5,432 research outputs found
Pair of Heavy-Exotic-Quarks at LHC
We study the production and signatures of heavy exotic quarks pairs at LHC in
the framework of the vector singlet model (VSM), vector doublet model (VDM) and
fermion-mirror-fermion (FMF) model. The pair production cross sections for the
electroweak and strong sector are computed.Comment: 7 pages, 6 figures. accept at Int. Jour. of Mod. Phy
Doubly charged Higgs from - scattering in the 3-3-1 Model
We studied the production and signatures of doubly charged Higgs bosons in
the process , where is a heavy lepton,
at the International Linear Collider (ILC) and CERN Linear Collider
(CLIC). The intermediate photons are given by the Weizscker-Williams
and laser backscattering distributions. We found that significant signatures
are obtained by bremsstrahlung and backward Comptom scattering of laser. A
clear signal can be obtained for doubly charged Higgs bosons, doubly charged
gauge bosons and heavy leptons
t-channel production of heavy charged leptons
We study the pair production of heavy charged exotic leptons at e+ e-
colliders in the SU(2)_L x SU(2)_I x U(1)_Y model. This gauge group is a
subgroup of the grand unification group E6; SU(2)_I commutes with the electric
charge operator, and the three corresponding gauge bosons are electrically
neutral. In addition to the standard photon and Z boson contributions, we also
include the contributions from extra neutral gauge bosons. A t-channel
contribution due to W_I-boson exchange, which is unsuppressed by mixing angles,
is quite important. We calculate the left-right and forward-backward
asymmetries, and discuss how to differentiate different models.Comment: Increased discussion of experimental signatures. Version accepted by
PR
Patrones de distribución de la cotorra argentina (Myiopsitta monachus) en un hábitat urbano
Varias especies invasoras han demostrado tener una marcada preferencia por los hábitats urbanos. El estudio de las variables responsables de la distribución de estas especies dentro de hábitats urbanos debe permitir predecir cuáles son las variables ambientales indicativas de su hábitat preferido, y diseñar las características del paisaje que hacen a estas áreas ser menos favorables para estas especies. La cotorra argentina Myiopsitta monachus es una especie invasora en muchos países de América y de Europa, siendo las ciudades uno de los hábitats más comunes para esta especie en las áreas invadidas. El propósito de este estudio fue identificar los factores principales que determinan la distribución de la cotorra argentina en Barcelona, una de las ciudades en el mundo con una de las densidades más grande de cotorras. Hemos definido nuestro modelo basado en ocho variables preseleccionadas mediante un modelo lineal generalizado (GLZ) y evaluamos el poder de cada modelo a través de un análisis de inferencia multimodelo basado en el valor AIC. Utilizamos la densidad de cotorra argentina como variable dependiente y restringimos el análisis a aquellos barrios de la ciudad ocupados por la especie, obteniendo un modelo con dos variables clave que explicaban la distribución de la especie. Las cotorras argentinas eran más abundantes en aquellos barrios con alta densidad de árboles y con un alto porcentaje de personas mayores de 65 años. Esto se interpreta por el hecho de que las cotorras utilizan los árboles como fuente de alimento y como lugar de nidificación, y porque las personas mayores a menudo alimentan a la especie. Los datos apoyan la hipótesis de ‘la actividad humana’ para explicar cómo las especies invasoras pueden exitosamente establecerse en un hábitat no nativo, y subraya cómo la limitación de las fuentes de alimento, especialmente la comida suministrada por los seres humanos, puede ser la forma más sencilla de ejercer cierto control sobre las poblaciones de cotorra argentina.Several invasive species have been shown to have a marked preference for urban habitats. The study of the variables responsible for the distribution of these species within urban habitats should allow to predict which environmental variables are indicative of preferred habitat, and to design landscape characteristics that make these areas less conducive to these species. The Monk parakeet Myiopsitta monachus is an invasive species in many American and European countries, and cities are one of its most usual habitats in invaded areas. The aim of this paper was to identify the main factors that determine distribution of the Monk parakeet in Barcelona, one of the cities in the world with the highest parakeet density. We defined our model based on eight preselected variables using a generalized linear model (GLZ) and evaluated the strength of support for each model using the AIC–based multi–model inference approach. We used parakeet density as a dependent variable, and an analysis restricted to occupied neighbourhoods provided a model with two key variables to explain the distribution of the species. Monk parakeets were more abundant in neighbourhoods with a high density of trees and a high percentage of people over 65 years. This is interpreted by the fact that parakeets use trees as food sources and support for the nests, and that older people often feed the species. Data support the ‘human–activity’ hypothesis to explain how invasive species can successfully establish in a non–native habitat, and stress how limiting food resources, especially food supplied by humans, may be the easiest way to exert some control on Monk parakeet populations.Varias especies invasoras han demostrado tener una marcada preferencia por los hábitats urbanos. El estudio de las variables responsables de la distribución de estas especies dentro de hábitats urbanos debe permitir predecir cuáles son las variables ambientales indicativas de su hábitat preferido, y diseñar las características del paisaje que hacen a estas áreas ser menos favorables para estas especies. La cotorra argentina Myiopsitta monachus es una especie invasora en muchos países de América y de Europa, siendo las ciudades uno de los hábitats más comunes para esta especie en las áreas invadidas. El propósito de este estudio fue identificar los factores principales que determinan la distribución de la cotorra argentina en Barcelona, una de las ciudades en el mundo con una de las densidades más grande de cotorras. Hemos definido nuestro modelo basado en ocho variables preseleccionadas mediante un modelo lineal generalizado (GLZ) y evaluamos el poder de cada modelo a través de un análisis de inferencia multimodelo basado en el valor AIC. Utilizamos la densidad de cotorra argentina como variable dependiente y restringimos el análisis a aquellos barrios de la ciudad ocupados por la especie, obteniendo un modelo con dos variables clave que explicaban la distribución de la especie. Las cotorras argentinas eran más abundantes en aquellos barrios con alta densidad de árboles y con un alto porcentaje de personas mayores de 65 años. Esto se interpreta por el hecho de que las cotorras utilizan los árboles como fuente de alimento y como lugar de nidificación, y porque las personas mayores a menudo alimentan a la especie. Los datos apoyan la hipótesis de ‘la actividad humana’ para explicar cómo las especies invasoras pueden exitosamente establecerse en un hábitat no nativo, y subraya cómo la limitación de las fuentes de alimento, especialmente la comida suministrada por los seres humanos, puede ser la forma más sencilla de ejercer cierto control sobre las poblaciones de cotorra argentina
Signal and Backgrounds for Leptoquarks at the LHC II: Vector Leptoquarks
We perform a detailed analyses of the CERN Large Hadron Collider (LHC)
capability to discover first generation vector leptoquarks through their pair
production. We study the leptoquark signals and backgrounds that give rise to
final states containing a pair e+e- and jets. Our results show that the LHC
will be able to discover vector leptoquarks with masses up to 1.3-2.1 TeV
depending on their couplings to fermions and gluons.Comment: 18 pages, 3 figures, REVTe
Much Ado About Leptoquarks: A Comprehensive Analysis
We examine the phenomenological implications of a 200 GeV leptoquark in light
of the recent excess of events at HERA. Given the relative predictions of
events rates in e^+p versus e^-p, we demonstrate that classes of leptoquarks
may be excluded, including those contained in E_6 GUT models. It is shown that
future studies with polarized beams at HERA could reveal the chirality of the
leptoquark fermionic coupling and that given sufficient luminosity in each
e^\pm_{L,R} channel the leptoquark quantum numbers could be determined. The
implications of 200-220 GeV leptoquarks at the Tevatron are examined. While
present Tevatron data most likely excludes vector leptoquarks and leptogluons
in this mass region, it does allow for scalar leptoquarks. We find that while
leptoquarks have little influence on Drell-Yan production, further studies at
the Main Injector are possible in the single production channel. We investigate
precision electroweak measurements as well as the process e^+e^-\to q\bar q at
LEP II and find they provide no further restrictions on these leptoquark
models. We then ascertain that cross section and polarization asymmetry
measurements at the NLC provide the only direct mechanism to determine the
leptoquark's electroweak quantum numbers. The single production of leptoquarks
in \gamma e collisions by both the backscattered laser and Weisacker-Williams
techniques at the NLC is also discussed. Finally, we demonstrate that we can
obtain successful coupling constant unification in models with leptoquarks,
both with or without supersymmetry. The supersymmetric case requires the GUT
group to be larger than SU(5) such as flipped SU(5)\times U(1)_X.Comment: Corrected single production cross section at Tevatron, updated atomic
parity violation constraints, 55 page
Signal and Backgrounds for the Single Production of Scalar and Vector Leptoquarks at the LHC
We perform a detailed analysis of the potentiality of the CERN Large Hadron
Collider to study the single production of leptoquarks via
leptoquark , with generated by the splitting of photons
radiated by the protons. Working with the most general
invariant effective lagrangian for scalar and vector leptoquarks, we analyze in
detail the leptoquark signals and backgrounds that lead to a final state
containing an and a hard jet with approximately balanced transverse
momenta. Our results indicate that the LHC will be able to discover leptoquarks
with masses up to 2--3 TeV, depending on their type, for Yukawa couplings of
the order of the electromagnetic one.Comment: Revtex, 23 pages, 11 postscript files. Uses axodraw.sty (included)
and epsfig.sty. Typos corrected. To be published in Phys. Rev.
Pseudo Goldstone Bosons Phenomenology in Minimal Walking Technicolor
We construct the non-linear realized Lagrangian for the Goldstone Bosons
associated to the breaking pattern of SU(4) to SO(4). This pattern is expected
to occur in any Technicolor extension of the standard model featuring two Dirac
fermions transforming according to real representations of the underlying gauge
group. We concentrate on the Minimal Walking Technicolor quantum number
assignments with respect to the standard model symmetries. We demonstrate that
for, any choice of the quantum numbers, consistent with gauge and Witten
anomalies the spectrum of the pseudo Goldstone Bosons contains electrically
doubly charged states which can be discovered at the Large Hadron Collider.Comment: 25 pages, 5 figure
The crater lake of Ilamatepec (Santa Ana) volcano, El Salvador: insights into lake gas composition and implications for monitoring
We here present the first chemical characterization of the volcanic gas plume issuing from the Santa Ana crater lake, a hyper-acidic crater lake (pH of − 0.2 to 2.5) in north-western El Salvador. Our results, obtained during regular surveys in 2017 and 2018 using a Multi-GAS instrument, demonstrate a hydrous gas composition (H2O/SO2 ratios from 32 to 205) and SO2 as the main sulfur species (H2S/SO2 = 0.03–0.1). We also find that gas composition evolved during our investigated period, with the CO2/SO2 ratio decreasing by one order of magnitude from March 2017 (37.2 ± 9.7) to November 2018 (< 3). This compositional evolution toward more magmatic (SO2-rich) compositions is interpreted in the context of the long-term evolution of the volcano following its 2005 and 2007 eruptions. We find that, in spite of reduced (background-level) seismicity, the magmatic gas supply into the lake was one order of magnitude higher in March 2017 (total volatile flux: 20,200–30,200 t/day) than in the following periods (total volatile flux: 900–10,167 t/day). We propose that the elevated magmatic/hydrothermal transport in March 2017, combined with a 15% reduction in precipitation, caused the volume of the lake to decrease, ultimately reducing its sulfur absorbing and scrubbing capacity, and hence causing the gas plume CO2/SO2 ratio to decrease. The recently observed increases in temperature, acidity, and salinity of the lake are consistent with this hypothesis. We conclude that the installation of a continuous, fully-automated Multi-GAS is highly desirable to monitor any future change in lake plume chemistry, and hence the level of degassing activity
Static quantities of the W boson in the SU_L(3) X U_X(1) model with right-handed neutrinos
The static electromagnetic properties of the boson, and
, are calculated in the SU_L(3)} \times U_X(1) model with
right-handed neutrinos. The new contributions from this model arise from the
gauge and scalar sectors. In the gauge sector there is a new contribution from
a complex neutral gauge boson and a singly-charged gauge boson .
The mass of these gauge bosons, called bileptons, is expected to be in the
range of a few hundreds of GeV according to the current bounds from
experimental data. If the bilepton masses are of the order of 200 GeV, the size
of their contribution is similar to that obtained in other weakly coupled
theories. However the contributions to both and are
negligible for very heavy or degenerate bileptons. As for the scalar sector, an
scenario is examined in which the contribution to the form factors is
identical to that of a two-Higgs-doublet model. It is found that this sector
would not give large corrections to and .Comment: New material included. Final version to apppear in Physical Review
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