Flavor Physics and CP Violation

Abstract

We currently live in the age of the CKM paradigm. The $3\times 3$ matrix that links $(d,\ s,\ b)$ quarks to $(u,\ c,\ t)$ in the charged current weak interaction, being complex and nominally with 18 parameters, can be accounted for by just 3 rotation angles and one $CP$ violating (CPV) phase, with unitarity and the CKM phases triumphantly tested at the B factories. But the CKM picture is unsatisfactory and has too many parameters. The main aim of Flavor Physics and $CP$ violation (FPCP) studies is the pursuit to uncover New Physics beyond the Standard Model (SM). Two highlights of LHC Run~1 period are the CPV phase $\phi_s$ of $B_s$ mixing and $B_s \to\mu^+\mu^-$ decay, which were found to be again consistent with SM, though the saga is yet unfinished. We also saw the emergence of the $P_5'$ angular variable anomaly in $B^0 \to K^{*0}\mu^+\mu^-$ decay and $R_{K^{(*)}}$ anomaly in $B \to K^{(*)}\mu^+\mu^-$ to $B \to K^{(*)}e^+e^-$ rate ratios, and the BaBar anomaly in $B \to D^{(*)}\tau\nu$ decays, which suggest possible New Physics in these flavor processes, pointing to extra $Z'$, charged Higgs, or leptoquarks. Charmless hadronic, semileptonic, purely leptonic and radiative $B$ decays continue to offer various further windows on New Physics. Away from $B$ physics, the rare $K \to \pi\nu\nu$ decays and $\varepsilon'/\varepsilon$ in the kaon sector, $\mu \to e$ transitions, muon $g-2$ and electric dipole moments of the neutron and electron, $\tau \to \mu\gamma,\ \mu\mu\mu,\ eee$, and a few charm physics probes, offer broadband frontier windows on New Physics. (See the document for the full abstract.)