Search for a heavy magnetic monopole at the Fermilab Tevatron and CERN LHC

If a heavy Dirac monopole exists, the light to light scattering below the monopole production threshold is enhanced due to the strong coupling of monopoles to photons. This effect could be observable in the collision of virtual photons at proton colliders. At the Tevatron it will be seen as pair production of photons with energies 200--400 GeV and roughly compensated transverse momenta 100--400 GeV/c. This effect could be seen at monopole masses about 1--2.5 TeV at the upgraded Tevatron and 7.4--19 TeV at LHC depending on monopole spin.Comment: 11 pages, 2 figures, Latex(Revtex), small changes in estimates of Sect.III and in Fig.2 due to corrected form factor scale of eq. (19), title made more precis

Charge asymmetry of pions in the process e−e+→e−e+π+π−e^-e^+\to e^-e^+\pi^+\pi^-

The study of the charge asymmetry of produced particles allows to investigate the interference of different production mechanisms and to determine new features of the corresponding amplitudes. In the process $e^- e^+ \to e^- e^+ \pi^+ \pi^-$ the two-pion system is produced via two mechanisms: two-photon (C-even state) and bremsstrahlung (C-odd state) production. We study the charge asymmetry of pions in a differential in the pion momenta cross section originating from an interference between these two mechanisms. At low effective mass of dipions this asymmetry is directly related to the s- and p-phases of elastic $\pi\pi$ scattering. At higher energies it can give new information about the $f_0$ meson family, $f_2(1270)$ meson, etc. The asymmetry is expressed via the pion form factor $F_\pi$ and helicity amplitudes $M_{ab}$ for the subprocess $\gamma^*\gamma\to \pi^+\pi^-$ as $\sum G_{ab}{\rm Re}(F_\pi^*M_{ab})$ where we have calculated analytically the coefficients $G_{ab}$ for the region giving the main contribution to the effect. Several distributions of pions are presented performing a numerical analysis in a model with point-like pions. In the region near the dipion threshold the asymmetry is of the order of 1%. We show that with suitable cuts the signal to background ratio can be increased up to about 10%.Comment: 16 pages, 10 figures, LaTeX, style files for EPJC include

Caregiver depression in families living with autism spectrum disorder: A meta-analysis based on ecological systems theory

This item is only available electronically.Background: Depressive symptoms in family caregivers of persons with autism spectrum disorder are highly prevalent, however the impact of family and social support systems on caregivers’ mental health outcomes is unclear. Aim: To review and map correlates of caregivers’ depressive symptoms using an ecological systems framework. Methods: Thirty-four studies, comprising a pooled sample of 4,968 caregivers, were identified from the Embase, PsycINFO and PubMed databases. Study reporting quality was assessed using the QualSyst tool. Pearsons r, along with fail-safe Ns and heterogeneity, were calculated using random effects modelling. The moderating effect of informal support (perceived, received, network characteristics) was examined. Results: Studies provided good to excellent methodological detail. Weak-to-moderate associations (rw range = -.199 to -.406) were noted between lowered depressive symptoms with positive family unit functioning, relationship quality (marital and parent-child), and informal support (from partners, family, friends). These results were not moderated by the operationalisation of informal support. Conclusions: Clinicians should assess the social and family networks of caregivers to identify those most vulnerable to developing depression. Intervention effectiveness can be enhanced by involving relevant family members in treatment.Thesis (B.PsychSc(Hons)) -- University of Adelaide, School of Psychology, 201

Two-point functions of quenched lattice QCD in Numerical Stochastic Perturbation Theory

We summarize the higher-loop perturbative computation of the ghost and gluon propagators in SU(3) Lattice Gauge Theory. Our final aim is to compare with results from lattice simulations in order to expose the genuinely non-perturbative content of the latter. By means of Numerical Stochastic Perturbation Theory we compute the ghost and gluon propagators in Landau gauge up to three and four loops. We present results in the infinite volume and $a \to 0$ limits, based on a general fitting strategy.Comment: 3 pages, 5 figures, talk at conference QCHS-IX, Madrid 201

Two-point functions of quenched lattice QCD in Numerical Stochastic Perturbation Theory. (I) The ghost propagator in Landau gauge

This is the first of a series of two papers on the perturbative computation of the ghost and gluon propagators in SU(3) Lattice Gauge Theory. Our final aim is to eventually compare with results from lattice simulations in order to enlight the genuinely non-perturbative content of the latter. By means of Numerical Stochastic Perturbation Theory we compute the ghost propagator in Landau gauge up to three loops. We present results in the infinite volume and $a \to 0$ limits, based on a general strategy that we discuss in detail.Comment: 27 pages, 11 figure