4th Year Projects in 2015

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Here you will find a list of the 4th year projects offered for Semester 1, 2015. These are representative of the sort of projects we can offer - we may alter some of these closer to the time or indeed add new possibilities.

Top quark production at the Large Hadron Collider

Supervisors: A/Prof Kevin Varvell,Dr Kevin Finelli
Contact: A/Prof Kevin Varvell,
Room: 344
Email: k.varvell AT physics.usyd.edu.au
Phone: (02) 9351 2539

The top quark is the most massive known fundamental particle, and it figures prominently in a number of new theories of particle physics. Despite having been discovered nearly two decades ago, our knowledge of how this particle is produced in high-energy collisions is rather limited. Ian Watson, a Sydney PhD student on the ATLAS experiment, developed a new technique to analyze the world’s largest dataset of top quarks to gain deeper insights into the production of this particle independent of the theoretical models of the quarks of the proton. This project will extend his technique of measuring the cross-section of top quark pairs as a function of kinematic variables and apply it to LHC collisions at centre-of-mass energy 8 TeV using the ATLAS detector. The student will have the opportunity to collaborate with scientists based at CERN and will be involved in statistical analysis of LHC data. This work would be suitable both for standalone honours projects and for projects leading into subsequent PhD research.


Simultaneous measurements of Standard Model cross-sections at the Large Hadron Collider

Supervisors: A/Prof Kevin Varvell,Dr Kevin Finelli
Contact: A/Prof Kevin Varvell,
Room: 344
Email: k.varvell AT physics.usyd.edu.au
Phone: (02) 9351 2539

The Large Hadron Collider is designed to produce exotic particles such as the Higgs boson, top quark, and W and Z bosons by colliding protons together and using gigantic detectors like ATLAS to examine the debris. By fitting data collected by ATLAS to predictions made by the Standard Model, the model which describes all fundamental interactions of elementary particles, we can simultaneously study the production mechanisms of several rare processes. This simultaneous measurement allows us to perform a global test of the Standard Model which has the potential to reveal new physical processes beyond the Standard Model, and will attempt to resolve or confirm discrepancies seen in other LHC measurements. The student will have the opportunity to collaborate with scientists based at CERN and will be involved in statistical analysis of LHC data. This work would be suitable both for standalone honours projects and for projects leading into subsequent PhD research.


Associated production of quarkonium-like states at ATLAS

Supervisor: Dr Bruce Yabsley
Contact: Dr Bruce Yabsley
Room: 363
Email: b.yabsley AT physics.usyd.edu.au
Phone: (02) 9351 6808

Some of the most surprising and interesting particle physics results in the last decade have been measurements of the quarkonia: the positronium-like spectra of cbar c and bbar b bound states. Several of the recently-discovered charmonium-like states, in particular the X(3872), do not fit into the expected cbar c spectrum and are likely exotic in structure. Quarkonium states are copiously produced at the LHC, and their production is being studied in detail, via J/ψ and Υ → μ+ μ- decays; an analysis of X(3872) → π+ π-, J/ψ is close to completion, and the search for a hidden-beauty analogue state, decaying to π+ π-, Υ, is being carried out in Sydney.

In this project we will take the next step and study the conditions under which π+ π-, Υ states are formed: are they produced together with heavy-flavour jets? With other, simpler quarkonium states? Is there rapidity- or transverse-momentum dependence? And what can this tell us about the fundamental processes by which these states are produced? A rich set of observables is available for study of associated production, and this subject is suitable both for a standalone honours project, and for honours work leading into subsequent PhD research.



Grand Unified Theories

Supervisor: Dr Archil Kobakhidze
Contact: Dr Archil Kobakhidze
Room: 367
Email: archilk AT physics.usyd.edu.au
Phone: (02) 9351 5349

Grand Unification is a theoretical paradigm, in which further unification of strong and electroweak fundamental interactions is achieved at high energies. It has interesting predictions, such as nucleon instability and relations between the masses of quarks and leptons. In this project we will study non-supersymmetric models of Grand Unification with additional particles and interactions at energies accessible in LHC experiments.


Classicalization at microscopic distances

Supervisor: Dr Archil Kobakhidze
Contact: Dr Archil Kobakhidze
Room: 367
Email: archilk AT physics.usyd.edu.au
Phone: (02) 9351 5439

In this project we study the phenomenon of classicalization, which may exhibit in some quantum mechanical systems at small distances. We first identify classical field configurations, the so-called classicalons, which are responsible for this phenomenon and then compute a scattering cross-section in the high-energy limit, involving these field configurations.

The phenomenon of classicalization may be relevant for high-energy behaviour of some scatterings at the Large Hadron Collider as well as in quantum gravity systems.


Dark Matter

Supervisor: Dr Michael Schmidt
Contact: Dr Michael Schmidt
Room: 368
Email: m.schmidt AT physics.usyd.edu.au
Phone: (02) 9351 3810

Several different astrophysical and cosmological observations at vastly different length scales indicate the existence of a new form of matter, dark matter (DM), which is about 5 times more abundant than ordinary matter. It does not interact with light and its existence has only been inferred from its gravitational interactions. The origin and the nature of DM is unknown, but it is commonly believed that it is a new particle. There are several different DM candidates in particle physics, which can explain the DM of the Universe. In this project you will study one of these candidates in more detail.


Neutrino Mass Generation

Supervisor: Dr Michael Schmidt
Contact: Dr Michael Schmidt
Room: 368
Email: m.schmidt AT physics.usyd.edu.au
Phone: (02) 9351 3810

Neutrinos naturally occur in processes mediated by weak interactions like beta decay. In the Standard Model (SM) of particle physics neutrinos are massless. However the observation of neutrino oscillations showed that at least two neutrinos are massive. The absolute mass scale is still unknown, but constrained by cosmology, beta decay and neutrino-less double beta decay experiments. Neutrinos are much lighter than the other leptons, electron, muon and tau. One possible explanation is that neutrinos only obtain there mass as a quantum effect. In this project you will study one model in which neutrinos obtain their mass as a quantum effect from a vector-like generation of leptons which can also be searched for at the LHC.


Mono-stop events in natural MSSM

Supervisors: Dr Lei Wu, Dr Archil Kobakhidze
Contact: Dr Lei Wu, Dr Archil Kobakhidze
Room: 364
Email: leiwu AT physics.usyd.edu.au, archilk AT physics.usyd.edu.au
Phone: (02) 9351 2712

Supersymmetry is a unique nontrivial extension of relativistic invariance, which is considered as a leading candidate for a new particle physics model. It provides a framework for a light Higgs boson without invoking unnatural fine-tuning of theory parameters. However, the recent discovery of a Standard Model (SM) Higgs-like particle with a mass around 125 GeV, in conjunction with non-observation of supersymmetric particles, has largely excluded the most studied parameter range within the minimal supersymmetric Standard Model (MSSM), for which the naturalness criterion is satisfied. Therefore, it is imperative to investigate the less explored space of parameters, where the theory maintains naturalness, and look for alternative strategies for verifying such natural SUSY models at the Large Hadron Collider (LHC). In this project, we investigate the possibility of monostop signals induced by the compressed spectrum at the 14 TeV high-luminosity LHC(HL-LHC) as a probe of natural SUSY.


New Physics in the Higgs self coupling at future colliders

Supervisors: Dr Lei Wu, Dr Archil Kobakhidze
Contact: Dr Lei Wu, Dr Archil Kobakhidze
Room: 364
Email: leiwu AT physics.usyd.edu.au, archilk AT physics.usyd.edu.au
Phone: (02) 9351 2712

Measuring the Higgs-self coupling is one of the most important tasks for experiments at the Large Hadron Collider (LHC) as well as at future colliders, such as the International Linear Collider (ILC). In the renormalizable Lagrangian of the Standard Model (SM), only the quartic Higgs coupling is allowed by the electroweak gauge symmetry. The measurement of the Higgs self-coupling is essential to reconstruct the Higgs potential and understand the electroweak symmetry-breaking mechanism. In some extensions of the SM, the self-coupling can be significantly distorted by quantum corrections from yet undiscovered particles and, thus, is sensitive to the new physics. In addition, large deviations in the Higgs self-coupling may have significant cosmological consequences, driving strongly first-order electroweak phase transitions in the early universe.

In this project, we investigate the observability of new physics in the Higgs self-coupling in future collider experiments, such as those at the high luminosity LHC and ILC.