Heavy ion collisions at RHIC and at the LHC produce an enormous amount of energy that enables the nuclei and its constituent particles to melt, thus releasing gluons, quarks and anti-quarks, travelling in different directions with different momenta. Studies of these collisions have shown that low transverse momentum observables describe a strongly coupled plasma (quark-gluon plasma), an almost...
Chemical and thermal equilibrium properties of infinite relativistic hadron matter are investigated using a microscopic transport model. This model is used to simulate the ultra-relativistic heavy ion collisions at different energy densities ε, namely the Ultra-relativistic Quantum Molecular Dynamics (UrQMD). The molecular dynamics simulation is performed for a system of zero baryon number...
Gauge-Higgs unification models give interesting solutions to the hierarchy problem in particle physics. The common study of this type of model is done by using a decomposition of 5-dimensional particles in 4-dimensional Kaluza-Klein modes, which is a handy way to compute the infinite sums appearing in the model. In order to take into account the running of coupling constants in these models,...
Composite Higgs models describe a strongly coupled gauge fermion sector which extends the Standard Model, introducing the Higgs boson as a new bound state arising due to the breaking of a global (flavour) symmetry. These models will be accompanied by light states generated by the same dynamics, the detection of which may present the first signs of compositeness. The subject of this work, a...
The production of a single top quark in association with a $W^{\pm}$ and $Z$ boson ($tW^{\pm}Z$) is sensitive to both the neutral and charged electroweak couplings of the top quark as the process involves the simultaneous production of a W boson and a Z boson in association with the top quark. However the process so rare that it has never been observed by any particle physics experiment. The...
The LHC is a top quark factory and the copious amounts of top quarks produced provide valuable insight into the standard model and beyond. Majority of the top quarks produced can be identifed using standard methods such as identifying features such as bottom quarks (b-tagging), W bosons or three jets with an invariant mass that is roughly equal to the top mass. However, some of the top quarks...
We investigate the discovery potential of a Stealth SUSY scenario involving squark decays by reconstructing the lightest neutralino decay products using a large-radius jet containing a high transverse momentum photon. Requirements on the event topology, such as photon and large-radius jet multiplicity result in less background than signal. We also estimated the sensitivity of our analysis and...
Recent studies in particle physics have shown that there are myriad possibilities for strong dark sector studies at the LHC. One signature is the case of semi-visible jets, where parton evolution includes dark sector emissions, resulting in jets overlapping with missing transverse energy. The implementation of semi-visible jets is done using the Pythia Hidden valley module to duplicate the...
The standard electron and jet reconstruction process using information from energy deposits in the electromagnetic (EM) and hadronic calorimeters are carried out independently. This results in an ambiguity in the reconstruction of these objects. to avoid such ambiguity, an overlap removal procedure is applied during electron and jet reconstruction since every reconstructed electron will have a...
Due to a number of features from proton-proton collisions taken during Run 1 data taking period at the LHC, a boson with a mass around the Electro-Weak scale was postulated such that a significant fraction of its decays would entail the Standard Model (SM) Higgs boson and an additional scalar, S. One of the phenomenological implications of a simplified model, where S is treated a SM Higgs...
Anomalies observed in several Standard Model (SM) results, with multiple leptons in the final state from the ATLAS and CMS experiments at the LHC, are interpreted in the context of new physics in Refs. arXiv:1711.07874 and arXiv:1901.05300. This new hypothesis extends the SM considering the presence of additional bosons through the production of a heavy boson, $H$, decaying into a SM Higgs...
With focus on the recent ATLAS search for top associated Higgs production in multi-lepton final states, an anomalous rate for the ttW background is unearthed and quantified in terms of theory uncertainties. This anomalous rate is explored in the context of the previously published multi-lepton anomalies at the LHC (JHEP 1910 (2019) 157), using a simplified new physics model. The impact of the...
As no definite signs of new physics has been observed at the LHC data yet, alternate approaches have been proposed. These include looking at unusual topologies, and using existing measurements to constrain models (CONTUR). In tis overview, I will discuss some of the recent developments along these directions, covering jet substructure methods to identify semivisible jets, a realistic detector...
This project studies a robust anti-QCD tagger with mass de-correlating jet image data produced using the pre-processing method introduced in arXiv: 1903.02032. A semi-supervised (where data is only trained on background) learning anomaly detection approach using convolutional autoencoder neural networks is explored as an anti-QCD tagger in this study. Jet image data is used to train the...
We propose a new approach to search for new resonances beyond the Standard Model (SM) of particle physics in topological configurations using Machine Learning techniques. This involves a novel classification procedure based on a combination of weak-supervision and full-supervision in conjunction with Deep Neural Network algorithms. The performance of this strategy is evaluated on the...
Unlike supervised learning which is known to assume a full knowledge of the underlying model, weak supervision allows with partial knowledge to extract new information from the data.
The objective of this study is to set up the search for heavy resonances at the electroweak scale with topological requirements. These resonances are expected to be produced with different production mechanisms....
What is typically referred to as the inverse problem in High Energy Physics (HEP) can be described as the use of data to extract key information to build new a theory. The search of new resonances beyond the Standard Model (SM) involves the use of different Machine Learning techniques. For this purpose, based on the recent and major successes in the field of deep learning, particularly Deep...
In the search for new physics Beyond the Standard Model, MVA techniques are used to extract specific signal from Standard Model background processes. In this study weakly-supervised machine learning techniques are developed and evaluated using the ATLAS experiment, di-lepton (e±μ∓) final state data, in the H → Sh search. These weakly-supervised techniques use labelled background data to...
Motivated by the statistically significant excesses in the multi-lepton final states compatible with physics at the electroweak scale, here we attempt a direct search for a heavy scalar resonance in the Z and photon system in the LHC Run 2 dataset. The study aims to extract the signal process using a machine learning algorithm.
Satellite data enables the efficient mapping and monitoring of the earth’s resources, ecosystems, and events. Machine Learning can be applied to this data to predict weather conditions. Machine Learning techniques can be used to model and extract useful information out of a data stream. This helps governments and industries to share information, to make informed decisions, to act on time and...
In this article we search for a heavy resonance decaying into two photons in association with $b$ jets. The search uses $139~\mbox{fb\(^{-1}\)}$ proton--proton collision data taken from the ATLAS detector at the centre-of mass energy of 13TeV during 2015 to 2018. Three models are tested in this final state. A Higgs boson like heavy scalar $X$ produced with top quarks, $b$ quarks or $Z$ boson...
The 4-lepton final state is a clean and important signal that is being studied at the ATLAS detector. In this study, we focus on four leptons originated from the $R\rightarrow SH\rightarrow 4\ell+E^{miss}_{T}$ signal. $R$ is a scalar boson produced via gluon--gluon fusion and decays to two lighter scalar bosons, $S$ and $H$. The $S$ decays to a pair of Standard Model of particle physics...
The Technology and Innovation Platform (TIP) is envisaged to promote applications spanning from the development of radiation detectors, special materials and development of industrial standard electronics. The TIP will be implemented at iThemba LABS to explore applications and partnership with industry for technology transfer purposes to benefit research and the economical sector. The TIP...
Organisations worldwide are under pressure from investors to reduce the rise in costs and maintain profits leading them to come up with innovative solutions to solve traditional and new problems. Automation of processes and the use of analytics is key in achieving this objective. This talk aims to discuss how basic and advanced classroom concepts (Mathematics, Statistics, Machine Learning) are...
The Transition Radiation Detector (TRD), part of the ALICE Experiment at CERN, is used for electron identification, triggering and tracking. This work presents a prototype of an event display, customised for the TRD, that provides a portable, projection based display of tracks, tracklets and raw data within the detector, outside the classic ROOT environment. The prototype provides a novel...
Photomultiplier tubes are susceptible to radiation damage within high energy and nuclear physics detectors, particularly due to neutrons. More specifically, the integrity of the photocathode materials responsible for the emission of the primary electron that then interacts with the electron dynodes that create cascades of electrons moving through the photomultiplier, are affected. The...
We report on the replacement of E3E4 (Crack) and refurbishment of Minimum Bias Trigger Scintillator (MBTS) counters as part of phase I upgrade for the ATLAS experiment at the European Organization for Nuclear Research. Crack and MBTS counters, located between the central and extended Tile Calorimeter barrels, are used for correcting the electromagnetic and hadronic energy responses,...
A complete redesign of the detector electronics is currently taking place to accommodate the readout and trigger architecture to the future HL-LHC conditions. The Tile PreProcessor (TilePPr) will be the core of the TileCal off-detector electronics after the Phase-II Upgrade. The TilePPr is composed of several FPGA-based boards including Tile Compact Processing Module (TileCPM) to operate and...
CERN will be undergoing an upgrade to the High Luminosity Large Hadron Collider. To connect the Phase 2 upgrade to the CERN network, a Gigabit Ethernet (GbE) switch mezzanine board is designed as a part of the Tile-PreProcessor (TilePPr). The boards that are being designs will undergo a variety of tests to determine their suitability for the Phase 2 upgrade at CERN. A variety of testing and...
The Tile Calorimeter (TileCal) is the central hadronic calorimeter ($|\eta|$ $<$ 1.7) of the ATLAS experiment, made out of iron plates and plastic scintillators. The TileCal is divided into three cylinders along the beam axis, each of which is azimuthally segmented into 64 wedge-shaped modules, staggered in the $\phi$ direction. TileCal online software is a set of Trigger and Data Acquisition...
The large-scale production of the LVPS bricks will involve the complete replacement of all power supply “bricks” in the TileCal (Tile Calorimeter) front-end electronics for the LHC-HL upgrade. A total of 1024 LV bricks (half needed for the entire detector) will be produced by the University of the Witwatersrand. Such an operation comprises of several steps which include the development of two...
School of Physics and Institute for Collider Particle Physics, University of the
Witwatersrand, Johannesburg, 2050, South Africa
thabo.james.lepota@cern.ch
This paper describes the development of test stations at the University of the Witwatersrand for the ATLAS Tile Calorimeter Low Voltage Power Supplies of the Large Hadron Collider. As part of phase II cycle, South Africa will produce...
The upgrade of the ATLAS hadronic tile-calorimeter Low-Voltage Power Supply (LVPS) falls under the high-luminosity LHC upgrade project. This presentation serves to provide a detailed overview of performance testing of an upgraded LVPS component known as a brick being undertaken by the Wits High energy physics institute in preparation for full-scale production within South Africa. This testing...
A feasibility study for the search for a heavy scalar boson (H) of mass around mH = 270 GeV is carried out in charged current mode at the future electron proton collider. The centre of mass energy of such collider varies from 1.3 – 5 TeV. In this work H decays to W-boson pairs, which further decays to hadronic jets. Due to complexity of final states and dominant backgrounds we carried the...
