[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 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.
[Show abstract][Hide abstract] 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.
Journal of High Energy Physics 07/2014; 2014(10). DOI:10.1007/JHEP10(2014)121 · 6.11 Impact Factor
[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 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
Physical Review D 03/2014; 90(4). DOI:10.1103/PhysRevD.90.045017 · 4.64 Impact Factor
[Show abstract][Hide abstract] 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.
The European Physical Journal Conferences 02/2014; 71. DOI:10.1051/epjconf/20147100012
[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 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. For a
supersymmetry scale greater than roughly 100 PeV, the Higgs mass is almost
independent of the supersymmetry scale and the stop mixing parameter, while the
observed value is achieved for tan beta between 1.3 and 1.8 depending on the
Journal of High Energy Physics 12/2013; 2014(5). DOI:10.1007/JHEP05(2014)113 · 6.11 Impact Factor
[Show abstract][Hide abstract] 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.
Journal of High Energy Physics 10/2013; 2014(2). DOI:10.1007/JHEP02(2014)015 · 6.11 Impact Factor
[Show abstract][Hide abstract] 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
Journal of High Energy Physics 11/2012; 2013(6). DOI:10.1007/JHEP06(2013)073 · 6.11 Impact Factor
[Show abstract][Hide abstract] 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.
International Journal of Modern Physics A 01/2012; 15(27). DOI:10.1142/S0217751X00002172 · 1.70 Impact Factor
[Show abstract][Hide abstract] 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.
[Show abstract][Hide abstract] 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.
Fortschritte der Physik 11/2011; 59(11-12). DOI:10.1002/prop.201100071 · 2.44 Impact Factor
[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 R-symmetry breaking originates entirely from a superpotential term κ3S3 and discuss the implications for the spectrum of the model.
Nuclear Physics B 10/2011; 851(3):445-461. DOI:10.1016/j.nuclphysb.2011.06.001 · 3.93 Impact Factor
[Show abstract][Hide abstract] 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.
Journal of High Energy Physics 05/2011; 8(8). DOI:10.1007/JHEP08(2011)120 · 6.11 Impact Factor
[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 R-symmetry 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.
Nuclear Physics B 03/2010; 840(1-2-840):1-28. DOI:10.1016/j.nuclphysb.2010.06.018 · 3.93 Impact Factor
[Show abstract][Hide abstract] 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.
New Journal of Physics 02/2010; 12. DOI:10.1088/1367-2630/12/7/075016 · 3.56 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We present formulae for the calculation of Dirac gaugino masses at leading
order in the supersymmetry breaking scale using the methods of analytic
continuation in superspace and demonstrate a link with kinetic mixing, even for
non-abelian gauginos. We illustrate the result through examples in field and
string theory. We discuss the possibility that the singlet superfield that
gives the U(1) gaugino a Dirac mass may be a modulus, and some consequences of
the D-term coupling to the scalar component. We give examples of possible
effects in colliders and astroparticle experiments if the modulus scalar
constitutes decaying dark matter.
Nuclear Physics B 08/2009; 830(1-830):315-329. DOI:10.1016/j.nuclphysb.2010.01.003 · 3.93 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We consider the minimal supersymmetric extension of the Standard Model allowing both Dirac and Majorana gauginos. The Dirac masses are obtained by pairing up extra chiral multiplets: a singlet S for U(1)_Y, a triplet T for SU(2) and an octet O for SU(3) with the respective gauginos. The electroweak symmetry breaking sector is modified by the couplings of the new fields S and T to the Higgs doublets. We discuss two limits: i) both the adjoint scalars are decoupled with the main effect being the modification of the Higgs quartic coupling; ii) the singlet remaining light, and due to its direct coupling to sfermions, providing a new contribution to the soft masses and inducing new decay/production channels. We discuss the LSP in this scenario; after mentioning the possibility that it may be a Dirac gravitino, we focus on the case where it is identified with the lightest neutralino, and exhibit particular values of the parameter space where the relic density is in agreement with WMAP data. This is illustrated for different scenarios where the LSP is either a bino (in which case it can be a Dirac fermion) or bino-higgsino/wino mixtures. We also point out in each case the peculiarity of the model with respect to dark matter detection experiments. Comment: 43 pages, 5 figures; one reference added. Corresponds to published version in JCAP
Journal of Cosmology and Astroparticle Physics 05/2009; 2009(08). DOI:10.1088/1475-7516/2009/08/027 · 5.81 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We extend the formulation by Meade, Seiberg and Shih of general gauge mediation of supersymmetry breaking to include Dirac masses for the gauginos. These appear through mixing of the visible sector gauginos with additional states in adjoint representations. We illustrate the method by reproducing the existing results in the literature for the gaugino and sfermion masses when preserving R-symmetry. We then explain how the generation of same sign masses for the two propagating degrees of freedom in the adjoint scalars can be achieved. We end by commenting on the use of the formalism for describing U(1) mixing.
Nuclear Physics B 11/2008; 816(1-816):185-203. DOI:10.1016/j.nuclphysb.2009.03.002 · 3.93 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We compute the two-point functions for chiral matter states in toroidal intersecting D6-brane models. In particular, we provide the techniques to calculate Moebius strip diagrams including the worldsheet instanton contribution.
Nuclear Physics B 06/2008; 805(1-2). DOI:10.1016/j.nuclphysb.2008.07.013 · 3.93 Impact Factor