Croatian Science Foundation Research Project


Principal Investigator (PI): Blaženka Melić, Prof. (Dr.rer.nat) - senior scientist, Rudjer Bošković Institute (RBI)

Starting date: 1.10.2014.

Ending date: 30.9.2018.

Project proposal summary

The proposed project situated in the realm of theoretical particle physics is devoted to selected investigations in the framework of the Standard Model (SM) and beyond. The proposed activities include SM calculations of pertubative and nonperturbative phenomena in Quantum Chromodynamics (QCD), theoretical and phenomenological analysis of top-quark physics and investigation of NP models by comparing with experimental data. The first results from the LHC have already provided triumphant discovery of the Higgs boson particle and considerable advances in flavour physics, all in the agreement with the SM predictions, and significant further progress is anticipated in the coming years. So far there is no compelling evidence for beyond SM physics in the quark sector, but the ongoing investigations at TeV scale could lead to the appearance of NP and a beginning of a new era.

The intellectual merit of the activities proposed here is to provide theoretical support and calculational tools necessary to fully exploit the collider physics potential, closely interacting with the Croatian experimental groups already involved in the experiments at LHC. The outlined proposal will be based on the research at two fronts: improving our understanding of the SM physics and searching for the theoretically-required evidence of New Physics (NP) beyond the Standard Model (BSM).

In high energy particle physics it is widely believed that the energy frontier experiments at LHC and the planned linear colliders, ILC and/or CLIC, together with ongoing and new experiments in neutrino and flavour physics will unravel fundamental problems in particle and astroparticle physics. A prerequisite for this progress is the complete understanding of the Standard model (SM) predictions. One of the triumphs of SM physics has been the extent to which QCD successfully describes strong interaction processes observed at colliders. More accurate QCD calculations are absolutely essential in understanding the enormous amount of available high-precision data, particularly since new physics effects are obscured by standard QCD processes. Our focus in that area will be to improve the description of hard exclusive processes by including higher-order contributions and by further developing the corresponding methods for automatic QCD calculations. Furthermore, we plan to do precision studies of top-quark production and decay observables which provide a unique view to the mechanism of electroweak symmetry breaking, important for understanding of particle mass generation. In the top-quark decay the information about its spin polarization imprinted by the production process is preserved, and can be calculated and measured in angular distributions of decay products providing other way to search for deviations from the SM expectations. Regarding new physics, the fact that neutrinos have a mass already requires an extension of the SM and calls for an understanding of the origin of neutrino masses. The seesaw mechanism, included in a theory as the one where left-right symmetry (parity) is restored at accessible LHC energies, stands out as a prominent theoretical candidate, and this theory links the origin of neutrino masses to new interactions at high energies and to the restoration of parity. A phenomenological investigation of these predictions is thus compelling and timely.


Conference attendance and talks

Organization of conferences and workshops

Defended Theses


Job openings

Particle Physics and Cosmology group at Theoretical Physics Division, Rudjer Boskovic Institute, Zagreb plans to make appointments in theoretical high energy physics for PhD and postdoc students in the context of the project Physics of Standard Model and Beyond (PhSMaB) starting in fall 2016.

Contact info

Prof. dr. Blazenka Melic, principal investigator
Head of Particle Physics and Cosmology Group
Division of Theoretical Physics
Rudjer Boskovic Institute
Zagreb, Croatia
tel: +385-1-4561033