Physics beyond the Standard Model

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Physics beyond the Standard Model deals with the theoretical problems and observational facts that are left unexplained by the current theory of the elementary particles and their interactions, the so-called Standard Model. These include the nature of dark matter, the origin of neutrino masses, the matter-antimatter asymmetry of the Universe, the origin of the electroweak scale and of the Higgs boson, the possible unification of fundamental interactions and quantum gravity. Physics beyond the Standard Model strives to give answers to these puzzles either in the framework of more fundamental theories involving new particles and interactions, or by employing effective field theory techniques to constrain the underlying new physics. Using both approaches and exploiting experimental data (high-energy collisions, cosmic rays, cosmological observations, neutrino oscillations, rare decays…), our research activities cover a wide range of topics. These include Higgs and collider physics, dark matter phenomenology, neutrino physics and baryogenesis, Grand Unification, as well as more theoretical work on effective field theories and their applications to particle physics and quantum gravity.

Research themes

Constraints on effective theories

Powerful non-perturbative constraints on effective field theories (known as “positivity bounds”) can be obtained from the requirement of unitarity, analyticity and crossing symmetry of the scattering amplitudes.  We have derived bounds on the Wilson coefficients of the operators that modify  Einstein gravity, under the assumption that the ultraviolet completion  is causal, unitary and Lorentz invariant (like e.g. string theory). We also study infrared modifications of gravity such as  ghost-free massive gravity and the galileon theory. The combination of  our theoretical bounds with experimental constraints on the graviton mass implies that ghost-free massive gravity is ruled out as a theory  capable of describing the observed gravitational phenomena.

BSM modelling

We study the effective theory  of a generic class of hidden sectors where supersymmetry is broken  together with an approximate R-symmetry at low energy. The light  spectrum contains the gravitino and the pseudo-Goldstone boson of the  R-symmetry, the R-axion. We have derived new model-independent constraints  on the R-axion decay constant for R-axion masses ranging from GeV to  TeV, which are of relevance for hadron and lepton colliders and for  B-factories.

Dark Matter

Although dark matter constitutes  26% of the total matter-energy budget  of the Universe, its nature is still unkown. There are strong hints  that it might be a new fundamental particle, not yet discovered. Our  research activities in the domain of particle dark matter are directly  related to the experimental search strategies: direct detection  (nuclear recoils in ultrapure experiments), indirect detection  (excesses in cosmic rays resulting from the annihilations of dark  matter particles) and production at colliders.  

Matter-antimatter asymmetry

One of the big unsolved  problems of particle physics and cosmology is the origin of the  matter-antimatter asymmetry of the Universe. An attractive possibility  is to generate it through the decays of heavy Majorana neutrinos - a  mechanism known as leptogenesis.  We also study variants  involving a scalar electroweak triplet instead of Majorana  neutrinos. 

Researchers involved

Permanent and emeritus researchers

Brando Bellazzini               
Stéphane Lavignac      
Marc Chemtob      
Carlos Savoy      


PhD students

Francesco Sgarlata (based at SISSA)               

Former staff members

Marco Cirelli               
Christophe Grojean      
Géraldine Servant      


Former Postdoctoral researchers

Guillermo Ballesteros               
Anibal Medina      
Bradley Kavanagh      
Filippo Sala      
Marco Taoso      

Former graduate students

Gaëlle Giesen               
Benoit Schmauch      
Andrea Vittino      


Networking, collaborations & fundings



Our weekly seminar takes place every Tuesday at 16:00.



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Postdoctoral positions are available each year in the Fall. Check this page or contact any staff member of the group.



Each member of the group can be contacted via email at 

The full postal adress of IPhT is: Institut de Physique Théorique,  CEA/Saclay, Bat 774 Orme des Merisiers, 91191 Gif-sur-Yvette Cedex, France.  

Here are directions to the IPhT.


Last update : 01/14 2019 (867)


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