dc.contributor.author | Lewis, Dave | |
dc.date.accessioned | 2017-09-26T13:06:02Z | |
dc.date.available | 2017-09-26T13:06:02Z | |
dc.date.issued | 2017-08-07 | |
dc.date.submitted | 2017-09-26T13:16:35.996Z | |
dc.identifier.citation | Lewis, D. 2017. New Physics at the LHC: Direct and Indirect Probes. Queen Mary University of London | en_US |
dc.identifier.uri | http://qmro.qmul.ac.uk/xmlui/handle/123456789/25903 | |
dc.description | PhD | en_US |
dc.description.abstract | This thesis presents the results for two searches for new physics performed with the ATLAS
experiment. The first, a search for the rare B-meson decay Bs ! and measurement of its
branching ratio, uses 25 fb1 of ps = 7 and 8 TeV data recorded during 2011 and 2012. After
observing a small number of these decays, a branching ratio of B(Bs ! ) = (0:9+1:1
��0:8) 10��9 is
measured, assuming non-negative event yields. This is compatible with the Standard Model at the
2 level. The second, a search for direct pair production of the supersymmetric top quark partner,
is performed using 36.07 fb��1 of
p
s = 13 TeV data recorded during 2015 and 2016. Final states
with a high jet multiplicity, no leptons and large missing transverse momentum are selected to
target these decays, with several signal regions designed to cover a wide range of particle masses.
No excess is observed, with all signal regions being compatible with the Standard Model within
2 . Limits are set on the stop mass, excluding up to m~t1 = 940 GeV for values of m~ 01
below 160
GeV, assuming a 100% branching fraction to ~t1 ! t~ 01
decays. In addition two reinterpretations of
this data are presented, for a gluino-mediated stop production scenario and a direct dark matter
production scenario. No excess is observed for either model, and limits are set on the mass of the
relevant particles. Finally a viability study into using machine learning techniques to improve on
existing SUSY search methods has been performed, with the initial results proving promising. | en_US |
dc.description.sponsorship | Science and Technology Facilities Council | en_US |
dc.language.iso | en | en_US |
dc.publisher | Queen Mary University of London | en_US |
dc.rights | The copyright of this thesis rests with the author and no quotation from it or information derived from it may be published without the prior written consent of the author | |
dc.subject | Physics | en_US |
dc.subject | Large Hadron Collider | en_US |
dc.subject | CERN ATLAS | en_US |
dc.title | New Physics at the LHC: Direct and Indirect Probes | en_US |
dc.type | Thesis | en_US |