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Physics beyond the Standard Model

Physics beyond the Standard Model refers to the search for a phenomenologically consistent theoretical framework providing a first-principle explanation of the known properties and deficiencies of the Standard Model being a low-energy effective field theory limit of a more fundamental ultraviolet-complete theory. Currently the group consists of two seniors: Roman Pasechnik and Johan Rathsman.

Despite the tremendous success of the Standard Model, there is an overwhelming phenomenological evidence that strongly suggests the need for a more complete theory. For instance, the existence of dark matter, evident from astrophysical measurements, such as galactic rotation curves, is becoming increasingly favoured by a particle physics interpretation that the Standard Model cannot offer. While the properties of the Standard Model are remarkably well measured in particle physics experiments, a firmly established first-principle explanation for its peculiar flavour and gauge structures is still missing. Among other open theoretical questions, the origin of the observed baryon asymmetry in the Universe is not explained within the Standard Model due to a lack of sufficient charge-parity violation and strong cosmological first-order phase transitions. A key theoretical challenge is to build a consistent and predictive framework where the above questions would find their natural explanation.

We have the privilege to live in an era when the amount of phenomenological information coming from various measurements is unprecedented. Direct searches for new particles in collider experiments such as the Large Hadron Collider (LHC) has not yet revealed the presence of New Physics at the TeV energy frontier but we are still far from exhausting all possible channels and signatures, and this work in ongoing. Besides, recently reported anomalies in the muon magnetic moment (g-2) and in flavour physics measurements at LHCb remain possible windows into New Physics. In a not too distant future, such multipurpose underground experiments as DUNE, Hyper-Kamiokande and JUNO will probe the fundamental properties of the elusive neutrino particles, as well as challenge the existing bounds on the proton lifetime crucial for verification of the Grand Unification paradigm. Last but not least, the recent Nobel-prize winning observation of gravitational waves has opened up a new era of gravitational-wave astronomy and, more generally, fundamental physics explorations. A potential observation of primordial gravitational waves may indicate possible New Physics beyond the Standard Model. Indeed, such an observation may become a novel probe for New Physics complementary to traditional collider and astro-particle physics measurements.  

Model building

This research direction pursues the following main aims:

  • To construct and explore theoretically and phenomenologically consistent scenarios for New Physics capable of addressing some of the basic deficiencies of the Standard Model;
  • To build a bridge between testable New Physics models and an ultraviolet-complete theory candidate (such as the Grand Unified theory framework) that potentially offers a first-principles explanation for the common origin of the gauge interactions and the flavour structure of the SM;
  • To explore fundamental aspects of strongly-coupled field theories and compositeness models and their theoretical and phenomenological implications. 

Collider phenomenology of New Physics

Here, the basic goals of our research are:

  • To study some of the most pronounced expected New Physics signatures potentially emerging due to possible modifications of the Higgs boson interactions, as well as due to possible presence of new scalars, vector-like fermions and vector bosons in observables that can be measured at the LHC and future colliders;
  • To develop efficient and comprehensive computational tools that enable to explore large parameter spaces in typical extensions of the Standard Model, to set constraints on the model parameters and to analyse the emergent New Physics signatures at the current and future measurements.

Phase transitions and gravitational waves

Our research here goes along the following pathways:

  • To improve our understanding of the dynamics of cosmological phase transitions in the early Universe in multi-scalar models;
  • To explore key phenomenological implications of New Physics scenarios by combining the searches for beyond the Standard Model signatures at collider experiments and at future gravitational-wave detectors.