44,729 research outputs found
Signatures of multi-TeV scale particles in supersymmetric theories
Supersymmetric particles at the multi-TeV scale will escape direct detection
at planned future colliders. However, such particles induce non-decoupling
corrections in processes involving the accessible superparticles through
violations of the supersymmetric equivalence between gauge boson and gaugino
couplings. In a previous study, we parametrized these violations in terms of
super-oblique parameters and found significant deviations in well-motivated
models. Here, we systematically classify the possible experimental probes of
such deviations, and present detailed investigations of representative
observables available at a future linear collider. In some scenarios, the
option and adjustable beam energy are exploited to achieve high
precision. It is shown that precision measurements are possible for each of the
three coupling relations, leading to significant bounds on the masses and
properties of heavy superparticles and possible exotic sectors.Comment: 37 pages including 17 figures, REVTe
Squark production in R-symmetric SUSY with Dirac gluinos: NLO corrections
R-symmetry leads to a distinct realisation of SUSY with a significantly
modified coloured sector featuring a Dirac gluino and a scalar colour octet
(sgluon). We present the impact of R-symmetry on squark production at the 13
TeV LHC. We study the total cross sections and their NLO corrections from all
strongly interacting states, their dependence on the Dirac gluino mass and
sgluon mass as well as their systematics for selected benchmark points. We find
that tree-level cross sections in the R-symmetric model are reduced compared to
the MSSM but the NLO K-factors are generally larger in the order of ten to
twenty per cent. In the course of this work we derive the required DREG
DRED transition counterterms and necessary on-shell renormalisation constants.
The real corrections are treated using FKS subtraction, with results cross
checked against an independent calculation employing the two cut phase space
slicing method.Comment: 46 pages, 15 figures; updated to match published versio
LHC Phenomenology of an Extended Standard Model with a Real Scalar Singlet
Gauge singlet extensions of the Standard Model (SM) scalar sector may help
remedy its theoretical and phenomenological shortcomings while solving
outstanding problems in cosmology. Depending on the symmetries of the scalar
potential, such extensions may provide a viable candidate for the observed
relic density of cold dark matter or a strong first order electroweak phase
transition needed for electroweak baryogenesis. Using the simplest extension of
the SM scalar sector with one real singlet field, we analyze the generic
implications of a singlet-extended scalar sector for Higgs boson phenomenology
at the Large Hadron Collider (LHC). We consider two broad scenarios: one in
which the neutral SM Higgs and singlet mix and the other in which no mixing
occurs and the singlet can be a dark matter particle. For the first scenario,
we analyze constraints from electroweak precision observables and their
implications for LHC Higgs phenomenology. For models in which the singlet is
stable, we determine the conditions under which it can yield the observed relic
density, compute the cross sections for direct detection in recoil experiments,
and discuss the corresponding signatures at the LHC.Comment: 39 pages, 11 figures, 2 table
Strategy towards Mirror-fermion Signatures
The existence of mirror fermions interacting strongly under a new gauge group
and having masses near the electroweak scale has been recently proposed as a
viable alternative to the standard-model Higgs mechanism. The main purpose of
this work is to investigate which specific experimental signals are needed to
clearly differentiate the mirror-fermion model from other new-physics models.
In particular, the case is made for a future large lepton collider with c.o.m.
energies of roughly 4 TeV or higher.Comment: 30 Latex pages, 2 postscript figure
Higgs Bosons in Extra Dimensions
In this paper, motivated by the recent discovery of a Higgs-like boson at the
LHC with a mass m_H\simeq 126 GeV, we review different models where the
hierarchy problem is solved by means of a warped extra dimension. In the
Randall-Sundrum model electroweak observables provide very strong bounds on the
mass of KK modes which motivates extensions to overcome this problem. Two
extensions are briefly discussed. One particular extension is based on the
deformation of the metric such that it strongly departs from the AdS_5
structure in the IR region while it goes asymptotically to AdS_5 in the UV
brane. This model has the IR brane close to a naked metric singularity (which
is outside the physical interval) characteristic of soft-walls constructions.
The proximity of the singularity provides a strong wave-function
renormalization for the Higgs field which suppresses the T and S parameters.
The second class of considered extensions are based on the introduction of an
extra gauge group in the bulk such that the custodial SU(2)_R symmetry is
gauged and protects the T parameter. By further enlarging the bulk gauge
symmetry one can find models where the Higgs is identified with the fifth
component of gauge fields and for which the Higgs potential, along with the
Higgs mass, can be dynamically determined by the Coleman-Weinberg mechanism.Comment: 29 pages, 13 figures. Invited review for IJMP
6D Higgsless Standard Model
We present a 6D Higgsless Standard Model with a realistic gauge sector. The
model uses only the Standard Model gauge group SU(2)xU(1) with the gauge bosons
propagating in flat extra dimensions which are compactified on a rectangle. The
electroweak symmetry is broken by boundary conditions, and the correct
splitting between the W and Z boson masses can be arranged by a suitable choice
of the compactification scales. The higher Kaluza-Klein excitations of the
gauge bosons decouple from the low-energy theory due to dominant brane kinetic
terms. The model has the following two key features compared to 5D models. The
bulk kinetic couplings, responsible for electroweak symmetry breaking using
mixed boundary conditions, are of order the electroweak scale. Moreover, the
agreement with the precision electroweak parameters is improved compared to 5D
warped or flat models. We also argue that the calculability of Higgsless models
can be ameliorated in more than five dimensions.Comment: 15 pages, 3 figures, discussion of fermion masses added, comment on
scalar degrees of freedom included, references adde
Applied aerodynamics: Challenges and expectations
Aerospace is the leading positive contributor to this country's balance of trade, derived largely from the sale of U.S. commercial aircraft around the world. This powerfully favorable economic situation is being threatened in two ways: (1) the U.S. portion of the commercial transport market is decreasing, even though the worldwide market is projected to increase substantially; and (2) expenditures are decreasing for military aircraft, which often serve as proving grounds for advanced aircraft technology. To retain a major share of the world market for commercial aircraft and continue to provide military aircraft with unsurpassed performance, the U.S. aerospace industry faces many technological challenges. The field of applied aerodynamics is necessarily a major contributor to efforts aimed at meeting these technological challenges. A number of emerging research results that will provide new opportunities for applied aerodynamicists are discussed. Some of these have great potential for maintaining the high value of contributions from applied aerodynamics in the relatively near future. Over time, however, the value of these contributions will diminish greatly unless substantial investments continue to be made in basic and applied research efforts. The focus: to increase understanding of fluid dynamic phenomena, identify new aerodynamic concepts, and provide validated advanced technology for future aircraft
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