Development of boosted jet triggers for new physics searches at ATLAS experiment


  • Call:

    IDPASC Portugal - PHD Programme 2015

  • Academic Year:

    2015 / 2016

  • Domain:

    Experimental Particle Physics

  • Supervisor:

    Patricia Conde Muino

  • Co-Supervisor:

    José Soares Augusto

  • Institution:

    Faculdade de Ciências - Universidade de Lisboa

  • Host Institution:

    Laboratório de Instrumentação e Física Experimental de Partículas

  • Abstract:

    The Large Hadron Collider, at CERN, is the most powerful proton-proton collider ever built. When it will re-start operation in 2015, it will collide protons with a center of mass energy of 13 TeV, at a rate of 40 Million times per second, with a data-flow of the order of 1 PB/s. Out of all these collisions, only a very small fraction is indeed interesting for physics analysis. The Trigger and Data Acquisition system of ATLAS has the main role of selecting and storing about 400 interactions per second for further analysis, using a combination of hardware and software based filtering systems. The LHC will be further upgraded in 2018 to be able to deliver an even higher rate of collisions, bringing an increase in data quantity of an order of magnitude or more. To find interesting physics embedded in a huge amount of data, complex algorithms involving lots of computation are needed. Several algorithms applied to LHC data are, already today, quite heavy on computations. Advanced algorithms, capable of efficient selection in harder conditions, will be even more time consuming. Running these algorithms in a short enough time slot will only be possible through its parallelization with the use of hardware accelerators like General Purpose Graphical Processing Units (GPGPUs). This proposal is focused on the development of a particular type of trigger that is essential to search for new heavy particles (predicted by new physics models) that decay to quarks, like heavy Higgs bosons. The quarks produced in the decay of the heavy particle hadronize forming a single large jet of collimated particles that can be identified with the ATLAS detector. This jet can be distinguished from other non-interesting jets, produced at a much larger rate, due to the typical substructure pattern of more than one energy maximum. The development of specific triggers to identify this kind of patterns will be essential for the new physics searches in the high luminosity phase of the LHC and will only be possible with the use of highly parallel algorithms that profit from the computational performance of GPGPUs. The jet substructure study is a very active field of research, with many different techniques available on the market. The work proposed for this thesis will start with the study of appropriate method to be used at trigger level, followed by the parallelization of the corresponding algorithm to be run on GPGPUs. This project will contribute to the development of the ATLAS Upgrade trigger algorithms and, as such, will be integrated in the Software Upgrade program of the ATLAS experiment.