Theoretical Particle Physics

Beyond the Standard Model

While the Standard Model has been hugely successful in explaining most observed phenomena it is an effective theory valid only up to a certain energy scale. It also has profound unanswered questions such as: what determines the electroweak scale (the scale at which everyday particles interact) and stablizes it with respect to quantum corrections? What is the origin of the pattern of elementary particle masses and mixings? We are involved in studying candidate theories extending the Standard Model and identifying ways in which they can be tested.

Large Extra Dimensions

The large disparity between the Planck scale (the energy where gravitational interactions between elementary particles becomes relevant) and the electroweak scale has led many to suggest there may be additional spatial dimensions, where the true (higher-dimensional) Planck scale can be lowered. In particular, we are interested in warped spaces, where it is possible to explain, amongst other things, the large hierarchy of fermion masses that we observe.


Supersymmetry is the unique nontrivial extension of spacetime symmetry, and as such prescribes a symmetry between matter and forces. It also offers an explanation for both the stability and smallness of the electroweak scale and improves the unification of the three gauge forces. All this makes it a particularly compelling idea which, if relevant to the weak scale, will almost certainly be observable at the LHC. We work on many aspects of supersymmetry including the resulting flavour and CP violation as well higher-dimensional terms in the superpotential.

Composite Higgs

A viable extension of the Standard Model that explains the huge difference between the Higgs mass and the Planck scale consider the Higgs not as an elementary particle, but rather a composite state of some strongly interacting theory. We study several composite-Higgs scenarios, exploring their phenomenology at colliders, as well as their implications for cosmology or precision observables like hadron decay rates.

Related members

Xavier CalmetStephan Huber, Sebastian Jaeger, Veronica Sanz