Thesis

Measurement of the Higgs boson Spin and CP quantum numbers using the WH associated production channel with the ATLAS detector at the LHC (CERN).

• Call:

  IDPASC Portugal - PHD Programme 2015

• Academic Year:

  2015 / 2016

• Domain:

  Experimental Particle Physics

• Supervisor:

  Patricia Conde Muino

• Co-Supervisor:

  Ricardo Gonçalo

• Institution:

  Faculdade de Ciências - Universidade de Lisboa

• Host Institution:

  Laboratório de Instrumentação e Física Experimental de Partículas

• Abstract:

  The Standard Model of Particle Physics (SM) is a very successful theory that describes the fundamental constituents of matter and their interactions. It is, however, incomplete since there are many questions it cannot explain, like the origin of Dark Matter in the Universe or why matter dominates over anti-matter. One of the missing pieces of the SM that has not been fully probed by experiments up to now is the mechanism through which the fundamental particles acquire mass, so-called Higgs mechanism. In the SM, this happens through the interaction with a new particle, the Higgs boson. The discovery of a Higgs boson at CERN by the ATLAS and CMS experiments in 2012 was a very important milestone in this quest. The focus of both collaborations goes now into the precise measurement of all the properties of this new particle, to probe its nature, testing the SM predictions and searching for new physics if deviations from the expectations are found. Objectives of the PhD thesis: This project proposes a study of one of the possible production mechanisms of the Higgs boson in the LHC proton-proton collisions, the so-called Higgs-strahlung process, in which the Higgs is produced in association with a W boson, when the Higgs decays to b-quark pairs and the W boson to a lepton and a neutrino. The spin and CP quantum numbers of the Higgs leave their footprint in the angles of the decay products of the Higgs and the W boson. By combining the information of the different decay particles it will be possible to measure the Higgs boson spin and CP properties. Any deviations with respect to the SM expectations can be a sign of new physics. This PhD project involves the analysis of the 13/14 TeV pp collisions that ATLAS will collect during the run II, starting in 2015. Analysis algorithms that use the standard ATLAS software tools will be developed to search for the Higgs decaying into b-quark pairs in the associated production channel and to study observables that are sensitive to its spin and CP properties. Comparisons with theoretical models, using Monte Carlo simulation, will be performed. In addition, the student will participate in the ATLAS data taking and physics analysis activities, with frequent trips to CERN to participate in shifts and in collaboration meetings.