16,292 research outputs found
Signals for New Spin-1 Resonances in Electroweak Gauge Boson Pair Production at the LHC
The mechanism of electroweak symmetry breaking (EWSB) will be directly
scrutinized soon at the CERN Large Hadron Collider (LHC). We analyze the LHC
potential to look for new vector bosons associated with the EWSB sector. We
present a possible model independent approach to search for these new spin--1
resonances. We show that the analyses of the processes pp --> l^+ l^- Emiss_T,
l^\pm j j Emiss_T, l^\pm l^+ l^- Emiss_T, and l^+ l^- j j (with l=e or \mu and
j=jet) have a large reach at the LHC and can lead to the discovery or exclusion
of many EWSB scenarios such as Higgsless models.Comment: 10 pages, 11 figure
VirologÃa, epidemiologÃa y mecanismos de transmisión del VHB
Illness due to the hepatitis B virus is an enormous problem for international public health, affecting over 300 million persons throughout the world, although its prevalence varies considerably between different geographic areas. The universal vaccination of the newly born, promulgated by the World Health Organisation, has made it possible to partially control the spread of the virus in many countries, including Spain. However, the vaccine does not generate protective antibodies in approximately 5% of the population. Besides, infection by the hepatitis B virus can produce few symptoms and the virus is easily transmitted, making its epidemiological control difficult. On the other hand, the growing flow of bi-directional migration of persons between geographical areas with a moderate or high prevalence and Spain also seems to be contributing to the persistence of the disease in our milieu. All of this makes it compulsory to deploy an ensemble of preventive measures based on an increasingly deep understanding of the biological cycle of the virus. In Spain, as in other regions with a low prevalence, the hepatitis B virus infection is considered chiefly to be a disease of sexual transmission, or else contagion takes place between patients who are users of intravenous drugs. On the other hand, blood transmission is of scarce importance in our milieu. Following exposure to the hepatitis B virus, prophylaxis with immunoglobins and also the administration of the vaccine is highly effective, and acquires special interest for all healthcare workers
Active galactic nuclei synapses: X-ray versus optical classifications using artificial neural networks
(Abridged) Many classes of active galactic nuclei (AGN) have been defined
entirely throughout optical wavelengths while the X-ray spectra have been very
useful to investigate their inner regions. However, optical and X-ray results
show many discrepancies that have not been fully understood yet. The aim of
this paper is to study the "synapses" between the X-ray and optical
classifications.
For the first time, the new EFLUXER task allowed us to analyse broad band
X-ray spectra of emission line nuclei (ELN) without any prior spectral fitting
using artificial neural networks (ANNs). Our sample comprises 162 XMM-Newton/pn
spectra of 90 local ELN in the Palomar sample. It includes starbursts (SB),
transition objects (T2), LINERs (L1.8 and L2), and Seyferts (S1, S1.8, and S2).
The ANNs are 90% efficient at classifying the trained classes S1, S1.8, and
SB. The S1 and S1.8 classes show a wide range of S1- and S1.8-like components.
We suggest that this is related to a large degree of obscuration at X-rays. The
S1, S1.8, S2, L1.8, L2/T2/SB-AGN (SB with indications of AGN), and SB classes
have similar average X-ray spectra within each class, but these average spectra
can be distinguished from class to class. The S2 (L1.8) class is linked to the
S1.8 (S1) class with larger SB-like component than the S1.8 (S1) class. The L2,
T2, and SB-AGN classes conform a class in the X-rays similar to the S2 class
albeit with larger fractions of SB-like component. This SB-like component is
the contribution of the star-formation in the host galaxy, which is large when
the AGN is weak. An AGN-like component seems to be present in the vast majority
of the ELN, attending to the non-negligible fraction of S1-like or S1.8-like
component. This trained ANN could be used to infer optical properties from
X-ray spectra in surveys like eRosita.Comment: 15 pages, 7 figures, accepted for publication in A&A. Appendix B only
in the full version of the paper here:
https://dl.dropboxusercontent.com/u/3484086/AGNSynapsis_OGM_online.pd
Probing Trilinear Gauge Boson Interactions via Single Electroweak Gauge Boson Production at the LHC
We analyze the potential of the CERN Large Hadron Collider (LHC) to study
anomalous trilinear vector-boson interactions W^+ W^- \gamma and W^+ W^- Z
through the single production of electroweak gauge bosons via the weak boson
fusion processes q q -> q q W (-> \ell^\pm \nu) and q q -> q q Z(-> \ell^+
\ell^-) with \ell = e or \mu. After a careful study of the standard model
backgrounds, we show that the single production of electroweak bosons at the
LHC can provide stringent tests on deviations of these vertices from the
standard model prediction. In particular, we show that single gauge boson
production exhibits a sensitivity to the couplings \Delta \kappa_{Z,\gamma}
similar to that attainable from the analysis of electroweak boson pair
production.Comment: 20 pages, 6 figure
Proper motions of the HH1 jet
We describe a new method for determining proper motions of extended objects,
and a pipeline developed for the application of this method. We then apply this
method to an analysis of four epochs of [S~II] HST images of the HH~1 jet
(covering a period of ~yr).
We determine the proper motions of the knots along the jet, and make a
reconstruction of the past ejection velocity time-variability (assuming
ballistic knot motions). This reconstruction shows an "acceleration" of the
ejection velocities of the jet knots, with higher velocities at more recent
times. This acceleration will result in an eventual merging of the knots in
~yr and at a distance of from the outflow source, close to
the present-day position of HH~1.Comment: 12 pages, 8 figure
Stellar density profile and mass of the Milky Way Bulge from VVV data
We present the first stellar density profile of the Milky Way bulge reaching
latitude . It is derived by counting red clump stars within the
colour\--magnitude diagram constructed with the new PSF-fitting photometry from
VISTA Variables in the V\'\i a L\'actea (VVV) survey data. The new stellar
density map covers the area between and
with unprecedented accuracy, allowing to establish a direct link between the
stellar kinematics from the Giraffe Inner Bulge Spectroscopic Survey (GIBS) and
the stellar mass density distribution. In particular, the location of the
central velocity dispersion peak from GIBS matches a high overdensity in the
VVV star count map. By scaling the total luminosity function (LF) obtained from
all VVV fields to the LF from Zoccali et al.(2003), we obtain the first fully
empirical estimate of the mass in stars and remnants of the Galactic bulge.
The Milky Way bulge stellar mass within (, ) is
.Comment: 4 pages, 5 figures, accepted for publication on A&
Piecing the Solar Neutrino Puzzle Together at SNO
We perform an oscillation parameter-independent analysis of solar neutrino
flux measurements from which we predict the charged-current rate at SNO
relative to Standard Solar Model to be for oscillations to active (sterile) neutrinos. By
alternately considering the B flux normalization fixed and free, we find
that the flux measured by Super-Kamiokande (SK) not being a result of
oscillations is strongly disfavored for oscillations to active neutrinos. SNO
will determine the best-fit value of the B flux normalization
(equal to the neutral-current rate), without recourse to neutral-current
measurements, from the derived relation . Using a simple parameterization of the fraction of high,
intermediate, and low energy solar neutrinos starting above resonance, we
reproduce the results of global analyses to good accuracy; we find that the LMA
solution with a normal mass hierarchy is clearly favored. With free,
our analysis for oscillations to active neutrinos gives
, which corresponds to .Comment: Version to appear in PL
- …