The "4th generation", B-CP anomalies & the LHC

TL;DR

The paper discusses anomalies in B and B_s meson mixings and decays, proposing a fourth quark family as a simple explanation, with implications for LHC searches and flavor physics constraints.

Contribution

It introduces a fourth quark family as a novel explanation for observed anomalies, providing a simple alternative to warped extra-dimensional models.

Findings

Fourth family quarks can account for CP-violation anomalies.

The t' quark can perturb sin 2β and dominate CP asymmetry in B_s decays.

Distinctive high p_t multilepton signatures are predicted at the LHC.

Abstract

Attention is drawn to the several 2-3 $\sigma$ "anomalies" in B, $B_s$ mixings and decays involving CP-observables. Perhaps the most interesting theoretical scenario that could cause such effects is based on warped extra-dimensional models and indeed some of the effects were predicted there. However, a rather simple explanation is that based on a fourth family of quarks with masses in the range of(400 - 600) GeV. The built-in hierarchy of the 4$\times$4 mixing matrix is such that the $t'$ readily provides a needed {\it perturbation} ($\approx 15%$) to $\sin 2 \beta$ as measured in $B \to \psi K_s$ and simultaneously is the dominant source of CP asymmetry in $B_s \to \psi \phi$. The latter mode is theoretically very clean (unlike the others) and therefore it would be extremely desirable that Fermilab gives a very high priority to clarify this anomaly at the earliest. 4th family explanation allows, with relative ease, to accomodate the stringent flavor changing constraints which usually can be quite challenging for new physics scenarios.Implications for the LHC are briefly discussed; $t'$ and $b'$ lead to high $p_t$ multilepton events, in particular $b'$ decays produce rather distinctive same sign leptons with asymmetric energies.