New physics searches at kaon and hyperon factories.

Rare meson decays are among the most sensitive probes of both heavy and light new physics. Among them, new physics searches using kaons benefit from their small total decay widths and the availability of very large datasets. On the other hand, useful complementary information is provided by hyperon decay measurements. We summarize the relevant phenomenological models and the status of the searches in a comprehensive list of kaon and hyperon decay channels. We identify new search strategies for under-explored signatures, and demonstrate that the improved sensitivities from current and next-generation experiments could lead to a qualitative leap in the exploration of light dark sectors.

Quark and Lepton Compositeness: A Renormalizable Model.

In the chiral SU(15) gauge theory presented here, the quarks and leptons are bound states ("prebaryons") of massless preons. The standard model charges of the preons imply three generations of quarks and leptons, plus some vectorlike fermions lighter than the confining scale Λ_{pre}. Under certain assumptions about the chiral dynamics, bound states of two prebaryons behave as Higgs fields. The QCD and electroweak groups may unify above Λ_{pre}, while SU(15) prevents rapid proton decay.

General Solution to the U(1) Anomaly Equations.

The anomaly cancellation equations for the U(1) gauge group can be written as a cubic equation in n-1 integer variables, where n is the number of Weyl fermions carrying the U(1) charge. We solve this Diophantine cubic equation by providing a parametrization of the charges in terms of n-2 integers, and prove that this is the most general solution.

W' Boson near 2 TeV: Predictions for Run 2 of the LHC.

We present a renormalizable theory that includes a W' boson of mass in the 1.8-2 TeV range, which may explain the excess events reported by the ATLAS Collaboration in a WZ final state, and by the CMS Collaboration in e(+)e(-)jj, Wh(0), and jj final states. The W' boson couples to right-handed quarks and leptons, including Dirac neutrinos with TeV-scale masses. This theory predicts a Z' boson of mass in the 3.4-4.5 TeV range. The cross section times branching fractions for the narrow Z' dijet and dilepton peaks at the 13 TeV LHC are 10 and 0.6 fb, respectively, for M_(Z')=3.4 TeV, and an order of magnitude smaller for M_(Z')=4.5 TeV.

Hidden GeV-scale interactions of quarks.

We explore quark interactions mediated by new gauge bosons of masses in the 0.3-50 GeV range. A tight upper limit on the gauge coupling of light Z(') bosons is imposed by the anomaly cancellation conditions in conjunction with collider bounds on new charged fermions. Limits from quarkonium decays are model dependent, while electroweak constraints are mild. We derive the limits for a Z(') boson coupled to baryon number and then construct a Z(') model with relaxed constraints, allowing quark couplings as large as 0.2 for a mass of a few GeV.

CP violation in B{s} mixing from heavy Higgs boson exchange.

The anomalous dimuon charge asymmetry reported by the D0 Collaboration may be due to the tree-level exchange of some spin-0 particles that mediate CP violation in B{s}-B{s} meson mixing. We show that, for a range of couplings and masses, the heavy neutral states in a two-Higgs doublet model can generate a large charge asymmetry. This range is natural in "uplifted supersymmetry" and may enhance the B{-}→τν and B{s}→µ^{+}µ{-} decay rates. However, we point out that on general grounds the reported central value of the charge asymmetry requires new physics not only in B{s}-B{s} mixing but also in ΔB=1 transitions or in B{d}-B{d} mixing.

Accumulating evidence for nonstandard leptonic decays of Ds mesons.

The measured rate for D{s}{+}-->l+nu decays, where l is a muon or tau, is larger than the standard model prediction, which relies on lattice QCD, at the 3.8sigma level. We discuss how robust the theoretical prediction is, and we show that the discrepancy with experiment may be explained by a charged Higgs boson or a leptoquark.

Massless gauge bosons other than the photon.

Gauge bosons associated with unbroken gauge symmetries, under which all standard model fields are singlets, may interact with ordinary matter via higher-dimensional operators. A complete set of dimension-six operators involving a massless U(1) field, gamma('), and standard model fields is presented. The mu-->egamma(') decay, primordial nucleosynthesis, star cooling, and other phenomena set lower limits on the scale of chirality-flip operators in the 1-15 TeV range if the operators have coefficients given by the corresponding Yukawa couplings. Simple renormalizable models induce gamma(') interactions with leptons or quarks at two loops, and may provide a cold dark matter candidate.