145,277 research outputs found
Higher dimensional operators in 2HDM
We present a complete (non-redundant) basis of CP- and flavour-conserving
six-dimensional operators in a two Higgs doublet model (2HDM). We include
Z_2-violating operators as well. In such a 2HDM effective field theory
(2HDMEFT), we estimate how constraining the 2HDM parameter space from
experiments can get disturbed due to these operators. Our basis is motivated by
the strongly interacting light Higgs (SILH) basis used in the standard model
effective field theory (SMEFT). We find out bounds on combinations of Wilson
coefficients of such operators from precision observables, signal strengths of
Higgs decaying into vector bosons etc. In 2HDMEFT, the 2HDM parameter space can
play a significant role while deriving such constraints, by leading to reduced
or even enhanced effects compared to SMEFT in certain processes. We also
comment on the implications of the SILH suppressions in such considerations.Comment: 34 pages, 6 figures; to appear in JHE
Particle swarm optimization for the Steiner tree in graph and delay-constrained multicast routing problems
This paper presents the first investigation on applying a particle swarm optimization (PSO) algorithm to both the Steiner tree problem and the delay constrained multicast routing problem. Steiner tree problems, being the underlining models of many applications, have received significant research attention within the meta-heuristics community. The literature on the application of meta-heuristics to multicast routing problems is less extensive but includes several promising approaches. Many interesting research issues still remain to be investigated, for example, the inclusion of different constraints, such as delay bounds, when finding multicast trees with minimum cost. In this paper, we develop a novel PSO algorithm based on the jumping PSO (JPSO) algorithm recently developed by Moreno-Perez et al. (Proc. of the 7th Metaheuristics International Conference, 2007), and also propose two novel local search heuristics within our JPSO framework. A path replacement operator has been used in particle moves to improve the positions of the particle with regard to the structure of the tree. We test the performance of our JPSO algorithm, and the effect of the integrated local search heuristics by an extensive set of experiments on multicast routing benchmark problems and Steiner tree problems from the OR library. The experimental results show the superior performance of the proposed JPSO algorithm over a number of other state-of-the-art approaches
Using parametric set constraints for locating errors in CLP programs
This paper introduces a framework of parametric descriptive directional types
for constraint logic programming (CLP). It proposes a method for locating type
errors in CLP programs and presents a prototype debugging tool. The main
technique used is checking correctness of programs w.r.t. type specifications.
The approach is based on a generalization of known methods for proving
correctness of logic programs to the case of parametric specifications.
Set-constraint techniques are used for formulating and checking verification
conditions for (parametric) polymorphic type specifications. The specifications
are expressed in a parametric extension of the formalism of term grammars. The
soundness of the method is proved and the prototype debugging tool supporting
the proposed approach is illustrated on examples.
The paper is a substantial extension of the previous work by the same authors
concerning monomorphic directional types.Comment: 64 pages, To appear in Theory and Practice of Logic Programmin
On Generalizations of Network Design Problems with Degree Bounds
Iterative rounding and relaxation have arguably become the method of choice
in dealing with unconstrained and constrained network design problems. In this
paper we extend the scope of the iterative relaxation method in two directions:
(1) by handling more complex degree constraints in the minimum spanning tree
problem (namely, laminar crossing spanning tree), and (2) by incorporating
`degree bounds' in other combinatorial optimization problems such as matroid
intersection and lattice polyhedra. We give new or improved approximation
algorithms, hardness results, and integrality gaps for these problems.Comment: v2, 24 pages, 4 figure
Bayesian Model comparison of Higgs couplings
We investigate the possibility of contributions from physics beyond the
Standard Model (SM) to the Higgs couplings, in the light of the LHC data. The
work is performed within an interim framework where the magnitude of the Higgs
production and decay rates are rescaled though Higgs coupling scale factors. We
perform Bayesian parameter inference on these scale factors, concluding that
there is good compatibility with the SM. Furthermore, we carry out Bayesian
model comparison on all models where any combination of scale factors can
differ from their SM values and find that typically models with fewer free
couplings are strongly favoured. We consider the evidence that each coupling
individually equals the SM value, making the minimal assumptions on the other
couplings. Finally, we make a comparison of the SM against a single "not-SM"
model, and find that there is moderate to strong evidence for the SM.Comment: 24 pages, 4 figure
Constraining models with vector-like fermions from FCNC in K and B physics
In this work, we update the constraints on tree level FCNC couplings in the
framework of a theory with n isosinglet vector-like down quarks. In this
context, we emphasize the sensitivity of the B -> J/psi K_S CP asymmetry to the
presence of new vector-like down quarks. This CP asymmetry, together with the
rare decays B -> X_{s,d} l bar{l} and K -> pi nu bar{nu} are the best options
to further constrain the FCNC tree level couplings or even to point out, in the
near future, the possible presence of vector-like quarks in the low energy
spectrum, as suggested by GUT theories or models of large extra dimensions at
the TeV scale.Comment: 29 pages 11 figures. Comments on the calculation of epsilon' added,
references included, conclusions unchange
Yukawa coupling and anomalous magnetic moment of the muon: an update for the LHC era
We study the interplay between a soft muon Yukawa coupling generated
radiatively with the trilinear A-terms of the minimal supersymmetric standard
model (MSSM) and the anomalous magnetic moment of the muon. In the absence of a
tree-level muon Yukawa coupling the lightest smuon mass is predicted to be in
the range between 750 GeV and 2700 GeV at 2 sigma, if the bino mass M_1 is
below 1 TeV. Therefore, a detection of a smuon (in conjunction with a sub-TeV
bino) at the LHC would directly imply a non-zero muon Yukawa coupling in the
MSSM superpotential. Inclusion of slepton flavor mixing could in principle
lower the mass of one smuon-like slepton below 750 GeV. However, the
experimental bounds on radiative lepton decays instead strengthen the lower
mass bound, with larger effects for smaller M_1, We also extend the analysis to
the electron case and find that a light selectron close to the current
experimental search limit may prove the MSSM electron Yukawa coupling to be
non-zero.Comment: 6 pages, 2 figures, references added, version accepted for
publication in PR
Perspectives on a Supersymmetric Extension of the Standard Model with a Higgs Triplet and a Singlet at the LHC
We investigate a supersymmetric extension of the Minimal Supersymmetric
Standard Model (MSSM), called the TNMSSM, containing a Higgs triplet
of hypercharge and a singlet superfields in the
corresponding superpotential. The model can be viewed, equivalently, as an
extension of the NMSSM with the addition of a interaction and
of an extra coupling of the triplet to the two Higgs doublets of the NMSSM. In
this scenario the Higgs particle spectrum at tree-level gets additional mass
contributions from the triplet and singlet scalar components respect to the
MSSM, which are particularly enhanced at low . We calculate the
one-loop Higgs masses for the neutral physical Higgs bosons by a
Coleman-Weinberg effective potential approach. In particular, we investigate
separately the impact of the radiative corrections due to the electroweak,
gauge-gaugino-higgsino, fermion-sfermion and Higgs self-interactions to the
Higgs masses. Due to the larger number of scalars and of triplet and singlet
couplings, the Higgs corrections can be larger than the strong corrections.
This reduces the amount of fine-tuning required to fit the recent Higgs data.
Using the expressions of the beta-functions of the model, we show that the
large triplet singlet coupling remains perturbative up to GeV.
The model is also characterized by a light pseudoscalar in the spectrum, which
is a linear combination of the triplet, doublet and singlet CP-odd components.
We discuss the production and decay signatures of the Higgs bosons in this
model, including scenarios with hidden Higgses, which could be investigated at
the LHC in the current run.Comment: 39 pages, 37 figures, comments added for the published versio
Hadronic decays of eta and eta-prime with coupled channels
The hadronic decays eta -> pi pi pi, eta-prime -> pi pi pi and eta-prime ->
eta pi pi are investigated within a U(3) chiral unitary approach. Final state
interactions are included by deriving the effective s-wave potentials for meson
meson scattering from the chiral effective Lagrangian and iterating them in a
Bethe-Salpeter equation. With only a small set of parameters we are able to
explain both rates and spectral shapes of these decays.Comment: 23 page
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