16,631 research outputs found
Charged Higgs bosons in Minimal Supersymmetry: Updated constraints and experimental prospects
We discuss the phenomenology of charged Higgs bosons in the MSSM with minimal
flavor violation. In addition to the constrained MSSM (CMSSM) with universal
soft supersymmetry breaking mass parameters at the GUT scale, we explore
non-universal Higgs mass models (NUHM) where this universality condition is
relaxed. To identify the allowed parameter space regions, we apply constraints
from direct searches, low energy observables, and cosmology. We find that
values of the charged Higgs mass as low as GeV can be
accommodated in the NUHM models, but that several flavor physics observables
disfavor large contributions, associated with high , quite
independently of MSSM scenario. We confront the constrained scenarios with the
discovery potentials reported by ATLAS and CMS, and find that the current
exclusion by indirect constraints is similar to the expected LHC discovery
reach with 30 fb of data. Finally, we evaluate the sensitivity of the
presented discovery potential to the choice of MSSM benchmark scenario. This
sensitivity is found to be higher in the case of a light ()
charged Higgs.Comment: 33 pages, 17 figures, v2: Minor revision, agrees with published
versio
Frequency tuning, nonlinearities and mode coupling in circular graphene resonators
We study circular nanomechanical graphene resonators by means of continuum
elasticity theory, treating them as membranes. We derive dynamic equations for
the flexural mode amplitudes. Due to geometrical nonlinearity these can be
modeled by coupled Duffing equations. By solving the Airy stress problem we
obtain analytic expressions for eigenfrequencies and nonlinear coefficients as
functions of radius, suspension height, initial tension, back-gate voltage and
elastic constants, which we compare with finite element simulations. Using
perturbation theory, we show that it is necessary to include the effects of the
non-uniform stress distribution for finite deflections. This correctly
reproduces the spectrum and frequency tuning of the resonator, including
frequency crossings.Comment: 21 pages, 7 figures, 3 table
Bottom-up derivation of an effective thermostat for united atoms simulations of water
In this article we derive the effective pairwise interactions in a Langevin
type united atoms model of water. The interactions are determined from the
trajectories of a detailed molecular dynamics simulation of simple point charge
water. A standard method is used for estimating the conservative interaction,
whereas a new "bottom-up" method is used to determine the effective dissipative
and stochastic interactions. We demonstrate that, when compared to the standard
united atoms model, the transport properties of the coarse-grained model is
significantly improved by the introduction of the derived dissipative and
stochastic interactions. The results are compared to a previous study, where a
"top-down" approach was used to obtain transport properties consistent with
those of the simple point charge water model.Comment: Submitted to J. Chem. Phy
Permanent-magnet atom chips for the study of long, thin atom clouds
Atom-chip technology can be used to confine atoms tightly using permanently magnetised videotape along with external magnetic fields. The one-dimensional (1D) gas regime can be realised and studied by trapping the atoms in high-aspect-ratio traps in which the radial motion of the system is confined to zero-point oscillation
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Cno Abundances Of Hydrogen-Deficient Carbon And R Coronae Borealis Stars: A View Of The Nucleosynthesis In A White Dwarf Merger
We present high-resolution (R similar to 50,000) observations of near-IR transitions of CO and CN of the five known hydrogen-deficient carbon (HdC) stars and four R Coronae Borealis (RCB) stars. We perform an abundance analysis of these stars by using spectrum synthesis and state-of-the-art MARCS model atmospheres for cool hydrogen-deficient stars. Our analysis confirms reports by Clayton and colleagues that those HdC stars exhibiting CO lines in their spectrum and the cool RCB star SAps are strongly enriched in (18)O(with (16)O/(18)Oratios ranging from 0.3 to 16). Nitrogen and carbon are in the form of (14)N and (12)C, respectively. Elemental abundances for CNO are obtained from C I, Ci2, CN, and CO lines. Difficulties in deriving the carbon abundance are discussed. Abundances of Na from Na I lines and S from S I lines are obtained. Elemental and isotopic CNO abundances suggest that HdC and RCB stars may be related objects, and that they probably formed from a merger of an He white dwarf with a C-O white dwarf.Robert A. Welch Foundation of Houston, TexasSwedish Research CouncilGS-2006A-C-13GS-2007A-DD-1McDonald Observator
H^\pm W^\mp production in the MSSM at the LHC
We investigate the viability of observing charged Higgs bosons (H^\pm)
produced in association with W bosons at the CERN Large Hadron Collider, using
the leptonic decay H^+ -> tau^+ nu_tau and hadronic W decay, within the Minimal
Supersymmetric Standard Model. Performing a parton level study we show how the
irreducible Standard Model background from W + 2 jets can be controlled by
applying appropriate cuts. In the standard m_h^max scenario we find a viable
signal for large tan beta and intermediate H^\pm masses (~ m_t).Comment: 3 pages, LaTeX, 4 eps figures, uses jpconf.cls, talk given by S.
Hesselbach at the 2007 Europhysics Conference on High Energy Physics,
Manchester, England, 19-25 July 200
The implications of household greywater treatment and reuse for municipal wastewater flows and micropollutant loads
An increasing worldwide interest in water recycling technologies such as greywater treatment and reuse suggests that additional research to elucidate the fate of xenobiotics during such practices would be beneficial. In this paper, scenario analyses supported by empirical data are used for highlighting the potential fate of a selection of xenobiotic micropollutants in decentralised greywater treatment systems, and for investigation of the possible implications of greywater recycling for the wider urban water cycle. Potential potable water savings of up to 43% are predicted for greywater recycling based on Danish water use statistics and priority substance monitoring at a greywater treatment plant in Denmark. Adsorption represents an important mechanism for the removal of cadmium, nickel, lead and nonylphenol from influent greywater and therefore the disposal route adopted for the generated sludge can exert a major impact on the overall efficiency and environmental sustainability of greywater treatment
Galerkin and Runge–Kutta methods: unified formulation, a posteriori error estimates and nodal superconvergence
Abstract. We unify the formulation and analysis of Galerkin and Runge–Kutta methods for the time discretization of parabolic equations. This, together with the concept of reconstruction of the approximate solutions, allows us to establish a posteriori superconvergence estimates for the error at the nodes for all methods. 1
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