423 research outputs found
Modelling strong interactions and longitudinally polarized vector boson scattering
We study scattering of the electroweak gauge bosons in 5D warped models.
Within two different models we determine the precise manner in which the Higgs
boson and the vector resonances ensure the unitarity of longitudinal vector
boson scattering. We identify three separate scales that determine the dynamics
of the scattering process in all cases. For a quite general background geometry
of 5D, these scales can be linked to a simple functional of the warp factor.
The models smoothly interpolate between a `composite' Higgs limit and a
Higgsless limit. By holographic arguments, these models provide an effective
description of vector boson scattering in 4D models with a strongly coupled
electroweak breaking sector.Comment: 30 pages, no figure
Unification in models with replicated gauge groups
We examine unification of gauge couplings in four dimensional renormalizable
gauge theories inspired by the latticized (deconstructed) SM or MSSM in five
dimensions. The models are based on replicated gauge groups, spontaneously
broken to the diagonal subgroup. The analysis is performed at one-loop level,
with the contribution from the heavy vector bosons included, and compared with
the analogous results in the SM or MSSM. Unification at or above the diagonal
breaking scale is discussed. We find that in the considered class of extensions
of the SM(MSSM) unification is possible for a wide range of unification scales
and with the similar accuracy as in the SM(MSSM). Unification above the
diagonal breaking scale is particularly attractive: it is a consequence of the
SM(MSSM) unification, but with the unification scale depending on the number of
replications of the gauge group.Comment: 19 pages, 3 figure
Simulation Application for the LHCb Experiment
We describe the LHCb detector simulation application (Gauss) based on the
Geant4 toolkit. The application is built using the Gaudi software framework,
which is used for all event-processing applications in the LHCb experiment. The
existence of an underlying framework allows several common basic services such
as persistency, interactivity, as well as detector geometry description or
particle data to be shared between simulation, reconstruction and analysis
applications. The main benefits of such common services are coherence between
different event-processing stages as well as reduced development effort. The
interfacing to Geant4 toolkit is realized through a facade (GiGa) which
minimizes the coupling to the simulation engine and provides a set of abstract
interfaces for configuration and event-by-event communication. The Gauss
application is composed of three main blocks, i.e. event generation, detector
response simulation and digitization which reflect the different stages
performed during the simulation job. We describe the overall design as well as
the details of Gauss application with a special emphasis on the configuration
and control of the underlying simulation engine. We also briefly mention the
validation strategy and the planing for the LHCb experiment simulation.Comment: Talk from the 2003 Computing in High Energy and Nuclear Physics
(CHEP03), La Jolla, Ca, USA, March 2003, 6 pages, LaTeX, 9 eps figures. PSN
TUMT00
A New bound on CP Violation in the Lepton Yukawa Coupling and electroweak baryogenesis
The origin of the matter-antimatter asymmetry in the Universe is a
fundamental question of physics. Electroweak baryogenesis is a compelling
scenario for explaining it but it requires beyond the Standard Model sources of
the CP symmetry violation. The simplest possibility is CP violation in the
third generation fermion Higgs couplings, widely investigated theoretically and
searched for experimentally. It has been found that the experimental bounds on
the CP violation in the quark Yukawa couplings exclude their significant role
in the electroweak baryogenesis, but it can be still played by the
lepton Yukawa coupling. It is shown in this paper that, within the context of
the Standard Model Effective Field Theory and assuming an underlying flavour
symmetry of the Wilson coefficients, the electron dipole moment bound on the
lepton Yukawa coupling is two orders of magnitude stronger than
previously reported. This sheds strong doubts on its role in the electroweak
baryogenesis, further stimulates the interest in its experimental verification
and makes electroweak baryogenesis even more difficult to explain.Comment: V2: references added; minor changes on the text; results unchanged;
version accepted for publication on JHE
The fine-tuning price of LEP
We quantify the amount of fine tuning of input parameters of the Minimal
Supersymmetric Extension of the Standard Model (MSSM) that is needed to respect
the lower limits on sparticle and Higgs masses imposed by precision electroweak
measurements at LEP, measurements of , and searches at LEP 2.
If universal input scalar masses are assumed in a gravity-mediated scenario, a
factor of \gappeq180 is required at , decreasing to
at . The amount of fine tuning is not greatly reduced
if non-universal input scalar Higgs masses are allowed, but may be
significantly reduced if some theoretical relations between MSSM parameters are
assumed.Comment: 13 pages, 5 figures. Two references added, one corrected. A typo
correcte
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Geometry description markup language for physics simulation and analysis applications
The Geometry Description Markup Language (GDML) is a specialized XML-based language designed as an application-independent persistent format for describing the geometries of detectors associated with physics measurements. It serves to implement ''geometry trees'' which correspond to the hierarchy of volumes a detector geometry can be composed of, and to allow to identify the position of individual solids, as well as to describe the materials they are made of. Being pure XML, GDML can be universally used, and in particular it can be considered as the format for interchanging geometries among different applications. In this paper we will present the current status of the development of GDML. After having discussed the contents of the latest GDML schema, which is the basic definition of the format, we will concentrate on the GDML processors. We will present the latest implementation of the GDML ''writers'' as well as ''readers'' for either Geant4 [2], [3] or ROOT [4], [10]
Quantum Isometrodynamics
Classical Isometrodynamics is quantized in the Euclidean plus axial gauge.
The quantization is then generalized to a broad class of gauges and the
generating functional for the Green functions of Quantum Isometrodynamics (QID)
is derived. Feynman rules in covariant Euclidean gauges are determined and QID
is shown to be renormalizable by power counting. Asymptotic states are
discussed and new quantum numbers related to the "inner" degrees of freedom
introduced. The one-loop effective action in a Euclidean background gauge is
formally calculated and shown to be finite and gauge-invariant after
renormalization and a consistent definition of the arising "inner" space
momentum integrals. Pure QID is shown to be asymptotically free for all
dimensions of "inner" space whereas QID coupled to the Standard Model
fields is not asymptotically free for D <= 7. Finally nilpotent BRST
transformations for Isometrodynamics are derived along with the BRST symmetry
of the theory and a scetch of the general proof of renormalizability for QID is
given.Comment: 38 page
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