance, France
