Standard model and beyond
Prerequisiti
Quantum field theory (Theoretical Physics I + II, QCD).
Programma
Introduction to the Standard Model. Field content and gauge symmetry. The Fermi interaction, beta decays, parity violation. Charged-current and neutral-current interactions. Minimal gauge Lagrangian, matter content of the SM and representations of the gauge group, hypercharge. 2-component spinors. The W and Z bosons, neutral currents and weak mixing angle, the parameters of the SM at tree-level, gauge boson masses, spontaneous symmetry breaking, Higgs mechanism. Quantization of spontaneously broken gauge theories, Ward identities and gauge fixing, Goldstone bosons. The Standard Model Lagrangian.
Global symmetries of the SM. Baryon and lepton number, axial charges and fermion masses, flavor symmetry. Majorana neutrinos and lepton number violation, see-saw mechanism. Custodial symmetry, Higgs sector in the gauge-less limit, chiral Lagrangian, Goldstone bosons, rho parameter. Determination of SM parameters and EW scheme. Hadronic corrections to lepton dipole moments, fine-structure constant, dispersion relations. Neutrino-electron scattering, vector and axial couplings of the Z boson. Electron-positron scattering, total cross-section, forward-backward asymmetry. Parity violation in atomic physics.
Precision measurements of Z couplings. Pseudo-observables and radiative corrections, effective couplings, rho parameter and effective mixing angle. Z pole observables: total and differential cross-section, asymmetries, partial widths, lepton universality. Radiative corrections in the SM, rho parameter at one loop, Higgs and top quark masses. EW precision tests: Altarelli-Barbieri parameters, oblique parameters and their symmetries. The Standard Model as an effective theory, renormalization and infrared logarithms.
Higgs boson phenomenology. Tree-level and one-loop decays, equivalence theorem, soft theorems. Higgs production at lepton and hadron colliders, soft and collinear radiation, splitting functions for transverse and longitudinal vector bosons. Higgs couplings, effective theory, pair production and self-coupling. Soft and collinear divergences in gauge theories, Sudakov logarithms, Sterman-Weinberg jets, e+e- cross-section into hadrons.
Chiral Lagrangian and EW symmetry breaking, longitudinal gauge boson scattering and unitarity. The hierarchy problem of the EW scale and possible solutions. Composite Higgs models, the Higgs as a Goldstone boson, SO(5)/SO(4) models, Higgs couplings and precision tests, the Higgs potential, fine-tuning.
The flavor sector. Yukawa interactions and flavor symmetry, CKM matrix and its physical parameters, CP violation, unitarity triangle. Determinations of CKM parameters: semi-leptonic decays, complex phases and CP violation. Neutral meson oscillation, mass difference and CP violation. Unitarity of the CKM matrix and GIM mechanism, determination of charm mass. Weak Effective Hamiltonian, one-loop matching of four-fermion operators, Wilson coefficients, anomalous dimension and RG-improvement. Heavy quark effective theory, QCD in the non-relativistic limit, form factors.
Anomalies in chiral gauge theories, anomaly cancellation in the Standard Model, charge quantization, baryon and lepton number anomalies, B-L. Unified theories: SU(5) and Pati-Salam models, SO(10), proton decay and other experimental limits.
Obiettivi formativi
The course offers an in-depth treatment of the Standard Model of elementary particles, from theoretical foundations to phenomenological aspects. Some of the main open problems in high-energy physics will be discussed, along with a selection of related topics in physics beyond the Standard Model. The course will provide students—both theorists and experimentalists—with the tools to pursue research in theoretical particle physics
Riferimenti bibliografici
- R. Barbieri, "Ten Lectures on the Electroweak Interactions" (Edizioni SNS).
- Donoghue, Golowich, Holstein, "Dynamics of the Standard Model" (Cambridge).
- K. Matchev, "TASI lectures on precision electroweak physics", hep-ph/0402031.
- Z. Ligeti, "TASI lectures on flavor physics", arXiv:1502.01372.
- A. J. Buras, "Weak Hamiltonian, CP violation and rare decays", hep-ph/9806471.
- R. Contino, "The Higgs as a composite Nambu-Goldstone Higgs", arXiv:1005.4269.
- G. Panico, A. Wulzer, "The composite Nambu-Golstone Higgs", arXiv:1506.01961.
- Y. Grossman, Y. Nir, "The Standard Model: from fundamental symmetries to experimental tests" (Princeton).
- A. V. Manohar, "Effective Field Theories", hep-ph/9606222.
- Scientific papers discussed during the lectures.