355 research outputs found

    UV Completions of Magnetic Inelastic Dark Matter and RayDM for the Fermi Line(s)

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    Models that seek to produce a line at ~130 GeV as possibly present in the Fermi data face a number of phenomenological hurdles, not the least of which is achieving the high cross section into gamma gamma required. A simple explanation is a fermionic dark matter particle that couples to photons through loops of charged messengers. We study the size of the dimension 5 dipole (for a pseudo-Dirac state) and dimension 7 Rayleigh operators in such a model, including all higher order corrections in 1/M_{mess}. Such corrections tend to enhance the annihilation rates beyond the naive effective operators. We find that while freezeout is generally dominated by the dipole, the present day gamma-ray signatures are dominated by the Rayleigh operator, except at the most strongly coupled points, motivating a hybrid approach. With this, the Magnetic inelastic Dark Matter scenario provides a successful explanation of the lines at only moderately strong coupling. We also consider the pure Majorana WIMP, where both freezeout and the Fermi lines can be explained, but only at very strong coupling with light (~200 - 300 GeV) messengers. In both cases there is no conflict with non-observation of continuum photons.Comment: 11 pages, 6 figure

    A Portalino to the Dark Sector

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    "Portal" models that connect the Standard Model to a Dark Sector allow for a wide variety of scenarios beyond the simplest WIMP models. Kinetic mixing of gauge fields in particular has allowed a broad range of new ideas. However, the models that evade CMB constraints are often non-generic, with new mass scales and operators to split states and suppress indirect detection signals. Models with a "portalino", a neutral fermion that marries a linear combination of a standard model neutrino and dark sector fermion and carries a conserved quantum number, can be simpler. This is especially interesting for interacting dark sectors; then the unmarried linear combination which we identify as the standard model neutrino inherits these interactions too, and provides a new, effective interaction between the dark sector and the standard model. These interactions can be simple ZZ' type interactions or lepton-flavor changing. Dark matter freezes out into neutrinos, thereby evading CMB constraints, and conventional direct detection signals are largely absent. The model offers different signals, however. The "portalino" mechanism itself predicts small corrections to the standard model neutrino couplings as well as the possibility of discovering the portalino particle in collider experiments. Possible cosmological and astroparticle signatures include monochromatic neutrino signals from annihilation, spectral features in high energy CR neutrinos as well as conventional signals of additional light species and dark matter interactions.Comment: v2 - minor changes, references adde

    Light Signals from a Lighter Higgs

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    With the Higgs search program already quite mature, there is the exciting possibility of discovering a new particle with rates near that of the SM Higgs. We consider models with a signal in γγ\gamma \gamma below the SM Higgs mass, taking the recent 2.9σ2.9\, \sigma (local) CMS excess at 95 GeV as a target. We discuss singlet models with additional vectorlike matter, but argue that a Type-I two Higgs doublet model provides a more economical scenario. In such a setup, going into regions of moderate-to-strong fermiophobia, the enhanced γγ\gamma \gamma branching ratio allows signals from VHVH+VBF production to yield σ×BRγγ\sigma \times BR_{\gamma\gamma} comparable to total SM rates. Light HH production can be dominated via rare top decays tbH+bWHt \rightarrow b H^+ \rightarrow b W^{*} H, which provides an alternate explanation of the excess. We consider this in the context of other Higgs anomalies, namely the LEP Higgs excess near the same mass, and excesses in ttˉht\bar{t}h searches at Tevatron and LHC. We find that with 140GeV<mH+<160GeV140\, \mathrm{GeV} < m_{H^+} < 160\, \mathrm{GeV}, tanβ5\tan \beta \sim 5 and a coupling to gauge bosons of sin2δ0.1\sin^2 \delta \sim 0.1, such a scenario can produce all the excesses simultanously, where tthtth arise from contamination from the rare top decays, as previously proposed. An implication of the Type-I scenario is that any γγ\gamma \gamma excess should be associated with additional elements that could reduce background, including bb-jets, forward jets or signs of vector boson production.Comment: 15 pages, 3 figure
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