192 research outputs found
WIMP Dark Matter and Unitarity-Conserving Inflation via a Gauge Singlet Scalar
A gauge singlet scalar with non-minimal coupling to gravity can drive
inflation and later freeze out to become cold dark matter. We explore this idea
by revisiting inflation in the singlet direction (S-inflation) and Higgs Portal
Dark Matter in light of the Higgs discovery, limits from LUX and observations
by Planck. We show that large regions of parameter space remain viable, so that
successful inflation is possible and the dark matter relic abundance can be
reproduced. Moreover, the scalar singlet can stabilise the electroweak vacuum
and at the same time overcome the problem of unitarity-violation during
inflation encountered by Higgs Inflation, provided the singlet is a real
scalar. The 2- Planck upper bound on imposes that the singlet
mass is below 2 TeV, so that almost the entire allowed parameter range can be
probed by XENON1T.Comment: 22 pages, 7 figures; v2: minor changes, references added, matches
published versio
On the importance of loop-induced spin-independent interactions for dark matter direct detection
The latest results from LHC searches for jets in association with missing
transverse energy place strong bounds on the scattering cross section of dark
matter. For the case of spin-dependent or momentum suppressed interactions
these limits seem to be superior to the bounds from direct detection
experiments. In this article, we show that loop contributions can significantly
alter this conclusion and boost direct detection bounds, whenever they induce
spin-independent interactions. This effect is most striking for tensor and
pseudotensor interactions, which induce magnetic and electric dipole moments at
loop level. For axialvector and anapole interactions a relevant contribution to
direct detection signals arises from loop-induced Yukawa-like couplings between
dark matter and quarks. We furthermore compare the resulting bounds to
additional constraints on these effective operators arising from indirect
searches and relic density requirements.Comment: 20 pages, 6 figures, 1 table. v2: new appendix, minor corrections,
references added - matches published versio
Exploring light mediators with low-threshold direct detection experiments
We explore the potential of future cryogenic direct detection experiments to
determine the properties of the mediator that communicates the interactions
between dark matter and nuclei. Due to their low thresholds and large
exposures, experiments like CRESST-III, SuperCDMS SNOLAB and EDELWEISS-III will
have excellent capability to reconstruct mediator masses in the MeV range for a
large class of models. Combining the information from several experiments
further improves the parameter reconstruction, even when taking into account
additional nuisance parameters related to background uncertainties and the dark
matter velocity distribution. These observations may offer the intriguing
possibility of studying dark matter self-interactions with direct detection
experiments.Comment: 19 pages, 10 figures + appendices. Matches published versio
QCD effects in mono-jet searches for dark matter
LHC searches for missing transverse energy in association with a jet allow to
place strong bounds on the interactions between dark matter and quarks. In this
article, we present an extension of the POWHEG BOX capable of calculating the
underlying cross sections at the next-to-leading order level. This approach
enables us to consistently include the effects of parton showering and to apply
realistic experimental cuts. We find significant differences from a fixed-order
analysis that neglects parton showering effects. In particular, next-to-leading
order corrections do not lead to a significant enhancement of the mono-jet
cross section once a veto on additional jets is imposed. Nevertheless, these
corrections reduce the theoretical uncertainties of the signal prediction and
therefore improve the reliability of the derived bounds. We present our results
in terms of simple rescaling factors, which can be directly applied to existing
experimental analyses and discuss the impact of changing experimental cuts.Comment: Added KITP affiliations, fixed 2 very minor typos, matches version
published in JHE
On the LHC sensitivity for non-thermalised hidden sectors
We show under rather general assumptions that hidden sectors that never reach
thermal equilibrium in the early Universe are also inaccessible for the LHC. In
other words, any particle that can be produced at the LHC must either have been
in thermal equilibrium with the Standard Model at some point or must be
produced via the decays of another hidden sector particle that has been in
thermal equilibrium. To reach this conclusion, we parametrise the cross section
connecting the Standard Model to the hidden sector in a very general way and
use methods from linear programming to calculate the largest possible number of
LHC events compatible with the requirement of non-thermalisation. We find that
even the HL-LHC cannot possibly produce more than a few events with energy
above 10 GeV involving states from a non-thermalised hidden sector.Comment: 7 pages, 2 figures, comments welcom
Dark matter self-interactions from a general spin-0 mediator
Dark matter particles interacting via the exchange of very light spin-0
mediators can have large self-interaction rates and obtain their relic
abundance from thermal freeze-out. At the same time, these models face strong
bounds from direct and indirect probes of dark matter as well as a number of
constraints on the properties of the mediator. We investigate whether these
constraints can be consistent with having observable effects from dark matter
self-interactions in astrophysical systems. For the case of a mediator with
purely scalar couplings we point out the highly relevant impact of
low-threshold direct detection experiments like CRESST-II, which essentially
rule out the simplest realization of this model. These constraints can be
significantly relaxed if the mediator has CP-violating couplings, but then the
model faces strong constraints from CMB measurements, which can only be avoided
in special regions of parameter space.Comment: 20 pages, 5 figures + appendices. v2: Matches published version. v3:
fixed typographical mistake in eq. (2.8). v4: fixed typographical mistake in
eq. (C.4
Directly detecting sub-GeV dark matter with electrons from nuclear scattering
Dark matter (DM) particles with mass in the sub-GeV range are an attractive
alternative to heavier weakly-interacting massive particles, but direct
detection of such light particles is challenging. If however DM-nucleus
scattering leads to ionisation of the recoiling atom, the resulting electron
may be detected even if the nuclear recoil is unobservable. We demonstrate that
including this effect significantly enhances direct detection sensitivity to
sub-GeV DM. Existing experiments set world-leading limits, and future
experiments may probe the cross sections relevant for thermal freeze-out.Comment: 8 pages revtex4, 5 figures; v2: analysis updated to include
constraints from XENON1T; accepted for publication in PR
- …