91 research outputs found
A Dark Sector for , and a Diphoton Resonance
We revisit a set of dark sector models, motivated by anomalies observed in
decays and the muon anomalous magnetic moment, in the light of a recently
reported diphoton excess around 750GeV. Interpreting the excess as a scalar
resonance associated with the symmetry breaking sector of a dark gauge group,
we show that a diphoton cross section of few fb can be accomodated, together
with anomalies in and within a minimal dark sector model. The
resulting prominent collider signatures are in the form of wide resonant
signals into top and muon pair final states below TeV. The model
further predicts a dark matter candidate, yet with a significantly
underabundant relic density, unless produced by an appropriate non-thermal
mechanism.Comment: 7 pages, 3 figure
A Dark Matter Relic From Muon Anomalies
We show that the recently reported anomalies in
transitions, as well as the long-standing discrepancy, can be
addressed simultaneously by a new massive abelian gauge boson with loop-induced
coupling to muons. Such a scenario typically leads to a stable dark matter
candidate with a thermal relic density close to the observed value. Dark matter
in our model couples dominantly to leptons, hence signals in direct detection
experiments lie well below the current sensitivity. The LHC, in combination
with indirect detection searches, can test this scenario through distinctive
signatures with muon pairs and missing energy.Comment: 10 pages, 7 figures, 1 tabl
Assisted freeze-out
We explore a class of dark matter models with two dark matter candidates,
only one interacts with the standard model sector. One of the dark matter is
thermalized with the assistance of the other stable particle. While both stable
particles contribute to the total relic density only one can elastically
scatter with nuclei, thus effectively reducing the direct detection rate.Comment: 16 pages, 13 figures, minor corrections, the final version published
in JCA
Scalar Singlet Dark Matter
We consider the minimal scalar singlet dark matter stabilised by a
symmetry. Due to the cubic term in the scalar potential, semi-annihilations,
besides annihilations, contribute to the dark matter relic density. Unlike in
the case, the dark matter spin independent direct detection cross section
is no more linked to the annihilation cross section. We study the extrema of
the potential and show that a too large cubic term would break the
symmetry spontaneously, implying a lower bound on the direct detection cross
section, and allowing the whole parameter space to be tested by XENON1T. In a
small region of the parameter space the model can avoid the instability of the
standard model vacuum up to the unification scale. If the semi-annihilations
are large, however, new physics will be needed at TeV scale because the model
becomes non-perturbative. The singlet dark matter mass cannot be lower than
53.8 GeV due to the constraint from Higgs boson decay into dark matter.Comment: 16 pages, 7 figures, metastability bounds added, conclusions
unchanged, version accepted by JCA
Signatures of sneutrino dark matter in an extension of the CMSSM
Current data (LHC direct searches, Higgs mass, dark matter-related bounds)
severely affect the constrained minimal SUSY standard model (CMSSM) with
neutralinos as dark matter candidates. But the evidence for neutrino masses
coming from oscillations requires extending the SM with at least right-handed
neutrinos with a Dirac mass term. In turn, this implies extending the CMSSM
with right-handed sneutrino superpartners, a scenario we dub CMSSM.
These additional states constitute alternative dark matter candidates of the
superWIMP type, produced via the decay of the long-lived next-to-lightest SUSY
particle (NLSP). Here we consider the interesting and likely case where the
NLSP is a : despite the modest extension with respect to the
CMSSM this scenario has the distinctive signatures of heavy, stable charged
particles. After taking into account the role played by neutrino mass bounds
and the specific cosmological bounds from the big bang nucleosynthesis in
selecting the viable parameter space, we discuss the excellent discovery
prospects for this model at the future runs of the LHC. We show that it is
possible to probe masses up to 600 GeV at the 14 TeV LHC with
fb when one considers a pair production of staus
with two or more hard jets through all SUSY processes. We also show the
complementary discovery prospects from a direct pair production,
as well as at the new experiment MoEDAL.Comment: 31 pages, 6 figures and 5 tables; v2 : discussions and references
added, conclusions unchanged. To appear in JHE
Caractérisation des interactions d'inhibiteurs de l'entrée du VIH dans un modèle de cellules dendritiques in vitro
Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal
Minimal semi-annihilating scalar dark matter
We study the dark matter from an inert doublet and a complex scalar singlet
stabilized by symmetries. This field content is the minimal one
that allows dimensionless semi-annihilation couplings for . We consider
explicitly the and cases and take into account
constraints from perturbativity, unitarity, vacuum stability, necessity for the
electroweak preserving vacuum to be the global minimum,
electroweak precision tests, upper limits from direct detection and properties
of the Higgs boson. Co-annihilation and semi-annihilation of dark sector
particles as well as dark matter conversion significantly modify the cosmic
abundance and direct detection phenomenology.Comment: 41 pages, 12 figure
Long-lived stau, sneutrino dark matter and right-slepton spectrum
The minimal supersymmetric (SUSY) standard model (MSSM) augmented by right chiral sneutrinos may lead to one such sneutrino serving as the lightest supersymmetric particle and a non-thermal dark matter candidate, especially if neutrinos have Dirac masses only. In such cases, if the lightest MSSM particle is a stau, the signal of SUSY at the LHC consists in stable charged tracks which are distinguishable from backgrounds through their time delay between the inner tracker and the muon chamber. We show how to determine in such scenarios the mass hierarchy between the lightest neutralino and right sleptons of the first two families. The techniques of neutralino reconstruction, developed in earlier works, are combined with the endpoint of the variable MT 2 in smuon (selectron) decays for this purpose. We show that one can thus determine the mass hierarchy for smuons (selectrons) and neutralinos up to 1 TeV, to the level of 5-10%
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