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R-parity conserving SUSY studies with jets and E T Miss Alexander Richards, UCL 1

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Outline Motivation R-Parity Analysis Aims Discriminating SUSY variables – E T Miss – S T – M eff plots QCD background rejection W e & Z backgrounds Future Studies Alexander Richards, UCL 2

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Motivation In SUSY we expect lots of: –Jets –Leptons –E T Miss (R-parity conserving) Generic Jets + E T Miss search is sensitive to most SUSY models Low multiplicity jets + E T Miss not really studied Most ATLAS SUSY use N jets 4 Alexander Richards, UCL 3

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R-Parity R = (-1) 2j + 3B + L SM particles have R = 1 SUSY sparticles have R = -1 Multiplicative

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QCD jet background Alexander Richards, UCL 4

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Analysis Aim Alexander Richards, UCL 4 Detect production and decay of squarks and gluinos Look for and optimise variable cuts that help discriminate SM backgrounds Analysis focused mainly on QCD jet background at the moment. Example Signal

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Discriminating Variables Alexander Richards, UCL In addition to these jet cuts, 3 SUSY variables investigated: E T Miss S T M eff Jet Cuts: N jets 3 E T jet1,2,3 = 180 GeV, 110GeV, 100GeV | jet1 | < 1.7 | jet2,3 | < 3 5

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Missing Transverse Energy, E T Miss Alexander Richards, UCL R-parity conserving SUSY ->LSP stable SUSY signals have large E T Miss Highly Discriminating variable for SUSY searches 6

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Missing Transverse Energy, E T Miss Alexander Richards, UCL R-parity conserving SUSY ->LSP stable SUSY signals have large E T Miss Highly Discriminating variable for SUSY searches 6 E T Miss >200GeV

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Transverse Sphericity, S T Alexander Richards, UCL A measure of the isotropy of the event perpendicular to beam axis. 0 S T 1 S T = 0S T = 1 7

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Transverse Sphericity, S T Alexander Richards, UCL S T is defined as: S T = 2 1 + 2 ) S ij = k p ki p kj Sphericity Tensor: 8

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Transverse Sphericity, S T Alexander Richards, UCL S T is defined as: S T = 2 1 + 2 ) S ij = k p ki p kj Sphericity Tensor: 8 S T > 0.2

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Effective Mass, M eff Alexander Richards, UCL M eff = E T Miss + p T jet1 + p T jet2 + p T jet3 Defined as: Normalised 10fb -1 9

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Effective Mass, M eff Alexander Richards, UCL M eff = E T Miss + p T jet1 + p T jet2 + p T jet3 Defined as: Normalised 10fb -1 9 M eff > 500GeV

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plots Alexander Richards, UCL Jet Cuts: N jets 3 E T jet1,2,3 > 180GeV, 110GeV, 100GeV | jet1 | < 1.7 | jet2,3 | < 3 1 = | jet1 – (E T Miss )| 2 = | jet2 – (E T Miss )| where: 10

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plots Alexander Richards, UCL R 1 = { 2 2 + ( – 1 ) 2 } 1/2 R 2 = { 1 2 + ( – 2 ) 2 } 1/2 cuts: R 1 > 0.5 radians R 2 > 0.5 radians 11

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Cuts Summary Alexander Richards, UCL Jet Cuts N jets 3 E T jet1,2,3 > 180GeV, 110GeV, 100GeV | jet1,2,3 | < 1.7, 3, 3 SUSY Variable Cuts E T Miss > 200GeV S T > 0.2 M eff > 500GeV Cuts R 1 > 0.5 radians R 2 > 0.5 radians 12

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Alexander Richards, UCL QCD Background Rejection Normalised 10fb -1 13 Jet Cuts

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QCD Background Rejection Alexander Richards, UCL 14 Normalised 10fb -1

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W e & Z backgrounds Alexander Richards, UCL 15

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W e & Z backgrounds Alexander Richards, UCL 15 same cuts as for QCD jet background Unfortunately low statistics Normalised 10fb -1

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Future Study More statistics Include additional backgrounds (ttbar etc.) Optimise cuts Look at 2 jets inclusive Trigger study 16

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Summary jets + E T Miss looks promising for R-parity conserving SUSY search Low multiplicity ->more statistics->better for early discovery? 17

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