24 research outputs found
Decay and Scattering
Using chiral low energy theorems and elastic unitarity assumption, the
decay is investigated. The vector and scalar form
factors are calculated. It is found that the spectrum is dominated by
the resonance. By measuring the forward-backward asymmetry, it is shown
that the S wave phase shift can be determined near the
resonance region. The calculated branching ratio and resonance parameters are
in good agreement with experiments.Comment: 15 pages, Tex, 6 included figure
A low-lying scalar meson nonet in a unitarized meson model
A unitarized nonrelativistic meson model which is successful for the
description of the heavy and light vector and pseudoscalar mesons yields, in
its extension to the scalar mesons but for the same model parameters, a
complete nonet below 1 GeV. In the unitarization scheme, real and virtual
meson-meson decay channels are coupled to the quark-antiquark confinement
channels. The flavor-dependent harmonic-oscillator confining potential itself
has bound states epsilon(1.3 GeV), S(1.5 GeV), delta(1.3 GeV), kappa(1.4 GeV),
similar to the results of other bound-state qqbar models. However, the full
coupled-channel equations show poles at epsilon(0.5 GeV), S(0.99 GeV),
delta(0.97 GeV), kappa(0.73 GeV). Not only can these pole positions be
calculated in our model, but also cross sections and phase shifts in the
meson-scattering channels, which are in reasonable agreement with the available
data for pion-pion, eta-pion and Kaon-pion in S-wave scattering.Comment: A slightly revised version of Zeitschrift fuer Physik C30, 615 (1986
A global fit of and elastic scattering in ChPT with dispersion relations
We apply the one-loop results of the ChPT suplemented
with the inverse amplitude method to fit the available experimental data on
and scattering. With esentially only three parameters we
describe accurately data corresponding to six different channels, namely
and . In addition we
reproduce the first resonances of the and channel with the
right mass corresponding to the and the particles.Comment: 19 pages, 5 figures available on request, FT/UCM/10/9
Isospin breaking corrections to low-energy pi-K scattering
We evaluate the matrix elements for the processes pi^0 K^0 -> pi^0 K^0 and
pi^- K^+ -> pi^0 K^0 in the presence of isospin breaking terms at leading and
next-to-leading order. As a direct application the releveant combination of the
S-wave scattering lengths involved in the pion-kaon atom lifetime is
determined. We discuss the sensitivity of the results with respect to the input
parameters.Comment: 33 pages, plain latex, 2 figure
- scattering lengths at finite temperature in the Nambu--Jona-Lasinio model
The transition amplitude for scattering is evaluated within the SU(3)
Nambu--Jona-Lasinio model. Ordering terms according to the expansion in
leads to a box-like diagram, channel diagrams that admit scalar isoscalar
exchanges, and a channel exchange of a scalar isodoublet
that has quantum numbers corresponding to the . Both
the Pauli-Villars and O(3) regularization procedures are used to evaluate the
T=0 values of the scattering lengths and . The
finite temperature dependence is studied. We find that the variation in the
channel in the calculation of leads to a change in of a
factor of about two over the temperature range of T=150 MeV
Sketching to remember: episodic free recall task support for child witnesses and victims with autism spectrum disorder
Deficits in episodic free-recall memory performance have been reported in children with autism spectrum disorder (ASD), yet best practice dictates that child witness/victim interviews commence with a free-recall account. No ‘tools’ exist to support children with ASD to freely recall episodic information. Here, the efficacy of a novel retrieval technique, Sketch reinstatement of context (Sketch-RC), is compared with mental reinstatement of context and a no support control. Ninety children (45 with ASD; 45 matched typically developing) viewed a stimulus film, and were interviewed using one of the aforementioned techniques. The Sketch-RC technique was most effective, improving ASD participants’ remembering without a concomitant increase in intrusions. This procedure offers a population-appropriate method for supporting free recall in criminal justice settings
Motor and cognitive outcome in patients with Parkinson's disease 8 years after subthalamic implants
Deep brain stimulation of the subthalamic nucleus represents the most important innovation for treatment of advanced Parkinson's disease. Prospective studies have shown that although the beneficial effects of this procedure are maintained at 5 years, axial motor features and cognitive decline may occur in the long term after the implants. In order to address some unsolved questions raised by previous studies, we evaluated a series of 20 consecutive patients who received continuous stimulation for 8 years. The overall motor improvement reported at 5 years (55.5% at Unified Parkinson's Disease Rating Scale-motor part, P < 0.001 compared with baseline) was only partly retained 3 years later (39%, P < 0.001, compared with baseline; -16.5%, P < 0.01, compared with 5 years), with differential effects on motor features: speech did not improve and postural stability worsened (P < 0.05). The preoperative levodopa equivalent daily dose was reduced by 58.2% at 5 years and by 60.3% at 8 years. In spite of subtle worsening of motor features, a dramatic impairment in functional state (-56.6% at Unified Parkinson's Disease Rating Scale-Activities of Daily Living, P < 0.01) emerged after the fifth year of stimulation. The present study did not reveal a predictive value of preoperative levodopa response, whereas few single features at baseline (such as gait and postural stability motor scores and the preoperative levodopa equivalent daily dose) could predict long-term motor outcome. A decline in verbal fluency (slightly more pronounced than after 5 years) was detected after 8 years. A significant but slight decline in tasks of abstract reasoning, episodic memory and executive function was also found. One patient had developed dementia at 5 years with further progression at 8 years. Executive dysfunction correlated significantly with postural stability, suggesting interplay between axial motor deterioration and cognition. Eight years after surgery, no significant change was observed on scales assessing depression or anxiety when compared with baseline. At 8 years, there was no significant increase of side-effects when compared with 5-year follow-up. In conclusion, deep brain stimulation of the subthalamic nucleus is a safe procedure with regard to cognitive and behavioural morbidity over long-term follow-up. However, the global benefit partly decreases later in the course of the disease, due to progression of Parkinson's disease and the appearance of medication- and stimulation-resistant symptoms