Bachelor projects

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Duration : 4 months average

SM projects: Z-meson, Penta-quark, B-mixing (Peter H. Hansen)

W mass measurement (Troels Christian Petersen)

ATLAS Testbeam / Cosmic analysis??? (Peter H. Hansen)

ATLAS data analysis : single beam/collisions, trigger response (Stefania Xella)


We are collecting right now a sample of events with beam activity or beam collisions in ATLAS. It is now time to look at these events with ATLAS event display program carefully, and then start comparing the response of the triggers to what is expected from simulations for minimum bias events. We take reduced real data samples with trigger information saved in them, and we apply some selection to distinguish single beams circulating the machine from collision event candidates. We then look more in details at the trigger response for collisions candidates for various triggers (jet/tau/electron/photon/MET), and compare to MC 900 GeV minimum bias samples.

New particles decaying into tau leptons (Higgs, Z', graviton, ...) (Stefania Xella, Mogens Dam)

Tau leptons can be used to find evidence for new physics, as described more in details here. In particular, Higgs searches in the context of the Standard Model or SuperSymmetry, prefer tau leptons final states in some range of scenarios. We can use simulated data samples form the ATLAS experiment, and consider scenarios with new particles decaying into a pair of tau leptons, and evaluate how clear the observation of such new particles can be, depending on the luminosity accumulated and the selection applied.

Determination of spin of new heavy resonances using tau leptons (Mogens Dam)

Trigger optimization for new particle searches (Stefania Xella)


High luminosity (10^33 cm-2 s-1) is needed to discover new particles within the first few years of LHC operation. To keep a good fraction of new physics signal among the data saved to disk, real analysis online in the trigger system needs to be performed. To handle the backgrounds online, two ways of proceeding when performing online selection of data are: asking for high energy single triggers, or combining triggers of various types with lower energy requirements. Both selections require a carefully study of how their efficiency can be measured on real data, this is preferred than relying on simulations. Two possible projects can be envisaged in this area. First of all, for multilepton or lepton+jets triggers, one needs to verify wether the trigger efficiencies of the single triggers can be used to measure the combined trigger efficiency. Typically the single trigger efficiencies can be measured on SM well known processes like W or Z production, at an early stage of the ATLAS experiment. Secondly, for high energy triggers, one should identify which SM physics processes allow the measurement of the efficiency for such triggers, and how much luminosity is needed to measure them from data. It is possible that a combination of simulation and real data needs to be used after all.

Physics BEYOND the Standard Model in the shadow of GRAVITY/HIGGSLESS


Finding a quantum theory of gravity has eluded the world’s best physicists for almost a century. As well as the fearsome mathematical challenge of marrying quantum theory with Einstein’s general theory of relativity, the extreme conditions at which quantum gravity applies — corresponding, for example, to the first 10^-43 seconds of the universe — make it virtually impossible to test in an experiment. But then...

In 1998, physicists realized that the natural scale of quantum gravity (the Planck scale, which corresponds to an energy of 10^19 GeV) could be 15 orders of magnitude lower if the universe has Extra Dimensions into which the true strength of gravity can “leak”. This raises the prospect of studying quantum gravity at CERN’s Large Hadron Collider (LHC), which will soon be smashing protons into one another to produce an energy of 14 TeV. Projects

Di-boson production in the Standard Model and model independent search for New Physics

DiBoson.jpg Tchannel.jpg

The self-interaction of the gauge bosons (the W, the Z, and the photon) is a consequence of the non-Abelian gauge symmetry (SU_2) of the Standard Model. The gauge boson self-interactions appear as vertices involving three gauge bosons, and result in the production of pairs of bosons (WW, Wgamma, WZ). Not all combinations are possible within the Standard Model though (GammaGamma, ZGamma, ZZ). The study of diboson production thus directly tests the predicted Standard Model couplings. Observations of anomalous couplings of known vertices or existence of new vertices would be a clear indication of New Physics beyond the Standard Model.

  • Study of Di-boson production at LHC (Jørgen Beck Hansen)
    • Neutral di-boson final states: ZZ, ZGamma, GammaGamma
    • Charged di-boson final states: WW, WZ, WGamma (Jørgen Beck Hansen)
  • Effects of anomalous Gauge-Boson-Couplings in pp collisions (Jørgen Beck Hansen)
    • Neutral bosons: ZZZ, ZZGamma, GammaGamma
    • Charged bosons: WWZ, WWGamma
    • Finding the energy-scale of new physics
    • Phenomenological studies using CompHEP and its related program LanHEP are also welcome :)

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