The Effective Field Theory path to New Physics

Abstract

The Effective Field Theory path to New Physics. Our understanding of the fundamental laws of Nature, built upon a wealth of experimental data spanning a wide range of scales, is encapsulated in the so-called Standard Model (SM), an extremely successful quantum field theory that describes how matter behaves at short distances, in terms of elementary constituents and their interactions. Theoretical arguments as well as unexplained phenomena in cosmological observations, however, point to the existence of New Physics (NP), whose exact nature and energy scale are currently unknown. A wide and diversified campaign of accurate measurements together with the direct search of new particles at the Large Hadron Collider, have not provided any clear indication of NP so far. The overarching goal of this proposal in theoretical physics is to obtain a series of conceptual, technical and phenomenological advances to significantly extend the sensitivity to heavy NP of current and future particle physics experiments above their direct reach, by interpreting their results in a global way through the SM Effective Field Theory (SMEFT). 1] Identify and establish the potential of specific observables at the LHC, focusing on the exploration of rare processes which might have sensitivity to new interactions, yet have not been studied in detail so far in the context of the SMEFT because of the complexity of the final state/small rates. 2] Explore the sensitivity of quantum observables, such entanglement and the corresponding measures (such as concurrency), to probe the presence of SMEFT operators.

Results achieved

: The project “The Effective Field Theory Path to New Physics” has contributed significantly to the development and application of Standard Model Effective Field Theory, a general theoretical framework for systematically interpreting possible indirect effects of new physics beyond the Standard Model. The work carried out focused on three main areas: improving the theoretical accuracy of SMEFT predictions, developing inference and global analysis tools, and phenomenological applications to observables relevant to current and future particle physics experiments. In particular, the effects of higher-order corrections, renormalization group evolution, and Wilson coefficient mixing on Higgs boson production processes at the LHC were studied, demonstrating the importance of consistently including these effects in precision analyses. A significant outcome of the project was the development of new lines of research related to quantum observables in collision processes. Quantum correlations, entanglement properties, and spin density matrices were investigated in processes involving heavy particles—such as top quark pairs or Higgs boson decays—as potential probes sensitive to deviations from the Standard Model. These activities have opened up new perspectives on the use of quantum information concepts in high-energy phenomenology. The project has also contributed to the development and consolidation of public computational tools used by the international community, including MadGraph5_aMC@NLO, HEPfit, and SMEFiT. These tools make it possible to combine measurements from different experimental areas—such as electroweak, Higgs, top, Drell-Yan, and flavor physics observables—thereby producing global constraints on the SMEFT coefficients. In particular, comprehensive analyses encompassing over one hundred SMEFT coefficients and several hundred observables have been completed and published, with a significant impact on the ability to consistently interpret experimental data collected at different energy scales. These activities have yielded numerous scientific results, including articles published or submitted to leading international journals in the field of high-energy physics. Topics covered include precision phenomenology for current and future colliders, the sensitivity of quantum observables to new physics, top quark pair production, Higgs boson physics, SMEFT phenomenology, and precision global analyses. The project also had an immediate impact on the international debate regarding future particle physics infrastructure. The tools and theoretical frameworks developed or maintained by project members—in particular HEPfit and SMEFiT—have been used in recent community studies to assess the sensitivity of future colliders to new physics. These contributions provided quantitative input to the scientific discussion related to the update of the European Strategy for Particle Physics. The results were disseminated through presentations at international conferences, workshops, and seminars. In particular, the project contributed to the organization of an international workshop on SMEFT, Higgs boson physics, and Effective Field Theory held in Bologna in June 2024, fostering dialogue between theorists and experimentalists and strengthening international collaborations.

Project details

Unibo Team Leader: Fabio Maltoni

Unibo involved Department/s:
Dipartimento di Fisica e Astronomia "Augusto Righi"

Coordinator:
ALMA MATER STUDIORUM - Università di Bologna(Italy)

Total Eu Contribution: Euro (EUR) 208.180,00
Total Unibo Contribution: Euro (EUR) 106.090,00
Project Duration in months: 24
Start Date: 28/09/2023
End Date: 28/02/2026