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BSM searches at HERA

BSM searches at HERA. John Martin University of Toronto / ZEUS for H1 and ZEUS. Running conditions. HERA-II running very well Lumi high and still increasing for both e + p and e - p ( 1.5 pb -1 /day achieved) Polarization at ~ 40% Expect >600 pb -1 /expt. from HERA-II by June 2007

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BSM searches at HERA

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  1. BSM searches at HERA John Martin University of Toronto / ZEUS for H1 and ZEUS

  2. Running conditions • HERA-II running very well • Lumi high and still increasing for both e+p and e-p (1.5 pb-1/day achieved) • Polarization at ~ 40% • Expect >600 pb-1/expt. from HERA-II by June 2007 • (HERA-I was ~120 pb-1/expt., almost all e+p) 2005 e-p 215 pb-1 LISHEP 2006 J. Martin

  3. Outline e,n e Q2 xP p General BSM searches • Intriguing excess in isolated lepton events? • Multi-lepton events • Search for eq type resonances • HERA good for single particle production with Yukawa coupling to eq • LQ, Rp violating SUSY, LFV • Gaugino and gravitino searches • Contact interactions • Magnetic monopoles NB: HERA generally has little SM background for BSM searches LISHEP 2006 J. Martin

  4. General search • H1: model independent search for new phenomena by topology (as D0) • isolated, high PT particles: e, , , jet,  • PTpart > 20 GeV, 10 < part < 140, D(- )part > 1.0 • use probability estimator sensitive to narrow resonances, unusual events, broad signals • similar sensitivity to dedicated searches • basic agreement with SM, except … -j- : 4 data / 0.8 ± 0.2 Data from HERA-I LISHEP 2006 J. Martin

  5. Intriguing excess at H1… n X e,m H1 • Isolated leptons and missing PT • SM W production ~ 1 pb-1 • Background from mis-measured DIS and di-lepton events e+p e-p LISHEP 2006 J. Martin

  6. The latest H1 numbers • Choose cut at PTX >25 GeV, ~ best discrimination between background and decay of a heavy particle, like top. 3.4 s excess LISHEP 2006 J. Martin % of SM expectation from W production

  7. But ZEUS… • ZEUS e+p data with similar cuts, purity: • H1 continues to see an excess in e+p (recall HERA I was almost all e+p), but not in e-p • ZEUS doesn’t confirm • Still a puzzle, more data needed LISHEP 2006 J. Martin

  8. What about the t channel? • Isolatedt events with PT,miss t hadrons use 6 jet-shape variables to suppress QCD background • ForPTX> 25 GeV • ZEUS observes 2 events • expect0.12 0.02 • Anomalous top, stop, another heavy particle?? • But, H1 sees no events • Both Hera-I data, await HERA-II results… LISHEP 2006 J. Martin

  9. Iso-lepton events: single top? • Anomalous FCNC couplings • Search for single top production via W decay to en, mn, or jets high PTX ( > 40 GeV, ZEUS) H1 cuts Mt > 140 GeV • SM background negligible: • No evidence found, set limits • H1 excess needs ktug ~ 0.2, still just about compatible with FCNC top production LISHEP 2006 J. Martin

  10. Or bosonic stop decay? • Consider model with : • For bosonic decay, slight excess only in jmPTmiss channel • No excess in ej channel • Iso-lepton events therefore unlikely to arise from bosonic decay of stop LISHEP 2006 J. Martin

  11. Multi-lepton events (H1) e+p • Search for  2 leptons (PT1 , PT2 > 10, 5 GeV) in sample of 209 pb-1 (45 pb-1e-p, 164 pb-1 e+p) • - interactions ~ 1pb-1 • Overall agreement with SM: • But, for PT > 100 GeV : Nobs = 4 (3 ee, 1 emm) Nexp = 0.81  0.14 • 3 ee, 3 eee, 2 emm events withM12 > 100 GeV H1 excess, not in ZEUS LISHEP 2006 J. Martin

  12. Multi-lepton events (update) (275 pb-1) • H1 analysis extended to include 05 data • no new 2e/3e event at high M12 • one new eμμ event at Mμμ > 100 GeV • one new eμμ event at Meμ > 100 GeV • for ΣPT > 100 GeV: Nobs = 4 Nexp = 1.1 0.2 • highest ΣPT events appear in e+p collisions LISHEP 2006 J. Martin

  13. Doubly charged Higgs? • H++(--) occurs in BSM models extending the Higgs sector, such as L-R symmetric models • Search for high massdi-leptons with same charge as beam • Only 1 ee event found, no mm, em, tt, et events • anomalous multi-lepton events unlikely to be doubly charged Higgs, so set limits • LEP, Tevatron better except for off-diagonal couplings LISHEP 2006 J. Martin

  14. Generic Leptoquarks q q + e e LQ LQ e e,n LQ q e,n depend on Yukawa coupling, l q e q q LQ q LQ + e q e LQ LQ • Search for resonance in e-jets, e-n • Likelihood analysis in Mej, cosq* • Coupling limits for BRW LQs • 7 scalars, 7 vectors LISHEP 2006 J. Martin

  15. Comparison to Tevatron • HERA complementary to Tevatron: • Tevatron good for high BR to eq. Background is severe for nq decay of LQ • HERA can reach to low BR to eq for reasonable coupling LISHEP 2006 J. Martin

  16. LQ mediated LFV • Search for high PTm, t • After optimizing cuts: • ZEUS: 0 candidates (SM: 0.43±0.08 m, 2.3±0.5 t ) • H1: 1 t candidate (SM: 0.56±0.16) • Low mass: set limits with ,eg,eq = q , q • High mass: set bounds on eq lq / M2LQ(TeV-2) • em: low energy limits generally better • et: ZEUS results generally better eb  ts Similar results from H1 eb  tb best non-ZEUS limit ZEUS limit LISHEP 2006 J. Martin

  17. R-parity violating SUSY ~ e+ d  u Lj via ’1j1 e- u  d Rk via ’11k ~ • At HERA probe: • Search in both l-jet and gauge decays (multi-jets and leptons) • No evidence found at ZEUS or H1 LISHEP 2006 J. Martin

  18. Coupling limits in MSSM • ZEUS: stop search with 1st and 2nd generation squark masses set to 1 TeV • H1: unconstrained model with sfermion masses free parameters, gluino mass ~ M3 at EW scale (common gaugino mass m1/2 at GUT scale) • Limits largely independent of MSSM parameters • Improved limits from HERA up to 255 GeV for LISHEP 2006 J. Martin

  19. Limits in mSUGRA model L3 (tan = 2) D0 Run I j=1,2 • in mSUGRA assume also a common scalar mass m0 at GUT scale (gives a 5 parameter SUSY model) • H1 HERA-I data: LEP limits better except for stop • Tevatron limits weaker due to large branching ratio to jets + missing ET • HERA-II will improve sensitivity to RPV stop LISHEP 2006 J. Martin

  20. Gaugino production • Production by RPV t-channel slepton exchange • Search in ejj channel with multi-variate discriminant against NC DIS background • No deviation from SM ZEUS Prelim., LP05 HERA extends LEP limits in part of parameter space LISHEP 2006 J. Martin

  21. If gravitino is the LSP • Gauge mediated symmetry breaking (GMSB) has N extra “messenger” fields of mass M to transmit the SB • NLSP is neutralino or slepton • Search for high PTg + missing ET (bkgrd: radiative CC) D0 bound D0 bound • For small m: neutralino masses up ~ 120 GeV are excluded for ’ = 1.0 • Complementary to Tevatron, where production is by pairs or LISHEP 2006 J. Martin

  22. Excited fermions • Fermion substructure excited fermions • For f/L=1/MF* , 95% upper limits: • e* 250 GeV (H1) • q* 205 GeV (ZEUS) • n* 135 (f=f’), 158 (f=-f’) GeV (ZEUS) • for n*, e-p 100x more sensitive than e+p • await HERA-II e-p analysis LISHEP 2006 J. Martin

  23. Contact interaction e- • HERA-I form factor fit gives Rq < 0.85 . 10-18 m • Can also set limits on eqeq contact interactions e+ • Similar limits from LEP, Tevatron • n extra dimensions? • Graviton exchange effective coupling Parity conserving u quark only APV limits Limits close to 1 TeV LISHEP 2006 J. Martin

  24. Magnetic monopoles? • Dirac monopoles: large magnetic charge, highly ionizing • Some BSM models predict light monopoles • Could stop in beampipe and stay trapped • Cut 1994-7 beampipe into strips • passed through superconducting coil • system sensitive to 0.1gD LISHEP 2006 J. Martin

  25. Summary • Many BSM scenarios have been studied at HERA • Most results still from HERA-I (~120 pb-1/expt, almost all e+p) • Competitive and/or complementary to LEP, Tevatron • Only possible sign of BSM physics are the anomalous W-like events from H1: need more data • HERA-II will provide a data set of > 600 pb-1/expt with lepton polarization, both e+p and e-p • new sensitivity to BSM physics with higher cross section in e-p • Still some chance of a discovery before the LHC LISHEP 2006 J. Martin

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