not the ATLAS Collabora<on LHC - ATLAS Dan Levin, University of Michigan on behalf of the ATLAS Collabora<on * LHCSKI 2016

Transcription

1 * not the ATLAS Collabora<on LHC - ATLAS Dan Levin, University of Michigan on behalf of the ATLAS Collabora<on * LHCSKI

2 DM Par<cle Interac<ons (if any) 1. Direct from astrophysical sources: ènuclear recoil from DM par<cle interac<ons Posi<ve results: from DAMA, COGENT/LIBRA08, CDMS (Excluded by: Xenon0 ) q q q q 2. Indirect astrophysical evidence è Positron excess observed by HEAT, PAMELA, AMS WIMP-WIMP annihila<on? q see: Secondary Produc/on as the origin of the CR Positron Excess Ahlen, Kruskal & Tarle ApJ (in press) arxiv q q 3. Produc<on in colliders: è Search for generic decay signatures q 2

3 Dark Maker LHC produc<on mechanisms χχ WIMP pairs models Effec<ve Field Theory Simplified UV Complete associated with Higgs Large Extra Dimensions Arkani-Hamad, Dimoupolis, Dvali (ADD) predicts Kaluza-Klein gravitons SUSY Lightest SUSY Par<cles

4 Mono-X χχ recoil against triggerable object X jet,γ,w,z,h q X your favorite interac<on here χ χχ escape undetected appear as Missing E T -q Event Signature qq à a thing + no thing 4

5 DM: Simplified UV Complete Models mono-jet/photon produc<on Z/A mediator: generic weak interac<on axial-vector, spin 1 4 free parameters: M Z = mediator mass m Χ = WIMP mass g q, = mediator-sm coupling g Χ = mediator-wimp coupling Γ = width defined from the free-parameters Events characterized by: ISR recoil of X XX escape undeteced à MET 5

6 DM: SUSY models squark produc<on where mass difference Δm = m ~q1 m ~Χ1 is small process 1: stop pair produc<on where: t1 c + χ process 2: sbokom pair produc<on: t1 b + χ process 3: squark pair produc<on : t1 q + χ Events characterized by: heavy flavor jets, b-jets, light jets XX escape undeteced à MET 6

7 Large Extra Dimensions ADD Model Arkani-Hamed, Dimopoulos, Dvali à addresses enormous difference between: Electroweak unifica<on scale O( 2 ) GeV Mike Lester Planck scale M Pl ~ O( 19 ) GeV 7

8 Large Extra Dimensions The ADD model Phys. Lek. B postulates n extra spa<al dimensions- size R, 2. defines a fundamental Planck scale in 4 + n dimensions: M D from generalized Gauss Law: M Pl 2 M D 2+n R n R A choice of R for a given n yields M D at electroweak scale. for n=2, M D ~ 0-00 GeV à R ~ mm 3. Extra spa<al dimensions are compac<fied: è Kaluza-Klein tower of massive graviton modes. 4. At LHC graviton modes may be excited in extra dimensions, è appear as non-interac<ng par<cles in 4 space, with jet or γ 8

9 DM: Effec<ve Field Theory J. Goodman et al arxiv v2 L. Carpenter et al arxiv Ø interac<on q/g + χ mediated by heavy M > m χ Ø suppression scale: Λ ~ M/(g 1 g 2 ) 1/2 Ø 4-momentum conserva<on: m χ < M/2 Ø perturba<on th.: g 1 g 2 < (4π) 2 è m χ < 2π Λ Ø EFT validity à momentum transfer Q 2 < M Ø two parameters: Λ (or M * ), m χ 9

10 Analysis Strategy 1) Look for a clean signature: high momentum object with large Missing E T 2) backgrounds understood via MC, data driven methods 3) kinema<c cuts define Signal Regions 4) count number of events in Signal Regions è look for excess over SM background Beyond SM Predictions Max Baak- CERN E T

11 4.3 km 1200 dipoles at 8.4 T N p = 100 Bunch crossing: 25 ns L = 27 km 11

12 LHC Opera4ons Run I Run II Peak lumi = cm -2 s -1 Peak lumi = 5 33 cm -2 s -1 12

13 Mono jets 13

14 Monojets Signal Genera<on WIMP signals (Powheg-Box v2) S-channel, spin-1 NLO with B-W propagator couplings: g Χ = 1, g q =0.25 grid of mass points: 1 GeV < M Χ < 1 TeV, GeV < M A < 2 TeV ADD Large Extra Dimensions: Dimensions n =2-6 Planck mass: M D = 2-5 TeV with Pythia 8 & NNPDF23LO pdf SUSY signals: stop, sbokom, squark pairs (Madgraph-5_aMC@NLO) 250 GeV Msquark < 700 GeV 5 GeV < Δm = m ~q1 m ~Χ1 < 25 GeV Full ATLAS detector simula=on with GEANT4 14

15 Monojet Analysis 20.3 ƒ S = 8 Tev arxiv ƒ S = 13 Tev Event & Signal Selec<on 1. E t high level trigger > 70 GeV 2. primary vertex in beam spot envelope & at least two tracks --- P t 3. E t > 250 GeV & leading jet: P t > 250 GeV, η < P t /E t > Δφ( P jet t, P t ) > 0.4 for all jets 6. veto events with: leptons (e/μ) > /20 GeV > 4 jets jets not consistent with p-p collision > 0.4 GeV Inclusive & exclusive signal regions: 15

16 Monojet Backgrounds Zà νν + jets 58% - 65% (low to high SR) Wà νl + jets 35% - 23% Z/γ à ll + jets, mul<jet, t, k diboson 7% - 12% Electroweak backgrounds determined from Control Regions and MC: à reversal of one cut: eg. for Zàνν+jets CR has final state lepton. but same requirements on jet P t, E t, subleading jet vetos, etc mul<jet bkg es<mated from jet enriched data sample (< 0.5% for most SRs) t, kbar, diboson bkg from MC 16

17 Monojet Control & Signal Regions W(àνµ) +jets Control Region removes lepton veto Signal Region > 250 GeV dominant Z(àνν)+jets Transfer factor from CR to SR Alas... only SM! 17

18 Monojet SUSY DM Results exclusion limits on stop produc<on exclusion limits on sbokom produc<on exclusion limits on squark produc<on 18

19 Monojet ADD Results Limits on modified Planck Mass Scale vs # of Large Extra Dimensions Observed 95% CL based on Signal Region E t > 400 GeV Increased lower limits are set WRT to Run-1 at 20.3 ƒ 8 TeV 19

20 Monojet WIMP Limits EFT: D5 Simplified Model mass limits Simplified Model cross sec<on limits 20

21 Mono Z/W (hadronic) 3.2 ƒ -1 S = 13 TeV Two DM produc<on models considered: EFT Dimension 7 operator arxiv Vector mediated simplified UV complete model arxiv

22 Mono Z/W (hadronic) Signal Selec<on Large E t (> 250 GeV) + large radius jet Large jet E t > 250 GeV, y < 1.2 Contains two narrow jets: 66 < M jet < 116 GeV Veto: addi<onal jets Pt > 40 GeV e,μ,γ Pt > GeV E t Backgrounds Z (à νν) +jets W( νl) +jets (undetected lepton) k, single t dibosons Cambridge-Aachen algorithm for large-r jet arxiv: y = min(p t1, P t2 )/m jet ΔR 22

23 Data agree with SM Mono Z/W Results EFT à Limits on M * Vector model à limits on signal strength μ over M med & M Χ 23

24 Mono Higgs+WIMPS (hà bb) 3.2 ƒ -1 S = 13 TeV ISR is Yukawa Supressed... Model 1: Simplified UV-complete, massive vector mediator (with baryon number) radiates Higgs, decays to WIMPS (also with Baryon number) specified by: g q g Z g Χ M Z M Χ, mixing angle sin ϑ: SM h to baryonic H Model 2 (2HDM): vector mediator (Z ) + two-higgs-doublet (five higgs s) Z à A 0 + regular Higgs h, A 0 à ΧΧ (BR ~ 1) specified by: g q g Χ M Z, M A M Χ, h H mixing angle α, tan β (ra<o of vev v 1 v 2 of the doublets) assumes alignment limit à cos(α-β)=0 Final state: hàbb two ( mostly b-tagged) jets + MET 24

25 Mono Higgs+WIMPS (hà bb) 3.2 ƒ -1 S = 13 TeV Event Selec<on E t > 150 GeV, P t > 30 GeV (central tracks only) lepton veto E t < 500 GeV à two central, ranked jets, ΔR < 0.4, b-tagged priority ) E t > 500 GeV à one large R jet ΔR < 1.0 (b-tagged prority ) Δφ (E t, P t ) < π/2 à suppress fake E t Δφ (E t, h ) > 120 o, Δφ (jet1, jet2 ) < 140 à suppress QCD di-jets Major Backgrounds process SR è E t GeV > 500 GeV k 72% 31% W/Z +jets 18% 47% single t 6% 8% diboson 1% % mul<jet 1% 0% 25

26 Mono Higgs+WIMPS Results 26

27 Mono Higgs+WIMPS Results ç Limits on WIMP Mass Vector Mediator mass Limits on 2DHM Model è pseuo-scalar heavy Higgs Mass vs Vector Mediator mass 27

28 Mono γ 3.2 ƒ -1 at 13 TeV 28

29 Signals 7 dimensional EFT operator (same as Mono-Z with k 1 = k 2 =1 arxiv Mono γ 3.2 ƒ -1 at 13 TeV Event Selec<on primary vertex, > 2 tracks at 0.4 GeV Photon P T > 120 GeV η < 2.0 E T > 150GeV leading γ η < or 1 jet P T > 30 GeV η < 4.5 Δϕ(jet/γ, E t ) > 0.4 Lepton veto E t trigger 70 gev (99.7% eff)jec Simplified UV model with g Χ =1 g q =0.25 Graviton model with g Χ =1 g q =0.25 Backgrounds Z νν + γ (ISR) W νl + γ (undetected lepton) Z ll + γ (undetected leptons) Z/W+jets k,γ_jets,mul<jets Electroweak from Control Region: Invert µ vetoà use to normalize the W +γ & Z+γ MC 29

30 Mono γ Results Events / 150 GeV 3 2 ATLAS Preliminary -1 s=13 TeV, 3.2 fb Single-muon CR data W( l ) Fake Photons Z( ll) Z( ) + jets 1 1 Data/Bkg [GeV] E T Events / 150 GeV ATLAS Preliminary -1 s=13 TeV, 3.2 fb Signal Region data DM150 M500 Z( ) W( l ) Fake Photons + jets Z( ll) Events / 150 GeV ATLAS Preliminary -1 s=13 TeV, 3.2 fb Signal Region data DM150 M500 Z( ) W( l ) Fake Photons + jets Z( ll) Data/Bkg Data/Bkg p [GeV] T [GeV] E T

31 Mono γ Results [GeV] m ATLAS Preliminary -1 s=13 TeV, 3.2 fb Axial-vector mediator Dirac DM g =0.25, g =1 q DM Observed 95% CL Observed ± 1 theo Expected 95% CL Expected ± 1 Relic density Perturbative limit [TeV] 95% CL lower limit on M D ATLAS Preliminary ADD model s = 13 TeV, 3.2 fb -1 observed limit truncated limit expected limit expected ± 1 expected ± 2 8 TeV observed limit m med [GeV] Number of extra dimentions [GeV] 95% CL lower limit on M * 900 ATLAS Preliminary observed limit 800 EW EFT model expected limit expected ± 1 s = 13 TeV, 3.2 fb expected ± 2 truncated limits m 4 3 [GeV] ] 2 -proton cross section [cm 34 ATLAS Preliminary s=13 TeV, 3.2 fb 90% CL limits 2 Axial-vector mediator Dirac DM, g =0.25, g =1 q DM PICO-2L XENON0 LUX 3 m 4 [GeV] 31

32 Mono jet vs γ Results mono-jet mono-γ ] 2 -proton cross section [cm 34 ATLAS Preliminary s=13 TeV, 3.2 fb 90% CL limits 2 Axial-vector mediator Dirac DM, g =0.25, g =1 q DM PICO-2L XENON0 LUX 3 4 m [GeV] 32

33 Conclusion Early ATLAS Run-2 analysis of 13 TeV data includes 3.2 ƒ -1 integrated luminosity Searches for new DM inspired physics in mono-x final states reveal (so far) that all results are compa<ble with SM physics. Limits are set for: Effec<ve Field Theory benchmarks Large Extra Dimensions SUSY Model Simplified WIMP benchmark models 33