Thesis

Heavy Flavour Jet Trigger using the ATLAS - Tilecal

• Call:

  IDPASC Portugal - PHD Programme 2014

• Academic Year:

  2014 /2015

• Domain:

  Experimental Particle Physics

• Supervisor:

  Helena Santos

• Co-Supervisor:

  Patricia Conde Muino

• Institution:

  Faculdade de Ciências - Universidade de Lisboa

• Host Institution:

  Laboratório de Instrumentação e Física Experimental de Partículas

• Abstract:

  The Large Hadron Collider will collide proton and lead ion beams with a center of mass energy of 13 TeV and 5.13 TeV, respectively, after the current shutdown for Accelerator and Detectors upgrades. ATLAS is one of the four detectors built at the LHC to look into the smallest constituents of matter. It was designed to search for the Higgs boson of the Standard Model (SM) of Particle Physics and for new particles predicted by new physics models beyond the SM. ATLAS participates also in the Heavy Ion Program of the LHC in order to study the Quark Gluon Plasma, a state of matter in which quarks and gluons are no longer confined under strong interaction. The LHC collides beam particles with a very high frequency, 40 MHz, but only a very small fraction is indeed interesting for physics analyses. The Trigger and Data Acquisition system of ATLAS has the main role to select and store about 400 interactions per second for further analysis. In order to achieve this goal, the trigger system is divided in three levels. The first one is hardware based, while the two following use dedicated software algorithms to confirm the selection done by the first level trigger. One important problem is the high rate of fake muons originating in the beam halos, or by accidental coincidence of hits of charged particles, like pions or kaons, in the muon spectrometer. These fake muons, in turn, produce high rate of fake heavy flavour jets (collimated sprays of particles) erroneously tagged as containing muons from B-meson decays. The outer layer of the Tile calorimeter can contribute significantly to eliminate these fake rates. In particular, the new read-out electronics of the calorimeter will improve significantly the signal to background ratio, enhancing the potential of rejecting fake muons in a wide window acceptance. The full integration of the new readout electronics is planned for the SLHC (after 2022), but a first prototype is planned to operate already in 2015. This prototype can be used to develop the heavy flavour jet trigger using the Tile calorimeter in both first and subsequent trigger levels. The work will be developed mostly at LIP - Laboratório de Instrumentação e Física Experimental de Partículas. The student will explore the possibility of using the outer layer of the Tile calorimeter at trigger level, in order to improve the efficiency and purity for tagging Heavy Flavour Jets. The student should have solid computing skills, namely in C++ programming, and must be available to travel to CERN for short periods (1, 2 weeks), several times in the year, for implementation tests.