2,764 research outputs found
Discovery Prospects for NMSSM Higgs Bosons at the High-Energy Large Hadron Collider
We investigate the discovery prospects for NMSSM Higgs bosons during the
13~TeV run of the LHC. While one of the neutral Higgs bosons is demanded to
have a mass around 125~GeV and Standard Model (SM)-like properties, there can
be substantially lighter, nearby or heavier Higgs bosons, that have not been
excluded yet by LEP, Tevatron or the 8~TeV run of the LHC. The challenge
consists in discovering the whole NMSSM Higgs mass spectrum. We present the
rates for production and subsequent decay of the neutral NMSSM Higgs bosons in
the most promising final states and discuss their possible discovery. The
prospects for pinning down the Higgs sector of the Natural NMSSM will be
analysed taking into account alternative search channels. We give a series of
benchmark scenarios compatible with the experimental constraints, that feature
Higgs-to-Higgs decays and entail (exotic) signatures with multi-fermion and/or
multi-photon final states. These decay chains furthermore give access to the
trilinear Higgs self-couplings. We briefly discuss the possibility of
exploiting coupling sum rules in case not all the NMSSM Higgs bosons are
discovered
Natural NMSSM Higgs Bosons
We study the phenomenology of Higgs bosons close to 126 GeV within the scale
invariant unconstrained next-to-minimal supersymmetric Standard Model (NMSSM),
focusing on the regions of parameter space favoured by low fine-tuning
considerations, namely stop masses of order 400 GeV to 1 TeV and an effective
parameter between 100-200 GeV, with large (but perturbative)
and low 2-4. We perform scans over the above parameter space,
focusing on the observable Higgs cross sections into , ,
, , final states, and study the correlations between these
observables. We show that the signal strength may be enhanced
up to a factor of about two not only due to the effect of singlet-doublet
mixing, which occurs more often when the 126 GeV Higgs boson is the
next-to-lightest CP-even one, but also due to light stops (and to a lesser
extent light chargino and charged Higgs loops). There may be also smaller
enhancements in the Higgs decay channels into , , correlated with the
enhancement. However there is no such correlation observed
involving the Higgs decay channels into , . The requirement of
having perturbative couplings up to the GUT scale favours the interpretation of
the 126 GeV Higgs boson as being the second lightest NMSSM CP-even state, which
can decay into pairs of lighter neutralinos, CP-even or CP-odd Higgs bosons,
leading to characteristic signatures of the NMSSM. In a non-negligible part of
the parameter range the increase in the rate is due to the
superposition of rates from nearly degenerate Higgs bosons. Resolving these
Higgs bosons would rule out the Standard Model, and provide evidence for the
NMSSM
Dynamic response of a flexible space beam
Dynamic response of a candidate flexible beam for a space experiment on control of flexible structures is investigated. Studies of natural frequencies reveal a beam length in which torsion and bending frequencies virtually coincide. Eccentric tip mass causes small shifts in natural frequencies but introduces coupled torsional/bending mode shapes. Transient response studies indicate significant effects on tip responses of low damping and first bending mode excitation at higher frequencies. Steady state response suggest displacement and acceleration measurements could be made up to 5 to 12 Hz for the actuator forces/torques assumed
Rydberg excitation of a single trapped ion
We demonstrate excitation of a single trapped cold Ca ion to
Rydberg levels by laser radiation in the vacuum-ultraviolet at 122 nm
wavelength. Observed resonances are identified as 3dD to 51 F, 52 F
and 3dD to 64F. We model the lineshape and our results imply a
large state-dependent coupling to the trapping potential. Rydberg ions are of
great interest for future applications in quantum computing and simulation, in
which large dipolar interactions are combined with the superb experimental
control offered by Paul traps.Comment: 4 pages, 3 figure
Vanishing Fe 3d orbital moments in single-crystalline magnetite
We show detailed magnetic absorption spectroscopy results of an in situ
cleaved high quality single crystal of magnetite. In addition the experimental
setup was carefully optimized to reduce drift, self absorption, and offset
phenomena as far as possible. In strong contradiction to recently published
data, our observed orbital moments are nearly vanishing and the spin moments
are quite close to the integer values proposed by theory. This very important
issue supports the half metallic full spin polarized picture of magnetite.Comment: 7 pages, 4 figure
High power, continuous-wave, single frequency fiber amplifier at 1091 nm and frequency doubling to 545.5 nm
We present a high power single-frequency ytterbium fiber amplifier system
with an output power of 30 W at 1091 nm. The amplifier system consists of two
stages, a preamplifier stage in which amplified spontaneous emission is
efficiently suppressed (>40 dB) and a high power amplifier with an efficiency
of 52 %. Two different approaches of frequency doubling are compared. We
achieve 8.6 W at 545.5 nm by single-pass frequency doubling in a MgO-doped
periodically poled stoichiometric LiTaO3 and up to 19.3 W at 545.5 nm by
frequency doubling with a lithium-triborate (LBO) crystal in an external
enhancement cavity
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Climate change increases riverine carbon outgassing, while export to the ocean remains uncertain
Any regular interaction of land and river during flooding affects carbon pools within the terrestrial system, riverine carbon and carbon exported from the system. In the Amazon basin carbon fluxes are considerably influenced by annual flooding, during which terrigenous organic material is imported to the river. The Amazon basin therefore represents an excellent example of a tightly coupled terrestrial–riverine system. The processes of generation, conversion and transport of organic carbon in such a coupled terrigenous–riverine system strongly interact and are climate-sensitive, yet their functioning is rarely considered in Earth system models and their response to climate change is still largely unknown. To quantify regional and global carbon budgets and climate change effects on carbon pools and carbon fluxes, it is important to account for the coupling between the land, the river, the ocean and the atmosphere. We developed the RIVerine Carbon Model (RivCM), which is directly coupled to the well-established dynamic vegetation and hydrology model LPJmL, in order to account for this large-scale coupling. We evaluate RivCM with observational data and show that some of the values are reproduced quite well by the model, while we see large deviations for other variables. This is mainly caused by some simplifications we assumed. Our evaluation shows that it is possible to reproduce large-scale carbon transport across a river system but that this involves large uncertainties. Acknowledging these uncertainties, we estimate the potential changes in riverine carbon by applying RivCM for climate forcing from five climate models and three CO2 emission scenarios (Special Report on Emissions Scenarios, SRES). We find that climate change causes a doubling of riverine organic carbon in the southern and western basin while reducing it by 20% in the eastern and northern parts. In contrast, the amount of riverine inorganic carbon shows a 2- to 3-fold increase in the entire basin, independent of the SRES scenario. The export of carbon to the atmosphere increases as well, with an average of about 30%. In contrast, changes in future export of organic carbon to the Atlantic Ocean depend on the SRES scenario and are projected to either decrease by about 8.9% (SRES A1B) or increase by about 9.1% (SRES A2). Such changes in the terrigenous–riverine system could have local and regional impacts on the carbon budget of the whole Amazon basin and parts of the Atlantic Ocean. Changes in riverine carbon could lead to a shift in the riverine nutrient supply and pH, while changes in the exported carbon to the ocean lead to changes in the supply of organic material that acts as a food source in the Atlantic. On larger scales the increased outgassing of CO2 could turn the Amazon basin from a sink of carbon to a considerable source. Therefore, we propose that the coupling of terrestrial and riverine carbon budgets should be included in subsequent analysis of the future regional carbon budget
Stress condensation in crushed elastic manifolds
We discuss an M-dimensional phantom elastic manifold of linear size L crushed
into a small sphere of radius R << L in N-dimensional space. We investigate the
low elastic energy states of 2-sheets (M=2) and 3-sheets (M=3) using analytic
methods and lattice simulations. When N \geq 2M the curvature energy is
uniformly distributed in the sheet and the strain energy is negligible. But
when N=M+1 and M>1, both energies appear to be condensed into a network of
narrow M-1 dimensional ridges. The ridges appear straight over distances
comparable to the confining radius R.Comment: 4 pages, RevTeX + epsf, 4 figures, Submitted to Phys. Rev. Let
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