1,763 research outputs found
Status and prospects of the nMSSM after LHC Run-1
The new minimal supersymmetric standard model (nMSSM), a variant of the
general next to minimal supersymmetric standard model (NMSSM) without
symmetry, features a naturally light singlino with a mass below 75 GeV. In
light of the new constraints from LHC Run-1 on the Higgs couplings, sparticles
searches and flavour observables, we define the parameter space of the model
which is compatible with both collider and dark matter (DM) properties. Among
the regions compatible with these constraints, implemented through NMSSMTools,
SModelS and MadAnalysis 5, only one with a singlino lightest supersymmetric
particle (LSP) with a mass around 5 GeV can explain all the DM abundance of the
universe, while heavier mixed singlinos can only form one of the DM components.
Typical collider signatures for each region of the parameter space are
investigated. In particular, the decay of the 125 GeV Higgs into light scalars
and/or pseudoscalars and the decay of the heavy Higgs into charginos and
neutralinos, provide distinctive signatures of the model. Moreover, the
sfermion decays usually proceed through heavier neutralinos rather than
directly into the LSP, as the couplings to the singlino are suppressed. We also
show that direct detection searches are complementary to collider ones, and
that a future ton-scale detector could completely probe the region of parameter
space with a LSP mass around 65 GeV.Comment: 33 pages, 9 figures. Version accepted for publication in JHE
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
Extracting constraints from direct detection searches of supersymmetric dark matter in the light of null results from the LHC in the squark sector
The comparison of the results of direct detection of Dark Matter, obtained
with various target nuclei, requires model-dependent, or even arbitrary,
assumptions. Indeed, to draw conclusions either the spin-dependent (SD) or the
spin-independent (SI) interaction has to be neglected. In the light of the null
results from supersymmetry searches at the LHC, the squark sector is pushed to
high masses. We show that for a squark sector at the TeV scale, the framework
used to extract contraints from direct detection searches can be redefined as
the number of free parameters is reduced. Moreover, the correlation observed
between SI and SD proton cross sections constitutes a key issue for the
development of the next generation of Dark Matter detectors.Comment: Figure 3 has been updated. Conclusions unchange
Use of modified polystyrene having the dual functionality of both binder and active material in electrochemical capacitors
Apports et limitations de la stratĂ©gie du greffage pour le stockage de lâĂ©lectricitĂ©
For over two decades, the electrochemical storage of electricity has embarked upon its organic revolution. Pseudo-supercapacitors, redox supercapacitors and fully organic hybrid systems have already won the scientific and industrial communities, although further efforts are needed regarding their energy density and stability in order to be integrated into structures having a long service life (aeronautic, automotive, building industry, etc.).
A recent strategy consists in grafting fast redox-active small molecules to a porous carbon network. Assembling these generic modular elements to infinity yields a wide range of possible combinations and specific rules must be followed in order to ensure that this grafting is beneficial.
This article presents the contributions and limitations of grafting and concludes with a novel alternative to the grafting on carbon
Catechol-Modified Activated Carbon Prepared by the Diazonium Chemistry for Application as Active Electrode Material in Electrochemical Capacitor
Activated carbon (Black Pearls 2000) modified with electroactive catechol groups was evaluated for charge storage application as active composite electrode material in an aqueous electrochemical capacitor. High surface area Black Pearls 2000 carbon, was functionalized by introduction of catechol groups by spontaneous reduction of catechol diazonium ions in situ prepared in aqueous solution from the corresponding amine. Change in the specific surface area and pore texture of the carbon following grafting was monitored by nitrogen gas adsorption measurements. The electrochemical properties and the chemical composition of the catechol-modified carbon electrodes were investigated by cyclic voltammetry. Such carbon-modified electrode combines well the faradaic capacitance, originating from the redox activity of the surface immobilized catechol groups, to the electrochemical double layer capacitance of the high surface area Black Pearls carbon. Due to the faradaic contribution, the catechol-modified electrode exhibits a higher specific capacitance (250 F/g) than pristine Carbon (150 F/g) over a potential range of -0.4 to 0.75 V in 1 M H2SO4. The stability of the modified electrode evaluated by long-time 1 charge/discharge cycling revealed a low decrease of the capacitance of the catechol-modified carbon due to the loss of the 1 catechol redox activity. Nonetheless, it was demonstrated that the benefit of redox groups persists for 10 000 constant current charge/discharge cycles
Use of an electroactive organic binder as active material for high energy density supercapacitor
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