Browsing by Author "Buthelezi, Zinhle"

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    Heavy-flavour production at forward rapidity as a function of charged-particle multiplicity with ALICE at the LHC
    (2020) Mhlanga, Sibaliso; Cleymans, Jean; Buthelezi, Zinhle
    Heavy-flavour hadrons are hadrons made up of at least a charm or beauty heavy quark. They are produced in the early stages of ultra-relativistic collisions via hard scatterings and are important tools for studying different aspects of Quantum Chromodynamics (QCD) in hadronic collisions. Charged-particle multiplicity gives information on the global characteristics of the event and could be used to characterize particle production mechanisms. In hadronic collisions at Large Hadron Collider (LHC) energies, there is a significant contribution of Multiple Parton Interactions (MPI), i.e. several hard partonic interactions occurring in a single collision between nucleons. Therefore, the measurement of heavy-flavour hadrons as a function of charged-particle multiplicity gives insight into the mechanisms influencing their production in hadronic collisions at these energies and is a tool to test the influence of MPIs. Furthermore, charged-particle multiplicity dependence of heavy-flavour hadron production is used to test the ability of QCD theoretical models to reproduce data. In this thesis we investigate the production of heavy flavours via the single muon decay channel at forward rapidity as a function of the charged-particle multiplicity measured at central rapidity in proton-lead (p–Pb) collisions at √ sNN = 8.16 TeV using ALICE (A Large Ion Collider Experiment) at the LHC. ALICE is a dedicated detector optimized to study ultra-relativistic heavy-ion collisions in which the Quark-Gluon Plasma (QGP - the state of matter which prevailed in the Early Universe shortly after the Big Bang) is created. ALICE also studies proton-proton (pp) and p–Pb collisions. In pp collisions, production cross sections obtained from data provide information used to test pQCD theories while in p–Pb collisions, where the energy density is believed to be too low to produce the QGP, the presence of additional nuclear matter can alter the wavefunction of the nucleus leading to modified observables - the so-called cold nuclear matter (CNM) effects. The study of the multiplicity dependence of heavy-flavour production in p-Pb collisions may give important information regarding initial-state effects in CNM. Both pp and p– Pb collisions provide reference for comparison with heavy-ion (Pb–Pb) collisions. ALICE measures hadrons, leptons, and photons up to very high transverse momentum (pT) ≈100 GeV/c. The detector consists of a central barrel, which covers a rapidity of |y| < 1 and a Muon Spectrometer which covers the forward rapidity, -4 < y < -2.5. In this thesis, the production of heavy flavours via the contribution of their muonic decays to the inclusive pT-differential muon yield at forward (2.03 < ycms < 3.53) and backward (-4.46 < ycms < -2.96) rapidity reconstructed with the Muon Spectrometer and charged-particle multiplicity using the Silicon Pixel Detector located in the central barrel (|y| <1) in p-Pb collisions at √ sNN = 8.16 TeV in the forward and backward rapidity are studied. The aim of the study is to probe the role of MPIs in the production of heavy flavours focusing on the contribution of hard and soft processes as well as to investigate effects of the presence of multiple binary nucleon-nucleon interactions and the initial state effects modified by CNM in particle production.
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    Implementation of a Custom Muon High Level Trigger Monitoring System
    (2010) Mohlalisi, Seforo; Fearick, Roger; Buthelezi, Zinhle; Vilakazi, Zeblon
    A Large Ion Collider Experiment (ALICE) is one of the 4 major experiments at the Large Hadron Collider (LHC) at CERN. Its main aim is to investigate the physics of strongly interacting matter in proton-proton, nucleus-nucleus and nucleus-proton or proton-nucleus collisions at ultra high energy densi- ties, where the Quark Gluon Plasma (QGP) is expected to form. The experiment is expected to produce data at very high rates of about 25 Gbytes/s however the bandwidth to permanent storage is limited to about 10% (1.25 Gbyte/s) of the total expected data rates. In order to reduce data to permanent storage a special level of selecting interesting/relevant physics events is required. In ALICE the trigger (selection) of signals is issued based on a series of levels varying from levels 0 (L0) up to the High Level Trigger (HLT). For the ALICE muon spectrometer, the role of the trigger is to select events containing muon tracks, with the transverse momentum (pt) above a given threshold. Due to the limited spatial resolution of the muon trigger chambers a pt cut above a few GeV with the L0 trigger is not possible. While the L0 signal for the muon spectrometer is issued at about 700 - 800 ns, the HLT is delivered at about 1 ms. The role of the HLT is to perform online and o ine reconstruction of the ALICE muon spectrometer data in order to improve the measured (L0) pT resolution. In this way a better separation between relevant physics events and unwanted events (background) can be attainable, which could eventu- ally lead to lower trigger rates. The HLT is designed to improve signal- to-background ratio in the raw data transferred to the storage. In order to facilitate online/o ine data analysis the HLT monitoring system which will enable the user to graphically view the events during the reconstruc- tion phase was developed in this study. The system will read and decode the reconstructed events from the HLT analysis chain using the HLT Online Monitoring Environment including ROOT (HOMER) and displaying them on the ALICE Event Visualization Environment (ALIEVE). In addition, the ii utility, dHLTdumpraw, that inspects, with ner detail, the contents of all muon HLT internal data blocks and the detector data link (DDL) raw data stream is also described.
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    Monte Carlo simulations of the iThemba LABS neutron beam facility
    (2010) Adam, Buthaina Abdalla Suleiman; Nchodu, Rudolph; Buthelezi, Zinhle
    The iThemba LABS neutron beam facility is currently being used for various applications of fast neutron studies, such as measurements of fission cross sections, the biological effectiveness of high-energy neutrons, calibration of detectors used for dose monitoring in space and aircrafts, and the development of neutron dose monitors. Neutron beams with energies up to 200 MeV are produced at iThemba LABS by irradiating thin targets of 7Li and 9Be with protons from the separated-sector cyclotron. The neutrons are collimated to produce a beam with a diameter of about 50 mm at a flight path of 7.7 m from the target. The collimator geometry is designed to maximize the central part of the beam resulting in a beam with a uniform intensity throughout its diameter and a small penumbra. Secondary neutrons produced from the interactions of the primary charged particles with structural parts e.g. beampipes, shielding wall, target holder, etc. have been observed in the measured neutron fluence spectra. The Monte Carlo radiation transport code FLUKA were used to study the effects of secondary neutrons on the neutron fluence spectra. Results obtained from the calculations were compared with those obtained experimentally.
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    User Logic Development for The Muon Identifier's Common Readout Unit for the ALICE Experiment at The Large Hadron Collider
    (2021) Boyles, Nathan; Buthelezi, Zinhle; Winberg, Simon; Mishra, Amit
    The Large Hadron Collider at CERN is set to undergo major upgrades starting in 2019 resulting in expected centre of mass energy for proton-proton collisions to be the nominal 14 TeV. In light of these upgrades the experiments, namely, ALICE, ATLAS, CMS and LHCB, are required to upgrade their detectors correspondingly. The work contained in this dissertation pertains to the upgrade of the ALICE detector and in particular to the Muon Trigger(MTR) Detector which will be renamed the Muon Identifier (MID). This detector has historically operated in triggered readout manner exchanging trigger signals with the Central Trigger Processor (CTP) when events of interest occur using a minimum bias. The upgrades include a transition from triggered readout to continuous readout time delimiting data payloads using periodic heartbeat signals. Continuous readout however results in data rates several orders of magnitude higher than previous operstion and as such would require vast storage resources for raw data thus a new computing system known as O2 is also being developed for real-time data reduction. Part of the system used to perform real-time data reduction is based on FPGA technology and is known as the Common Readout Unit. As its name implies, the CRU is common to many detectors regardless of their differences in design. As such, each detector requires customer logic to meet their unique requirements, known as the user logic. This project concerns development of the ALICE MID user logic which will interface to the Core CRU firmware and perform real-time data extraction, reformatting, zero suppression, data synchronization and transmission of the processed data to the Core CRU firmware. It presents the development of a conceptual design and a prototype for the user logic of the ALICE MID. The research methodology employed involved the identification of relevant documentation as well as in-depth meetings with the developers of the periphery systems to ascertain requirements and constraints of the project. The resulting prototype shows the ability to meet the established requirements in effective and optimized manner. Additionally, the modular design approach employed, allows for more features to be easily introduced.