Searches for SUSY & Exotics with ATLAS

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1 Searches for SUSY & Exotics with ATLAS Evelyn Thomson University of Pennsylvania May BLV 2017 Cleveland, Ohio 1

2 Outline Introduction Supersymmetry searches Gluinos Scalar top Electroweakinos Exotic searches Dilepton Dijet Diboson Vector-like quarks Dark matter Summary ATLAS speakers in parallel sessions Exotics at the LHC Search for New Phenomena in Dijet Events Lydia Beresford (May 15 14:20) Searches for new phenomena in leptonic final states Chikuma Kato (May 15 14:40) Search for vector-like quarks Takuya Tashiro (May 15 15:00) Lepton number violation searches Antonio Salvucci (May 16 14:50) Dark Matter Dark Matter searches with the ATLAS Detector Stanislav Suchek (May 15 14:40) 2

3 The Large Hadron Collider Run 2 proton collisions at s=13 TeV Delivered 42 fb -1 in Goal 90 fb -1 more in Run Goal 300 fb -1 Phase II upgrades -> High Luminosity Goal 3000 fb -1 3

4 Searching for Supersymmetry SUSY pair production R-Parity R=(-1) 3B-3L+2s 1 pb 1 pb 1 fb arxiv: , arxiv:hep-ph/ Status and implications of BSM searches E. Halkiadakis, G. Redlinger, D. Shih Ann.Rev.Nucl.Part.Sci. 64 (2014)

5 Searching for Supersymmetry SUSY pair production LHC signature depends on LSP and R-Parity R-Parity R=(-1) 3B-3L+2s 1 pb Figure from S. Spinner 1 fb arxiv: , arxiv:hep-ph/ ATLAS-CONF Run 1 Constraints on promptly decaying SUSY particles with lepton-number-violation and RPV 5

6 Solving rapid proton decay in SUSY R-Parity Conservation R=(-1) 3B-3L+2s Forbids violation of baryon and lepton number Proton stable Lightest Supersymmetric Particle (LSP) stable Significant consequences for LHC signatures Pair production of superpartners High MET from stable LSPs LSP is a dark matter candidate (must be neutralino) ad hoc introduction of new quantum number R-Parity Violation R=(-1) 3B-3L+2s Allows violation of baryon OR lepton number Proton stable LSP decays through small RPV couplings Significant consequences for LHC signatures Pair production of superpartners No MET since collider LSP decays Decaying dark matter Add an extra local gauge symmetry to MSSM 6

7 Gluino pair production Simplified model with squarks decoupled Direct decay to LSP Four high p T jets High MET High effective mass (m eff ) from scalar sum of jet p T and MET Exclude gluino up to 2000 GeV for low LSP mass Similar limits for more complicated decay chains and pmssm ATLAS-CONF

8 Background estimation Showing control regions for major backgrounds t t τυq q b b and hadronic tau decay Z+jets with Z υ υ W+jets with W τυ and hadronic tau decay Normalize backgrounds using control regions Check in validation regions (not shown here) ATLAS-CONF

9 Scalar top search Direct production of stop pairs 4 high p T jets, 1 b-tag MET > 250 GeV Exclude stop up to 950 GeV for low LSP Improved reach in region where stop mass close to sum of top and LSP New search region with ISR Exclude stop between GeV ATLAS-CONF see also for 1 lepton and for 2 lepton 9

10 Exploring LSP type One step decay Two step decay significant and W bosons may be off-shell For results, please see Keisuke Yoshihara s talk at LHCP this morning and ATLAS-CONF

11 Gluino with RPV LSP has baryon-number violating decay One lepton 5 to 12 or more jets, b-tags No MET Data-driven backgrounds Exclude gluino up to 2100 GeV for Bino LSP arxiv:

12 Stop with RPV (Bino LSP or Higgsino LSP) LSP has baryon-number violating decay One lepton 5 to 12 or more jets, b-tags No MET Data-driven backgrounds Interpretation for scalar top production Bino LSP LSP Wino LSP (no leptons) Higgsino LSP arxiv:

13 Stop RPV 2x2 Baryon-number violating decay 2 resonances decay to 2 jets No MET, background from QCD multijets Data-driven estimate Preselection data Preselection data Average mass of di-jet pairs For each m avg bin N D =N A xn F /N C Mass Asymmetry Production angle ATLAS-CONF

14 Stop RPV 2x2 Baryon-number violating decay 2 resonances decay to 2 jets Decay to two light quarks Exclude stop from 100 to 410 GeV ATLAS-CONF

15 Stop RPV 2x2 Baryon-number violating decay 2 resonances decay to 2 jets Decay to two light quarks Exclude stop from 100 to 410 GeV Decay to a b quark and light quark Exclude stop from 100 to 470 and 480 to 610 GeV ATLAS-CONF

16 Stop RPV with U(1) B-L Minimal model with extra U(1) B-L gauge group, spontaneously broken by RH sneutrino Stop LSP with lepton number violating decay 2 resonances decay to lepton and b-quark 2 leptons ee, eμ, μμ, 2 jets, 1 b-tag Backgrounds normalized in control regions t t, Wt, Z/γ*+jets τbτb μbμb PLB 732 (2014) 325 ebeb Mass Asymmetry ATLAS-CONF Highest Mass Lepton b-jet pair 16

17 Decreasing M Electroweakinos Decay via scalar leptons Decay via W, Z, h bosons Run 1 results, Run 2 results soon Increasing M Assumptions: LSP is pure bino; NLSP is pure wino; large M between NLSP and LSP ATLAS SUSY summary plots 17

18 Electroweakinos 4 lepton (RPV) LSP has lepton-number violating decay 4 isolated leptons from massive LSP decays Backgrounds ttz, ZZ with 4 leptons Reducible with 1 or 2 fake leptons Exclude wino NLSP below 1000 GeV for LSP decays to electrons or muons ATLAS-CONF

19 Run mm Run mm Disappearing track IBL 33 mm New pixel layer at 33 mm for Run 2 (IBL) New tracklet reconstruction (4 hits) completely in pixel detector Sensitive to charged particles with shorter lifetimes than Run 1 Long-lived Chargino small M for Wino LSP ATLAS-CONF

20 Long-lived particles summary Long-lived chargino Long-lived gluino R-hadron Only 2015 data SUSY-Summary-Plots See new ATLAS-CONF displaced vertices 20

21 Outline Introduction Supersymmetry searches Gluinos Scalar top Electroweakinos Exotic searches Dilepton Dijet Diboson Vector-like quarks Dark matter Summary Highest dijet invariant mass 8.12 TeV, both jets have p T 3.79 TeV 21

22 Dijet resonances Data-driven background Dijet invariant mass Angular distribution arxiv:

23 Searches with same flavor leptons 20 GeV for ee Experimental mass resolution at 3 TeV 420 GeV for μμ ATLAS-CONF

24 Searches with same flavor leptons Exclude Z with mass below 4 TeV at 95% CL Exclude llqq contact interactions with energy scale Λ below 23 to 40 TeV ATLAS-CONF

25 Searches with Lepton Flavor Violation Only 2015 data Updates for summer Eur. Phys. J. C76 (2016)

26 Diboson resonances Search for VH q q b b with high Lorentz boost Two high p T large R=1.2 jets (450, 250 GeV) Jet mass > 50 GeV Higher mass jet with 1 or 2 b-tagged track jets Lower mass jet has two-prong substructure Background 90% from QCD multijets Data-driven background from sidebands Above 2.5 TeV, Higgs Lorentz boost high enough for overlap of decay of two b hadrons 1 tag has better sensitivity above 2.5 TeV ATLAS-CONF

27 Diboson resonances Search for VH q q b b with high Lorentz boost Two high p T large R=1.2 jets (450, 250 GeV) Jet mass > 50 GeV Higher mass jet with 1 or 2 b-tagged track jets Lower mass jet has two-prong substructure Data are in agreement with Standard Model expectations Largest excess observed at 3.0 TeV Local significance of 3.3σ Global significance of this excess is 2.2σ ATLAS-CONF

28 Vector-like Quarks: ZtZt final state Spin-1/2 but not chiral like standard model quarks Vector: same left and right-handed couplings Bare mass terms allowed in Lagrangian Solves hierarchy problem for Higgs boson mass TT pair production One T Zt decay with Z υ υ Signature One lepton 4 high p T jets MET Exclude T mass below 1.16 TeV with 100% T Zt Here T->Zt ATLAS-CONF See also for T->Wb EXOT See also for T->Ht ATLAS-CONF HtHt ZtZt WbWb 28

29 Vector-like Quarks: WbWb final state Optimized for TT, also sensitive to BB, XX, YY One T Wb decay with W lυ Signature One lepton, MET 3 high p T jets 1 b-tag Large R jet for boosted W Exclude T mass below 1.35 TeV with 100% T Wb Exclude B mass below 1.25 TeV with 100% B Wt HtHt EXOT ZtZt WbWb 29

30 Dark matter search Mono-photon+MET Backgrounds Z υ υ + QED ISR Cleaner background than in mono-jet+met with QCD ISR ATLAS-EXOT

31 Dark matter search Mono-photon+MET Set limits in 2D plane (mediator mass, DM mass) Proton collisions so larger g q gives better limits ATLAS-EXOT

32 Dark matter and dijets Dark matter mediator produced in protonproton collisions, so must also decay to dijets Dijet searches give strong limits for g q =0.25, weaker limits for smaller g q =0.1 Exotics summary plots 32

33 Summary Searches for strongly produced SUSY not showing any deviations from SM yet Searches for rarer electroweak produced SUSY starting to explore new territory in Run 2 Searches for exotics not showing any deviations from SM yet New Supersymmetry results New Exotics results 33

34 Backup 34

35 Gluino pair production: 3 rd gen ATLAS-CONF All final states have 4 b-jets Require 3 b-tags Combine multiple search regions 4-9 jets Low-Int-High effective mass 0 or 1 lepton Exclude gluino below 1900 GeV for low LSP mass, expected limits slightly higher 0 tops 4 tops 35

36 Pileup Reconstruction of charged particle tracks important to remove effects of pileup Select anti-kt jets with tracks from primary vertex (hard scatter) Calculate MET with calibrated objects and other tracks from primary vertex 36

37 Standard Model Three Fundamental Forces of Nature precisely described by Quantum Field Theory SU(3) x SU(2) L x U(1) Strong force (QCD) carried by massless gluons Electro-Weak force carried by massless photon (QED) and massive W +, W -, Z 0 (Weak) Higgs field provides mass to W and Z, and to elementary particles? Right-handed neutrinos don t interact with any of the force-carriers? Is it valid up to Planck scale (10 19 GeV) where gravity becomes important? Hierarchy problem for scalar Higgs boson: fine-tune radiative corrections to 1 part in

38 Dark Matter All observed particles are only 1/5 of mass in the universe What is dark matter? Does it interact with the Higgs? Is it a supersymmetric particle? Is it the QCD axion? Solar System M31 Galaxy 38