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Search for electroweakly produced supersymmetric particles in final states including two charged leptons with the ATLAS experiment at the LHC

Three analyses searching for electroweakly produced supersymmetric particles in proton-proton collisions are presented. The collisions were recorded by the ATLAS experiment at the Large Hadron Collider. Two leptons (electrons or muons), jets and missing transverse energy are expected in the final st...

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Autor principal: Wittkowski, Josephine
Lenguaje:eng
Publicado: 2015
Materias:
Acceso en línea:http://cds.cern.ch/record/2093513
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author Wittkowski, Josephine
author_facet Wittkowski, Josephine
author_sort Wittkowski, Josephine
collection CERN
description Three analyses searching for electroweakly produced supersymmetric particles in proton-proton collisions are presented. The collisions were recorded by the ATLAS experiment at the Large Hadron Collider. Two leptons (electrons or muons), jets and missing transverse energy are expected in the final states. Simplified models as well as the phenomenological Minimal Supersymmetric Standard Model (pMSSM) are used to study the production and decay of pairs of gauginos, i.e. charginos and neutralinos. The first analysis is performed with an integrated luminosity of 4.7 fb^-1 of ATLAS data, recorded in 2011 at a centre-of-mass energy of sqrt(s) = 7 TeV. Direct slepton production and three scenarios in which pairs of gauginos decay via intermediate sleptons are addressed. Particular attention is paid to the trigger strategy. No excess is observed in the number of data events. In the simplified model that assumes the direct slepton production, left-handed slepton masses between 85 and 195 GeV are excluded at 95% confidence level for a 20 GeV neutralino. The second analysis uses 20.3 fb^-1 of ATLAS data recorded in 2012 at sqrt(s) = 8 TeV. Seven signal regions address supersymmetric decay scenarios with two oppositely charged leptons in the final state. The dominating Standard Model background processes are, analogously to the 2011 analysis, ttbar, Z/gamma^*+jets and diboson processes. A combination of dilepton triggers is used to select the events. The results are in agreement with the Standard Model expectations and are interpreted in the context of the pMSSM. chi_1^pm masses between 100 and 105 GeV, 120 and 135 GeV and 145 and 160 GeV can be excluded at 95% confidence level for m_chi_1^0= 0 GeV in the simplified model for which chi_1^+ chi_1^- -> W^+ chi_1^0 W^- chi_1^0 -> l^+ nu chi_1^0 l^- nu chi_1^0. Slepton masses between 90 and 325 GeV can be excluded at 95% CL for a neutralino mass of less than 30 GeV when the direct slepton production is simulated in a simplified model. A third analysis is also performed on the 2012 data addressing a scenario in which a chargino-neutralino pair decays via a W- and a Higgs boson into a final state with two same-sign leptons, two quarks and two lightest neutralinos. The dominating background is due to non-prompt leptons and is estimated by a data-driven method. The contribution due to diboson background is suppressed e.g. by cuts on the invariant mass of the decay products of the Higgs boson and on the effective mass, which is the scalar sum of the p_T of the leptons, jets and of the missing transverse energy. The results for this analysis are not yet published. The three mass points with the neutralino masses of less than 10 GeV and chargino masses of less than 150 GeV are expected to be excluded at 95% CL.
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spelling cern-20935132019-09-30T06:29:59Zhttp://cds.cern.ch/record/2093513engWittkowski, JosephineSearch for electroweakly produced supersymmetric particles in final states including two charged leptons with the ATLAS experiment at the LHCParticle Physics - ExperimentThree analyses searching for electroweakly produced supersymmetric particles in proton-proton collisions are presented. The collisions were recorded by the ATLAS experiment at the Large Hadron Collider. Two leptons (electrons or muons), jets and missing transverse energy are expected in the final states. Simplified models as well as the phenomenological Minimal Supersymmetric Standard Model (pMSSM) are used to study the production and decay of pairs of gauginos, i.e. charginos and neutralinos. The first analysis is performed with an integrated luminosity of 4.7 fb^-1 of ATLAS data, recorded in 2011 at a centre-of-mass energy of sqrt(s) = 7 TeV. Direct slepton production and three scenarios in which pairs of gauginos decay via intermediate sleptons are addressed. Particular attention is paid to the trigger strategy. No excess is observed in the number of data events. In the simplified model that assumes the direct slepton production, left-handed slepton masses between 85 and 195 GeV are excluded at 95% confidence level for a 20 GeV neutralino. The second analysis uses 20.3 fb^-1 of ATLAS data recorded in 2012 at sqrt(s) = 8 TeV. Seven signal regions address supersymmetric decay scenarios with two oppositely charged leptons in the final state. The dominating Standard Model background processes are, analogously to the 2011 analysis, ttbar, Z/gamma^*+jets and diboson processes. A combination of dilepton triggers is used to select the events. The results are in agreement with the Standard Model expectations and are interpreted in the context of the pMSSM. chi_1^pm masses between 100 and 105 GeV, 120 and 135 GeV and 145 and 160 GeV can be excluded at 95% confidence level for m_chi_1^0= 0 GeV in the simplified model for which chi_1^+ chi_1^- -> W^+ chi_1^0 W^- chi_1^0 -> l^+ nu chi_1^0 l^- nu chi_1^0. Slepton masses between 90 and 325 GeV can be excluded at 95% CL for a neutralino mass of less than 30 GeV when the direct slepton production is simulated in a simplified model. A third analysis is also performed on the 2012 data addressing a scenario in which a chargino-neutralino pair decays via a W- and a Higgs boson into a final state with two same-sign leptons, two quarks and two lightest neutralinos. The dominating background is due to non-prompt leptons and is estimated by a data-driven method. The contribution due to diboson background is suppressed e.g. by cuts on the invariant mass of the decay products of the Higgs boson and on the effective mass, which is the scalar sum of the p_T of the leptons, jets and of the missing transverse energy. The results for this analysis are not yet published. The three mass points with the neutralino masses of less than 10 GeV and chargino masses of less than 150 GeV are expected to be excluded at 95% CL.CERN-THESIS-2014-338oai:cds.cern.ch:20935132015-11-13T08:15:05Z
spellingShingle Particle Physics - Experiment
Wittkowski, Josephine
Search for electroweakly produced supersymmetric particles in final states including two charged leptons with the ATLAS experiment at the LHC
title Search for electroweakly produced supersymmetric particles in final states including two charged leptons with the ATLAS experiment at the LHC
title_full Search for electroweakly produced supersymmetric particles in final states including two charged leptons with the ATLAS experiment at the LHC
title_fullStr Search for electroweakly produced supersymmetric particles in final states including two charged leptons with the ATLAS experiment at the LHC
title_full_unstemmed Search for electroweakly produced supersymmetric particles in final states including two charged leptons with the ATLAS experiment at the LHC
title_short Search for electroweakly produced supersymmetric particles in final states including two charged leptons with the ATLAS experiment at the LHC
title_sort search for electroweakly produced supersymmetric particles in final states including two charged leptons with the atlas experiment at the lhc
topic Particle Physics - Experiment
url http://cds.cern.ch/record/2093513
work_keys_str_mv AT wittkowskijosephine searchforelectroweaklyproducedsupersymmetricparticlesinfinalstatesincludingtwochargedleptonswiththeatlasexperimentatthelhc