7,277 research outputs found
Applications of Graphene at Microwave Frequencies
In view to the epochal scenarios that nanotechnology discloses, nano-electronics has the potential to introduce a paradigm shift in electronic systems design similar to that of the transition from vacuum tubes to semiconductor devices. Since low dimensional (1D and 2D) nano-structured materials exhibit unprecedented electro-mechanical properties in a wide frequency range, including radio-frequencies (RF), microwave nano-electronics provides an enormous and yet widely undiscovered opportunity for the engineering community. Carbon nano-electronics is one of the main research routes of RF/microwave nano-electronics. In particular, graphene has shown proven results as an emblematic protagonist, and a real solution for a wide variety of microwave electronic devices and circuits. This paper introduces graphene properties in the microwave range, and presents a paradigm of novel graphene-based devices and applications in the microwave/RF frequency range
Slepton production in polarized hadron collisions
We calculate cross sections and asymmetries for slepton pair production
through neutral and charged electroweak currents in polarized hadron collisions
for general slepton masses and including mixing of the left- and right-handed
interaction eigenstates relevant for third generation sleptons. Our analytical
results confirm and extend a previous calculation. Numerically, we show that
measurements of the longitudinal single-spin asymmetry at the existing
polarized pp collider RHIC and at possible polarization upgrades of the
Tevatron or the LHC would allow for a determination of the tau slepton mixing
angle and/or the associated supersymmetry breaking parameters Lambda for gauge
mediation and A0 for minimal supergravity. Furthermore, the Standard Model
background from tau pair production can be clearly distinguished due to the
opposite sign of the associated asymmetry.Comment: 16 pages, 4 figures; Tevatron/LHC polarization and tau identification
discussed, typos correcte
Squark and Gaugino Hadroproduction and Decays in Non-Minimal Flavour Violating Supersymmetry
We present an extensive analysis of squark and gaugino hadroproduction and
decays in non-minimal flavour violating supersymmetry. We employ the so-called
super-CKM basis to define the possible misalignment of quark and squark
rotations, and we use generalized (possibly complex) charges to define the
mutual couplings of (s)quarks and gauge bosons/gauginos. The cross sections for
all squark-(anti-)squark/gaugino pair and squark-gaugino associated production
processes as well as their decay widths are then given in compact analytic
form. For four different constrained supersymmetry breaking models with
non-minimal flavour violation in the second/third generation squark sector
only, we establish the parameter space regions allowed/favoured by low-energy,
electroweak precision, and cosmological constraints and display the chirality
and flavour decomposition of all up- and down-type squark mass eigenstates.
Finally, we compute numerically the dependence of a representative sample of
production cross sections at the LHC on the off-diagonal mass matrix elements
in the experimentally allowed/favoured ranges.Comment: 35 pages, 29 (partly colour) figures. Some typos corrected, wording
of several paragraphs improved, version accepted by Nucl. Phys.
Transverse-Momentum Resummation for Slepton-Pair Production at the LHC
We perform a first precision calculation of the transverse-momentum (q_T)
distribution of slepton pair and slepton-sneutrino associated production at the
CERN Large Hadron Collider (LHC). We implement soft-gluon resummation at the
next-to-leading logarithmic (NLL) level and consistently match the obtained
result to the pure fixed-order perturbative result at leading order (LO) in the
QCD coupling constant, i.e. O(alpha_s). We give numerical predictions for
stau_1 stau_1^* and stau_1 sneutrino_tau^* + stau_1^* sneutrino_tau production,
also implementing recent parameterizations of non-perturbative effects. The
results show a relevant contribution of resummation both in the small and
intermediate q_T-regions and little dependence on unphysical scales and
non-perturbative contributions.Comment: 4 pages, 2 figure
Transverse-momentum resummation and the spectrum of the Higgs boson at the LHC
We consider the transverse-momentum (q_T) distribution of generic high-mass
systems (lepton pairs, vector bosons, Higgs particles, ....) produced in hadron
collisions. At small q_T, we concentrate on the all-order resummation of the
logarithmically-enhanced contributions in QCD perturbation theory. We elaborate
on the -space resummation formalism and introduce some novel features: the
large logarithmic contributions are systematically exponentiated in a
process-independent form and, after integration over q_T, they are constrained
by perturbative unitarity to give a vanishing contribution to the total cross
section. At intermediate and large q_T, resummation is consistently combined
with fixed-order perturbative results, to obtain predictions with uniform
theoretical accuracy over the entire range of transverse momenta. The formalism
is applied to Standard Model Higgs boson production at LHC energies. We combine
the most advanced perturbative information available at present for this
process: resummation up to next-to-next-to-leading logarithmic accuracy and
fixed-order perturbation theory up to next-to-leading order. The results show a
high stability with respect to perturbative QCD uncertainties.Comment: 48 pages, 13 postscript figure
Polarization and Resummation in Slepton Production at Hadron Colliders
In R-parity conserving supersymmetric (SUSY) models, sleptons are produced in
pairs at hadron colliders through neutral and charged electroweak currents. We
demonstrate that the polarization of the initial hadron beams allows for a
direct extraction of the slepton mixing angle and thus for a determination of
the underlying SUSY-breaking mechanism. We also perform a first precision
calculation of the transverse-momentum (q_T) spectrum of the slepton pairs by
resumming soft multiple-gluon emission at next-to-leading logarithmic order.
The results show a relevant contribution of resummation both in the small and
intermediate q_T-regions, which strongly influences the extraction of the
missing transverse-momentum signal and the subsequent slepton
mass-determination, and little dependence on unphysical scales and
non-perturbative contributions.Comment: Contribution to Loops and Legs 2006, 5 pages, 4 figure
Z\gamma\gamma production with leptonic decays and triple photon production at NLO QCD
We present a calculation of the O(alpha_s) QCD corrections to the production
of a Z boson in association with two photons and to triple photon production at
hadron colliders. All final-state photons are taken as real. For the Z boson,
we consider the decays both into charged leptons and into neutrinos including
all off-shell effects. Numerical results are obtained via a Monte Carlo program
based on the structure of the VBFNLO program package. This allows us to
implement general cuts and distributions of the final-state particles. We find
that the NLO QCD corrections are sizable and significantly exceed the
expectations from a scale variation of the leading-order result. In addition,
differential distributions of important observables change considerably. The
prediction of two-photon-associated Z production with Z decays into neutrinos
from the charged-lepton rate works well, once we use an additional cut on the
invariant mass of the charged-lepton pair.Comment: 14 pages, 10 figures, 2 table
SIW cavity-backed slot (multi-)antenna systems for the next generation IoT applications
Substrate integrated waveguide (SIW) cavity-backed slot antenna topologies are promising candidates to adress the specific design challenges posed by the Internet of Things (IoT). In this contribution, we demonstrate their potential by discussing two designs on two different, application-specific, innovative substrate materials. First, a compact, ultra-wideband three-element array with very low mutual coupling is presented for integration into furniture. In the second design, the half-mode SIW technique is applied to obtain a miniaturized ultra-wideband design, enabling invisible integration into cork floor and wall tiles. The compactness, integrability, and stable, high performance of both designs in different operating conditions, make them ideal candidates for IoT applications
UAV surveying for a complete mapping and documentation of archaeological findings. The early Neolithic site of Portonovo
The huge potential of 3D digital acquisition techniques for the documentation of archaeological sites, as well as the related findings, is almost well established. In spite of the variety of available techniques, a sole documentation pipeline cannot be defined a priori because of the diversity of archaeological settings. Stratigraphic archaeological excavations, for example, require a systematic, quick and low cost 3D single-surface documentation because the nature of stratigraphic archaeology compels providing documentary evidence of any excavation phase. Only within a destructive process each single excavation cannot be identified, documented and interpreted and this implies the necessity of a re- examination of the work on field. In this context, this paper describes the methodology, carried out during the last years, to 3D document the Early Neolithic site of Portonovo (Ancona, Italy) and, in particular, its latest step consisting in a
photogrammetric aerial survey by means of UAV platform. It completes the previous research delivered in the same site by means of terrestrial laser scanning and close range techniques and sets out different options for further reflection in terms of site coverage, resolution and campaign cost. With the support of a topographic network and a unique reference system, the full documentation of the site is managed in order to detail each excavation phase; besides, the final output proves how the 3D digital methodology can be completely integrated with reasonable costs during the excavation and used to interpret the archaeological context. Further contribution of this work is the comparison between several acquisition techniques (i.e. terrestrial and aerial), which could be useful as decision support system for different archaeological scenarios. The main objectives of the comparison are: i) the evaluation of 3D mapping
accuracy from different data sources, ii) the definition of a standard pipeline for different archaeological needs and iii) the provision of different level of detail according to the user need
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