158 research outputs found
Higgsino-like Dark Matter From Sneutrino Late Decays
We consider Higgsino-like dark matter (DM) in the Minimal Supersymmetric
Standard Model (MSSM) with additional right-handed neutrino chiral superfields,
and propose a new non-thermal way of generating the right amount of relic DM
via sneutrino late decays. Due to the large DM annihilation cross-section,
decays must occur at lower temperatures than the freeze-out temperature , implying a mostly right-handed lightest
sneutrino with very small Yukawa interactions. In that context, the right
amount of Higgsino-like DM relic density can be accounted for if sneutrinos are
produced via thermal freeze-in in the early Universe.Comment: 10 pages, 2 figures. Final version PL
Implications of diphoton searches for a Radion in the Bulk-Higgs Scenario
In this work we point out that the apparent diphoton excess initially
presented by the ATLAS and CMS collaborations could have originated from a
radion in the bulk Higgs scenario within a warped extra dimension. In this
scenario the couplings of the radion to massive gauge bosons are suppressed,
allowing it to evade existing searches. In the presence of mixing with the
Higgs, due to the strong constraints from diboson searches, only points near
what we denominate the alignment region were able to explain the diphoton
signal and evade other experimental constraints. In light of the new
measurements presented at ICHEP 2016 by both LHC collaborations, which do not
confirm the initial diphoton excess, we study the current and future collider
constraints on a radion within the bulk-Higgs scenario. We find that searches
in the diphoton channel provide the most powerful probe of this scenario and
already exclude large regions of parameter space, particularly for smaller warp
factors. The radion has a sizeable branching ratio into top pairs and this
channel may also give competitive constraints in the future. Finally, diHiggs
searches can provide a complementary probe in the case of non-zero radion-Higgs
mixing but strong alignment.Comment: 20 pages, 12 figures. Several changes including consequences from
ICHEP2016. Final version accepted by journa
Radion/Dilaton-Higgs Mixing Phenomenology in Light of the LHC
Motivated by the bulk mixing between a massive radion
and a bulk scalar Higgs in warped extra dimensions, we construct an effective
four dimensional action that---via the AdS/CFT correspondence---describes the
most general mixing between the only light states in the theory, the dilaton
and the Higgs. Due to conformal invariance, once the Higgs scalar is localized
in the bulk of the extra-dimension the coupling between the dilaton and the
Higgs kinetic term vanishes, implying a suppressed coupling between the dilaton
and massive gauge bosons. We comment on the implications of the mixing and
couplings to Standard Model particles. Identifying the recently discovered 125
GeV resonance with the lightest Higgs-like mixed state , we study the
phenomenology and constraints for the heaviest radion-like state . In
particular we find that in the small mixing scenario with a radion-like state
in the mass range [150,250] GeV, the diphoton channel can provide
the best chance of discovery at the LHC if the collaborations extend their
searches into this energy range.Comment: 28 pages, 6 figures; v2: version published in JHE
Novel Collider and Dark Matter Phenomenology of a Top-philic Z'
We consider extending the Standard Model by including an additional Abelian
gauge group broken at low energies under which the right-handed top quark is
the only effectively charged Standard Model fermion. The associated gauge boson
is then naturally top-philic and couples only to the rest of the SM
particle content at loop-level or via kinetic mixing with the hypercharge gauge
boson which is assumed to be small. Working at the effective theory level, we
demonstrate that such a minimal extension allows for an improved fitting of the
excess observed in searches at the LHC in a region
of parameter space that satisfies existing collider constraints. We also
present the reach of the LHC at 13 TeV in constraining the relevant region of
parameter space. Additionally we show that within the same framework a suitably
chosen fermion charged only under the exotic Abelian group can, in the region
of parameter space preferred by the measurements, simultaneously
explain the dark matter relic density and the -ray excess at the
galactic center observed by the Fermi-LAT experiment.Comment: 30 pages, 11 figures; v2: version published in JHE
The price of being SM-like in SUSY
We compute the tuning in supersymmetric models associated with the
constraints from collider measurements of the Higgs couplings to fermions and
gauge bosons. In supersymmetric models, a CP-even state with SM Higgs couplings
mixes with additional, heavier CP-even states, causing deviations in the Higgs
couplings from SM values. These deviations are reduced as the heavy states are
decoupled with large soft masses, thereby exacerbating the tuning associated
with the electroweak scale. This new source of tuning is different from that
derived from collider limits on stops, gluinos and Higgsinos. It can be offset
with large tan beta in the MSSM, however this compensating effect is limited in
the NMSSM with a large Higgs-singlet coupling due to restrictions on large tan
beta from electroweak precision tests. We derive a lower bound on this tuning
and show that the level of precision of Higgs coupling measurements at the LHC
will probe naturalness in the NMSSM at the few-percent level. This is
comparable to the tuning derived from superpartner limits in models with a low
messenger scale and split families. Instead the significant improvement in
sensitivity of Higgs coupling measurements at the ILC will allow naturalness in
these models to be constrained at the per-mille level, beyond any tuning
derived from direct superpartner limits.Comment: 29 pages, 6 figure
Leptophilic Dark Matter with interactions
We consider a scenario where dark matter (DM) interacts exclusively with
Standard Model (SM) leptons at tree level. Due to the absence of tree-level
couplings to quarks, the constraints on leptophilic dark matter arising from
direct detection and hadron collider experiments are weaker than those for a
generic WIMP. We study a simple model in which interactions of DM with SM
leptons are mediated by a leptophilic boson, and determine constraints on
this scenario arising from relic density, direct detection, and other
experiments. We then determine current LHC limits and project the future
discovery reach. We show that, despite the absence of direct interactions with
quarks, this scenario can be strongly constrained.Comment: 12 pages, 15 figure
- …