DSpace Collection:http://hdl.handle.net/2440/123542015-10-09T08:51:06Z2015-10-09T08:51:06ZLight meson form factors at near physical massesOwen, B.J.Kamleh, W.Leinweber, D.B.Mahbub, M.S.Menadue, B.J.http://hdl.handle.net/2440/950892015-10-07T22:41:29Z2014-12-31T13:30:00ZTitle: Light meson form factors at near physical masses
Author: Owen, B.J.; Kamleh, W.; Leinweber, D.B.; Mahbub, M.S.; Menadue, B.J.
Abstract: The ability for most hadrons to decay via strong interactions prevents the direct measurement of their electromagnetic properties. However, a detailed understanding of how these resonant states feature in scattering processes can allow one to disentangle such information from photo production processes. In particular, there has been increasing interest in the determination of magnetic dipole moments using such methods. In a recent study [1], Gudiño et al. provide the first experimental determination of the magnetic dipole moment of the rho meson. To facilitate a comparison with this experimental determination, we present a calculation of the rho meson and pion electromagnetic form factors calculated in the framework of lattice QCD. Using the PACS-CS 2 + 1 flavor full QCD gauge field configurations, we are able to access low Q² values at near-physical quark masses. Through the use of variational techniques, we control excited state systematics in the matrix elements of the lowest-lying states and gain access to the matrix elements of the first excited state. Our determination of the rho meson g-factor gᵨ = 2.21(8) is in excellent agreement with this experimental determination, but with a significantly smaller uncertainty.2014-12-31T13:30:00ZDevelopment of a radiation track structure clustering algorithm for the prediction of DNA DSB yields and radiation induced cell death in Eukaryotic cellsDouglass, M.Bezak, E.Penfold, S.http://hdl.handle.net/2440/950852015-10-07T22:33:31Z2014-12-31T13:30:00ZTitle: Development of a radiation track structure clustering algorithm for the prediction of DNA DSB yields and radiation induced cell death in Eukaryotic cells
Author: Douglass, M.; Bezak, E.; Penfold, S.
Abstract: The preliminary framework of a combined radiobiological model is developed and calibrated in the current work. The model simulates the production of individual cells forming a tumour, the spatial distribution of individual ionization events (using Geant4-DNA) and the stochastic biochemical repair of DNA double strand breaks (DSBs) leading to the prediction of survival or death of individual cells. In the current work, we expand upon a previously developed tumour generation and irradiation model to include a stochastic ionization damage clustering and DNA lesion repair model. The Geant4 code enabled the positions of each ionization event in the cells to be simulated and recorded for analysis. An algorithm was developed to cluster the ionization events in each cell into simple and complex double strand breaks. The two lesion kinetic (TLK) model was then adapted to predict DSB repair kinetics and the resultant cell survival curve. The parameters in the cell survival model were then calibrated using experimental cell survival data of V79 cells after low energy proton irradiation. A monolayer of V79 cells was simulated using the tumour generation code developed previously. The cells were then irradiated by protons with mean energies of 0.76 MeV and 1.9 MeV using a customized version of Geant4. By replicating the experimental parameters of a low energy proton irradiation experiment and calibrating the model with two sets of data, the model is now capable of predicting V79 cell survival after low energy (<2 MeV) proton irradiation for a custom set of input parameters. The novelty of this model is the realistic cellular geometry which can be irradiated using Geant4-DNA and the method in which the double strand breaks are predicted from clustering the spatial distribution of ionisation events. Unlike the original TLK model which calculates a tumour average cell survival probability, the cell survival probability is calculated for each cell in the geometric tumour model developed in the current work. This model uses fundamental measurable microscopic quantities such as genome length rather than macroscopic radiobiological quantities such as alpha/beta ratios. This means that the model can be theoretically used under a wide range of conditions with a single set of input parameters once calibrated for a given cell line.2014-12-31T13:30:00ZLimit on the ultrahigh-energy neutrino flux from lunar observations with the Parkes radio telescopeBray, J.D.Ekers, R.D.Roberts, P.Reynolds, J.E.James, C.W.Phillips, C.J.Protheroe, R.J.McFadden, R.A.Aartsen, M.G.http://hdl.handle.net/2440/950602015-10-06T22:03:16Z2014-12-31T13:30:00ZTitle: Limit on the ultrahigh-energy neutrino flux from lunar observations with the Parkes radio telescope
Author: Bray, J.D.; Ekers, R.D.; Roberts, P.; Reynolds, J.E.; James, C.W.; Phillips, C.J.; Protheroe, R.J.; McFadden, R.A.; Aartsen, M.G.
Abstract: We report a limit on the ultrahigh-energy neutrino flux based on a nondetection of radio pulses from neutrino-initiated particle cascades in the Moon, in observations with the Parkes radio telescope undertaken as part of the LUNASKA project. Because of the improved sensitivity of these observations, which had an effective duration of 127 hours and a frequency range of 1.2–1.5 GHz, this limit extends to lower neutrino energies than those from previous lunar radio experiments, with a detection threshold below 1020 eV. The calculation of our limit allows for the possibility of lunar-origin pulses being misidentified as local radio interference, and includes the effect of small-scale lunar surface roughness. The targeting strategy of the observations also allows us to place a directional limit on the neutrino flux from the nearby radio galaxy Centaurus A.2014-12-31T13:30:00ZPion valence-quark parton distribution functionChang, L.Thomas, A.W.http://hdl.handle.net/2440/949942015-10-05T23:18:19Z2014-12-31T13:30:00ZTitle: Pion valence-quark parton distribution function
Author: Chang, L.; Thomas, A.W.
Abstract: Within the Dyson–Schwinger equation formulation of QCD, a rainbow ladder truncation is used to calculate the pion valence-quark distribution function (PDF). The gap equation is renormalized at a typical hadronic scale, of order 0.5 GeV, which is also set as the default initial scale for the pion PDF. We implement a corrected leading-order expression for the PDF which ensures that the valence-quarks carry all of the pion's light-front momentum at the initial scale. The scaling behavior of the pion PDF at a typical partonic scale of order 5.2 GeV is found to be (1−x)ν, with ν≃1.6, as x approaches one.2014-12-31T13:30:00Z