59,120 research outputs found
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
Large N Effects and Renormalization of the Long-Range Coulomb Interaction in Carbon Nanotubes
We develop a dimensional regularization approach to deal with the low-energy
effects of the long-range Coulomb interaction in 1D electron systems. The
method allows us to avoid the infrared singularities arising from the
long-range Coulomb interaction at D = 1, providing at the same time insight
about the fixed-points of the theory. We show that the effect of increasing the
number N of subbands at the Fermi level is opposite to that of approaching the
bare Coulomb interaction in the limit D --> 1. Then, we devise a double scaling
limit, in which the large N effects are able to tame the singularities due to
the long-range interaction. Thus, regular expressions can be obtained for all
observables right at D = 1, bearing also a dependence o the doping level of the
system. Our results imply a variation with N in the value of the exponent for
the tunneling density of states, which is in fair agreement with that observed
in different transport experiments involving carbon nanotubes. As the doping
level is increased in nanotubes of large radius and multi-walled nanotubes, we
predict a significant reduction of order N^{-1/2} in the critical exponent of
the tunneling density of states.Comment: 16 pages, 5 figures, PACS codes: 73.40, 11.10.
Meson-baryon threshold effects in the light-quark baryon spectrum
We argue that selected wave meson-baryon channels may play a key role to
match poor baryon mass predictions from quark models with data. The
identification of these channels with effective inelastic channels in data
analysis allows to derive a prescription which could improve the extraction and
identification of baryon resonances.Comment: 17 pages, 3 figures. Accepted for publication in Phys. Rev.
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