Search for squarks and gluinos at the ATLAS experiment

The aim of Particle Physics is to understand the nature of the constituents of matter and the forces that bind them together. In the early part of the last century our knowledge grew from concepts of atoms to the discovery of the nucleus and its constituent, protons and neutrons. Later it was discovered that the protons and neutrons also had a sub-structure of quarks held together by gluons. A picture emerged of 6 different quarks, up and down, charm and strange, top and bottom (and their antiparticles), arranged into 3 families, and 4 different forces, strong nuclear force, electromagnetic force, weak nuclear force and gravity. A similar structure was found among leptons, the particles that do not interact via the strong force: electron, muon and tau and their corresponding neutrinos. The Standard Model (SM) of particle physics describes how these particles and forces interact, but ignores the gravitational force. Although high-precision experiments have verified its predictions, the SM is often regarded as a low energy effective theory for several open questions. Among others, it does not explain the origin of particle masses and the Higgs boson, the postulated particle necessary to generate elementary particle mass, has not been observed yet and its own mass is unspecified. Several theoretical scenarios have been proposed to describe physics at very high energies, of which SuperSymmetry (SUSY) and Extra-Dimension (ED) are the most compelling ones. In the large majority of cases, these scenarios foresee the existence of new particles. In SUSY inspired models, for example, the usual particle spectrum is at least doubled and every particle has a 'superpartner' differing in spin by a half unit, possibly much heavier in mass. This solves one of the difficulties in the SM of keeping the Higgs mass stable. The best way to explore the 'Beyond Standard Model' territory is to study collisions between fundamental constituents of matter at extremely high energies, to the TeV scale and beyond. To accomplish this, the High Energy Physics community has designed the most powerful accelerator: the Large Hadron Collider (LHC). Built at CERN, the LHC will collide protons at unprecedented energies. ATLAS, one of the two general purpose experiments at the LHC, will try to find the fingerprints of unknown particles, which might manifest themselves as resonances or through various complex signatures hidden underneath large SM background processes. The primary aim of my proposed programme is to discover new physics with the ATLAS detector at the earliest stage of the LHC turn-on, while simultaneously performing measurements of SM processes in preparation for more detailed longer term searches over the next 5 years. Precision SM measurements are not only important in their own right but also constitute unavoidable backgrounds to searches for SUSY particles. Furthermore, they provide the essential means to optimize the calibration of the detector. Exploiting the knowledge acquired from these studies in terms of detector performances, I shall carry out searches for squarks and gluinos, the superpartner of quarks and gluons, in final state events including jets of hadrons, leptons and large unbalanced transverse momentum. If SUSY is discovered, I will measure the kinematics of squark and gluino decay chains and evaluate their fundamental parameters. The beginning of the LHC era represents a milestone in particle physics and it is imperative to have a well-defined analysis search strategy in the aim of maximizing the potential to find new physics. My research will largely benefit from the combination of the experience I gained at the Tevatron collider and the Liverpool group expertise. This is an exciting time for our field. We have the unique ability to explore the uncharted territory at the energy frontier, and I am eager to be at the forefront of the ATLAS physics programme.