Recent Results from Tommaso Lari INFN Milano SUSY searches in - PowerPoint PPT Presentation

Interpreting the LHC data, Trieste 2019/05/28 Recent Results from Tommaso Lari INFN Milano SUSY searches in ATLAS On behalf of the ATLAS Collaboration

WHAT WE ARE LOOKING FOR Mixing of winos, binos, zinos, higgsinos That’s a lot of new particles and decay modes we can potentially discover ❖ Couplings are fixed by the symmetry with SM ❖ Masses are unknown, until we figure out how the symmetry is broken ❖

WHY SUSY IS COOL arXiv:1110.6926v1 ˜ L i , ˜ e i ˜ B ˜ u 1 , 2 , ˜ Q 1 , 2 , ˜ d 1 , 2 ˜ W ˜ b R • Electroweak symmetry breaking ˜ g predicted and natural ˜ ˜ t L t R ˜ b L • SUSY Particles closely related to the Higgs ˜ H mass required to be light by naturalness. natural SUSY decoupled SUSY • Dark Matter candidate ~ • Require R-parity conservation - lightest χ particle stable, pair production • Unification of Forces • … Bullet Cluster (astro-ph/0608407) � 3

OUTLINE Strong production - light flavour squarks and gluinos ❖ Strong production - third generation squarks ❖ Electroweak production - sleptons, charginos, neutralinos ❖ Focus on recent results � 4

STRONG PRODUCTION (LIGHT FLAVOUR SQUARKS AND GLUINOS) NLO + NLL, pp, s = 13 TeV Cross-section [pb] ∼ ∼ 0 ± t χ χ (higgsino-like) 4 10 1 2 ∼ ∼ 0 ± (wino-like) χ χ 1 2 3 ~ ~ 10 g g ¯ t ~ ~ � g 2 q q 10 p ~ ~ t t χ 0 � 10 1 1 χ 0 � − 1 10 1 p � 2 − g 10 t 100 events 3 − 10 in run2 4 − 10 ¯ t − 5 10 0 500 1000 1500 2000 2500 Susy particle mass [GeV] ❖ High cross section => probing high masses ❖ R-parity conservation => lightest particle (LSP) stable, missing momentum ❖ High p T jets � 5

GLUINO SUMMARY PLOT ATLAS SUSY summary plots ❖ Each curve is a different model, combining limits from relevant channels ❖ All curve but yellow have neutralino LSP (mass on y- axis) ❖ For light LSP, limits in 1800-2250 GeV ❖ For small g-LSP mass ~ difference, mass down to 1000-1200 GeV allowed � 6

ATLAS-CONF-2019-015 139 fb -1 NEW SS SEARCH Two same sign (SS) or three leptons : clean channel, small SM backgrounds Several target models : q q t t W W t W ⇤ W Z p p d p p ˜ ˜ g ˜ t 1 g ˜ χ 0 b χ ± χ 0 χ 0 χ 0 ˜ χ ± ˜ ˜ χ 0 ˜ ˜ ˜ ˜ 1 1 1 χ ± 2 1 b 2 1 ˜ ˜ t λ 00 1 313 χ ⌥ ˜ χ 0 ˜ ˜ χ ± t χ ± b ˜ � 1 χ 0 ˜ χ 0 2 χ 0 � χ 0 ˜ ˜ ˜ ˜ ˜ 1 1 ˜ t 1 g 1 g ˜ 2 ˜ 1 1 b p p p p W ⇤ d Z W q q ¯ t W ⌥ W t t (a) Several (“cut and count”) selections target different model / mass regions : E miss E miss SR [GeV] m e ff [GeV] / m e ff SUSY n ` n b n j T T 1 ! qq 0 ( � 00 , 0 ) � 2 ( ` ± ` ± ) g ! t ˜ t ⇤ 1 , ˜ t ⇤ � 0 � 6 ( p T > 40 GeV ) > 2600 ˜ Rpv2L � � � 0 � 0 t ˜ 1 , ˜ 1 ! 3 q ( � 00 , 0 ) g ! t ¯ ˜ � 0 � 0 1 ! qq 0 ` ( � 0 , 0 ) q ˜ 1 , ˜ g ! q ¯ ˜ � 0 � 2 ( ` ± ` ± ) q 0 WZ ˜ Rpc2L0b = 0 � 6 ( p T > 40 GeV ) > 200 > 1000 > 0 . 2 g ! q ¯ ˜ 1 � 0 � 2 ( ` ± ` ± ) b 1 ! tW ˜ ˜ Rpc2L1b � 1 � 6 ( p T > 40 GeV ) > 0 . 25 � � 1 � 0 � 2 ( ` ± ` ± ) b 1 ! tW ˜ ˜ Rpc2L2b � 2 � 6 ( p T > 25 GeV ) > 300 > 1400 > 0 . 14 1 � 0 t ˜ g ! t ¯ ˜ 1 � 0 � 3 ( ` ± ` ± ` ± ) t 1 ! tW ± ( W ⇤ ) ˜ ˜ Rpc3LSS1b � 1 no cut but veto 81 GeV < m e ± e ± < 101 GeV > 0 . 14 1 2 leptons (e, µ ) with p T > 20 GeV � 7 Either SS or with third lepton with p T > 10 GeV

ATLAS-CONF-2019-015 BACKGROUND ESTIMATE ❖ Irreducible from MC, the main ones (ttW, ttZ, WZ) compared to data in dedicated validation regions ❖ Charge flip electrons : 2 OS ee in data reweighted by measured (in Z events) charge flip probability ❖ Fake and non prompt leptons : matrix method (loose selection in data, plus loose-to-tight probabilities measured in control samples) � 8

ATLAS-CONF-2019-015 RESULTS Events ATLAS Preliminary Data Total uncertainty Fake/non-prompt 3 -1 10 s = 13 TeV, 139 fb Charge-flip t(W)Z, t t H, t t VV, 3t, 4t t t Z t t W WZ WW, ZZ, VH, VVV 2 10 10 1 Data/SM 1.5 1 0.5 VRttV VRWZ4j VRWZ5j Rpc2L0b Rpc2L1b Rpc2L2b Rpv2L Rpc3LSS1b No significant excess Signal selections are not orthogonal � 9

ATLAS-CONF-2019-015 GLUINO LIMITS ~ ~ ~ ~ ~ ~ ~ ~ ~ ∼ 0 ∼ ∼ 0 ∼ 0 ∼ ∼ 0 ± ± g g production, g qqWZ ; m( ) = (m( g ) + m( ))/2, m( ) = (m( ) + m( ))/2 g g production, g t t , t b d → χ χ χ χ χ χ → → 1 1 1 2 1 1 ) [GeV] ) [GeV] 2500 ATLAS Preliminary ATLAS Preliminary 2000 Expected Limit ( ± 1 σ ) Expected Limit ( ± 1 σ ) exp exp -1 -1 s =13 TeV, 139 fb s =13 TeV, 139 fb ~ t 0 1 SUSY SUSY Observed Limit ( 1 ) m( Observed Limit ( 1 ) ± σ ± σ ∼ χ All limits at 95% CL All limits at 95% CL 1800 m( theory theory -1 -1 SS/3L obs. 36 fb SS/3L obs. 36 fb 2000 [arXiv:1706.03731] [arXiv:1706.03731] 1600 ) < m(Z) 0 ∼ ) χ ) < m( 0 ∼ 1 0 χ ~ ∼ , 1400 g χ m( 1 m( 1500 2 Δ ) < m(W ), 0 ∼ χ ∼ ± , 1200 ) + m(t) χ m( 2 1 Δ ~ t ) < m( 1000 1000 ~ g m( 800 500 600 400 1000 1200 1400 1600 1800 2000 2200 600 800 1000 1200 1400 1600 1800 2000 2200 ~ ~ m( g ) [GeV] m( g ) [GeV] q q W t Z p p d ˜ g χ 0 g χ 0 ˜ ˜ χ ± ˜ ˜ 1 2 1 b ˜ t λ 00 313 ˜ t b χ ± ˜ χ 0 χ 0 ˜ ˜ ˜ g 1 ˜ g 2 1 p p d Z t q q � 10 W

THIRD GENERATION SQUARKS DIRECT PRODUCTION NLO + NLL, pp, s = 13 TeV Cross-section [pb] ∼ ∼ 0 ± χ χ (higgsino-like) 4 10 1 2 ∼ ∼ 0 ± (wino-like) χ χ 1 2 3 ~ ~ 10 g g ~ ~ 2 q q 10 ~ ~ t t 10 1 − 1 10 2 − 10 100 events 3 − 10 in run2 4 − 10 − 5 10 0 500 1000 1500 2000 2500 Susy particle mass [GeV] � 11

STOP SUMMARY PLOT ATLAS SUSY summary plots ❖ The simplest model has a stop decaying directly to top LSP ( blue curve ) ❖ If charginos and heavy neutralinos are in the decay chain, more complex final states ❖ Typical limits range from 400 GeV (small mass difference) to 1000 GeV (light LSP) ❖ Here focus on some recent results � 12

ATLAS-CONF-2019-017 139 fb -1 STOP 3-BODY 1 [GeV] b ∆ m = m ˜ ∆ m > ` t 1 − m ˜ χ 0 χ 0 ∆ m > m ˜ 1 1 t ] m ˜ ∆ m > m W + m b ∆ m > 0 m t p ⌫ W > ∆ m > m ˜ m t m ˜ t 1 < m ˜ χ 0 ∆ ˜ t 0 100 1 χ 0 � 0 m > m W + ˜ χ 0 ˜ 1 ˜ 1 f � 1 χ 0 0 W t 1 → c ˜ 1 ˜ f 1 χ b b t � 0 ˜ → → → 1 ˜ ˜ ˜ t ˜ ˜ 1 t 1 t 1 t p q W 0 q 0 100 200 0 100 200 300 ] m ˜ t 1 [GeV] b ❖ Direct decay to LSP, but mass difference not enough for on-shell top quark ❖ Limits 36 fb -1 : 420-580 GeV on stop mass ❖ Soft decay products, difficult S/B discrimination � 13

ATLAS-CONF-2019-017 STOP 3-BODY ANALYSIS Pre-selection ❖ Neural network to discriminate signal and background ❖ Top MC normalized to data at low NN classifier values (+ tighter M T cut to increase purity) Events 5 Discriminating variables 10 Total SM t t 2L ATLAS Simulation Preliminary t t 1L W+jets -1 s = 13 TeV, 139.0 fb Single top Multi-boson Preselection 4 t t +V 10 ~ ∼ 0 m( t , )=(450,300) GeV χ 1 ~ ∼ 0 m( t , )=(500,380) GeV χ 3 10 1 2 10 10 1 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 NN bWN � 14

ATLAS-CONF-2019-017 STOP 3-BODY RESULTS ~ ~ ~ ~ ~ ∼ 0 ∼ 0 ∼ 0 t t production, t bff' , t bW , t t → χ → χ → χ 1 1 1 1 1 Events 1 1 1 ) [GeV] 800 ATLAS Preliminary Data Total SM ATLAS Preliminary Observed limit ( 1 ) ± σ -1 s = 13 TeV, 139.0 fb 5 t t t t +V th 10 -1 s = 13 TeV, 139.0 fb 700 Expected limit ( 1 ) W+jets Single top ± σ exp Multi-boson Limit at 95% CL JHEP 06 (2018) 108 4 10 0 1 ~ 0 ∼ 600 ∼ m( t , )=(500,380) GeV χ χ 1 1 m( 3 500 10 400 2 10 ) < 0 0 ∼ 300 χ )- m( 1 ~ 10 t ) > m(W) + m(b) m( 1 200 0 ∼ χ ) - m( ) > m(t) Significance 2 1 ~ t 0 m( ∼ 100 1 1 χ ) - m( 1 ~ 0 t m( 1 1 − 0 2 − 200 300 400 500 600 700 800 0.4 0.5 0.6 0.7 0.8 0.9 1 ~ NN m( t ) [GeV] bWN 1 ❖ Cut and count for discovery ❖ Considerable extension of previous limits ❖ Shape of NN output for ❖ Sensitive to part of the 4-body decay region as well exclusion � 15