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Title: Search for di-Higgs production to the b¯bτ +τ − final state using Support Vector Machines with the ATLAS detector at the Large Hadron Collider in pp collisions at √s = 13TeV
Author: Stevenson, Thomas James
ISNI:       0000 0004 7653 7920
Awarding Body: Queen Mary University of London
Current Institution: Queen Mary, University of London
Date of Award: 2018
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This thesis presents a search for resonant and standard model non-resonant di-Higgs production in theb¯bτ +τ− decay channel, with the semi-leptonic ditau state. The search uses data collected by the ATLAS experiment at the LHC of pp-collisions at √s=13 TeV during 2015 and 2016, corresponding to an instantaneous luminosity of 36:1fb-1. No deviation from the Standard Model prediction is observed. For the non-resonant standard model di-Higgs production an upper limit is set on the cross-section compared to the Standard Model prediction,σ/σSM< 24:44 @ 95%CL. Upper limits are set on the cross-section times branching ratio for the resonant searches, where the results are interpreted in terms of constraints on a 2HDM heavy scalar Higgs model and a Randall-Sundrum Kaluza-Klein graviton model. The use of Support Vector Machines is investigated and benchmarked against the nominal results of the Boosted Decision Tree multivariate analysis, in pursuit of potential future improvements.
Supervisor: Not available Sponsor: Science and Technology Facilities Council
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Particle Physics ; di-Higgs production