6,267 research outputs found
Phenomenological Comparison of Models with Extended Higgs Sectors
Beyond the Standard Model (SM) extensions usually include extended Higgs
sectors. Models with singlet or doublet fields are the simplest ones that are
compatible with the parameter constraint. The discovery of new non-SM
Higgs bosons and the identification of the underlying model requires dedicated
Higgs properties analyses. In this paper, we compare several Higgs sectors
featuring 3 CP-even neutral Higgs bosons that are also motivated by their
simplicity and their capability to solve some of the flaws of the SM. They are:
the SM extended by a complex singlet field (CxSM), the singlet extension of the
2-Higgs-Doublet Model (N2HDM), and the Next-to-Minimal Supersymmetric SM
extension (NMSSM). In addition, we analyse the CP-violating 2-Higgs-Doublet
Model (C2HDM), which provides 3 neutral Higgs bosons with a pseudoscalar
admixture. This allows us to compare the effects of singlet and pseudoscalar
admixtures. Through dedicated scans of the allowed parameter space of the
models, we analyse the phenomenologically viable scenarios from the view point
of the SM-like Higgs boson and of the signal rates of the non-SM-like Higgs
bosons to be found. In particular, we analyse the effect of
singlet/pseudoscalar admixture, and the potential to differentiate these models
in the near future. This is supported by a study of couplings sums of the Higgs
bosons to massive gauge bosons and to fermions, where we identify features that
allow us to distinguish the models, in particular when only part of the Higgs
spectrum is discovered. Our results can be taken as guidelines for future LHC
data analyses, by the ATLAS and CMS experiments, to identify specific benchmark
points aimed at revealing the underlying model.Comment: Matches journal version; figures for NMSSM changed; conclusions
unchange
Blind adaptive constrained reduced-rank parameter estimation based on constant modulus design for CDMA interference suppression
This paper proposes a multistage decomposition for blind adaptive parameter estimation in the Krylov subspace with the code-constrained constant modulus (CCM) design criterion. Based on constrained optimization of the constant modulus cost function and utilizing the Lanczos algorithm and Arnoldi-like iterations, a multistage decomposition is developed for blind parameter estimation. A family of computationally efficient blind adaptive reduced-rank stochastic gradient (SG) and recursive least squares (RLS) type algorithms along with an automatic rank selection procedure are also devised and evaluated against existing methods. An analysis of the convergence properties of the method is carried out and convergence conditions for the reduced-rank adaptive algorithms are established. Simulation results consider the application of the proposed techniques to the suppression of multiaccess and intersymbol interference in DS-CDMA systems
One-loop conformal anomaly in an implicit momentum space regularization framework
In this paper we consider matter fields in a gravitational background in
order to compute the breaking of the conformal current at one-loop order.
Standard perturbative calculations of conformal symmetry breaking expressed by
the non-zero trace of the energy-momentum tensor have shown that some violating
terms are regularization dependent, which may suggest the existence of spurious
breaking terms in the anomaly. Therefore, we perform the calculation in a
momentum space regularization framework in which regularization dependent terms
are judiciously parametrized. We compare our results with those obtained in the
literature and conclude that there is an unavoidable arbitrariness in the
anomalous term .Comment: in European Physical Journal C, 201
The Casimir spectrum revisited
We examine the mathematical and physical significance of the spectral density
sigma(w) introduced by Ford in Phys. Rev. D38, 528 (1988), defining the
contribution of each frequency to the renormalised energy density of a quantum
field. Firstly, by considering a simple example, we argue that sigma(w) is well
defined, in the sense of being regulator independent, despite an apparently
regulator dependent definition. We then suggest that sigma(w) is a spectral
distribution, rather than a function, which only produces physically meaningful
results when integrated over a sufficiently large range of frequencies and with
a high energy smooth enough regulator. Moreover, sigma(w) is seen to be simply
the difference between the bare spectral density and the spectral density of
the reference background. This interpretation yields a simple `rule of thumb'
to writing down a (formal) expression for sigma(w) as shown in an explicit
example. Finally, by considering an example in which the sign of the Casimir
force varies, we show that the spectrum carries no manifest information about
this sign; it can only be inferred by integrating sigma(w).Comment: 10 pages, 4 figure
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