107 research outputs found
Effective couplings approach to neutralino dark matter relic density
In this work, we analyze the electroweak loop corrections to the Neutralino
dark matter relic density in the framework of effective coupling. In the first
part, we comment on the generic features of the corrections and quantitative
changes to the predicted relic density. We analyze the correlation between the
characteristics of effective couplings to the nature of neutralino. Effective
couplings, however, absorb only the most dominant one loop corrections and are
not an exact calculation. In the second part, we assess the validity of
effective couplings by comparing them to the full one loop calculations in
various regions of parameter space.Comment: Moriond EW 2012 proceedings, 4 pages, 2 figure
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
Heavy neutrino production via at the lifetime frontier
We investigate the pair production of right-handed neutrinos from the decay
of an additional neutral boson in the gauged model. Taking
into account current constraints on the mass and the associated
gauge coupling , we analyse the sensitivity of proposed
experiments at the lifetime frontier, FASER 2, CODEX-b, MATHUSLA as well as a
hypothetical version of the MAPP detector to a long lived heavy neutrino
originating in the decays of the . We further complement this study
with determining the reach of LHCb and a CMS-type detector for the
high-luminosity LHC run. We demonstrate that in a background free scenario with
near the current limit, FASER 2 is sensitive to the
active-sterile neutrino mixing down to , while a
reach of can be obtained for CODEX-b and LHCb, in a
mass regime of GeV and GeV.
Finally, MATHUSLA can probe and cover the mixing
regime expected in a canonical seesaw scenario of light neutrino mass
generation.Comment: 20 pages, 6 figures, matches published versio
One jet to rule them all: monojet constraints and invisible decays of a 750 GeV diphoton resonance
The ATLAS and CMS collaborations recently reported a mild excess in the
diphoton final state pointing to a resonance with a mass of around 750 GeV and
a potentially large width. We consider the possibility of a scalar resonance
being produced via gluon fusion and decaying to electroweak gauge bosons, jets
and pairs of invisible particles, stable at collider scales. We compute limits
from monojet searches on such a resonance and test their compatibility with the
requirement for a large width. We also study whether the stable particle can be
a a dark matter candidate and investigate the corresponding relic density
constraints along with the collider limits. We show that monojet searches rule
out a large part of the available parameter space and point out scenarios where
a broad diphoton resonance can be reconciled with monojet constraints.Comment: Matches published versio
The Flavour of Natural SUSY
An inverted mass hierarchy in the squark sector, as in so-called "natural
supersymmetry", requires non-universal boundary conditions at the mediation
scale of supersymmetry breaking. We propose a formalism to define such boundary
conditions in a basis-independent manner and apply it to generic scenarios
where the third-generation squarks are light, while the first two generation
squarks are heavy and near-degenerate. We show that not only is our formalism
particularly well-suited to study such hierarchical squark mass patterns, but
in addition the resulting soft terms at the TeV scale are manifestly compatible
with the principle of minimal flavour violation, and thus automatically obey
constraints from flavour physics.Comment: 19 pages, 4 figures; v2: matches journal versio
Light stop in the MSSM after LHC Run 1
The discovery of a Higgs boson with a mass of 126 GeV at the LHC when
combined with the non-observation of new physics both in direct and indirect
searches imposes strong constraints on supersymmetric models and in particular
on the top squark sector. The experiments for direct detection of dark matter
have provided with yet more constraints on the neutralino LSP mass and its
interactions. After imposing limits from the Higgs, flavour and dark matter
sectors, we examine the feasibility for a light stop in the context of the
pMSSM, in light of current results for stop and other SUSY searches at the LHC.
We only require that the neutralino dark matter explains a fraction of the
cosmologically measured dark matter abundance. We find that a stop with mass
below 500 GeV is still allowed. We further study various probes of the
light stop scenario that could be performed at the LHC Run - II either through
direct searches for the light and heavy stop, or SUSY searches not currently
available in simplified model results. Moreover we study the characteristics of
heavy Higgs for the points in the parameter space allowed by all the available
constraints and illustrate the region with large cross sections to fermionic or
electroweakino channels. Finally we show that nearly all scenarios with a small
stopLSP mass difference will be tested by Xenon1T provided the NLSP is a
chargino, thus probing a region hard to access at the LHC.Comment: 54 pages, minor changes in the text, to appear in JHE
The Thermal Abundance of Semi-Relativistic Relics
Approximate analytical solutions of the Boltzmann equation for particles that
are either extremely relativistic or non-relativistic when they decouple from
the thermal bath are well established. However, no analytical formula for the
relic density of particles that are semi-relativistic at decoupling is yet
known. We propose a new ansatz for the thermal average of the annihilation
cross sections for such particles, and find a semi-analytical treatment for
calculating their relic densities. As examples, we consider Majorana- and
Dirac-type neutrinos. We show that such semi-relativistic relics cannot be good
cold Dark Matter candidates. However, late decays of meta-stable
semi-relativistic relics might have released a large amount of entropy, thereby
diluting the density of other, unwanted relics.Comment: 22 pages, 5 figures. Comments and references adde
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