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The elliptic flow of heavy-flavour decay electrons is measured at midrapidity |eta| < 0.8 in three centrality classes (0-10%, 10-20% and 20-40%) of Pb-Pb collisions at sqrt(sNN) = 2.76TeV with ALICE at LHC. The collective motion of the particles inside the medium which is created in the heavy-ion collisions can be analyzed by a Fourier decomposition of the azimuthal anisotropic particle distribution with respect to the event plane. Elliptic flow is the component of the collective motion characterized by the second harmonic moment of this decomposition. It is a direct consequence of the initial geometry of the collision which is translated to a particle number anisotropy due to the strong interactions inside the medium. The amount of elliptic flow of low-momentum heavy quarks is related to their thermalization with the medium, while high-momentum heavy quarks provide a way to assess the path-length dependence of the energy loss induced by the interaction with the medium.
The heavy-quark elliptic flow is measured using a three-step procedure.
First the v2 coefficient of the inclusive electrons is measured using the event-plane and scalar-product methods. The electron background from light flavours and direct photons is then simulated, calculating the decay kinematics of the electron sources which are initialised by their respective measured spectra. The final result of this work emerges by subtracting the background from the inclusive measurement. A significant elliptic flow is observed after this subtraction. Its value is decreasing from low to intermediate pT and from semi-central to central collisions.
The results are described by model calculations with significant elastic interactions of the heavy quarks with the expanding strongly-interacting medium.
This thesis presents the implementation of the online reconstruction, calibration and monitoring of the data of the Transition Radiation Detector of ALICE. This reconstruction is performed on the High Level Trigger, the third level of the ALICE trigger system, and enables online calibration and monitoring of the incoming data. Additionally, the HLT can steer the data storage, such that only physical interesting events are saved. The online reconstruction, as well as the calibration, makes use of the existing offline algorithms. Therefore, interfaces between the HLT and these offline algorithms were implemented. For being able to reach the speed of 2000 Hz in proton-proton collisions, and 200 Hz in leadlead collisions, the algorithms had to be accelerated. Bottlenecks were tracked down using dedicated tools, and respective code was either reimplemented or it is being skipped during the online reconstruction. The quality of the output data was monitored throughout the implementation, to assure that it is not being cut too much.