1,645 research outputs found
Fast and slow light in zig-zag microring resonator chains
We analyze fast and slow light transmission in a zig-zag microring resonator
chain. This novel device permits the operation in both regimes. In the
superluminal case, a new ubiquitous light transmission effect is found whereby
the input optical pulse is reproduced in an almost simultaneous manner at the
various system outputs. When the input carrier is tuned to a different
frequency, the system permits to slow down the propagating optical signal.
Between these two extreme cases, the relative delay can be tuned within a broad
range
Present Bounds on New Neutral Vector Resonances from Electroweak Gauge Boson Pair Production at the LHC
Several extensions of the Standard Model predict the existence of new neutral
spin-1 resonances associated to the electroweak symmetry breaking sector. Using
the data from ATLAS (with integrated luminosity of L=1.02 fb^{-1}) and CMS
(with integrated luminosity of L=1.55 fb^{-1}) on the production of W+W- pairs
through the process pp -> l^+ l^{\prime -} \sla{E}_T, we place model
independent bounds on these new vector resonances masses, couplings and widths.
Our analyses show that the present data excludes new neutral vector resonances
with masses up to 1-2.3 TeV depending on their couplings and widths. We also
demonstrate how to extend our analysis framework to different models working a
specific example.Comment: 10 pages, 6 figure
Constraining anomalous Higgs interactions
The recently announced Higgs discovery marks the dawn of the direct probing
of the electroweak symmetry breaking sector. Sorting out the dynamics
responsible for electroweak symmetry breaking now requires probing the Higgs
interactions and searching for additional states connected to this sector. In
this work we analyze the constraints on Higgs couplings to the standard model
gauge bosons using the available data from Tevatron and LHC. We work in a
model--independent framework expressing the departure of the Higgs couplings to
gauge bosons by dimension--six operators. This allows for independent
modifications of its couplings to gluons, photons and weak gauge bosons while
still preserving the Standard Model (SM) gauge invariance. Our results indicate
that best overall agreement with data is obtained if the cross section of Higgs
production via gluon fusion is suppressed with respect to its SM value and the
Higgs branching ratio into two photons is enhanced, while keeping the
production and decays associated to couplings to weak gauge bosons close to
their SM prediction.Comment: v3: Added acknowledgment to FP7 ITN INVISIBLES (Marie Curie Actions
PITN-GA-2011-289442). Nothing else changed with respect to v
The Higgs Legacy of the LHC Run I
Based on Run I data we present a comprehensive analysis of Higgs couplings.
For the first time this SFitter analysis includes independent tests of the
Higgs-gluon and top Yukawa couplings, Higgs decays to invisible particles, and
off-shell Higgs measurements. The observed Higgs boson is fully consistent with
the Standard Model, both in terms of coupling modifications and effective field
theory. Based only on Higgs total rates the results using both approaches are
essentially equivalent, with the exception of strong correlations in the
parameter space induced by effective operators. These correlations can be
controlled through additional experimental input, namely kinematic
distributions. Including kinematic distributions the typical Run I reach for
weakly interacting new physics now reaches 300 to 500 GeV.Comment: 29 pages, 15 figure
Searching for Scuti-type pulsation and characterising northern pre-main-sequence field stars
A photometric variability study of a sample of northern field stars, which
previously classified as either PMS or Herbig Ae/Be objects, has been
undertaken with the purpose of detecting {\delta} Scuti-type pulsations.
Determination of physical parameters for these stars has also been carried out
to locate them on the HR diagram and check the instability strip for this type
of pulsators. Multichannel photomultiplier and CCD time series photometry in
the uvby Str\"omgren and BVI Johnson bands were obtained during four
consecutive years from 2007 to 2010. The light curves have been analysed, and a
variability criterion has been established. Among the objects classified as
variable stars, we have selected those which present periodicities above 4
d^(-1), which was established as the lowest limit for {\delta} Scuti-type
pulsations in this investigation. Finally, these variable stars have been
placed in a colour-magnitude diagram using the physical parameters derived with
the collected uvby{\beta} Str\"omgren-Crawford photometry. Five PMS {\delta}
Scuti- and three probable {\beta} Cephei-type stars have been detected. Two
additional PMS {\delta} Scuti stars are also confirmed in this work. Moreover,
three new {\delta} Scuti- and two {\gamma} Doradus-type stars have been
detected among the main-sequence objects used as comparison or check stars.Comment: Accepted for publication in Section 14. Catalogs and data of
Astronomy and Astrophysics. The official date of acceptance is 17/06/2014. 12
pages, 4 figures and 8 table
Complejo granuloma eosinofílico
El complejo granuloma eosinofílico agrupa tres entidades clínico/histológicas denominadas granuloma colagenolítico, placa eosinofílica y úlcera indolente. En el presente artículo se describe su etiología y sus aspectos clínicos y terapéuticos.The eosinophilic granuloma complex is comprised of three clinical/histological entities: collagenolytic granuloma, eosinophilic plaque and indolent ulcer. In this article, its etiology, clinical aspects and therapy are discussed
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