239 research outputs found
Relations between the K_{l3} and tau --> K pi nu_tau decays
We investigate the relations between the K_{l3} and tau --> K pi nu_tau
decays using the meson dominance approach. First, the experimental branching
fractions (BF) for K^-_{e3} and K^0_{e3} are used to fix two normalization
constants (isospin invariance is not assumed). Then, the BF of tau^- -->
K^*(892)^- nu_tau is calculated in agreement with experiment. We further argue
that the nonzero value of the slope parameter lambda_0 of the K^-_{mu3} and
K^0_{mu3} form factors f_0(t) implies the existence of the tau^- -->
K_0^*(1430)^- nu_tau decay. We calculate its BF, together with BF's of the
K^-_{mu3}, K^0_{mu3}, tau- --> K^- pi^0 nu_tau, and tau- --> antiK^0 pi^0
nu_tau decays, as a function of the lambda_0 parameter. At some value of
lambda_0, different for charged and neutral kaons, calculated BF's seem to
match existing data and a prediction is obtained for the tau^- --> K pi nu
decays going through the K_0^*(1430)^- resonance.Comment: 14 pages, RevTeX, epsf.sty, 3 embedded figure
VAMOS: a Pathfinder for the HAWC Gamma-Ray Observatory
VAMOS was a prototype detector built in 2011 at an altitude of 4100m a.s.l.
in the state of Puebla, Mexico. The aim of VAMOS was to finalize the design,
construction techniques and data acquisition system of the HAWC observatory.
HAWC is an air-shower array currently under construction at the same site of
VAMOS with the purpose to study the TeV sky. The VAMOS setup included six water
Cherenkov detectors and two different data acquisition systems. It was in
operation between October 2011 and May 2012 with an average live time of 30%.
Besides the scientific verification purposes, the eight months of data were
used to obtain the results presented in this paper: the detector response to
the Forbush decrease of March 2012, and the analysis of possible emission, at
energies above 30 GeV, for long gamma-ray bursts GRB111016B and GRB120328B.Comment: Accepted for pubblication in Astroparticle Physics Journal (20 pages,
10 figures). Corresponding authors: A.Marinelli and D.Zaboro
GRB091127/SN2009nz and the VLT/X-shooter spectroscopy of its host galaxy: probing the faint end of the mass-metallicity relation
We perform a detailed study of the gamma-ray burst GRB091127/SN2009nz host
galaxy at z=0.490 using the VLT/X-shooter spectrograph in slit and
integral-field unit (IFU). From the analysis of the optical and X-ray afterglow
data obtained from ground-based telescopes and Swift-XRT we confirm the
presence of a bump associated with SN2009nz and find evidence of a possible jet
break in the afterglow lightcurve. The X-shooter afterglow spectra reveal
several emission lines from the underlying host, from which we derive its
integrated properties. These are in agreement with those of previously studied
GRB-SN hosts and, more generally, with those of the long GRB host population.
We use the Hubble Space Telescope and ground based images of the host to
determine its stellar mass (M_star). Our results extend to lower M_star values
the M-Z plot derived for the sample of long GRB hosts at 0.3<z<1.0 adding new
information to probe the faint end of the M-Z relation and the shift of the
LGRB host M-Z relation from that found from emission line galaxy surveys.
Thanks to the IFU spectroscopy we can build the 2D velocity, velocity
dispersion and star formation rate (SFR) maps. They show that the host galaxy
has a perturbed rotation kinematics with evidence of a SFR enhancement
consistent with the afterglow position.Comment: 10 pages, 6 figures, accepted for publication in A&A. Major revision
on the host metallicit
The association between alcohol use, alcohol use disorders and tuberculosis (TB). A systematic review
<p>Abstract</p> <p>Background</p> <p>In 2004, tuberculosis (TB) was responsible for 2.5% of global mortality (among men 3.1%; among women 1.8%) and 2.2% of global burden of disease (men 2.7%; women 1.7%). The present work portrays accumulated evidence on the association between alcohol consumption and TB with the aim to clarify the nature of the relationship.</p> <p>Methods</p> <p>A systematic review of existing scientific data on the association between alcohol consumption and TB, and on studies relevant for clarification of causality was undertaken.</p> <p>Results</p> <p>There is a strong association between heavy alcohol use/alcohol use disorders (AUD) and TB. A meta-analysis on the risk of TB for these factors yielded a pooled relative risk of 2.94 (95% CI: 1.89-4.59). Numerous studies show pathogenic impact of alcohol on the immune system causing susceptibility to TB among heavy drinkers. In addition, there are potential social pathways linking AUD and TB. Heavy alcohol use strongly influences both the incidence and the outcome of the disease and was found to be linked to altered pharmacokinetics of medicines used in treatment of TB, social marginalization and drift, higher rate of re-infection, higher rate of treatment defaults and development of drug-resistant forms of TB. Based on the available data, about 10% of the TB cases globally were estimated to be attributable to alcohol.</p> <p>Conclusion</p> <p>The epidemiological and other evidence presented indicates that heavy alcohol use/AUD constitute a risk factor for incidence and re-infection of TB. Consequences for prevention and clinical interventions are discussed.</p
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