30 research outputs found
The Dark Side of Electroweak Naturalness Beyond the MSSM
Weak scale supersymmetry (SUSY) remains a prime explanation for the radiative
stability of the Higgs field. A natural account of the Higgs boson mass,
however, strongly favors extensions of the Minimal Supersymmetric Standard
Model (MSSM). A plausible option is to introduce a new supersymmetric sector
coupled to the MSSM Higgs fields, whose associated states resolve the little
hierarchy problem between the third generation squark masses and the weak
scale. SUSY also accomodates a weakly interacting cold dark matter (DM)
candidate in the form of a stable neutralino. In minimal realizations, the
thus-far null results of direct DM searches, along with the DM relic abundance
constraint, introduce a level of fine-tuning as severe as the one due to the
SUSY little hierarchy problem. We analyse the generic implications of new SUSY
sectors parametrically heavier than the minimal SUSY spectrum, devised to
increase the Higgs boson mass, on this little neutralino DM problem. We focus
on the SUSY operator of smallest scaling dimension in an effective field theory
description, which modifies the Higgs and DM sectors in a correlated manner.
Within this framework, we show that recent null results from the LUX experiment
imply a tree-level fine-tuning for gaugino DM which is parametrically at least
a few times larger than that of the MSSM. Higgsino DM whose relic abundance is
generated through a thermal freeze-out mechanism remains also severely
fine-tuned, unless the DM lies below the weak boson pair-production threshold.
As in the MSSM, well-tempered gaugino-Higgsino DM is strongly disfavored by
present direct detection results.Comment: 41 pages, 8 figures, references adde
Revisiting light neutralino scenarios in the MSSM
We revisit the case of a light neutralino LSP in the framework of the MSSM.
We consider a model with eleven free parameters. We show that all scenarios
where the annihilation of light neutralinos rely mainly on the exchange of a
light pseudoscalar are excluded by direct detection searches and by Fermi
measurements of the gamma-flux from dwarf spheroidal galaxies. On the other
hand, we find scenarios with light sleptons that satisfy all collider and
astroparticle physics constraints. In this case, the lower limit on the LSP
mass is 12.6 GeV. We discuss how the parameter space of the model will be
further probed by new physics searches at the LHC.Comment: 7 pages, 8 figure
Tools for Dark Matter in Particle and Astroparticle Physics
Despite several indirect confirmations of the existence of dark matter, the
properties of a new dark matter particle are still largely unknown. Several
experiments are currently searching for this particle underground in direct
detection, in space and on earth in indirect detection and at the LHC. A
confirmed signal could select a model for dark matter among the many extensions
of the standard model. In this paper we present a short review of the public
codes for computation of dark matter observables.Comment: 10 pages, 2 figures, to appear in the Proceedings of 13th
International Workshop on Advanced Computing and Analysis Techniques in
Physics Research, February 2010, Jaipur, Indi
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
Mixed sneutrino dark matter in light of the 2011 XENON and LHC results
In the context of supersymmetric models in which small Dirac neutrino masses
are generated by supersymmetry breaking, a mainly right-handed (RH) mixed
sneutrino can be an excellent cold dark matter (DM) candidate. We perform a
global analysis of the Minimal Supersymmetric Standard Model (MSSM)+RH neutrino
parameter space by means of Markov Chain Monte Carlo scans. We include all
relevant constraints from collider and dark matter searches, paying particular
attention to nuclear and astrophysical uncertainties. Two distinct cases can
satisfy all constraints: heavy sneutrino DM with mass of order 100 GeV, as well
as light sneutrino DM with mass of about 3-6 GeV. We discuss the implications
for direct and indirect dark matter searches, as well as for SUSY and Higgs
searches at the LHC for both, the light and the heavy sneutrino dark matter
case. The light sneutrino case is excluded by the 125-126 GeV Higgs signal.Comment: 38 pages, 13 figures; v3: appendix added, minor corrections, note
added on the 2012 XENON100 results; matches version accepted by JCA
Probing the flavor violating scalar top quark signal at the LHC
The Large Hadron Collider(LHC) has completed its run at 8 TeV with the
experiments ATLAS and CMS having collected about 25 of data each.
Discovery of a light Higgs boson, coupled with lack of evidence for
supersymmetry at the LHC so far, has motivated studies of supersymmetry in the
context of naturalness with the principal focus being the third generation
squarks. In this work, we analyze the prospects of the flavor violating decay
mode at 8 and 13 TeV center of mass energy
at the LHC. This channel is also relevant in the dark matter context for the
stop-coannihilation scenario, where the relic density depends on the mass
difference between the lighter stop quark () and the lightest
neutralino() states. This channel is extremely challenging to
probe, specially for situations when the mass difference between the lighter
stop quark and the lightest neutralino is small. Using certain kinematical
properties of signal events we find that the level of backgrounds can be
reduced substantially. We find that the prospect for this channel is limited
due to the low production cross section for top squarks and limited luminosity
at 8 TeV, but at the 13 TeV LHC with 100 luminosity, it is possible
to probe top squarks with masses up to 450 GeV. We also discuss how the
sensitivity could be significantly improved by tagging charm jets.Comment: 24 pages, 6 figures, 6 tables. Version accepted for publication in
Physical Rev. D. Some changes in presentation of figures and text made.
Result remains unchange
Co-scattering in micrOMEGAs: a case study for the singlet-triplet dark matter model
In scenarios with very small dark matter (DM) couplings and small mass
splittings between the DM and other dark sector particles, so-called
"co-scattering" or "conversion-driven freeze-out" can be the dominant mechanism
for DM production. We present the inclusion of this mechanism in micrOMEGAs
together with a case study of the phenomenological implications in the
fermionic singlet-triplet model. For the latter, we focus on the transition
between co-annihilation and co-scattering processes. We observe that
co-scattering is needed to describe the thermal behaviour of the DM for very
small couplings, opening up a new region in the parameter space of the model.
The triplet states are often long-lived in this region; we therefore also
discuss LHC constraints from long-lived signatures obtained with SModelS.Comment: 22 pages, 11 figures; typos correcte
LHC constraints on light neutralino dark matter in the MSSM
Light neutralino dark matter can be achieved in the Minimal Supersymmetric
Standard Model if staus are rather light, with mass around 100 GeV. We perform
a detailed analysis of the relevant supersymmetric parameter space, including
also the possibility of light selectons and smuons, and of light higgsino- or
wino-like charginos. In addition to the latest limits from direct and indirect
detection of dark matter, ATLAS and CMS constraints on electroweak-inos and on
sleptons are taken into account using a "simplified models" framework.
Measurements of the properties of the Higgs boson at 125 GeV, which constrain
amongst others the invisible decay of the Higgs boson into a pair of
neutralinos, are also implemented in the analysis. We show that viable
neutralino dark matter can be achieved for masses as low as 15 GeV. In this
case, light charginos close to the LEP bound are required in addition to light
right-chiral staus. Significant deviations are observed in the couplings of the
125 GeV Higgs boson. These constitute a promising way to probe the light
neutralino dark matter scenario in the next run of the LHC.Comment: 18 pages, 6 figures; matches version accepted for publication in
Physics Letters