Conveners
Nuclear, Particle and Radiation Physics
- Rudolph Nchodu (iThemba LABS)
Nuclear, Particle and Radiation Physics
- Sahal Yacoob (University of Cape Town)
Nuclear, Particle and Radiation Physics
- Simon Connell (University of Johannesburg)
Nuclear, Particle and Radiation Physics
- There are no conveners in this block
Nuclear, Particle and Radiation Physics
- Rudolph Nchodu (iThemba LABS)
Nuclear, Particle and Radiation Physics
- James Keaveney (UCT)
Nuclear, Particle and Radiation Physics
- XIFENG RUAN (University of the witwatersrand)
The National Nuclear Regulator's (NNR) mandate is to protect the people, property and environment from radiological damage. NNR is currently involved in projects to establish the radioactivity of drinking water in the vicinity of authorised sites. It is important that before this, preliminary reference levels which will be used to assess the radioactivity levels in collected samples are...
The iThemba LABS fast neutron beam facility (D-line vault) is an international niche facility that can provide ns-pulsed quasi-monoenergetic neutron beams in the energy range of 30 to 200 MeV. Available neutron beam facilities with energy range similar to this facility are described in details by the EURADOS (European Radiation Dosimetry) Report [1]. The facility has remained practically...
In December 2017, the Executive Board of the SA-CERN Consortium approved an investment in the local research infrastructure at the University of Zululand. As a result, an Electronics Research Laboratory was developed and completed in 2019. The laboratory host state of the art electronics test equipment and it was enhanced when the Centre for High Performance Computing (CHPC) in Cape Town...
This study presents the results of irradiation tests used to qualify the End-of-Substructure (EoS) card for operation within the ATLAS Inner Tracker (ITk) at the High Luminosity Large Hadron Collider (HL-LHC). The EoS card is responsible for interfacing the data, command, and power signals between on and off-detector electronics. The radiation environment within the ITk poses a challenge for...
Four major experiments for the High Luminosity Large Hardron Collider (HL-LHC) are upgraded to accommodate an increase in luminosity. ATLAS (A Toroidal LHC ApparatuS) is part of these four major experiments and it is upgraded to investigate a wide range of physics. The detector is divided into long barrel and two extended barrels. The Tile Calorimeter (TileCal) is part of the ATLAS detector...
In the beginning of 2025, the Large Hadron Collider (LHC) will be shutdown in order for the final upgrades to the High Luminosity LHC (HL-LHC) to commence. This will almost quadruple the amount of collisions in the LHC, increasing the amount of data the detectors will have to deal with. Since the detectors were not designed to operate at these levels, they will also need an upgrade to deal...
Power Electronics used in high-energy physics experiments at the Large Hadron
Collider (LHC) more specifically the ATLAS detector, which are custom built and have to work reliably in the presence of ionizing radiation and an ever present magnetic field. In many such applications, owing to cost constraints, Commercial Off-The-Shelf (COTS) components are often used instead of components that...
The start of the operation of the High Luminosity LHC (HL-LHC) is planned
for the year 2027. The planned increase in luminosity provides the opportunity for further
scientific discoveries within the field of particle physics as well as many technical challenges
associated with the new HL-LHC environment. Due to these environmental changes the ATLAS
Tile-Calorimeter (TileCal) is to undergo...
The study present the measurement of the contribution, purity, of $Z + \gamma$ and $Z+$ jet background events in the search for high-mass $Z\gamma$ resonances. The study uses events were the $Z$ boson decays into a pairs of oppositely charged electrons or muons. The events used consist of 139 fb${}^{-1}$ of proton-proton, $pp$, collisions data at $\sqrt{s} = 13$ TeV, recorded by the ATLAS...
One indication that the Standard Model of particle physics is incomplete lies in the unanswered question of neutrino mass generation. Most popular among the possible explanations of this mystery is the see-saw mechanism which postulates that small neutrino masses arise from the exchange of heavy force-carriers. Additionally, a framework for this mechanism is the so-called Left-Right Symmetric...
Search for the presence of a new heavy resonance, produced via gluon-gluon fusion and decaying to the four-lepton ($4\ell$) final state, in association with missing transverse energy ($E^{\text{miss}}_{\text{T}}$), with $\ell$ = $e$, $\mu$. The search uses 2015–2018 proton–proton collision data at $\sqrt{s}$ = 13 TeV, corresponding to an integrated luminosity of 139 fb$^{-1}$, collected by the...
Several astronomical observations have revealed the existence of larger matter quantities which are thought to occupy 27% of the universe. Many hypotheses exist about the nature of these elusive dark matter particles. One of these hypotheses predicts the existence of a hypothetical dark photon. The unique signature of this particle can be searched for at the Large Hadron Collider (LHC) at...
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. Owing to the unusual MET-along-the-jet event topology, this is yet an unexplored domain within ATLAS. In...
The recent anomalous magnetic moment of the muon (muon g-2) result presents a pattern of deviation from the standard model prediction in the interaction of muons with a surrounding magnetic field. A similar deviation from the standard model prediction is seen in the LHCb results on rare B-meson decay. Plausible explanations of these anomalies are leptoquarks. Leptoquarks when coupled with a...
A search for a heavy resonance pseudo-scalar, A, decaying into a $Z$ boson and another heavy scalar boson, $H$, is carried out at the LHC using a data sample corresponding to an integrated luminosity of 139 fb$^{-1}$ from proton-proton collisions at $\sqrt{s}$ = 13 TeV. In these studies, the scalars $H$ will decay to two scalars $S$ or an $S$ and a Standard Model Higgs boson $H$ via an...
The connection between the multi-lepton anomalies at the Large Hadron Collider and astrophysics can be described by a two Higgs doublet model with an additional singlet scalar (2HDM+S). We make studies on the interaction mechanism of singlet S to dark matter. This is achieved from the annihilation of Dark Matter (DM). We demonstrate that using this model we could also describe the ...
In this presentation an account of the multi-lepton (electrons and muons) anomalies at the LHC will be given. These include the excess production of opposite sign leptons with and without $b$-quarks, including a corner of the phase-space with a full hadronic jet veto; same sign leptons with and without b-quarks; three leptons with and without $b$-quarks, including also the presence of a $Z$....
A search for $tWZ$ production using events containing three leptons from Run 2 ATLAS proton-proton collision data with a centre of mass energy of 13 TeV will be presented. An event selection scheme was developed using simulation to select $tWZ$ events and to broadly suppress background events. Events were then separated into mutually-exclusive regions of phase space to increase the amount of...
This paper presents the search for the Higgs boson, with mass 125GeV, decaying to two new intermediate states and then into four lepton final states, H → ZdZd → 4l together with the search for a double Zd1 and Zd2 hypothesis. The analysis is conducted using the Run II data set from pp collisions collected with the ATLAS detector corresponding to a total integrated luminosity of 140fb−1 at a...
A search for the non-resonant production of a pair of the Standard Model Higgs boson $h$ via gluon-fusion, $gg\rightarrow hh$, is performed. Each Higgs boson decays to either $W^+W^-W^+W^-$, $ZZZZ$ or $ZZW^+W^-$ leading to $4\ell+X$ in the final state. The $\ell$ could be an electron or a muon, and $X$ is missing transverse energy or jets. The b-tagged as jets is vetoed in this analysis. The...
Studies towards a measurement of the leptonic charge asymmetry in top quark pair production in association with a W boson($t\bar{t}W^{\pm} $) at 13 TeV with the ATLAS experiment are presented. Previous measurements of the $t\bar{t}W^{\pm} $ cross-section have been shown to be higher than that predicted by the standard model indicating a potential discrepancy in the modeling of the...
We search for a heavy resonance decaying into diphoton in association with at least one b jet. The search uses Run II proton-proton collision data with an integrated luminosity of 139~fb^{−1} recorded by the ATLAS experiment at a centre-of-mass energy of \sqrt{s} = 13~TeV during 2015 to 2018 at the Large Hadron Collider. Three models are tested in this final state. A Higgs boson like heavy...
Presented are the studies of the production of the Standard Model Higgs boson in association with a $W$ or $Z$ boson, where the Higgs decays to $b\bar{b}$ and the $W/Z$ bosons decay leptonically. The $H\rightarrow b\bar{b}$ decay has a branching fraction of $\sim58\%$, so this study allows the probing of the dominant Higgs decay mode, as well as providing the best sensitivity to the $WH$ and...
The top quark is the heaviest particle in the standard model and reducing the uncertainty of the top quark mass directly speaks to/ affects precision tests of the consistency of the standard model, where breaks from this consistency would point to the existence of more massive particles. Since the top quark decays before hadronizing, either the kinematic properties of the decay products or...
Classifying a jet initiated from quarks or gluons based on its substructure is one of the most challenging problems at the LHC. The difference in the color structure of quarks and gluons can reflect in the amount of energy loss or the pattern of radiated energy of a jet originated from quarks or gluons. The low-level detector output can be used to identify parton jets using Machine learning...
In this project, ideas for the implementation of a data-quality early warning system (DQEWS) are explored. The DQEWS project aims to use supervised machine learning (ML) methods to evaluate data-quality from the ATLAS detector for each sequential luminosity-block over the course of a run. The idea is to then
make use of feature extraction from the results of the classification procedure in...
Unlike supervised learning which is known to assume a full knowledge of the underlying model, semi-supervised learning, weak supervision in particular 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 could be produced with...
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...
When utilizing semi-supervised techniques in training machine learning models in the search for bosons at ATLAS, the overtraining of the model must be investigated. In particle physics internal fluctuations of the phase space and bias in training can cause semi-supervised models to label false signals within the phase space due to overfitting. The issue of false signal generation in...
Nuclear forensic science is a relatively young discipline that has evolved because of the need to study banned nuclear or radioactive material needed to determine its origin. Nuclear forensic science basically makes use of observable material properties, referred to as "signatures," which provide clues on the material's history. The work done in this research was to investigate morphological...
Radon is a non-reactive, naturally occurring gas that is released during the decay of uranium-238 (238U) to radium-226 (226Ra) then radon-222 (222Rn). Radon is colourless, odourless and invisible and it can be found in air, soil, water and building materials. Its presence can only be detected by the use of detectors that can give out its concentration levels. This radioactive gas can be...
This study aims to explore the (p,p'$\gamma$) detection capabilities of the K600 magnetic spectrometer coupled to the Ball of Germanium and Lanthanum bromide detectors (BaGeL) at zero degrees at iThemba LABS. This is being done through an investigation into the low-lying dipole strength of $^{58}\mathrm{Ni}$ using the (p,p'$\gamma$) reaction at E$_{\mathrm{p}}$ = 80 MeV. The use of proton...
Illicit trafficking of radioactive material and especially nuclear material (thorium, uranium, and plutonium) has been an issue of concern since the beginning of the 1990s, when the first seizures of nuclear material were reported to the International Atomic Energy Agency. In this work, twenty samples selected for investigation originate from South Africa and Namibia uranium mines. The aim of...
The technique of semi-supervision can be used in searches for new physics where the signal plus background regions are not labelled. We employ semi-supervision but this technique has over-fitting issues. We resort to GANs to mimic a Monte Carlo (MC) simulation which is very expensive computationally in order to perform toy MC studies. We propose Generative Adversarial Networks (GANs) as our...
The iThemba LABS fast neutron beam facility (D-line) is an international niche facility that can provide quasi mono-energetic neutron beams in the energy range of 30 MeV – 200 MeV using proton beams available from the separated sector cyclotron (SSC) [1]. The D-line is undergoing a major upgrade and redevelopment in order for it to meet the requirements to become designated as a medium- and...
This study presents a search for the high-mass resonances in $Z\gamma$ final states. The search is performed using the Monte Carlo simulated signal samples of mass up to 5 TeV, corresponding to an integrated luminosity of 139 fb$^{-1}$ dataset recorded by the ATLAS experiment in proton-proton collisions during the LHC Run-2. Only leptonic decay of the $Z$ boson to a lepton-antilepton pair...
Extending the Standard Model with second Higgs doublet populate the scalar particle spectrum. Here we take an opportunity to search heavy scalar H resonance of mass around double of Higgs boson, mH = [250 - 270] GeV at future electron-proton (e-p) collider in charged current process. We consider the hadronic decay of H→W+W−→jjjj and use machine learning tools to reconstruct the mass of H....
As the shape of the nucleus changes, statistical properties such as the nuclear level density (NLD) and γ-strength function (γSF) are expected to be affected. In particular, the evolution of the resonance modes such as the scissors resonance (SR) depends on the deformation of the isotopes. The SR resonance in the isotopic chain of samarium is being studied by comparing the scissors resonance...
Top-quark is the known heaviest elementary particle of the Standard Model (SM) and it is said to have large couplings to hypothetical new physics in many models beyond the SM. With the mass and spin correlations of the top-quark together with W-boson helicity fractions already being measured, interesting characteristics of the top-quark are accessible due to the large center-of-mass energy and...
The pygmy dipole resonance (PDR) is a cluster of 1- states around and below the neutron separation energy and has gained traction in nuclear structure studies. The microscopic nature of the PDR is still an open question in particular, whether these 1- states are of single-particle or collective nature. The study here presented is a first attempt to investigate the single-particle or the...
Much of dark matter (DM) research has focused on DM candidate particles which are heavy and have little interaction with baryonic matter. However, many theories have proposed DM candidates that do indeed interact with observable matter, particularly resulting in the formation of jets. In certain models, only a portion of dark hadrons produced in a collision will decay back to SM quarks, while...
