arXiv subjects

David Blyth

Publications and source records attributed to David Blyth.

4 recordsLinked to original sources

arXiv2023

Supermassive black holes in a mass-limited galaxy sample

The observed scaling relations between supermassive black hole masses and their host galaxy properties indicate that supermassive black holes influence the evolution of galaxies. However, the scaling relations may be affected by selection biases. We propose to measure black hole masses in a mass-limited galaxy sample including all non-detections to inprove constraints on galaxy mass - black hole mass scaling relations and test for selection bias. We use high spatial resolution spectroscopy from the Keck and Gemini telescopes, and the Jeans Anisotropic Modelling method to measure black hole masses in early type galaxies from the Virgo Cluster. We present four new black hole masses and one upper limit in our mass-selected sample of galaxies of galaxy mass (1.0-3.2) x $10^{10} M_\odot$. This brings the total measured to 11 galaxies out of a full sample of 18 galaxies, allowing us to constrain scaling relations. We calculate a lower limit for the average black hole mass in our sample of 3.7 x $10^{7} M_\odot$. This is at an average galaxy stellar mass of (1.81 +/- 0.14) x $10^{10} M_\odot $ and an average bulge mass of (1.31 +/- 0.15) x $10^{10} M_\odot$. This lower limit shows that black hole masses in early type galaxies are not strongly affected by selection biases.

astro-ph.GA↗

arXiv2021

LGAD Detector Concept for TOPSiDE Project

We report a concept low gain avalanche diode (LGAD) detector to be integrated into TOPSiDE, which is being developed for EIC (Electron-Ion Collider) project. The LGAD detector will be taking its place to resolve requirement of time-of-flight measurement for the TOPSiDE project. To achieve the required timing resolution of 10 ps, the LGAD will be completely monolithic structure, eliminating the parasitic elements from hybridization. The detector itself will be consist of the LGAD sensor, amplification and discrimination, and time-over-threshold logic components. At this stage, we are optimizing the LGAD sensor design and preparing a discrete component based readout circuitry. In this work, we will present simulation result of a conceptual LGAD silicon detector and constant-fraction discriminator (CFD) circuit implementation. The timing resolution of the conceptual detector was simulated with EDA tools such as Silvaco Atlas and LTSpice with conjunction of a Monte-Carlo simulator to resolve Landau distribution into the circuit readout simulation. The best timing resolution we achieved was 23 ps.

physics.ins-det↗

arXiv2020

Delocalised kinetic Monte Carlo for simulating delocalisation-enhanced charge and exciton transport in disordered materials

Charge transport is well understood in both highly ordered materials (band conduction) or highly disordered ones (hopping conduction). In moderately disordered materials -- including many organic semiconductors -- the approximations valid in either extreme break down, making it difficult to accurately model the conduction. In particular, describing wavefunction delocalisation requires a quantum treatment, which is difficult in disordered materials that lack periodicity. Here, we present the first three-dimensional model of partially delocalised charge and exciton transport in materials in the intermediate disorder regime. Our approach is based on polaron-transformed Redfield theory, but overcomes several computational roadblocks by mapping the quantum-mechanical techniques onto kinetic Monte Carlo. Our theory, delocalised kinetic Monte Carlo (dKMC), shows that the fundamental physics of transport in moderately disordered materials is that of charges hopping between partially delocalised electronic states. Our results reveal why standard kinetic Monte Carlo can dramatically underestimate mobilities even in disordered organic semiconductors, where even a little delocalisation can substantially enhance mobilities, as well as showing that three-dimensional calculations capture important delocalisation effects neglected in lower-dimensional approximations.

physics.chem-ph↗

arXiv2019

Monte Carlo calculation and verification of the geometrical factors for the NPDGamma experiment

The NPDGamma experiment measures the parity-violating asymmetry in $\gamma$-ray emission in the capture of polarized neutrons on liquid parahydrogen. The sensitivity to the asymmetry for each detector in the array is used as a parameter in the extraction of the physics asymmetry from the measured data. The detector array is approximately cylindrically symmetric around the target and a step-wise sinusoidal function has been used for the sensitivity in the previous iteration of the NPDGamma experiment, but deviations from cylindrical symmetry necessitate the use of a Monte Carlo model to determine corrections to the geometrical factors. For the calculations, source code modifications to MCNPX were done in order to calculate the sensitivity of each cesium iodide detector to the physics asymmetry. We describe the MCNPX model and results from calculations and how the results are validated through measurement of the parity violating asymmetry of $\gamma$-rays from neutron capture on chlorine.

physics.ins-det↗