4th Year Projects in 2009

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4th Year Projects in 2009

Quarkonium states: towards first data from ATLAS

Supervisor: Dr Bruce Yabsley
Contact: Dr Bruce Yabsley
Room: 366
Email: B.Yabsley AT physics.usyd.edu.au
Phone: 9351 5970
Current?: revised 2009/01/12 (initially posted 2008/08/22)

The quarkonia - bound states of a heavy quark and its antiquark - are among the most important particles in experimental work, and have played a key role in the development of the Standard Model. In particular, the lowest lying vector states, the J/ψ and the Υ(1S), have a very clean experimental signature (to μ+ μ-), are ideal for detector calibration, and serve as important signals for other physics processes. They will be copiously produced in pp collisions at the Large Hadron Collider, and will be accessible in the first data taken by the ATLAS experiment.

In this project we will work on the recognising J/ψ to μ+ μ- and Υ(1S) to μ+ μ- in simulated ATLAS data, and study the feasibility of searching for other particles decaying to J/ψ or Υ. The aim is to be ready to make measurements with first ATLAS data, which may become available later in 2009.


Discovering the Charged Higgs with ATLAS

Supervisor: Dr Aldo F. Saavedra
Contact: Dr Aldo F. Saavedra
Room: 366
Email: A.Saavedra AT physics.usyd.edu.au
Phone: 9351 5970

In the Standard Model the Higgs sector is comprised of only one complex Higgs doublet. This results in only one physical neutral Higgs scalar whose discovery potential with ATLAS has been extensively studied. Non-minimal Higgs models such as supersymmetric extensions of the Standard Model sometimes feature additional Higgs doublets. The minimal two-Higgs doublet model (THDM) has five physical Higgs bosons of which two are charged and three are neutral. The discovery of a Charged Higgs would definite signal the existence of New Physics beyond the Standard Model. Perhaps supersymmetry since the most studied type of THDM is the mininal supersymmetric extension of the Standard Model (MSSM). The focus of the project will be the discovery potential of the Charged Higgs decaying into a tau lepton and a number of associated jets.

This project was undertaken by Mark Scarcella.


Supersymmetry and Tau Lepton Number Violation in ATLAS

Contact: Dr Aldo F. Saavedra
Room: 366
Email: A.Saavedra AT physics.usyd.edu.au
Phone: 9351 5970

Supersymmetry (SUSY) is an attractive extension of the Standard Model which solves some of its shortcomings. Whilst there is no current evidence for SUSY, there are arguments that suggest that the masses of the lightest SUSY particles should lie in the TeV range and hence be accessible to the new generation of experiments at the Large Hadron Collider (LHC). In some SUSY scenarios, lepton number violation is allowed in sparticle decays. In this project, we will consider a specific scenario in which tau lepton number is violated, and examine the ability of ATLAS to detect a signal for such a process and disentangle it from Standard Model backgrounds. The work will build on a previous study made elsewhere, adding a more realistics treatment of triggering and tau lepton reconstruction than was used previously.

This project was undertaken by Cameron Cuthbert.


Semileptonic B meson decays to η and η mesons in Belle

Supervisor: Dr Kevin Varvell
Contact: Dr Kevin Varvell
Room: 355
Email: K.Varvell AT physics.usyd.edu.au
Phone: 9351 2539

Using the Belle experiment's large data set and a technique known as full reconstruction, we have been successful in measuring the rate at which B mesons decay to final states containing a lepton (electron or muon), a neutrino, and a single particle containing an up quark (specifically π, ρ or ω mesons). These decays, which are rare (of order one in ten thousand B decays are of this type) are important inasmuch as their rate determines a parameter of the Standard Model, known as Vub, related to CP violation.

This project will build on this work using the latest available data from Belle, in particular to search for two other related decay modes, where the meson produced is an η or η. The rates determined by previous studies have rather large uncertainties and we may well be able to do better. The project will involve the study of real and simulated data with existing computer analysis tools.

This project was undertaken by Yasmin Clarke.


Radiative transitions of D mesons in Belle data

Supervisor: Dr Bruce Yabsley
Contact: Dr Bruce Yabsley
Room: 366
Email: B.Yabsley AT physics.usyd.edu.au
Phone: 9351 5970

Radiative transitions between related mesons (cf. transitions between different energy levels in atomic physics) are important for understanding meson structure, and the binding potential between quark and antiquark. Meson spectroscopy has been shaken up in recent years by the discovery of unexpected states in data from the B-factories (Belle and BaBar), and measurement of theoretically clean transitions is an important constraint on models. This project will use a mix of "toy" and full Monte Carlo, data processing in ROOT, and some Belle data to develop and test a method for analysis of 1P to 1S radiative transitions of D mesons. These transitions can only be studied at the B-factories and have not yet been measured. This project has the potential to open onto post-honours work, for example PhD research on Belle.

This project was undertaken by Ian Watson.