Searches for dark matter suggest that it couples to ordinary matter only very weakly and possibly only through the Higgs or other scalar bosons. On the other hand, neutrinos might not couple to the ...Higgs boson directly, but only through a loop of dark matter particles, which would naturally explain the small neutrino masses. We demonstrate that current experimental constraints on such a ‘‘scotogenic’’ scenario allow to make the linear dependence of the lightest neutrino mass on the dark sector-Higgs coupling explicit, so that a measurement by the KATRIN experiment would directly determine its value.
We present a calculation of Higgsino and gaugino pair production at the LHC at next-to-next-to-leading logarithmic (NNLL) accuracy, matched to approximate next-to-next-to-leading order (aNNLO) QCD ...corrections. We briefly review the formalism for the resummation of large threshold logarithms and highlight the analytical results required at aNNLO + NNLO accuracy. Our numerical results are found to depend on the mass and nature of the produced charginos and neutralinos. The differential and total cross sections for light Higgsinos, which like sleptons are produced mostly at small x and in the s -channel, are found to be again moderately increased with respect to our previous results. The differential and total cross sections for gauginos are, however, not increased any more due to the fact that gauginos, like squarks, are now constrained by ATLAS and CMS to be heavier than about 1 TeV, so that also t - and u -channels play an important role. The valence quarks probed at large x then also induce substantially different cross sections for positively and negatively charged gauginos. The Higgsino and gaugino cross sections are both further stabilized at aNNLO + NNLL with respect to the variation of renormalization and factorization scales. We also now take mixing in the squark sector into account and study the dependence of the total cross sections on the squark and gluino masses as well as the trilinear coupling controlling the mixing in particular in the sbottom sector.
A
bstract
We propose and study a new minimal model for two-component dark matter. The model contains only three additional fields, one fermion and two scalars, all singlets under the Standard Model ...gauge group. Two of these fields, one fermion and one scalar, are odd under a
Z
2
symmetry that renders them simultaneously stable. Thus, both particles contribute to the observed dark matter density. This model resembles the union of the singlet scalar and the singlet fermionic models but it contains some new features of its own. We analyze in some detail its dark matter phenomenology. Regarding the relic density, the main novelty is the possible annihilation of one dark matter particle into the other, which can affect the predicted relic density in a significant way. Regarding dark matter detection, we identify a new contribution that can lead either to an enhancement or to a suppression of the spin-independent cross section for the scalar dark matter particle. Finally, we define a set of five benchmarks models compatible with all present bounds and examine their direct detection prospects at planned experiments. A generic feature of this model is that both particles give rise to observable signals in 1-ton direct detection experiments. In fact, such experiments will be able to probe even a subdominant dark matter component at the percent level.
With the KATRIN experiment, the determination of the absolute neutrino mass scale down to cosmologically favored values has come into reach. We show that this measurement provides the missing link ...between the Standard Model and the dark sector in scotogenic models, where the suppression of the neutrino masses is economically explained by their only indirect coupling to the Higgs field. We determine the linear relation between the electron neutrino mass and the scalar coupling λ5 associated with the dark neutral scalar mass splitting to be λ5 = 3.1 × 10−9mνe / eV. This relation then induces correlations among the dark matter (DM) and new scalar masses and their Yukawa couplings. Together, KATRIN and future lepton flavor violation experiments can then probe the fermion DM parameter space, irrespective of the neutrino mass hierarchy and CP phase.
We demonstrate that not only the production of virtual photons decaying into low- mass lepton pairs, but also the one of weak bosons at large transverse momenta is dominated by quark-gluon ...scattering. Measurements of these processes at the LHC can therefore provide useful constraints on the parton densities in the proton, in particular the one of the gluon, and their nuclear modifications.
We present a complete analysis of threshold resummation effects on direct light and heavy gaugino pair production at the Tevatron and the LHC. Based on a new perturbative calculation at ...next-to-leading order of SUSY-QCD, which includes also squark mixing effects, we resum soft gluon radiation in the threshold region at leading and next-to-leading logarithmic accuracy, retaining at the same time the full SUSY-QCD corrections in the finite coefficient function. This allows us to correctly match the resummed to the perturbative cross section. Universal subleading logarithms are resummed in full matrix form. We find that threshold resummation slightly increases and considerably stabilizes the invariant mass spectra and total cross sections with respect to the next-to-leading order calculation. For future reference, we present total cross sections and their theoretical errors in tabular form for several commonly used SUSY benchmark points, gaugino pairs, and hadron collider energies.
PDF
