Project Details
Projekt
Precise Standard Model corrections to New Physics searches with unitarity tests of the Cabibbo-Kobayashi-Maskawa quark mixing matrix
Applicant
Dr. Mikhail Gorshteyn
Subject Area
Nuclear and Elementary Particle Physics, Quantum Mechanics, Relativity, Fields
Term
since 2022
Project identifier
Deutsche Forschungsgemeinschaft (DFG) - Project number 495329596
Discovery of the Higgs boson has completed the quest for the particles that were predicted by the Standard Model (SM), required by its symmetries and breaking thereof. Extremely successful in particle physics, SM fails to describe a body of cosmological observations, which motivates searches for hidden particle and interaction sectors beyond SM (BSM). If new heavy particles are present in nature, they should become visible at the energy frontier reachable with colliders. Although the LHC operates at unprecedentedly high energies, no signs of BSM have been observed. Future colliders will expand the energy frontier horizons.Surprisingly, hints to possible BSM signals are observed at lower energies. The magnetic moment of the muon is 4.2σ away from the SM theory prediction, while an agreement for the electron is observed. Semileptonic B-meson decays exhibit a 4σ departure from lepton flavor universality. Universality of weak interaction is reflected in unitarity of the Cabibbo- Kobayashi-Maskawa (CKM) quark mixing matrix yet the measurements combine to a 3σ unitarity deficit.This deficit may be interpreted as an effect of heavy BSM physics which is probed by the LHC and β decays in a complementary and competitive way. Upcoming β decay experiments with improved precision will maintain this complementarity in the following years. To empower this sensitivity to BSM, precise theoretical calculations of SM correctionsare vital. Due to confinement, weak processes involving quarks are only accessible with their bound states, hadrons. Quantum Chromodynamics (QCD) that describes this binding and the properties of the compound is very complex and a perturbation expansion at low energies has only limited applicability. Our ability to reliably compute effects of strong interaction is central to the interpretation of low-energy precision tests.This project is dedicated to hadronic and nuclear structure effects in the determination of the top left corner CKM matrix element Vud. These effects cannot be distinguished from BSM signals experimentally, and need to be subtracted from the results of the experimental analyses. This puts forth the requirement of controlling theoretical uncertainties.I am a widely recognized expert in the theory of electroweak box diagrams where I developed the dispersion relation framework that fulfills this requirement and is now considered the state-of-the-art. The innovative research proposed here builds upon this expertise and is enriched by the cooperation with experts on nuclear theory and radiative corrections. It will deliver crucial theoretical ingredients for constraining BSM with CKM unitarity, with a potential of a BSM discovery, and will open up new research avenues.
DFG Programme
Research Grants
International Connection
Mexico
