Multilepton Signatures at Tevatron: SUPERSYMMETRY (SUSY)

1. Multilepton Signatures at Tevatron Maxim Titov UNIVERSITY OF FREIBURG (ON BEHALFOFTHECDFANDDØCOLLABORATIONS) Luminosity vs Projections: 2 fb-1 2007 Aspen Winter Conference “New Physics at the Electroweak Scale and New Signals at Hadron Colliders”, January 8-14, 2007

2. SUperSYmmetry (SUSY) • Supersymmetric extensions of the SM provide a consistent framework • for gauge unification and stabilization of EWK scale • Each SM particle gets a SUSY partner (spin differ by DS = ½) • Superpartners are heavy  SUSY must be broken • Several SUSY breaking scenario under consideration: • mSUGRA, Gauge-Mediated SB, Anomaly-Mediated SB  determines SUSY structure Typical mass spectrum of SUSY particles: (important decays are shown Strong limits on SUSY searches from LEP: M(c+) > 103.5 GeV; Mslepton > 95 GeV

3. L L B Phenomenology R-Parity Violating (RPV) SUSY SUSY / Gauge invariance do not require R-parity conservation Define multiplicative quantum number:Rp = (-1)3B + L+ 2S(+1 for SM; -1 for SUSY partners) Superpotential of general MSSM with R-parity violation term (W = WMSSM + WRPV): WRPV = lijkLiLjEk+ l’ijkLiLjDk + l’’ijk UiUjDk 45 NEW YUKAWA COUPLINGS, ASSUME ONLY ONE COUPLING DOMINATE AT A TIME ! • Experimental signatures • @ Tevatron: • Pair productionandRPV decays of LSP • -- land l’ couplings • Resonant sparticle production: • -- l’ and l’’ couplings • R-parity is violated (RPV): • SUSY particles can be singly produced • The LSP is unstable and decays to SM • particles  no dark matter candidate • SUSY particles decay into quarks, • leptons, neutrinos •  multi-jet, multi-leptons, small ETmiss • R-parity is conserved (RPC): • SUSY particles are pair produced • Lightest SUSY particle (LSP) is • stable  dark matter candidate • The LSP (neutral, colourless) interacts • only weakly with matter •  Large ETmiss from LSP (SUSY signature)

4. ~ c 0 Minimal SuperGravity (mSUGRA) EW scale • THE SYMMETRY BREAKING TAKES PLACE IN A • “HIDDEN SECTOR” AND IS TRANSMITTED TO • THE “VISIBLE SECTOR” BY GRAVITATION • Only FIVE parameters: • m0: common scalar (Higgs, • sleptons, squarks) mass at the GUT scale • m1/2: common gaugino (bino, • wino, gluino) mass at the GUT scale • A0: common trilinear scalar • couplings at the GUT scale • (sfermion mixing) • tan b: ratio of Higgs vacuum • expectation values • Sign(m): higgsino mass parameter • LIGHTEST SUPERSYMMETRIC PARTICLE • ( ) STABLE, if RPV IS CONSERVED GUT scale Tevatron Assume mSUGRA mass relation: m (c1+) ~ m (c20) ~ 0.8 m1/2 m (c10) ~ 0.4 m1/2

5. Experimental Signature Production Decay l l + ETmiss + X c1+c1+c1+ lnc10 c20c20c20  llc10; c20  nnc10 l l l  lc10; l  nc1+; c1+ lnc10 l l l + ETmiss + X c1+c20c1+ lnc10; c20  llc10 c20c20 c20 llc10; c20  llc10 l ll lc20; c20  llc10 l nl lc20; c20  llc10; n  lc1+ l l +  1 j + ETmiss + X c1+c20c1+ qq’c10; c20  llc10 g g, qq g  qq’c1+; q q’c1+ t t t  bc1+; c1+  lnc10 l l l +  1 j + ETmiss + X c1+c30c1+ lnc10; c30 qqc20 g g, qq g  qq’c1+;g  qqc20;q qc20 l l+  0 j+X c10c10 lln; l, nl  lc10; c10  qq’l, n  ll l l l +  0 j+ X c1+c20, c1+c1+, c20c20c1+ lnc10; c20  llc10; c10  lln • R-parity conserving signatures (RPC)  LSP (c10) is stable ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ • R-parity violating signatures (RPV)  LSP (c10) decays into SM particles ~ ~ ~ ~ SUSY in Multilepton Signatures Many SUSY models give rise to multi-lepton signatures  cascade decays from charginos, neutralinos, sleptons, squarks(topics presented in this talk are shown in red)

6. Tevatron Experiments: CDF & D0 Excellent particle ID, coverage, tracking and powerful trigger system Mature understanding of detectors Data taking efficiency ~ 85 - 90 % • General Purpose Detectors: CDF DØ • Electron ID acceptance |η|<2.0 |η|<3.0 • Muon ID acceptance |η|<1.5 |η|<2.0 • & trigger |η|<1.0 |η|<2.0 • Precision tracking (Si) |η|<2.0 |η|<3.0 • Jet ID |η|<3.6 |η|<4.2

7. Searches for SUSY (R-parity Conserved) Lepton signatures indicate presence of top, W, Z, weak gauginos and sleptons

8. SUSY GOLDEN MODE:3 l+ 2+X ~ ~ ~ ~ c c ± ± c c 0 0 1 1 2 2 ~ c 0 Chargino / Neutralino Production and Decays • ( ) DEPEND ON GAUGINO- HIGGSINO MIXING, SQUARK MASSES Destructive interference between s- and t-channels: t - channel s - channel • Clean signature: 3 charged leptons + ETmiss (low SM bkg) • Electroweak production  small event rates (s x Br (3l) ~ 0.1- 0.5 pb) • Large cross section  low gaugino masses (m1/2), large squark masses • Large leptonic branching fraction  low slepton masses  low m0 • Large e(m) branching fraction  low degree of stau mixing  low tan b

9. miss Charginos and Neutralinos in 3 leptons + E T • Experimental challenge: low-pT leptons • Need multilepton triggers w/ low pT-thresholds • Need efficient lepton ID @ low pT • ANALYSIS STRATEGY / SIGNATURE: • 3 leptons + ETmiss • -- 2 leading PT leptons and tight ID criteria • -- Isolated 3rd track PT ~ 3-5 GeV (no ID) • (3rd track = e, m, t, including hadronic thad) • 2 leptons + ETmiss • -- 2 Like-sign leptons • -- No 3rd track requirement • (important when 3rd lepton PT is very soft) • Major SM Backgrounds: • WZ/ZZ 3 l(irreducible) • Fake Leptons: • (g-conversion or fake leptons: p0) • W + g/jet 1 l + 2 fakes • Z/g* + g/jet 2 l + fake • WW + g/jet 2 l + fake • ttbar  2 l + fake • QCD multijet  no isolated • leptons(determined from data)

10. miss Charginos and Neutralinos in 3 leptons + E T 6 D0 ANALYSIS: 1  LS (m+m+), 3 ll (e,m) + track; 2 (e/m + thad+ track) ANALYSIS CHANNEL (ee + track): PTe1 > 12 GeV; PTe2 > 8 GeV Anti Z/g*  ee Cuts: 18 GeV < Mee< 60 GeV;Dj (e,e) < 2.9 Anti - ttbar Cut: HT = SPTjet < 80 GeV ETmiss-based Cuts: ETmiss > 22 GeV; ETsignificance > 8 MT (e, ETmiss) > 20 GeV Third Isolated Track: PT > 4 GeV, calorimeter & tracker isolation Anti –W Cut: pT3rd track> 7 GeV, if MT(e,ETmiss)> 65 GeV Product of ETmiss and 3rd track PT: ETmiss * PT3rd track > 220 GeV2  ℒ dt ~ 1.1 fb-1 Mee ETmiss * PT3rd track

11. + + Trilepton Analysis: Selection m m _ _ Increase acceptance by requiring 2 out of 3 leptons, while reducing SM bkg  ℒ dt ~ 0.9 fb-1 M (m+,m+) Preselection (2 isolated LS-muons): PTm1 > 13 GeV; PTm2 > 8 GeV Anti Z/g*  mm & Anti-QCD Cuts: 25 GeV < Mm+m-< 65 GeV; Dj (m,m) < 2.9 ETmiss-based Cuts: ETmiss > 10 GeV; ETsignificance > 12 15 GeV < MT (ETmiss, pTm2) < 65 GeV LS Invariant Mass Cut: 12 GeV < M (m+,m+) < 110 GeV Product of ETmiss and 3rd track PT: ETmiss * PT3rd track > 160 GeV2 MT LS dilepton channel is also sensitive to squark / gluino production

12. ~ ~ l l ~ ~ l c 0 2 RPC Chargino / Neutralino Limits in mSUGRA • mSUGRA - inspired Model: • s x Br (3 l) is mainly a function • of m( ) and m ( ) • Degenerate slepton masses: • (no slepton mixing) • ms = mse = m s Combine analysis: ee+track (1.1 fb-1), em+track (0.3 fb-1), mm+track (0.3 fb-1), LS m+m+(0.9 fb-1) DM < 0: 2-body decay into real sleptons DM < - 6 GeV: High efficiency, Br(c20c1+e,m) dominant -6 GeV < DM < 0 GeV: Soft 3rd lepton PT limit set by LS m+ m+ DM > 0: 3-body decay via virtual or W/Z DM  0 -exchange dominates Large Br(c20c1+e,m)  “3l-max”scenario DM >> 0: W/Z*-exchange dominates Small Br(c20c1+e,m): “large-m0”scenario DM = M(slepton) – M (c02) (GeV)

13. ~ ~ ~ ~ ~ ~ l l l l c c 0 0 2 2 ~ ~ ~ ~ q c c c ± ± ± 1 1 1 RPC Chargino / Neutralino Limits in mSUGRA Combination: ee+track (1.1 fb-1), em+track (0.3 fb-1), mm+track (0.3 fb-1), m+m+(0.9 fb-1) “3 l – MAX” SCENARIO: M ( ) M ( ) (sfermion decay dominates) M ( ) > 140 GeV; s * Br < 0.07 pb “HEAVY SQUARKS”: M ( ) >> M ( ) (no scalar mass unification) M ( ) > 155 GeV s * Br < 0.06 pb “LARGE - m0” SCENARIO: M ( ) >> M ( , ) (large masses, small Br (3l)  W*, Z* decays dominate) No Sensitivity t – channel suppressed

14. miss Charginos and Neutralinos in 3 leptons + E T 14 CDF ANALYSIS: 6  LS (l+l+), 7  trilepton (lll), 1  ee+track ℒdt ~ 1 fb-1 • Analysis Channels:ell, mel, • mml(high-PT rrigger),mml(low-pT trigger) • 2 leading pT leptons (l = e,m) • 20 GeV < Mll <76 GeV & Mll >106 GeV • ETmiss > 15 GeV • Njets (PTjet > 20 GeV) < 2 • 3rd lepton PT > 5 GeV e+e/m+e/m: ℒdt ~ 0.7 fb-1 m + e + m/e: ℒdt ~ 0.7 fb-1 m + m + m/e:

15. + + l l Trilepton Analysis: and ee+track _ _ • Analysis: l+l+ (e+e+, e+m+, m+m+) • 2 leading pT LS leptons, Mll>25 GeV • ETmiss > 15 GeV & Z-veto • Challenge: modelling SM bkg (conversions) • Analysis Channel : e e + track • 2 leading pT electrons • 20 GeV < Mll < 60 GeV & M ll>106 GeV • ETmiss > 20 GeV; Min MT > 10 GeV • Dj(e1,e2) < 2.8; HT = SPT jet < 80 GeV • PT (3rd track) > 4 GeV ℒdt ~ 1 fb-1 l+l+: ℒdt ~ 1 fb-1 ℒdt ~ 1 fb-1 ee + track: ee + track:

16. ~ c ± M ( ) > 130 GeV 1 RPC Chargino / Neutralino Limits in mSUGRA mSUGRA inspired: tan b = 3; A = 0; m > 0; M0 = 60 GeV; M1/2 = 162 - 230 GeV Slepton mixing is on: No slepton mixing: s * Br < 0.25 pb W/Z decays dominate: No sensitivity M(c1+) expected limit is 160 GeV @ 95%CL  s * Br < 0.1 pb

17. ~ ~ c c ± ± M ( ) > 140 GeV M ( ) > 130 GeV 1 1 ~ ~ ~ ~ ~ ~ l l l l c c 0 0 2 2 ~ ~ c c ± ± 1 1 RPC Chargino / Neutralino Observed Limits • Degenerate slepton masses • Stau mixing is on • m0 = 60 GeV, m ( ) < m ( )  • 2-body decays via real enhanced • M ( ) > 130 GeV; s * Br < 0.25 pb DIFFERENT LUMINOSITIES, ANALYSIS CHANNELS AND SLIGHTLY DIFFERENT SCENARIOS: • Degenerate slepton masses • Stau mixing is off • m0 ~ 100 GeV, m ( ) m ( )  • only3-body decays • via off-shell enhanced • M ( ) > 140 GeV; s * Br < 0.07 pb

18. Search for Direct Production of Scalar Top Quarks Squark mixing ~ mq stop might be the lightest squark • Heavy stop: • t  tc10 • Medium stop: • tbc1+bln • Light stop: • t  cc10 ~ FINAL STATE: Pair production of lightest stop quark with subsequent decays via virtual charginos: t1t1 bbllnnc10c10 (n nc10) ~ ~ ~ ~ ~ SIGNATURE:2l (ee, em) + 2 jets + ETmiss ~ Stop exclusion up to m top: 2 different analysis to improve sensitivity: em,mm em: optimized for different Dm= (Mstop – Msneutrino) Cuts: 2 l(opposite sign) + at least 1 b-jet ETmiss > 15 GeV (nnc10) + topological cuts Background: Z/g*  tt; ttbar

19. Searches for SUSY (R-parity Violation)

20. ~ ~ ~ ~ c c c c ± 0 0 0  + X  4 l + ETmiss + X 1 1 2 1 ~ c ~ 0 c 0 1 1 ~ m  m +  2m + 2j RPV in Production and Decay of SUSY Particles RPV DECAY OF LSP ( ) INTO SM FERMIONS: RESONANT SPARTICLE PRODUCTION: (For non-zero LiLjEk - coupling) (For non-zero LiLjDk -coupling) Experimental Signatures at Hadron Colliders: l121 eeee, eeem or eemm + nn l122 mmmm, mmme or mmee + nn l133 tttt, ttte or ttee + nn (l’211 coupling) Single sparticle productionrate depends on l’ijk coupling strength:s ~ (l’ijk)2 Decay of LSP: The lijk coupling strength influences only lifetime (decay length): a)lijk > O (10-2)  prompt decay b)lijk< O (10-2)  long lived particle, decay outside detector

21. ~ ~ c ± c 0 1 1 l l R-Parity Violation: Couplings 112 122 • FINAL STATE: • RPC SUSY Production • Sparticles cascade decay into c10 • Prompt RPV decay of c10 via l121 or l122 SIGNATURE : At least4 l + 2 n SIMILAR TO TRILEPTON ANALYSIS: Cuts:optimized for  3 leptons to improve acceptance (eel, mml) pTl1  20 GeV; pTl2  8 GeV; pTl3 > 5 GeV + channel dependent cuts (anti-Z/g*) Background: Drell – Yan Z/g* Sensitive to all new physics with > 4 leptons in the final state mSUGRA limits: l121 from eel (l = e,m) l122 from mml (l = e,m)

22. ~ ~ c ± c 0 1 1 l l R-Parity Violation: Couplings R-Parity Violation: LLE Couplings 1jk 1jk Analysis require 3 charged leptons: eel (l = e,m), mml (l =m,e), eethad channels & loose ETmiss cut m0 = 1 TeV – conservative choice (heavy sleptons)  limits should be valid for any m0 eel, mml, eethad analysis are combined to set limits for each coupling l121, l122, l133 No-GUT MSSM: mSUGRA: Phys. Lett. B 638, 441-449 (2006)

23. ~ ~ ~ ~ ~ ~ m m m m m m l ' Resonant Smuon Production: Coupling 211 FINAL STATE: RPV in resonant production and decay via l’211 d u   mc10  mm du l’211 exclusion contours within mSUGRA _ _ SIGNATURE : 2  + 2 jets (no ETmiss) Cuts:pT1  15 GeV; pT2  8 GeV; pTjets(1,2)  15 GeV; R (,jets)  0.5 Background: Z/g*+2 jets, QCD Final Cuts depend on the reconstructed mass: M ( ) = M (mmjj); M(c10) = M (mjj) M (mmjj) Phys. Rev. Lett. 97, 111801 (2006)

24. ll Signature-based Searches in Channel g Signature-based Approach: Investigate events by the final state products  Quasi-model independent technique

25. Signature-based Searches in Dilepton + X Look for excess above SM prediction in eeg, mmg and emg + X final states • Motivation: • CDF Run I eegg + ETmiss event  rare in SM, expected in GMSB or l*l*  llgg • Excess in the l g ETmiss + X events above the SM predictions No excess over the SM predictions in ~ 1 fb-1 of dataset mmg eeg llg ETmiss in eeg events: ETmiss in mmg events:

26. Summary and Outlook • CDFandDØ searches are exploring new territory beyond LEP limits • No evidence of any SUSY signal yet • Start counting on > 2 fb-1 data sample •  We hope that chargino and neutralino are light enough to find them at Tevatron The results of 2 fits based on the current experimental results for the precision observables MW, sin2eff, (g-2), BR(bs) Expected sensitivity in the search for SUSY via trilepton decay signature (D0 + CDF): Fit to Electroweak precision data JHEP02 (2005)013 (2005) M(c20), M (c1+) (GeV)