2,330 research outputs found
Probing Intermediate Mass Higgs Interactions at the CERN Large Hadron Collider
We analyze the potentiality of the CERN Large Hadron Collider to probe the
Higgs boson couplings to the electroweak gauge bosons. We parametrize the
possible deviations of these couplings due to new physics in a model
independent way, using the most general dimension--six effective lagrangian
where the SU(2)_L x U(1)_Y is realized linearly. For intermediate Higgs masses,
the decay channel into two photons is the most important one for Higgs searches
at the LHC. We study the effects of these new interactions on the Higgs
production mechanism and its subsequent decay into two photons. We show that
the LHC will be sensitive to new physics scales beyond the present limits
extracted from the LEP and Tevatron physics.Comment: 13 pages, 1 figure included using epsfig, RevTe
Effective action of N = 4 super Yang-Mills: N = 2 superspace approach
Using the N = 2 off-shell formulation in harmonic superspace for N = 4 super
Yang-Mills theory, we present a representation of the one-loop effective action
which is free of so-called coinciding harmonic singularities and admits a
straightforward evaluation of low-energy quantum corrections in the framework
of an N = 2 superfield heat kernel technique. We illustrate our approach by
computing the low-energy effective action on the Coulomb branch of SU(2) N = 4
super Yang-Mills. Our work provides the first derivation of the low-energy
action of N = 4 super Yang-Mills theory directly in N = 2 superspace without
any reduction to N = 1 superfields and for a generic background N = 2
Yang-Mills multiplet.Comment: 12 pages, latex, no figures, references adde
Human metapneumovirus: Mechanisms and molecular targets used by the virus to avoid the immune system
Indexación: Scopus.This work was supported by Comisión Nacional de Investigación Científica y Tecnolígica (CONICYT) N◦21151028 and FONDECYT (N◦1070352 and N◦1170964) and the Millennium Institute on Immunology and Immunotherapy (P09/016-F).Human metapneumovirus (hMPV) is a respiratory virus, first reported the year 2001. Since then, it has been described as one of the main etiological agents that causes acute lower respiratory tract infections (ALRTIs), which is characterized by symptoms such as bronchiolitis, wheezing and coughing. Susceptible population to hMPV-infection includes newborn, children, elderly and immunocompromised individuals. This viral agent is a negative-sense, single-stranded RNA enveloped virus, that belongs to the Pneumoviridae family and Metapneumovirus genus. Early reports-previous to 2001-state several cases of respiratory illness without clear identification of the responsible pathogen, which could be related to hMPV. Despite the similarities of hMPV with several other viruses, such as the human respiratory syncytial virus or influenza virus, mechanisms used by hMPV to avoid the host immune system are still unclear. In fact, evidence indicates that hMPV induces a poor innate immune response, thereby affecting the adaptive immunity. Among these mechanisms, is the promotion of an anergic state in T cells, instead of an effective polarization or activation, which could be induced by low levels of cytokine secretion. Further, the evidences support the notion that hMPV interferes with several pattern recognition receptors (PRRs) and cell signaling pathways triggered by interferon-associated genes. However, these mechanisms reported in hMPV are not like the ones reported for hRSV, as the latter has two non-structural proteins that are able to inhibit these pathways. Several reports suggest that viral glycoproteins, such as G and SH, could play immune-modulator roles during infection. In this work, we discuss the state of the art regarding the mechanisms that underlie the poor immunity elicited by hMPV. Importantly, these mechanisms will be compared with those elicited by other common respiratory viruses. © 2018 Frontiers Media S.A. All rights reserved.https://www.frontiersin.org/articles/10.3389/fimmu.2018.02466/ful
Neutrinoless double-beta decay with three or four neutrino mixing
Considering the scheme with mixing of three neutrinos and a mass hierarchy
that can accommodate the results of solar and atmospheric neutrino experiments,
it is shown that the results of solar neutrino experiments imply a lower bound
for the effective Majorana mass in neutrinoless double-beta decay, under the
natural assumptions that massive neutrinos are Majorana particles and there are
no unlikely fine-tuned cancellations among the contributions of the different
neutrino masses. Considering the four-neutrino schemes that can accommodate
also the results of the LSND experiment, it is shown that only one of them is
compatible with the results of neutrinoless double-beta decay experiments and
with the measurement of the abundances of primordial elements produced in
Big-Bang Nucleosynthesis. It is shown that in this scheme, under the
assumptions that massive neutrinos are Majorana particles and there are no
cancellations among the contributions of the different neutrino masses, the
results of the LSND experiment imply a lower bound for the effective Majorana
mass in neutrinoless double-beta decay.Comment: 18 pages including 2 figures, RevTe
Precision Neutrino Oscillation Physics with an Intermediate Baseline Reactor Neutrino Experiment
We discuss the physics potential of intermediate km
baseline experiments at reactor facilities, assuming that the solar neutrino
oscillation parameters and lie in the
high-LMA solution region. We show that such an intermediate baseline reactor
experiment can determine both and with a
remarkably high precision. We perform also a detailed study of the sensitivity
of the indicated experiment to , which drives the
dominant atmospheric () oscillations, and to
- the neutrino mixing angle limited by the data from the CHOOZ and
Palo Verde experiments. We find that this experiment can improve the bounds on
. If the value of is large enough, \sin^2\theta
\gtap 0.02, the energy resolution of the detector is sufficiently good and if
the statistics is relatively high, it can determine with extremely high
precision the value of . We also explore the potential of
the intermediate baseline reactor neutrino experiment for determining the type
of the neutrino mass spectrum, which can be with normal or inverted hierarchy.
We show that the conditions under which the type of neutrino mass hierarchy can
be determined are quite challenging, but are within the reach of the experiment
under discussion.Comment: 25 page
On the two-loop four-derivative quantum corrections in 4D N = 2 superconformal field theories
In \cN = 2, 4 superconformal field theories in four space-time dimensions,
the quantum corrections with four derivatives are believed to be severely
constrained by non-renormalization theorems. The strongest of these is the
conjecture formulated by Dine and Seiberg in hep-th/9705057 that such terms are
generated only at one loop. In this note, using the background field
formulation in \cN = 1 superspace, we test the Dine-Seiberg proposal by
comparing the two-loop F^4 quantum corrections in two different superconformal
theories with the same gauge group SU(N): (i) \cN = 4 SYM (i.e. \cN = 2 SYM
with a single adjoint hypermultiplet); (ii) \cN = 2 SYM with 2N hypermultiplets
in the fundamental. According to the Dine-Seiberg conjecture, these theories
should yield identical two-loop F^4 contributions from all the supergraphs
involving quantum hypermultiplets, since the pure \cN = 2 SYM and ghost sectors
are identical provided the same gauge conditions are chosen. We explicitly
evaluate the relevant two-loop supergraphs and observe that the F^4 corrections
generated have different large N behaviour in the two theories under
consideration. Our results are in conflict with the Dine-Seiberg conjecture.Comment: 26 pages, 4 EPS figures. V2: comments, appendix added. V3: a misprint
removed, discussion in the appendix of cancellation of divergences improved.
V4: typos corrected, the version to appear in NPB. V5: error in eq. (4.12)
corrected, conclusions unchange
Neutrinoless Double Beta Decay in Light of SNO Salt Data
In the SNO data from its salt run, probably the most significant result is
the consistency with the previous results without assuming the 8B energy
spectrum. In addition, they have excluded the maximal mixing at a very high
confidence level. This has an important implication on the double beta decay
experiments. For the inverted or degenerate mass spectrum, we find
|_{ee}| > 0.013 eV at 95% CL, and the next generation experiments can
discriminate Majorana and Dirac neutrinos if the inverted or degenerate mass
spectrum will be confirmed by the improvements in cosmology, tritium data beta
decay, or long-baseline oscillation experiments.Comment: REVTEX4, three figures. Now uses the updated SK atmospheric data
rather than naive rescaling. Conclusion unchanged. References adde
Matter effects and CP violating neutrino oscillations with non-decoupling heavy neutrinos
The evolution equation for active and sterile neutrinos propagating in
general anisotropic or polarized background environment is found and solved for
a special case when heavy neutrinos do not decouple, resulting in non-unitary
mixing among light neutrino states. Then new CP violating neutrino oscillation
effects appear. In contrast to the standard unitary neutrino oscillations these
effects can be visible even for two flavour neutrino transitions and even if
one of the elements of the neutrino mixing matrix is equal to zero. They do not
necessarily vanish with and they are different for various
pairs of flavour neutrino transitions (), (), (). Neutrino oscillations in vacuum and Earth's
matter are calculated for some fixed baseline experiments and a comparison
between unitary and non-unitary oscillations are presented. It is shown, taking
into account the present experimental constraints, that heavy neutrino states
can affect CP and T asymmetries. This is especially true in the case of
oscillations.Comment: 18 pages, 6 fig
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