Search for energetic cosmic axions utilizing terrestrial/celestial magnetic fields

Orbiting $\gamma$-detectors combined with the magnetic field of the Earth or the Sun can work parasitically as cosmic axion telescopes. The relatively short field lengths allow the axion-to-photon conversion to be coherent for $m_{axion} \sim 10^{-4}$ eV, if the axion kinetic energy is above $\sim 500$ keV (Earth's field), or, $\sim 50$ MeV (Sun's field), allowing thus to search for axions from $e^+e^-$ annihilations, from supernova explosions, etc. With a detector angular resolution of $\sim 1^o$, a more efficient sky survey for energetic cosmic axions passing {\it through the Sun} can be performed. Axions or other axion-like particles might be created by the interaction of the cosmic radiation with the Sun, similarly to the axion searches in accelerator beam dump experiments; the enormous cosmic energy combined with the built-in coherent Primakoff effect might provide a sensitive detection scheme, being out of reach with accelerators. The axion signal will be an excess in $\gamma$-rays coming either from a specific celestial place behind the Sun, e.g. the Galactic Center, or, from any other direction in the sky being associated with a violent astrophysical event, e.g. a supernova. Earth bound detectors are also of potential interest. The axion scenario also applies to other stars or binary systems in the Universe, in particular to those with superstrong magnetic fields.Comment: 9 pages, LaTeX, small changes in text and bibliograph

Examining Men’s Perceptions of GBV Prevention Programming Content

As global efforts to engage men in preventing gender-based violence (GBV) continue to grow, understanding male participants’ perceptions of prevention events is needed. Data from a global sample of 319 men who had attended GBV prevention events were used to (a) assess men’s perceptions of what topics were covered, (b) determine whether profiles of these perceptions could be identified, and (c) describe the degree to which content prerception profiles are associated with levels of men’s motivation and confidence related to antiviolence action. Latent class analysis identified four perception profiles of prevention topics. Implications for GBV prevention programming are discussed. © The Author(s) 2018

Walking the Walk or Just Talk?: A Global Examination of Men’s Intentions to Take Violence Preventative Action

Given the increasing prominence of both bystander-based approaches to gender-based violence (GBV) prevention and of proactively engaging men and boys to join efforts to end GBV, understanding the factors that support men’s antiviolence bystander behavior is important. This study examined correlates of willingness to engage in violence preventative bystander behavior in a global sample of 299 adult men engaged in GBV prevention events or work. Participants came from over 50 countries and provided data via an online, anonymous survey available in English, Spanish, and French. Path analysis was used to model participants’ willingness to engage in a variety of violence-preventative behaviors in the future, with variable selection guided by the Theory of Planned Behavior (TPB) and by research implicating gender-related attitudes in bystander willingness and behavior. Findings suggest that bystander willingness was supported by past bystander behavior, self-efficacy to engage in bystander behavior, positive beliefs about the contributions of antiviolence involvement, and by an awareness of male privilege. Social network support for GBV prevention work, and support for gender equity were not significant correlates of bystander willingness in the full path model. These findings held across participants from the Global North and Global South, suggesting that self-efficacy, an awareness of male privilege, and positive attitudes toward antiviolence work are factors which may support men’s violence preventative actions across broad regional contexts. © 2018 Taylor & Franci

Quantum Monte Carlo treatment of elastic exciton-exciton scattering

We calculate cross sections for low energy elastic exciton-exciton scattering within the effective mass approximation. Unlike previous theoretical approaches, we give a complete, non-perturbative treatment of the four-particle scattering problem. Diffusion Monte Carlo is used to calculate the essentially exact energies of scattering states, from which phase shifts are determined. For the case of equal-mass electrons and holes, which is equivalent to positronium-positronium scattering, we find a_s = 2.1 a_x for scattering of singlet-excitons and a_s= 1.5 a_x for triplet-excitons, where a_x is the excitonic radius. The spin dependence of the cross sections arises from the spatial exchange symmetry of the scattering wavefunctions. A significant triplet-triplet to singlet-singlet scattering process is found, which is similar to reported effects in recent experiments and theory for excitons in quantum wells. We also show that the scattering length can change sign and diverge for some values of the mass ratio m_h/m_e, an effect not seen in previous perturbative treatments.Comment: 6 pages, 6 figures. Revision has updated figures, improved paper structure, some minor correction

Simulation study of the inhomogeneous Olami-Feder-Christensen model of earthquakes

Statistical properties of the inhomogeneous version of the Olami-Feder-Christensen (OFC) model of earthquakes is investigated by numerical simulations. The spatial inhomogeneity is assumed to be dynamical. Critical features found in the original homogeneous OFC model, e.g., the Gutenberg-Richter law and the Omori law are often weakened or suppressed in the presence of inhomogeneity, whereas the characteristic features found in the original homogeneous OFC model, e.g., the near-periodic recurrence of large events and the asperity-like phenomena persist.Comment: Shortened from the first version. To appear in European Physical Journal

Hyperons analogous to the \Lambda(1405)

The low mass of the $\Lambda(1405)$ hyperon with $j^P = 1/2^-$, which is higher than the ground state $\Lambda(1116)$ mass by 290 MeV, is difficult to understand in quark models. We analyze the hyperon spectrum in the bound state approach of the Skyrme model that successfully describes both the $\Lambda(1116)$ and the $\Lambda(1405)$. This model predicts that several hyperon resonances of the same spin but with opposite parity form parity doublets that have a mass difference of around 300 MeV, which is indeed realized in the observed hyperon spectrum. Furthermore, the existence of the $\Xi(1620)$ and the $\Xi(1690)$ of $j^P=1/2^-$ is predicted by this model. Comments on the $\Omega$ baryons and heavy quark baryons are made as well.Comment: 4 pages, talk presented at the Fifth Asia-Pacific Conference on Few-Body Problems in Physics 2011 (APFB2011), Aug. 22-26, 2011, Seoul, Kore

Methods to Determine Neutrino Flux at Low Energies:Investigation of the Low ν\nu Method

We investigate the "low-$\nu$" method (developed by the CCFR/NUTEV collaborations) to determine the neutrino flux in a wide band neutrino beam at very low energies, a region of interest to neutrino oscillations experiments. Events with low hadronic final state energy $\nu<\nu_{cut}$ (of 1, 2 and 5 GeV) were used by the MINOS collaboration to determine the neutrino flux in their measurements of neutrino ($\nu_\mu$) and antineutrino (\nub_\mu) total cross sections. The lowest $\nu_\mu$ energy for which the method was used in MINOS is 3.5 GeV, and the lowest \nub_\mu energy is 6 GeV. At these energies, the cross sections are dominated by inelastic processes. We investigate the application of the method to determine the neutrino flux for $\nu_\mu$, \nub_\mu energies as low as 0.7 GeV where the cross sections are dominated by quasielastic scattering and $\Delta$(1232) resonance production. We find that the method can be extended to low energies by using $\nu_{cut}$ values of 0.25 and 0.50 GeV, which is feasible in fully active neutrino detectors such as MINERvA.Comment: 25 pages, 32 figures, to be published in European Physics Journal

Excited Baryons in Lattice QCD

We present first results for the masses of positive and negative parity excited baryons calculated in lattice QCD using an O(a^2)-improved gluon action and a fat-link irrelevant clover (FLIC) fermion action in which only the irrelevant operators are constructed with APE-smeared links. The results are in agreement with earlier calculations of N^* resonances using improved actions and exhibit a clear mass splitting between the nucleon and its chiral partner. An correlation matrix analysis reveals two low-lying J^P=(1/2)^- states with a small mass splitting. The study of different Lambda interpolating fields suggests a similar splitting between the lowest two Lambda1/2^- octet states. However, the empirical mass suppression of the Lambda^*(1405) is not evident in these quenched QCD simulations, suggesting a potentially important role for the meson cloud of the Lambda^*(1405) and/or a need for more exotic interpolating fields.Comment: Correlation matrix analysis performed. Increased to 400 configurations. 22 pages, 13 figures, 15 table

Nuclear muon capture by 3He: meson exchange currents for the triton channel

Exchange current corrections are calculated using currents found from the hard-pion model and AV14+3BF wavefunctions. Results are given for the rate and spin observables. Their sensitivity to g_P, the nucleon pseudoscalar form factor, is reported.Comment: 35 pages, uuencoded gz-compressed tar file 42 Kbyte

Resonances in the three-neutron system

A study of 3-body resonances has been performed in the framework of configuration space Faddeev equations. The importance of keeping a sufficient number of terms in the asymptotic expansion of the resonance wave function is pointed out. We investigated three neutrons interacting in selected force components taken from realistic nn forces.Comment: 38 pages, 11 tables, 4 figure