Statistical interpretation of exotics monojet data in search of an invisibly decaying Higgs Boson

Mwewa, Chilufya

Statistical interpretation of exotics monojet data in search of an invisibly decaying Higgs Boson

Master Thesis

2014

Publisher

University of Cape Town

Department

Department of Physics

Faculty

Faculty of Science

Abstract

Following the recent discovery of a Standard Model Higgs-like particle at the Large Hadron Collider, this study searches for the evidence of invisible decays of this particle. Assuming that this is the Standard Model Higgs boson, its decay to invisible particles is not expected to be measurable in the current data. However, it could have a large contribution from its decay to stable non-Standard Model particles such as the hypothetical dark matter particles. This study corresponds to 4.7 fb!1 of 7 TeV proton-proton collisions and 20.3 fb!1 of 8 TeV proton-proton collisions. At the time of thesis submission, the 8 TeV results were not unblinded by the ATLAS Collaboration, so toy-data are presented here to demonstrate the procedure. The performance of the statistical framework to be used in the combination of the 7 TeV data with the real 8 TeV data is assessed and is found to perform very well. The results are interpreted to set 95 confidence level limits on the branching ratio to invisible particles of the newly discovered Higgs-like particle at a mass of 125 GeV. Limits are also set on the production cross section ⇥ branching ratio of additional Higgs-like particles that decay invisibly in the mass range: 115 GeV to 300 GeV. In the combination of the 7 TeV data and 8 TeV toy-data, an expected (observed) upper limit of0.89 (0.59) is set on the branching ratio to invisible particles of a 125 GeV Higgs boson. In the mass range 115 to 300 GeV, no excess beyond the Standard Model expectation is observed.

Description

Includes bibliographical references.

Reference:

Collections

Masters

Full item page