Theoretical Physics at the Energy Frontier
The modeling of the fundamental interactions that control the quantum-relativistic behavior of matter requires the determination of properties such as mass, spin, and charge of each elementary particle, through effects that manifest themselves in high-energy collisions and decays, both controlled, as occurs in collision events at accelerators such as the Large Hadron Collider at CERN, and in spontaneous reactions, such as the scattering of cosmic rays in the atmosphere and radioactive decays, or other astrophysical and cosmological phenomena. The Standard Model (SM) of Elementary Particles describes these interactions through gauge theories, controlled by symmetries related to the conservation of properties that are not altered during collision and decay processes. The SM describes the behavior of elementary particles known so far, but it is considered to be an incomplete theory, unsuitable to describe phenomena in which Gravity shows its effects. Scattering amplitudes and cross sections represent the contact between Quantum Field Theory (QFT) and the reality emerging from experimental verifications, and constitute the ideal “theoretical laboratory” for the study of fundamental interactions through the direct production of real particles or the indirect determination of their virtual effects. Precision verifications and measurements, and the study of conserved or violated quantities, are therefore crucial to detect signals of New Physics that push the limits of our knowledge beyond the confines of the SM (Beyond Standard Model, BSM). Combining quantum field theory (QFT), effective theories (EFT), mathematics, and scientific computing, our group works on the development and application of advanced models and methods for the calculation of scattering amplitudes and cross sections for both SM and BSM processes, and on the relations between scattering properties in gauge theories, effective theories, and classical and quantum gravity, relevant to Particle Physics and Gravitational Wave Physics.
Staff
Full Professors: Pierpaolo Mastrolia, Fabio Zwirner
Associate Professors: Ramona Groeber
Assistant Professors: Manoj K. Mandal
Post-doc
Wojciech Flieger Stefano Laporta
PhD students
Giacomo Brunello, Giulio E. Crisanti, Stefano Di Noi, Sid Oliver Smith, Konstantin Schmid
External collaborators
Massimo Passera (INFN), Luca Vecchi (INFN)
Research activities
Higgs boson Physics
The Higgs boson has been the subject of research for decades. Its existence was experimentally confirmed in 2012 by the LHC at CERN. This discovery marked a turning point in the understanding of the Standard Model, confirming theoretical predictions made more than half a century earlier. From a theoretical point of view, the comparison with experimental data requires precise predictions that often require new methods and the development of new Monte Carlo programs. Several properties of the Higgs boson, such as couplings to light quarks or Higgs self-couplings, have not yet been measured precisely. Therefore, in this activity we propose the development of new strategies to measure these properties more accurately.
Contacts: Ramona Groeber
Effective Field Theories
Description: Effective field theory (EFT) is a powerful tool in theoretical physics, ideal for exploring fundamental interactions within the Standard Model and beyond. In the context of the Standard Model EFT (SMEFT) and the Higgs EFT (HEFT), a formal framework is developed that allows the effects of new physics at higher energy scales to be included in a systematic way, even when this new physics cannot be directly observed. Such theories are fundamental for interpreting data from high-energy experiments. This line of research is devoted to the development of theoretical methodologies and the creation of practical programs that facilitate the interpretation of experimental data through the use of effective field theory operators.
Contacts: Ramona Groeber
Anomalous Magnetic Moment of Muon and Electron
The determination of the electron and muon magnetic moments are fundamental tests of the Standard Model (SM). Regarding the former, our group is active in the determination of QED contributions at higher perturbative orders, which require the calculation of Feynman diagrams beyond 4 loops. Regarding the latter, there is a long-standing discrepancy between the experimental value and the theoretical prediction, due to the limitations on the knowledge of hadronic corrections. The MUonE experiment at CERN proposes to measure the effective electromagnetic coupling by elastically scattering high-energy muons on atomic electrons, from which the hadronic contribution is extracted by subtracting the leptonic contributions, which therefore must be calculated with extreme theoretical precision. Our group aims to provide the theoretical support, essential for the success of the MUonE experiment, with the calculation of 2- and 3-loop scattering amplitudes.
Contacts: Massimo Passera, Ramona Groeber, Stefano Laporta, Pierpaolo Mastrolia
Scattering Amplitudes in Particle Physics
Scattering amplitudes and their related cross sections represent the interface between Quantum Field Theory (QFT) and experimental verification, and constitute the ideal “theoretical laboratory” for the study of fundamental interactions through the direct production of real particles or the indirect determination of their virtual effects. Our group is active in the study and calculation of scattering amplitudes relevant to Higgs boson physics, top quark physics, and, in general, to particle production in the Standard Model, with particular emphasis on QED and QCD corrections. This line of research requires the development and application of advanced computational techniques for Feynman integrals, where techniques based on integration by parts identities, differential equations and finite difference equations are combined with on-shell methods and techniques based on generalized unitarity, and integrand decomposition.
Contacts: Pierpaolo Mastrolia, Stefano Laporta, Manoj K. Mandal
Scattering Amplitudes in Astrophysics and Cosmology
The formalism for the computation of scattering amplitudes, introduced in Quantum Field Theory (QFT), can be combined with the approach of Effective Field Theories (EFT) and applied also to the computation of observables in General Relativity. Our group contributes to the development and application of computational methods based on Feynman integrals for the evaluation of Post-Newtonian and Post-Minkowskian corrections to the gravitational potential of coalescing binary systems, formed by black holes and neutron stars, relevant for Gravitational Wave Physics. In recent projects we have extended the scope of our techniques also to the study of correlation functions in Cosmology.
Contacts: Manoj K. Mandal, Pierpaolo Mastrolia, Stefano Laporta
Effective Field Theories and Scattering Amplitudes
Scattering Amplitudes methods have been proven to provide a powerful tool to study the renormalization group flow of gauge theories. We plan to elaborate on the application of these methods to the renormalization of Effective Field Theories relevant to particle physics. In particular, this study will provide a valuable mean to interpret experimental measurements of low-energy observables, such as flavor violating processes or electric and magnetic dipole moments, as induced by new physics emerging above the electroweak scale.
Contacts: Mastrolia, Paradisi
Mathematical Methods for Feynman Integrals and Scattering Amplitudes
The computation of scattering amplitudes and Feynman integrals requires the development of computational techniques dedicated to special functions, and represents a formal research area, where concepts from Quantum Field Theory are combined with Algebraic and Differential Geometry, Topology, Combinatorics and Number Theory. Our group develops computational methods for Feynman integrals and scattering amplitudes based on contiguity relations, differential equations and finite difference equations, on the theory of special functions with complex variables, intersection theory by de Rham co-homology, in combination with on-shell methods and generalized unitarity. These innovative techniques allow the study of scattering amplitudes in gauge theories and in general relativity, as well as the study of special functions, such as Aomoto-Gauss, Euler-Mellin and GKZ integrals, which appear in different scientific fields.
Contacts: Pierpaolo Mastrolia, Manoj K. Mandal, Stefano Laporta
Feynman Integrals, Neural Networks and SuperCalculus
Machine Learning and Cooperative Game Theory techniques are very valid for the analysis of scattering process data. Our group works on the applications of these techniques for the study of Higgs boson couplings, and the detection of potential anomalies to be ascribed to new physics effects. In parallel, since Feynman integrals, and more generally Aomoto-Gauss, Euler-Mellin and GKZ integrals satisfy linear systems of contiguity relations, differential equations and finite difference equations. Our group works on the development and application of computational methods based on neural networks, of the PINN (Physics Informed Neural Network) type, for the resolution of the aforementioned systems of equations. Our group leads the phenomenology of elementary particles initiative for the High Performance Computing project at the Leonardo CINECA supercomputer, within the PNRR.
Contacts: Pierpaolo Mastrolia, Ramona Groeber, Manoj K. Mandal
