1,693 research outputs found
On the amplitudes for the CP-conserving rare decay modes
The amplitudes for the rare decay modes and
are studied with the aim of obtaining predictions for
them, such as to enable the possibility to search for violations of
lepton-flavour universality in the kaon sector. The issue is first addressed
from the perspective of the low-energy expansion, and a two-loop representation
of the corresponding form factors is constructed, leaving as unknown quantities
their values and slopes at vanishing momentum transfer. In a second step a
phenomenological determination of the latter is proposed. It consists of the
contribution of the resonant two-pion state in the wave, and of the leading
short-distance contribution determined by the operator-product expansion. The
interpolation between the two energy regimes is described by an infinite tower
of zero-width resonances matching the QCD short-distance behaviour. Finally,
perspectives for future improvements in the theoretical understanding of these
amplitudes are discussed.Comment: 49 pages, 11 figures, matches the published versio
Assuming Regge trajectories in holographic QCD: from OPE to Chiral Perturbation Theory
The soft wall model in holographic QCD has Regge trajectories but wrong
operator product expansion (OPE) for the two-point vectorial QCD Green
function. We modify the dilaton potential to comply OPE. We study also the
axial two-point function using the same modified dilaton field and an
additional scalar field to address chiral symmetry breaking. OPE is recovered
adding a boundary term and low energy chiral parameters, and ,
are well described analytically by the model in terms of Regge spacing and QCD
condensates. The model nicely supports and extends previous theoretical
analyses advocating Digamma function to study QCD two-point functions in
different momentum regions.Comment: Major changes to improve the presentation of the paper but main
results unchanged. Added appendix on Regge progressio
Standard Model and New Physics contributions to and into four leptons
We study the and decays into four leptons () where we use a form factor
motivated by vector meson dominance, and show the dependence of the branching
ratios and spectra from the slopes. A precise determination of short distance
contribution to is affected by our ignorance on the sign of the
amplitude but we show a possibility to
measure the sign of this amplitude by studying and decays in four
leptons. We also investigate the effect of New Physics contributions for these
decays.Comment: Improvements of the text and references adde
Spin-1 resonance contributions to the weak Chiral Lagrangian: the vector field formulation
We use the Vector formulation to evaluate vector and axial-vector exchange
contributions to the O(p^4) weak Chiral Lagrangian. We recover in this
framework the bulk of the contributions found previously by Ecker et al. in the
antisymmetric formulation of vectors and axial-vectors, but new interesting
features arise: i) most of our results are independent of Factorization and ii)
novel contributions to non-leptonic kaon decays, proper of this formulation and
phenomenologically interesting, are found. The phenomenological implications
for K -> pi pi (pi) and radiative (anomalous and non-anomalous) non-leptonic
kaon decays are thus investigated and found particularly relevant.Comment: 34 pages, plain LaTeX file, uses rotating.sty also include
Rare Kaon Decays Revisited
We present an updated discussion of K\ra\pi \bar{l} l decays in a combined
framework of chiral perturbation theory and Large-- QCD, which assumes the
dominance of a minimal narrow resonance structure in the invariant mass
dependence of the pair. The proposed picture reproduces very well,
both the experimental K^+\ra\pi^+ e^+ e^- decay rate and the invariant mass spectrum. The predicted Br(K_S\ra\pi^0 e^+ e^-) is, within errors,
consistent with the recently reported result from the NA48 collaboration.
Predictions for the K\ra\pi \mu^{+}\mu^{-} modes are also obtained. We find
that the resulting interference between the {\it direct} and {\it indirect}
CP--violation amplitudes in K_L\ra\pi^0 e^+ e^- is constructive
Evans Syndrome Presented with Marginal Zone Lymphoma and Duodenal Neuroendocrine Tumor in an Elderly Woman
Summary Evans syndrome (ES) is an autoimmune disorder characterized by simultaneous or sequential development of autoimmune hemolytic anemia, immune thrombocytopenia, and/or neutropenia. ES can be classified as a primary (idiopathic) or secondary (associated with an underlying disease) syndrome. We report a case of ES in an elderly patient in the presence of multiple trigger factors such as recent influenza vaccine, marginal zone lymphoma, and neuroendocrine tumor G1. Whether this association is casual or causal remains a matter of speculation. It is however necessary to have a thorough work-up in a newly diagnosed ES and a more accurate search of miscellaneous factors especially in elderly patients
Role of permanent atrial fibrillation (AF) on long-term mortality in community-dwelling elderly people with and without chronic heart failure (CHF)
Permanent AF is characterized by an increased mortality in elderly subjects with CHF. Moreover, AF increased the risk of mortality also in elderly subjects without CHF. Thus, we examined long-term mortality in community-dwelling elderly people with and without CHF. A total of 1332 subjects aged 65 and older were selected from the electoral rolls of Campania, a region of southern Italy. The relationship between AF and mortality during a 12-year follow-up in 125 subjects with CHF and in 1.143 subjects without CHF were studied. Elderly subjects showed a higher mortality in those with respect to those without AF (72.1% vs. 51.8%; p < 0.01). Similarly, elderly subjects without CHF showed a higher mortality in those with respect to those without AF (61.8% vs. 49.8%; p < 0.05). In contrast, elderly subjects with CHF showed a similar mortality in those with respect to those without AF (74.7% vs. 82.4%; p = 0.234). Multivariate analysis shows that AF was predictive of mortality in all elderly subjects (Hazard Risk = HR = 1.39, 95% confidence interval (CI) = 1.25-2.82; p < 0.001). When the analysis was conducted considering the presence and the absence of CHF, AF was strongly predictive of mortality in elderly subjects without CHF (HR = 1.95, 95% CI = 1.25-4.51; p < 0.001) but not in those with CHF (HR = 1.12, 95% CI = 0.97-3.69; p = 0.321). We concluded that AF is able to predict long-term mortality in elderly subjects. Moreover, AF is strongly predictive of long-term mortality in the absence but not in the presence of CHF. (C) 2011 Elsevier Ireland Ltd. All rights reserved
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