848 research outputs found
Flavor constraints on two-Higgs-doublet models with general diagonal Yukawa couplings
We consider constraints from flavor physics on two-Higgs-doublet models
(2HDM) with general, flavor-diagonal, Yukawa couplings. Analyzing the charged
Higgs contribution to different observables, we find that
transitions and restrict the coupling of the
top quark (corresponding to in models with a symmetry) to
for GeV. Stringent constraints from
meson decays are obtained also on the other third generation couplings
and , but with stronger dependence on
. For the second generation, we obtain constraints on combinations of
, , and from leptonic and
decays. The limits on the general couplings are translated to the common
2HDM types I -- IV with a symmetry, and presented on the
plane. The flavor constraints are most excluding in the
type II model which lacks a decoupling limit in . We obtain a lower
limit GeV in models of type II and III, while no lower
bound on is found for types I and IV.Comment: 24 pages, 11 figures. v2: Minor changes to text and numerics, results
and conclusions unchanged. References adde
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
Improved prediction for the mass of the W boson in the NMSSM
Electroweak precision observables, being highly sensitive to loop
contributions of new physics, provide a powerful tool to test the theory and to
discriminate between different models of the underlying physics. In that
context, the boson mass, , plays a crucial role. The accuracy of the
measurement has been significantly improved over the last years, and
further improvement of the experimental accuracy is expected from future LHC
measurements. In order to fully exploit the precise experimental determination,
an accurate theoretical prediction for in the Standard Model (SM) and
extensions of it is of central importance. We present the currently most
accurate prediction for the boson mass in the Next-to-Minimal
Supersymmetric extension of the Standard Model (NMSSM), including the full
one-loop result and all available higher-order corrections of SM and SUSY type.
The evaluation of is performed in a flexible framework, which facilitates
the extension to other models beyond the SM. We show numerical results for the
boson mass in the NMSSM, focussing on phenomenologically interesting
scenarios, in which the Higgs signal can be interpreted as the lightest or
second lightest CP-even Higgs boson of the NMSSM. We find that, for both Higgs
signal interpretations, the NMSSM prediction is well compatible with the
measurement. We study the SUSY contributions to in detail and investigate
in particular the genuine NMSSM effects from the Higgs and neutralino sectors.Comment: 43 pages, 21 figure
Implementation of Singly Diagonally Implicit Runge-Kutta Methods with Constant Step Sizes
Runge–Kutta methods can be used for solving ordinary differential equations of the form y0 = f(t, y) with initial condition y(t0) = y0 and where f : R x R^m -> R^m. The idea is to find a method that is efficient to implement. But it is also important for the method to be of high order and be stable. Diagonally Implicit RK-methods reduces an sm x sm matrix to s systems of m x m linear equations. Singly Diagonally Implicit RK-methods have only a single eigenvalue, which results in a reduction to only one LU-decomposition per time step. Combining the two methods, we get Singly Diagonally Implicit RK-methods.Many problems in engineering science, natural science and even social and life sciences can be better understood by mathematical simulations. There are often several methods that can solve the same problem with. When choosing which method to use there are properties that needs to be considered, for instance time efficency and accuracy. These properties depend on the problem to solve and what criterias there are on the solution. In this thesis only a specific class of methods are considered, for solving differential equations. These methods are called Runge–Kutta methods. Further on, some properties are described and also problems that can appear when implementing the method. A specific subclass of Runge–Kutta methods, namely Singly Diagonally Implicit Runge–Kutta methods, is constructed such that these common implementation issues are not a problem. The benefits from implementing and using these methods are described further and some tests are made to verify these statements
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