Flavor Physics and CP Violation

TL;DR

This review discusses the current status of flavor physics and CP violation studies, highlighting recent experimental results, anomalies suggesting potential new physics, and the ongoing quest to go beyond the Standard Model in understanding fundamental particles.

Contribution

It provides a comprehensive overview of recent experimental findings and anomalies in flavor physics, emphasizing the search for new physics beyond the Standard Model.

Findings

Consistent results for CPV phase $\,\phi_s$ and $B_s o \,\mu^+\mu^-$ decay with SM

Emergence of anomalies like $P_5'$ and $R_{K^{(*)}}$ suggesting possible new physics

Various rare decays and transitions as windows for discovering beyond Standard Model physics

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.)