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Search Results: 1 - 10 of 200629 matches for " P. Blunden "
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Interpretation of the neutron quantum gravitational states in terms of isospectral potentials
S. Kondratyuk,P. G. Blunden
Physics , 2009,
Abstract: The recently observed quantum states of neutrons bound in a gravitational field are analyzed in the framework of one-parameter isospectral hamiltonians. Potentials isospectral to the usual Newton potential are explicitly constructed for the first time, then constrained using measured properties of the neutron gravitational states. The corresponding wave functions and the neutron fluxes are also calculated and analyzed in a simple model, including the ground state and the excited state contributions. The constructed isospectral potentials are discussed as candidates for a possible modification of Newton's law at a submillimetre scale. Our results indicate that significant deviations from the Newtonian gravity at submillimetre distances could be compatible with experiment.
Contribution of spin 1/2 and 3/2 resonances to two-photon exchange effects in elastic electron-proton scattering
S. Kondratyuk,P. G. Blunden
Physics , 2007, DOI: 10.1103/PhysRevC.75.038201
Abstract: We calculate contributions of hadron resonances to two-photon exchange effects in electron-proton scattering. In addition to the nucleon and P33 resonance, the following heavier resonances are included as intermediate states in the two-photon exchange diagrams: D13, D33, P11, S11 and S31. We show that the corrections due to the heavier resonances are smaller that the dominant nucleon and P33 contributions. We also find that there is a partial cancellation between the contributions from the spin 1/2 and spin 3/2 resonances, which results in a further suppression of their aggregate two-photon exchange effect.
Connection between the high energy-scale evolution of the P- and T-odd $πN N$ coupling constant and the strong $πN N$ interaction
P. G. Blunden,S. Kondratyuk
Physics , 2007, DOI: 10.1088/0954-3899/35/11/115001
Abstract: The large energy-scale behaviour of the parity and time-reversal violating (PTV) pion-nucleon coupling constant is analyzed in a model combining renormalization-group techniques and the dressing of the PTV vertex with a pion loop. With the strong $\pi N N$ vertex as a mixture of the pseudovector and pseudoscalar couplings, we show that depending on the admixture parameter, two qualitatively distinct types of behaviour are obtained for the PTV coupling constant at high energy scales: an asymptotic freedom or a fixed-point. We find a critical value of the admixture parameter which delineates these two scenarios. Several examples of the high-energy scale behaviour of the PTV $\pi N N$ constant are considered, corresponding to realistic hadronic models of the strong pion-nucleon interaction.
P- and T-violating $πN N$ form factor
S. Kondratyuk,P. G. Blunden
Physics , 2006, DOI: 10.1016/j.nuclphysa.2006.12.054
Abstract: The form factor of the parity and time-reversal violating (PTV) pion-nucleon interaction is calculated from one-loop vertex diagrams. The degrees of freedom included in the effective lagrangian are nucleons, pions, $\eta$, $\rho$ and $\omega$ mesons. We show that by studying the form factor one can constrain the PTV meson-nucleon coupling constants. We evaluate the mean square radius associated with the PTV $\pi N N$ vertex. Using the mean square radius, we estimate the effect of the PTV $\pi N N$ vertex on the neutron electric dipole moment, and find a very small correction. We also extract the renormalisation group $\beta$ function and use it to discuss evolution of the PTV $\pi N N$ coupling constant beyond the hadronic mass scale.
Q^2-evolution of the electric and magnetic polarizabilities of the proton
A. Sibirtsev,P. G. Blunden
Physics , 2013, DOI: 10.1103/PhysRevC.88.065202
Abstract: The generalized Baldin sum rule at finite four-momentum transfer Q^2 is evaluated utilizing a structure function parameterization fit to recent experimental data. The most recent measurements on F_1 from Hall C at Jlab, as well as the F_2 structure function data from Hall B at Jlab and SLAC, were used in constructing our parameterization. We find that at Q^2 below 1 GeV^2 the dominant contribution to the electric and magnetic polarizabilities of the nucleon comes from the resonance region.
Calculation of two-photon exchange effects for $Δ$ production in electron-proton collisions
S. Kondratyuk,P. G. Blunden
Physics , 2006, DOI: 10.1016/j.nuclphysa.2006.07.038
Abstract: We present an evaluation of a two-photon exchange correction to the cross section for unpolarized $\Delta$ isobar production in electron-proton collisions, using a relativistic, crossing symmetric and gauge invariant approach. The calculated box and crossed-box diagrams include nucleon and $\Delta$ intermediate states. We find a relation between the angular nonlinearity of the two-photon exchange contribution and the value of the $\gamma \Delta \Delta$ coupling constant.
Computational Model for Electron-Nucleon Scattering and Weak Charge of the Nucleon
A. Aleksejevs,S. Barkanova,P. G. Blunden
Physics , 2007, DOI: 10.1088/0954-3899/36/4/045101
Abstract: We show how computational symbolic packages such as FeynArts and FormCalc can be adopted for the evaluation of one-loop hadronic electroweak radiative corrections for electron-nucleon scattering and applied to calculations of the nucleon weak charge. Several numerical results are listed, and found to be in good agreement with the current experimental data.
Radiative corrections and parity-violating electron-nucleon scattering
S. Barkanova,A. Aleksejevs,P. G. Blunden
Physics , 2002,
Abstract: Radiative corrections to the parity-violating asymmetry measured in elastic electron-proton scattering are analyzed in the framework of the Standard Model. We include the complete set of one-loop contributions to one quark current amplitudes. The contribution of soft photon emission to the asymmetry is also calculated, giving final results free of infrared divergences. The one quark radiative corrections, when combined with previous work on many quark effects and recent SAMPLE experimental data, are used to place some new constraints on electroweak form factors of the nucleon.
Review of two-photon exchange in electron scattering
J. Arrington,P. G. Blunden,W. Melnitchouk
Physics , 2011, DOI: 10.1016/j.ppnp.2011.07.003
Abstract: We review the role of two-photon exchange (TPE) in electron-hadron scattering, focusing in particular on hadronic frameworks suitable for describing the low and moderate Q^2 region relevant to most experimental studies. We discuss the effects of TPE on the extraction of nucleon form factors and their role in the resolution of the proton electric to magnetic form factor ratio puzzle. The implications of TPE on various other observables, including neutron form factors, electroproduction of resonances and pions, and nuclear form factors, are summarized. Measurements seeking to directly identify TPE effects, such as through the angular dependence of polarization measurements, nonlinear epsilon contributions to the cross sections, and via e+ p to e- p cross section ratios, are also outlined. In the weak sector, we describe the role of TPE and gamma-Z interference in parity-violating electron scattering, and assess their impact on the extraction of the strange form factors of the nucleon and the weak charge of the proton.
Behavioural Sleep Disorders across the Developmental Age Span: An Overview of Causes, Consequences and Treatment Modalities  [PDF]
Sarah Lee Blunden
Psychology (PSYCH) , 2012, DOI: 10.4236/psych.2012.33035
Abstract: Behavioural sleep problems, that is, sleep problems that do not have a physiological aetiology, but rather a behavioural or psychological aetiology, are reported in between 20% - 40% of children and adolescents. These sleep disorders are categorised as Behavioural Insomnia of Childhood (BIC) in the International Classification of Sleep Disorders. BIC can result in short sleep duration and poor quality sleep and can have wide ranging effects on mental and physical health, cognitive and social functioning and development in infants, pre-schoolers, school aged children and adolescents. Each age group have a particular set of behaviourally based sleep disorders. This paper presents a broad overview of BIC and covers essential information about these sleep disorders, their aetiologies, effects on development and non medical treatment modalities.
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