Authors:	Urrejola Pereira, Pedro Salvador
Title:	Search for Supersymmetry in the 1-Lepton plus Jets Final States with the ATLAS Detector
Online publication date:	11-Feb-2020
Year of first publication:	2020
Language:	english
Abstract:	The LHC remarkable 7 and 8 TeV data taking campaigns were used to test precision measurements for standard model processes, search for physics beyond SM and for the search and consequent discovery of the higgs boson. After 2012 the LHC prepared for its first long shutdown during which the hardware and software of the machine were upgraded and prepared for the next runs at higher energies and collision rates. In 2015 the LHC started collecting data from 13 TeV center of mass proton proton collisions every 25 ns, reaching a peak luminosity of 5×10³³ cm⁻²s⁻¹ and a total delivered luminosity of 4.2 fb⁻¹. This document presents searches for Supersymmetry in the final states with one lepton, jets and missing transverse energy. The analyses uses statistically independent control regions to control dominant Standard Model backgrounds, signal regions to probe for possible supersymmetric events and validation regions for validation purposes. A simultaneous fit to data normalizes the main backgrounds in the control regions using a profile likelihood method for precise background estimates in the signal regions. The results and interpretation of 8 TeV one lepton analysis were re-interpreted in a much general supersymmetric framework as the phenomenological Supersymmetric Standard Model (pMSSM). The re-interpretation results were combined with the results from many other searches to cover all reachable regions of the phase space. The ATLAS analyses constraints to strong pMSSM production showed that all models with gluino masses below 700 GeV can be excluded. For models with neutralino LSP masses below 500 GeV, the previous limit extends to 1 TeV. For the models that could not be excluded by any of the searches, a study was done looking for blind spots in the parameter space, that could be covered by one lepton searches. The results showed that in most of the cases the leptons came from secondary channels, confirming that searches with no hard leptons are the most sensitive among a vast region of the phase space. The document also presents the results of the ATLAS one lepton analysis using the full 2015 dataset at 13 TeV. The search was optimized for a simplified signal model assuming direct gluino pair production, both decaying in via lightest chargino to the lightest neutralino with 100% BR. The results were consistent with the null hypothesis and were interpreted as model independent upper limits, and as 95% CL exclusion limits for the gluino simplified models. The new limits extend the reach of previous searches in different regions. For low neutralino LSP masses, gluino masses of up to 1.6 TeV can be excluded, while for compressed scenarios gluino masses of only up to 870 GeV can be excluded.
DDC:	530 Physik 530 Physics
Institution:	Johannes Gutenberg-Universität Mainz
Department:	FB 08 Physik, Mathematik u. Informatik
Place:	Mainz
ROR:	https://ror.org/023b0x485
DOI:	http://doi.org/10.25358/openscience-2682
URN:	urn:nbn:de:hebis:77-diss-1000033654
Version:	Original work
Publication type:	Dissertation
License:	In Copyright
Information on rights of use:	https://rightsstatements.org/vocab/InC/1.0/
Extent:	xii, 222 Seiten
Appears in collections:	JGU-Publikationen