Online Audio-Visual Multi-Source Tracking and Separation: A Labeled Random Finite Set Approach

The dissertation proposes an online solution for separating an unknown and time-varying number of moving sources using audio and visual data. The random finite set framework is used for the modeling and fusion of audio and visual data. This enables an online tracking algorithm to estimate the source positions and identities for each time point. With this information, a set of beamformers can be designed to separate each desired source and suppress the interfering sources

Over-Determined Source Separation and Localization Using Distributed Microphones

This work was supported by the U.K. Engineering and Physical Sciences Research Council (EPSRC) under Grant EP/K007491/1

Expected Performance of the ATLAS Experiment - Detector, Trigger and Physics

A detailed study is presented of the expected performance of the ATLAS detector. The reconstruction of tracks, leptons, photons, missing energy and jets is investigated, together with the performance of b-tagging and the trigger. The physics potential for a variety of interesting physics processes, within the Standard Model and beyond, is examined. The study comprises a series of notes based on simulations of the detector and physics processes, with particular emphasis given to the data expected from the first years of operation of the LHC at CERN

On-belt Tomosynthesis: 3D Imaging of Baggage for Security Inspection

This thesis describes the design, testing and evaluation of `On-belt Tomosynthesis' (ObT): a cost-e ective baggage screening system based on limited angle digital x-ray tomosynthesis and close-range photogrammetry. It is designed to be retro tted to existing airport conveyor-belt systems and to overcome the limitations of current systems creating a pseudo-3D imaging system by combining x-ray and optical imaging to form digital tomograms. The ObT design and set-up consists of a con guration of two x-ray sources illuminating 12 strip detectors around a conveyor belt curve forming an 180 arc. Investigating the acquired ObT x-ray images' noise sources and distortions, improvements were demonstrated using developed image correction methods. An increase of 45% in image uniformity was shown as a result, in the postcorrection images. Simulation image reconstruction of objects with lower attenuation coe cients showed the potential of ObT to clearly distinguish between them. Reconstruction of real data showed that objects of bigger attenuation di erences (copper versus perspex, rather than air versus perspex) could be observed better. The main conclusion from the reconstruction results was that the current imaging method needed further re nements, regarding the geometry registration and the image reconstruction. The simulation results con rmed that advancing the experimental method could produce better results than the ones which can currently be achieved. For the current state of ObT, a standard deviation of 2 mm in (a) the source coordinates, and 2 in (b) the detector angles does not a ect the image reconstruction results. Therefore, a low-cost single camera coordination and tracking solution was developed to replace the previously used manual measurements. Results obtained by the developed solution showed that the necessary prerequisites for the ObT image reconstruction could be addressed. The resulting standard deviation was of an average of 0.4 mm and 1 degree for (a) and (b) respectively

MEASURING CHARGE ASYMMETRIES IN B-HADRON DECAYS USING TOP QUARK EVENTS WITH THE ATLAS EXPERIMENT

PhDThe large number of top-antitop pair events produced in pp collisions at the Large Hadron Collider (LHC) provides a unique source of b-quarks that can be used to probe the CP violation in heavy-flavour mixing and decay. The measurement presented in this thesis focuses on semi-leptonic top-antitop events where one of the W-bosons decays hadronically and the other one decays leptonically. The charge of the lepton (electron or muon) from the W-boson tags the charge of the b-quark at production. In events where a muon is associated to the semi-leptonic decay of the b-quark (either directly or after a b ! c hadronic transition), two charge asymmetries (CA) and several CP asymmetries, based on the charges of the lepton from the W-boson and this muon, can be measured. My contribution to the first measurement of the CA and CP asymmetries in heavy flavour b- or c-decays from top-antitop lepton+jets events is presented, using the data collected with the ATLAS detector during Run 1 of the LHC (20.3 fb 1) at a centre of mass energy of p s = 8 TeV. However, most of the thesis focuses on my (larger) contribution to this same measurement, performed with data collected by the ATLAS experiment during Run 2, 2015-16 data taking periods, corresponding to an integrated luminosity of 36.1 fb 1 at a centre of mass energy of p s = 13 TeV. Four CP asymmetries (one mixing and three direct) were measured, using Run 1 data, and they are found to be consistent with the Standard Model. The Run 2 analysis results in the measurement of two charge asymmetries, both compatible with zero and consistent with the Standard Model expectations. The overall uncertainty on the Run 2 measurement is halved with respect to the Run 1 result

An investigation of the Higgs Bosun production channel ttH 0, H0→bb with the ATLAS detector at the LHC.

The Large Hadron Collider, due for completion at the end of 2007, will provide an essential piece in the puzzle of electroweak symmetry breaking. Precision measure ments from LEP predict a low mass Standard Model Higgs boson close to the current experimental lower limit. In this mass region identification of the Higgs boson will be difficult, requiring more than one channel to be studied. ttH0, H0 → bb is one of three channels proposed for this purpose. In order to reduce the large backgrounds full reconstruction of the two top-quarks in the event is necessary. This thesis inves tigates a number of new techniques to improve the reconstruction procedure of this channel using the fast simulation of the ATLAS detector, Atlfast. Methods inves tigated include the introduction of hadronic W candidates created from three jets combined with a new energy rescaling method for the W candidates. A new quantity to choose the jet pairings in the event, utilising jet and lepton energy uncertainties from Atlfast, is studied. An Artificial Neural Network is trained to select signal from background events. An increase in the expected signal significance from 1.8 to 2.4 for an integrated luminosity of 30fb_1 and Higgs mass of 120GeV is observed from the techniques proposed. An important tool for any high energy physics experiment is an event display program. Visual representation is the most efficient way to transfer data from a computer to the human brain, providing the user with a powerful tool to investigate specific events. The Atlantis event display for the ATLAS experiment is presented, along with the development carried out to enable its use in the 2004 Combined Test Beam. The test beam used a full slice of the detector to provide an essential study of the performance capabilities of ATLAS

Fusing the vector bosons: Higgs production through VBF and WW scattering at the current and future LHC

A long search for the Higgs boson was successfully concluded in the summer of 2012. Ever since, efforts are put into precisely measuring all its properties, its production and decay rates, to verify if this is indeed the particle predicted by the Standard Model (SM) or a first evidence of some New Physics. This thesis describes the search for a specific combination of the Higgs boson production and decay modes which have not been observed so far - the Vector Boson Fusion (VBF) production with the Higgs boson decaying into a pair of W bosons. After the introduction, this thesis is divided into two parts: ‘the first run at the LHC’ and ‘the future runs at the LHC’. The first part describes the theoretical overview of the SM and the Higgs boson in chapters 1 and 2, respectively, followed by the description of the LHC and the ATLAS detector in chapter 3, event and object reconstruction in chapter 4 and the VBF H -> WW analysis in chapters 5 through 7. One of the focuses of this thesis is the treatment of systematic uncertainties of one of the largest backgrounds in the VBF H->WW analysis, the top-quark decays, and is presented in chapter 6. The second part of this thesis starts by describing the scheduled upgrades of the LHC and the ATLAS detector in chapter 8. Chapters 9 and 10 are dedicated to two different feasibility studies; the first one analyses the benefits future LHC runs may bring to the VBF H->WW measurement and the second one studies the impact of the future ATLAS detector on the significance measurement of vector boson scattering (another processes which allows us to study the nature of the Higgs boson) and the sensitivity for New Physics. The thesis finishes with the conclusion and summary

Cross-section measurements of top-quark pair production in association with a hard photon at 13 TeV with the ATLAS detector

25 years after the top quark's discovery, the Large Hadron Collider at CERN produces proton-proton collision data on unprecedented scales at unprecedented energies - and has heralded an era of top-quark precision measurements. The production of a top-quark pair in association with a photon ($t\bar{t}\gamma$) gives access to the electromagnetic top-photon coupling, one of the fundamental properties of the top quark. Various extensions of the Standard Model predict modifications of the coupling strength or structure, and deviations from the Standard Model prediction of the $t\bar{t}\gamma$ production cross-section would indicate new physics. With enough statistics available from the Large Hadron Collider, the electron-muon channel has gained particular interest due to its high signal purity and precise available theory predictions. This thesis presents results with the full Run 2 dataset collected with the ATLAS detector in proton-proton collisions at the Large Hadron Collider between 2015 and 2018 at 13 TeV centre-of-mass energy, corresponding to an integrated luminosity of 139 fb$^{-1}$. In order to compare the results to fixed-order calculations that include non-doubly-resonant diagrams, a combined measurement of $t\bar{t}\gamma + tW\gamma$ is performed. The focus is placed on a measurement of the fiducial inclusive cross-section in the electron-muon channel. Furthermore, the ATLAS data is unfolded to parton level and measurements of differential cross-sections as functions of several observables are presented. Both fiducial inclusive and differential results are compared to state-of-the-art fixed-order calculations at next-to-leading order in QCD. An additional focus of the thesis is placed on studies to use machine-learning techniques, in particular deep neural networks, for the identification of prompt photons.Comment: PhD dissertation (Univ. of G\"ottingen), 173 pages, 75 figures, 25 tables. Available on CERN CDS at https://cds.cern.ch/record/2725289

Broadband and statistical characterization of echoes from random scatterers : application to acoustic scattering by marine organisms

Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution February 2013The interpretation of echoes collected by active remote-sensing systems, such as sonar and radar, is often ambiguous due to the complexities in the scattering processes involving the scatterers, the environment, and the sensing system. This thesis addresses this challenge using a combination of laboratory and fi eld experiments, theoretical modeling, and numerical simulations in the context of acoustic scattering by marine organisms. The unifying themes of the thesis are 1) quantitative characterization of the spectral, temporal, and statistical features derived from echoes collected using both broadband and narrowband signals, and 2) the interpretation of echoes by establishing explicit links between echo features and the sources of scattering through physics principles. This physics-based approach is distinct from the subjective descriptions and empirical methods employed in most conventional fisheries acoustic studies. The fi rst part focuses on understanding the dominant backscattering mechanisms of live squid as a function of orientation. The study provides the first broadband backscattering laboratory data set from live squid at all angles of orientation, and conclusively con firms the fluidlike, weakly-scattering material properties of squid through a series of detailed comparisons between data and predictions given by models derived based on the distorted-wave Born approximation. In the second part, an exact analytical narrowband model and a numerical broadband model are developed based on physics principles to describe the probability density function of the amplitudes of echo envelopes (echo pdf) of arbitrary aggregations of scatterers. The narrowband echo pdf model signi cantly outperforms the conventional mixture models in analyzing simulated mixed assemblages. When applied to analyze fish echoes collected in the ocean, the numerical density of sh estimated using the broadband echo pdf model is comparable to the density estimated using echo integration methods. These results demonstrate the power of the physics-based approach and give a rst-order assessment of the performance of echo statistics methods in echo interpretation. The new data, models, and approaches provided here are important for advancing the eld of active acoustic observation of the ocean.Taiwan Merit Scholarship (NSC-095-SAF-I-564-021-TMS), Office of Naval Research (ONR; grants N00014-10-1-0127, N00014-08-1-1162, N00014-07-1-1034), National Science Foundation (NSF; grant OCE-0928801), Naval Oceanographic Offi ce (grant N62306007-D9002), WHOI Ocean Life Institute, and the WHOI Academic Programs O ffice funds