Binding energy corrections in positronium decays

Positronium annihilation amplitudes that are computed by assuming a factorization approximation with on-shell intermediate leptons, do not exhibit good analytical behavior. We propose an ansatz which allows to include binding energy corrections and obtain the correct analytical and gauge invariance behavior of these QED amplitudes. As a consequence of these non-perturbative corrections, the parapositronium and orthopositronium decay rates receive corrections of order alpha^4 and alpha^2, respectively. These new corrections for orthopositronium are relevant in view of a precise comparison between recent theoretical and experimental developments. Implications are pointed out for analogous decays of quarkonia .Comment: 11 pages, 1 .ps figure, submitted for publicatio

Parapositronium Decay and Dispersion Relations

Positronium decay rates are computed at the one-loop level, using convolution-type factorized amplitudes. The dynamics of this factorization is probed with dispersion relations, showing that unallowed approximations are usually made, and some ordre alpha^2 corrections missed. Further, we discuss the relevance of the Schrodinger wavefunction as the basis for perturbative calculations. Finally, we apply our formalism to the parapositronium two-photon decay.Comment: LaTeX, 13 pages, 1 eps figur

Analytical Behaviour of Positronium Decay Amplitudes

Positronium annihilation amplitudes that are computed by assuming a factorization approximation with on-shell intermediate leptons do not exhibit good analytical behaviour. Using dispersion techniques, we find new contributions that interfere with the known results to restore analytical properties. Those new amplitudes which cannot be obtained using standard factorized amplitude formalism, contribute at order alpha^2. Therefore they have to be evaluated before any theoretical conclusion can be drawn upon the orthopositronium lifetime puzzle.Comment: LaTeX, 22 pages, 3 eps figure

A New Basis for QED Bound State Computations

A simple method to compute QED bound state properties is presented, in which binding energy effects are treated non-perturbatively. It is shown that to take the effects of all ladder Coulomb photon exchanges into account, one can simply perform the derivative of standard QED amplitudes with respect to the external momentum. For example, the derivative of the light-by-light scattering amplitude gives an amplitude for orthopositronium decay to three photons where any number of Coulomb photon exchanges between the e-e+ is included. Various applications are presented. From them, it is shown that binding energy must be treated non-perturbatively in order to preserve the analyticity of positronium decay amplitudes. Interesting perspectives for quarkonium physics are briefly sketched.Comment: LaTeX, 23 pages, 16 figures. Minor corrections. Some comments adde

Positronium Decay : Gauge Invariance and Analyticity

The construction of positronium decay amplitudes is handled through the use of dispersion relations. In this way, emphasis is put on basic QED principles: gauge invariance and soft-photon limits (analyticity). A firm grounding is given to the factorization approaches, and some ambiguities in the spin and energy structures of the positronium wavefunction are removed. Non-factorizable amplitudes are naturally introduced. Their dynamics is described, especially regarding the enforcement of gauge invariance and analyticity through delicate interferences. The important question of the completeness of the present theoretical predictions for the decay rates is then addressed. Indeed, some of those non-factorizable contributions are unaccounted for by NRQED analyses. However, it is shown that such new contributions are highly suppressed, being of order alpha^3. Finally, a particular effective form factor formalism is constructed for parapositronium, allowing a thorough analysis of binding energy effects and analyticity implementation.Comment: 34 pages, 13 figure

Soft Photon Spectrum in Orthopositronium and Vector Quarkonium Decays

QED gauge invariance, when combined with analyticity, leads to constraints on the low energy end of the emitted photon spectra. This is known as Low's theorem. It is shown that the Ore-Powell result, as well as further developments for the orthopositronium differential decay rate, are in contradiction with Low's theorem, i.e. that their predicted soft photon spectra are incorrect. A solution to this problem is presented. The implications for the orthopositronium lifetime puzzle, the charmonium rho-pi puzzle, the prompt photon spectrum in inclusive quarkonium decays and the extraction of alpha_S from quarkonium annihilation rates are briefly commented.Comment: LaTeX, 10 page

Exploring the synergy between promoting active participation in work and in society and social, health and long-term care strategies

The purpose of this study is to provide information that can help the Commission and EU Member States engage in policy discussion on how social, health and long-term care systems can help enhance participation in work and family, social and community activities and how, in turn, participation in paid employment, family, social and community activities can contribute to healthy and autonomous living at present and in the future. Part I presents a review of the literature on the synergy between health and activity/work. Health affects work and social participation but on the other side work and activity affect health. We focus on people aged 55 and over as this interrelation (double causality) seems to be significant for important life events (retirement decision, social participation, etc.) of this age group. Part II presents a quantitative analysis and tries to identify national specificities. It presents the lessons which we can draw from European surveys. It presents a quantitative analysis based on the LFS, the EU-SILC, the ECHP UDB and SHARE surveys. The fourth step summarises national policies and gives a comparative analysis, while the fifth step presents the best practices. Finally, the last part summarises the main conclusions and the policy implications

Low-dose ketamine for children and adolescents with acute sickle cell disease related pain: A single center experience

Background: Opioids are the mainstay of therapy for painful vasoocclusive episodes (VOEs) in sickle cell disease (SCD). Based on limited studies, low-dose ketamine could be a useful adjuvant analgesic for refractory SCD pain, but its safety and efficacy has not been evaluated in pediatric SCD. Procedure: Using retrospective chart review we recorded and compared characteristics of hospitalizations of 33 children with SCD hospitalized with VOE who were treated with low-dose ketamine and opioid PCA vs. a paired hospitalization where the same patients received opioid PCA without ketamine. We seek to 1) describe a single center experience using adjuvant low-dose ketamine with opioid PCA for sickle cell related pain, 2) retrospectively explore the safety and efficacy of adjuvant low-dose ketamine for pain management, and 3) determine ketamine’s effect on opioid consumption in children and adolescents hospitalized with VOE. Results: During hospitalizations where patients received ketamine, pain scores and opioid use were higher (6.48 vs. 5.99; p=0.002 and 0.040 mg/kg/h vs. 0.032 mg/kg/h; p=0.004 respectively) compared to hospitalizations without ketamine. In 3 patients, ketamine was discontinued due to temporary and reversible psychotomimetic effects. There were no additional short term side effects of ketamine. Conclusions: Low-dose ketamine has an acceptable short-term safety profile for patients with SCD hospitalized for VOE. Lack of an opioid sparing effect of ketamine likely represents use of low-dose ketamine for patients presenting with more severe VOE pain. Prospective randomized studies of adjuvant low-dose ketamine for SCD pain are warranted to determine efficacy and long-term safety

About estimations of an one-photon background in neutrino oscillation experiments at low neutrino energies

The possible sources of one-photon radiation as background for quasi-elastic reaction nu_mu+n to mu^-+p are considered. The ones are relevant in experiments on determination of oscillation parameters at low neutrino energies (E_nu^lab~1 GeV). The estimation for the cross section of reaction nu_mu+n to mu^-+p+gamma is given at E_nu^lab=0.7 GeV as 0.65% from the corresponding cross section of quasi-elastic reaction.Comment: 17 pages, 10 figure