Search

We present a generic Z2 X Z2-invariant scalar field theory with four real scalar fields in six-dimensional Minkowskian spacetime which yields solutions consisting of two intersecting domain-wall kinks which are each paired by fields with lumplike profiles. For a special parameter choice, analytic solutions can be obtained. We show that the Z2 X Z2 symmetry can be maintained while coupling fermions by introducing scalar Yukawa couplings to one kink-lump pair and six-dimensional pseudoscalar Yukawa couplings to the other, and we show that there exists a zero mode localized to the domain-wall junction in this case. We also show that scalar fields can be localized. [ABSTRACT FROM AUTHOR]

We propose an extension of the 4 + 1-dimensional SU(5) domain-wall braneworld of Davies, George and Volkas which includes the addition of a discrete A4 flavor symmetry. We show that lepton mixing and light Majorana neutrino masses can be generated from the additional A4 physics while at the same time sufficient parameter freedom can be maintained in the charged fermion sector to produce charged fermion masses and quark mixing naturally from the split fermion mechanism. Importantly, we show that the vacuum realignment problem typical of discrete flavor symmetry models of quark and lepton mixing can be solved by separating the appropriate flavons in the extra dimension, leading to exponentially sensitive suppression of the operators responsible for vacuum realignment. [ABSTRACT FROM AUTHOR]

We study the two scalar leptoquarks capable of generating chirally enhanced, sign-dependent contributions to lepton magnetic dipole moments (MDMs) and electric dipole moments (EDMs), R2∼(3,2,7/6) and S1∼(3,1,-1/3). We consider the case in which the electron and muon sectors are decoupled, and leptoquark couplings are assigned complex values. Adopting the coupling ansatz that the electron dipole operator is generated by charm-containing loops, and muon dipole operator by top-containing loops, we find that both minimal leptoquark models remain viable solutions for reconciling anomalies in the muon and electron MDMs, accounting for either of the two current (disparate) electron MDM results from Cs and Rb interferometry experiments. We also examine the correlated corrections to the muon and electron masses generated by these models, and argue that to minimize fine-tuning this introduces an upper bound on viable leptoquark (ϕ) masses, mϕ

We identify the two scalar leptoquarks capable of generating sign-dependent contributions to leptonic magnetic moments, R2∼(3,2,7/6) and S1∼(3,1,-1/3), as favored by current measurements. We consider the case in which the electron and muon sectors are decoupled, and real-valued Yukawa couplings are specified using an up-type quark mass-diagonal basis. Contributions to Δae arise from charm-containing loops and Δaμ from top-containing loops--hence avoiding dangerous LFV constraints, particularly from μ→eγ. The strongest constraints on these models arise from contributions to the Z leptonic decay widths, high-pT leptonic tails at the LHC, and from (semi)leptonic kaon decays. To be a comprehensive solution to the (g-2)e/μ puzzle we find that the mass of either leptoquark must be ≲65  TeV. This analysis can be embedded within broader flavor anomaly studies, including those of hierarchical leptoquark coupling structures. It can also be straightforwardly adapted to accommodate future measurements of leptonic magnetic moments, such as those expected from the Muon g-2 collaboration in the near future. [ABSTRACT FROM AUTHOR]

We analyze the phenomenology of a model of neutrino masses inspired by unification in E6 in which the exotic neutrinos can be present at low scales. The model introduces vector-like isosinglet down-type quarks, vector-like isodoublet leptons, neutrino singlets and two Z' bosons. The seesaw mechanism can be achieved with exotic neutrino masses as low as 100 GeV and Yukawa couplings of order 10-3. We find that the lightest Z' boson mass is required to be above 2.8 TeV, the exotic quark masses are required to be above 1.3 TeV (810 GeV) if they are collider stable (promptly decaying), and the exotic lepton mass bounds remain at the LEP value of 102 GeV. The model also presents a type-II two-Higgs-doublet model (2HDM) along with two heavy singlet scalars. The 2HDM naturally has the alignment limit enforced thanks to the large vacuum expectation values of the exotic scalars, thereby avoiding most constraints. [ABSTRACT FROM AUTHOR]

Neutrino masses and mixings can be generated in many different ways, with some of these scenarios featuring new physics at energy scales relevant for Large Hadron Collider searches. A systematic approach to constructing a large class of models for Majorana neutrinos may be founded upon a list of gauge-invariant effective operators—formed from quarks, leptons and the Higgs doublet—that violate lepton-number conservation by two units. By opening up these operators in all possible ways consistent with some minimality assumptions, a complete catalog of a class of minimal radiative neutrino mass models may be produced. In this paper we present an analysis of Feynman diagram topologies relevant for the ultraviolet completions of these effective operators and collect these into a simple recipe that can be used to generate radiative neutrino mass models. Since high mass-dimension effective operators are suppressed by powers of the scale of new physics, many of the resulting models can be meaningfully tested at the Large Hadron Collider. [ABSTRACT FROM AUTHOR]