An Indirect Model-Dependent Probe of the Higgs Self-Coupling

The Higgs associated production cross section at an $e^+ e^-$ collider is indirectly sensitive to the Higgs self-coupling, $h^3$, at next-to-leading order (NLO). Utilizing this, a new indirect method is proposed for constraining deviations in the self-coupling below the di-Higgs production threshold in certain models. Although this indirect constraint is model-dependent, making it valid only under specific assumptions, meaningful indirect constraints on the self-coupling may be realized. Specific realistic scenarios where the indirect constraint applies are discussed and in particular it is shown that in the well-motivated class of two Higgs-doublet models there exist regions of parameter space in which the NLO effects from a modified self-coupling dominate over the LO modifications, demonstrating a concrete scenario in which large modifications of the Higgs self-coupling may be indirectly constrained using the proposed method. Other models, such as strongly coupled scenarios, are also discussed. The indirect method would give valuable constraints on deviations in the Higgs self-coupling, and would be complementary to the direct measurements possible with di-Higgs production at other colliders, providing precious additional information in the effort to unravel the properties of the Higgs boson.Comment: 8 pages, 4 figures. Eq.10 Typo corrected and rearranged to neater form. Note added with additional references. Plots and numerical results unchange

Capture of Inelastic Dark Matter in White Dwarves

We consider the capture of inelastic dark matter in white dwarves by inelastic spin-independent scattering on nuclei. We show that if the dark matter annihilates to standard-model particles then, under the assumption of primordial globular cluster formation, the observation of cold white dwarves in the globular cluster M4 appears inconsistent with explanations of the observed DAMA/LIBRA annual modulation signal based on spin-independent inelastic dark matter scattering. Alternatively if the inelastic dark matter scenario were to be confirmed and it was found to annihilate to standard-model particles then this would imply a much lower dark matter density in the core of M4 than would be expected if it were to have formed in a dark matter halo. Finally we argue that cold white dwarves constitute a unique dark matter probe, complementary to other direct and indirect detection searches.Comment: 8 pages, 5 figures. Typos corrected. References and discussion added. Figures updated. Main conclusions unchanged. v3 Journal versio

Neutrino Masses from Neutral Top Partners

We present theories of `Natural Neutrinos' in which neutral fermionic top partner fields are simultaneously the right-handed neutrinos (RHN), linking seemingly disparate aspects of the Standard Model structure: a) The RHN top partners are responsible for the observed small neutrino masses, b) They help ameliorate the tuning in the weak scale and address the little hierarchy problem, and c) The factor of $3$ arising from $N_c$ in the top-loop Higgs mass corrections is countered by a factor $3$ from the number of vector-like generations of RHN. The RHN top partners may arise in pseudo-Nambu-Goldstone-Boson (pNGB) Higgs models such as the Twin Higgs, as well as more general Composite, Little, and Orbifold Higgs scenarios, and three simple example models are presented. This framework firmly predicts a TeV-scale seesaw, as the RHN masses are bounded to be below the TeV scale by naturalness. The generation of light neutrino masses relies on a collective breaking of lepton number, allowing for comparatively large neutrino Yukawa couplings and a rich associated phenomenology. The structure of the neutrino mass mechanism realizes in certain limits the Inverse or Linear classes of seesaw. Natural Neutrino models are testable at a variety of current and future experiments, particularly in tests of lepton universality, searches for lepton flavor violation, and precision electroweak and Higgs coupling measurements possible at high energy $e^+ e^-$ and hadron colliders.Comment: 18 pages, 5 figures; v2: references added, additional discussion of proton deca

Modified Higgs Sectors and NLO Associated Production

Many beyond the Standard Model (BSM) scenarios involve Higgs couplings to additional electroweak fields. It is well established that these new fields may modify Higgs gamma-gamma and gamma-Z decays at one-loop. However, one unexplored aspect of such scenarios is that by electroweak symmetry one should also expect modifications to the Higgs Z-Z coupling at one-loop and, more generally, modifications to Higgs production and decay channels beyond tree-level. In this paper we investigate the full BSM modified electroweak corrections to associated Higgs production at both the LHC and a future lepton collider in two simple SM extensions. From both inclusive and differential NLO associated production cross sections we find BSM-NLO corrections can be as large as O(>10%) when compared to the SM expectation, consistent with other precision electroweak measurements, even in scenarios where modifications to the Higgs diphoton rate are not significant. At the LHC such corrections are comparable to the involved QCD uncertainties. At a lepton collider the Higgs associated production cross section can be measured to high accuracy (O(1%) independent of uncertainties in total width and other couplings), and such a deviation could be easily observed even if the new states remain beyond kinematic reach. This should be compared to the expected accuracy for a model-independent determination of the Higgs diphoton coupling at a lepton collider, which is O(15%). This work demonstrates that precision measurements of the Higgs associated production cross section constitute a powerful probe of modified Higgs sectors and will be valuable for indirectly exploring BSM scenarios.Comment: 22 pages, 8 figure

A Clockwork Theory

The clockwork is a mechanism for generating light particles with exponentially suppressed interactions in theories which contain no small parameters at the fundamental level. We develop a general description of the clockwork mechanism valid for scalars, fermions, gauge bosons, and gravitons. This mechanism can be implemented with a discrete set of new fields or, in its continuum version, through an extra spatial dimension. In both cases the clockwork emerges as a useful tool for model-building applications. Notably, the continuum clockwork offers a solution to the Higgs naturalness problem, which turns out to be the same as in linear dilaton duals of Little String Theory. We also elucidate the similarities and differences of the continuum clockwork with large extra dimensions and warped spaces. All clockwork models, in the discrete and continuum, exhibit novel phenomenology with a distinctive spectrum of closely spaced resonances.Comment: Body of text 26 page

Dark Nuclei I: Cosmology and Indirect Detection

In a companion paper (to be presented), lattice field theory methods are used to show that in two-color, two-flavor QCD there are stable nuclear states in the spectrum. As a commonly studied theory of composite dark matter, this motivates the consideration of possible nuclear physics in this and other composite dark sectors. In this work, early Universe cosmology and indirect detection signatures are explored for both symmetric and asymmetric dark matter, highlighting the unique features that arise from considerations of dark nuclei and associated dark nuclear processes. The present day dark matter abundance may be composed of dark nucleons and/or dark nuclei, where the latter are generated through it dark nucleosynthesis. For symmetric dark matter, indirect detection signatures are possible from annihilation, dark nucleosynthesis, and dark nuclear capture and we present a novel explanation of the galactic center gamma ray excess based on the latter. For asymmetric dark matter, dark nucleosynthesis may alter the capture of dark matter in stars, allowing for captured particles to be processed into nuclei and ejected from the star through dark nucleosynthesis in the core. Notably, dark nucleosynthesis realizes a novel mechanism for indirect detection signals of asymmetric dark matter from regions such as the galactic center, without having to rely on a symmetric dark matter component.Comment: 31 pages, 9 figure

The New Flavor of Higgsed Gauge Mediation

Recent LHC bounds on squark masses combined with naturalness and flavor considerations motivate non-trivial sfermion mass spectra in the supersymmetric Standard Model. These can arise if supersymmetry breaking is communicated to the visible sector via new extended gauge symmetries. Such extended symmetries must be spontaneously broken, or confined, complicating the calculation of soft masses. We develop a new formalism for calculating perturbative gauge-mediated two-loop soft masses for gauge groups with arbitrary patterns of spontaneous symmetry breaking, simplifying the framework of "Higgsed gauge mediation." The resulting expressions can be applied to Abelian and non-Abelian gauge groups, opening new avenues for supersymmetric model building. We present a number of examples using our method, ranging from grand unified threshold corrections in standard gauge mediation to soft masses in gauge extensions of the Higgs sector that can raise the Higgs mass through non-decoupling D-terms. We also outline a new mediation mechanism called "flavor mediation", where supersymmetry breaking is communicated via a gauged subgroup of Standard Model flavor symmetries. Flavor mediation can automatically generate suppressed masses for third-generation squarks and implies a nearly exact U(2) symmetry in the first two generations, yielding a "natural SUSY" spectrum without imposing ad hoc global symmetries or giving preferential treatment to particular generations.Comment: 13 pages, 3 figures; v2: typos corrected, references adde

Multiple Gamma Lines from Semi-Annihilation

Hints in the Fermi data for a 130 GeV gamma line from the galactic center have ignited interest in potential gamma line signatures of dark matter. Explanations of this line based on dark matter annihilation face a parametric tension since they often rely on large enhancements of loop-suppressed cross sections. In this paper, we pursue an alternative possibility that dark matter gamma lines could arise from "semi-annihilation" among multiple dark sector states. The semi-annihilation reaction with a single final state photon is typically enhanced relative to ordinary annihilation into photon pairs. Semi-annihilation allows for a wide range of dark matter masses compared to the fixed mass value required by annihilation, opening the possibility to explain potential dark matter signatures at higher energies. The most striking prediction of semi-annihilation is the presence of multiple gamma lines, with as many as order N^3 lines possible for N dark sector states, allowing for dark sector spectroscopy. A smoking gun signature arises in the simplest case of degenerate dark matter, where a strong semi-annihilation line at 130 GeV would be accompanied by a weaker annihilation line at 173 GeV. As a proof of principle, we construct two explicit models of dark matter semi-annihilation, one based on non-Abelian vector dark matter and the other based on retrofitting Rayleigh dark matter.Comment: 15 pages of text, 8 figures. v2: refs adde

Dark Nuclei II: Nuclear Spectroscopy in Two-Colour QCD

We consider two-colour QCD with two flavours of quarks as a possible theory of composite dark matter and use lattice field theory methods to investigate nuclear spectroscopy in the spin $J=0$ and $J=1$ multi-baryon sectors. We find compelling evidence that $J=1$ systems with baryon number $B=2,3$ (and their mixed meson-baryon counterparts) are bound states - the analogues of nuclei in this theory. In addition, we estimate the $\sigma$-terms of the $J=0$ and $J=1$ single baryon states which are important for the coupling of the theory to scalar currents that may mediate interactions with the visible sector.Comment: 40 pages, 26 figure