Dark Matter and SUSY at ATLAS IMPRS Young Scientist Workshop Friday, - PowerPoint PPT Presentation

Dark Matter and SUSY at ATLAS IMPRS Young Scientist Workshop Friday, 7 th September 2018 Nicolas Köhler Max Planck Institute for Physics 
 (Werner-Heisenberg-Institut)

How does SUSY explain Dark Matter? • Neutral and weakly interacting particle • Stable particle - Assume R-parity conservation - obtain stable LSP Nicolas Köhler Ringberg Workshop 2018 � 2 / 13

How does SUSY explain Dark Matter? • Neutral and weakly interacting particle • Stable particle - Assume R-parity conservation - obtain stable LSP χ 0 • Possibly neutralino ˜ 1 Nicolas Köhler Ringberg Workshop 2018 � 2 / 13

How does SUSY explain Dark Matter? • Neutral and weakly interacting particle • Stable particle - Assume R-parity conservation - obtain stable LSP χ 0 • Possibly neutralino ˜ ˜ or gravitino G 1 ˜ Gravity G G Nicolas Köhler Ringberg Workshop 2018 � 2 / 13

What is the lightest supersymmetric particle? • Depending on SUSY breaking mechanism • Most popular candidates: mSUGRA 
 GMSB 
 (minimal SuperGravity) (Gauge mediated SUSY Breaking) U. Uwer, Lecture Notes B. Schneider, SUSY18, Barcelona Nicolas Köhler Ringberg Workshop 2018 � 3 / 13

What is the lightest supersymmetric particle? • Depending on SUSY breaking mechanism • Most popular candidates: mSUGRA 
 GMSB 
 (minimal SuperGravity) (Gauge mediated SUSY Breaking) U. Uwer, Lecture Notes B. Schneider, SUSY18, Barcelona Lightest neutralino Nicolas Köhler Ringberg Workshop 2018 � 3 / 13

What is the lightest supersymmetric particle? • Depending on SUSY breaking mechanism • Most popular candidates: mSUGRA 
 GMSB 
 (minimal SuperGravity) (Gauge mediated SUSY Breaking) U. Uwer, Lecture Notes B. Schneider, SUSY18, Barcelona Lightest neutralino Gravitino Nicolas Köhler Ringberg Workshop 2018 � 3 / 13

What is the lightest supersymmetric particle? • Depending on SUSY breaking mechanism • Most popular candidates: mSUGRA 
 GMSB 
 (minimal SuperGravity) (Gauge mediated SUSY Breaking) U. Uwer, Lecture Notes B. Schneider, SUSY18, Barcelona Always search for missing transverse energy E miss T Lightest neutralino Gravitino Nicolas Köhler Ringberg Workshop 2018 � 3 / 13

Neutralino from gaugino decays • Search for 3 leptons • m ` + ` − ∼ m Z • No b-tagged jets • Transverse mass of and > 110 GeV arxiv:1803.02762 E miss ` T • Dominating SM processes: 
 Diboson • No excess above SM pred. Nicolas Köhler Ringberg Workshop 2018 � 4 / 13

Neutralino from gaugino decays • Search for 3 leptons • m ` + ` − ∼ m Z • No b-tagged jets • Transverse mass of and > 110 GeV arxiv:1803.02762 E miss ` T • Dominating SM processes: 
 Diboson • No excess above SM pred. Excluded Nicolas Köhler Ringberg Workshop 2018 � 4 / 13

Neutralino from stop decays t • TeV-stop favoured to solve hierarchy problem p ˜ χ 0 t ˜ • Consider decay into top quark and neutralino 1 χ 0 ˜ ˜ t 1 p t Nicolas Köhler Ringberg Workshop 2018 Ringberg Workshop 2018 � 5 / 13

Neutralino from stop decays q b • TeV-stop favoured to solve hierarchy problem q p t W ˜ t • Consider decay into top quark and neutralino χ 0 ˜ 1 χ ⌥ ˜ χ 0 • Consider fully-hadronic top quark decays 1 ˜ 1 ˜ t p q W q b Nicolas Köhler Ringberg Workshop 2018 Ringberg Workshop 2018 � 5 / 13

Neutralino from stop decays q b • TeV-stop favoured to solve hierarchy problem q p t W ˜ t • Consider decay into top quark and neutralino χ 0 ˜ 1 χ ⌥ ˜ χ 0 • Consider fully-hadronic top quark decays 1 ˜ 1 ˜ t p q W • No leptons, multiple jets, large E miss T q b Nicolas Köhler Ringberg Workshop 2018 Ringberg Workshop 2018 � 5 / 13

Neutralino from stop decays q b • TeV-stop favoured to solve hierarchy problem q p t W ˜ t • Consider decay into top quark and neutralino χ 0 ˜ 1 χ ⌥ ˜ χ 0 • Consider fully-hadronic top quark decays 1 ˜ 1 ˜ t p q W • No leptons, multiple jets, large E miss T q b For m ˜ t 1 � m ˜ χ 0 1 • Decay products of top strongly collimated • Jet clustering with large radius parameter allows to collect the top in single object • Discriminate against SM processes not containing top quarks • Dominating SM processes left: and 
 t ¯ t +jets Z ( → νν ) https://www.quantumdiaries.org/ Nicolas Köhler Ringberg Workshop 2018 Ringberg Workshop 2018 � 5 / 13

Neutralino from stop decays q b • TeV-stop favoured to solve hierarchy problem q p t W ˜ t • Consider decay into top quark and neutralino χ 0 ˜ 1 χ ⌥ ˜ χ 0 • Consider fully-hadronic top quark decays 1 ˜ 1 ˜ t p q W • No leptons, multiple jets, large E miss T q b arxiv:1709.04183 For m ˜ t 1 � m ˜ χ 0 1 • Decay products of top strongly collimated • Jet clustering with large radius parameter allows to collect the top in single object • Discriminate against SM processes not containing top quarks • Dominating SM processes left: and 
 t ¯ t +jets Z ( → νν ) https://www.quantumdiaries.org/ Excluded No excess above SM expectation found 
 -> Calculate exclusion limits: Nicolas Köhler Ringberg Workshop 2018 Ringberg Workshop 2018 � 5 / 13

Neutralino from stop decays t • No top squark found in all decay p ˜ χ 0 t ˜ scenarios 1 χ 0 ˜ ˜ t 1 p https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/CombinedSummaryPlots/SUSY/ t b W p ˜ t χ 0 ˜ 1 χ ± ˜ 1 χ ⌥ ˜ 1 χ 0 ˜ ˜ t 1 p W b f b f p ˜ t χ 0 ˜ 1 χ 0 ˜ 1 ˜ t p f f b Nicolas Köhler Ringberg Workshop 2018 � 6 / 13

Neutralino from light squark decays • Consider production of ˜ u 1 , ˜ d 1 , ˜ c 1 , ˜ s 1 • Veto leptons • At least two jets with 
 > 50 GeV p T arxiv:1712.02332 • Large missing transverse energy • Requirements on scalar sum of transverse momenta Excluded Nicolas Köhler Ringberg Workshop 2018 � 7 / 13

Neutralino from light squark decays • Consider production of ˜ u 1 , ˜ d 1 , ˜ c 1 , ˜ s 1 • Veto leptons • At least two jets with 
 > 50 GeV p T arxiv:1712.02332 • Large missing transverse energy • Requirements on scalar sum of transverse momenta • Dominating SM t ¯ backgrounds: W+jets, t Excluded Nicolas Köhler Ringberg Workshop 2018 � 7 / 13


 Neutralino from gluino decays • Veto leptons • At least four high-energetic jets • Large E miss T • Discriminating variable: 
 P p T + E miss T jets • Dominating SM backgrounds: 
 W+jets, t ¯ t • No excess above SM expectation found Nicolas Köhler Ringberg Workshop 2018 � 8 / 13


 Neutralino from gluino decays • Veto leptons • At least four high-energetic jets • Large E miss T arxiv:1712.02332 • Discriminating variable: 
 P p T + E miss T jets • Dominating SM backgrounds: 
 W+jets, t ¯ t Excluded • No excess above SM expectation found Nicolas Köhler Ringberg Workshop 2018 � 8 / 13

G ⌧ 1 GeV Gravitino as the LSP m ˜ • Require at least two photons with >75 GeV E T • Large E miss T • Large P p T + P p T jets γ arxiv:1802.03158 • Dominating SM backgrounds: 
 production 
 γγ +jets production 
 γ Multijet production Excluded • No excess above SM expectation found Nicolas Köhler Ringberg Workshop 2018 � 9 / 13

Did we miss anything? • What if the NLSP does not decay instantaneously? • Secondary displaced vertex of interest appears in the event arxiv:1112.0180 Nicolas Köhler Ringberg Workshop 2018 � 10 / 13

Long-lived neutralino • If neutralino has non-zero lifetime, 
 two displaced photons are present • Require pair of photons and E miss T • Exploit finely segmented LAr arxiv:1409.5542 EM calorimeters • Look at difference in 
 z-coordinate between primary vertex and closest approach of photon to beam line ∆ z γ Nicolas Köhler Ringberg Workshop 2018 � 11 / 13

Long-lived neutralino • If neutralino has non-zero lifetime, 
 two displaced photons are present • Require pair of photons and E miss T • Exploit finely segmented LAr arxiv:1409.5542 EM calorimeters • Look at difference in 
 z-coordinate between primary vertex and closest approach of photon to beam line ∆ z γ Nicolas Köhler Ringberg Workshop 2018 � 11 / 13

Long-lived neutralino • Photons reach EM calorimeter with slight time delay arxiv:1409.5542 • Measure time of arrival t γ • Fit in bins of ∆ z γ t γ • SM background: One photon is misidentified electron/jet • No excess above SM expectation Nicolas Köhler Ringberg Workshop 2018 � 12 / 13

Long-lived neutralino • Photons reach EM calorimeter with slight time delay arxiv:1409.5542 • Measure time of arrival t γ • Fit in bins of ∆ z γ t γ • SM background: One photon is misidentified electron/jet Excluded • No excess above SM expectation Nicolas Köhler Ringberg Workshop 2018 � 12 / 13