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

LISHEP 2006 J. Martin2 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) e - p 215 pb

LISHEP 2006 J. Martin3 Outline 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, R p violating SUSY, LFV Gaugino and gravitino searches Contact interactions Magnetic monopoles NB: HERA generally has little SM background for BSM searches Q2Q2 e e, p xPxP

LISHEP 2006 J. Martin4 General search H1: model independent search for new phenomena by topology (as D0) isolated, high P T particles: e, , , jet, P T part > 20 GeV, 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. Martin5 Intriguing excess at H1… Isolated leptons and missing P T X e,e, SM W production ~ 1 pb -1 Background from mis-measured DIS and di-lepton events H1 e+pe+p e-pe-p

LISHEP 2006 J. Martin6 The latest H1 numbers Choose cut at P T X >25 GeV, ~ best discrimination between background and decay of a heavy particle, like top. % of SM expectation from W production 3.4  excess

LISHEP 2006 J. Martin7 But ZEUS… 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 H1 and ZEUS expectations from SM agree for electron analysis ZEUS muon analysis not yet finished Still a puzzle, more data needed Isolated e candidates12 < P T X < 25 GeVP T X > 25 GeV ZEUS (prel.) HERA I (66 pb -1 )1 / 1.04 ± 0.11 (57%)1 / 0.92 ± 0.09 (79%) ZEUS (prel.) HERA II (40 pb -1 )0 / 0.46 ± 0.10 (64%)0 / 0.58 ± 0.09 (76%) ZEUS e + p data with similar cuts, purity:

LISHEP 2006 J. Martin8 Isolated  events with P T,miss  hadrons use 6 jet-shape variables to suppress QCD background For P T X > 25 GeV ZEUS observes 2 events expect Anomalous top, stop, another heavy particle?? But, H1 sees no events Both Hera-I data, await HERA-II results… What about the  channel?

LISHEP 2006 J. Martin9 Anomalous FCNC couplings Search for single top production via W decay to e, , or jets high P T X ( > 40 GeV, ZEUS) H1 cuts M t > 140 GeV SM background negligible: No evidence found, set limits H1 excess needs  tu  ~ 0.2, still just about compatible with FCNC top production Iso-lepton events: single top?

LISHEP 2006 J. Martin10 Or bosonic stop decay? Consider model with : For bosonic decay, slight excess only in j  P T miss channel No excess in ej channel Iso-lepton events therefore unlikely to arise from bosonic decay of stop

LISHEP 2006 J. Martin11 Search for  2 leptons (P T 1, P T 2 > 10, 5 GeV) in sample of 209 pb -1 (45 pb -1 e - p, 164 pb -1 e + p)  -  interactions ~ 1pb -1 Overall agreement with SM: But, for  P T > 100 GeV : N obs = 4 (3 ee, 1 e  N exp = 0.81  ee, 3 eee, 2 e  events with  M 12 > 100 GeV Multi-lepton events (H1) e+pe+p H1 excess, not in ZEUS

LISHEP 2006 J. Martin12 H1 analysis extended to include 05 data no new 2e/3e event at high M 12 one new eμμ event at M μμ > 100 GeV one new eμμ event at M eμ > 100 GeV for ΣP T > 100 GeV: N obs = 4 N exp = 1.1  0.2 highest ΣP T events appear in e + p collisions Multi-lepton events (update) (275 pb -1 )

LISHEP 2006 J. Martin13 Doubly charged Higgs? H ++(--) occurs in BSM models extending the Higgs sector, such as L-R symmetric models Search for high mass di-leptons with same charge as beam Only 1 ee event found, no  e  e  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. Martin14 Generic Leptoquarks Search for resonance in e-jets, e- Likelihood analysis in M ej, cos  * e + e LQ q q depend on Yukawa coupling, LQ e q e, q LQ e + e q q e q q ee Coupling limits for BRW LQs 7 scalars, 7 vectors

LISHEP 2006 J. Martin15 Comparison to Tevatron HERA complementary to Tevatron: Tevatron good for high BR to eq. Background is severe for q decay of LQ HERA can reach to low BR to eq for reasonable coupling

LISHEP 2006 J. Martin16 LQ mediated LFV Search for high P T  After optimizing cuts: ZEUS: 0 candidates (SM: 0.43±0.08 , 2.3±0.5  ) H1: 1  candidate (SM: 0.56±0.16) Low mass: set limits with,eg, eq =  q,  q High mass: set bounds on eq lq / M 2 LQ (TeV -2 ) e  : low energy limits generally better e  : ZEUS results generally better eb   b eb   s Similar results from H1 best non-ZEUS limit ZEUS limit

LISHEP 2006 J. Martin17 R-parity violating SUSY At HERA probe: Search in both l-jet and gauge decays (multi-jets and leptons) No evidence found at ZEUS or H1 e + d  u L j via ’ 1j1 e - u  d R k via ’ 11k ~ ~

LISHEP 2006 J. Martin18 Limits largely independent of MSSM parameters Improved limits from HERA up to 255 GeV for Coupling limits in MSSM H1: unconstrained model with sfermion masses free parameters, gluino mass ~ M 3 at EW scale (common gaugino mass m 1/2 at GUT scale) ZEUS: stop search with 1 st and 2 nd generation squark masses set to 1 TeV

LISHEP 2006 J. Martin19 in mSUGRA assume also a common scalar mass m 0 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 E T HERA-II will improve sensitivity to RPV stop Limits in mSUGRA model L3 (tan  = 2) D0 Run I j=1,2

LISHEP 2006 J. Martin20 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. Martin21 For small  m: neutralino masses up ~ 120 GeV are excluded for ’ = 1.0 Complementary to Tevatron, where production is by pairs or 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 P T  + missing E T (bkgrd: radiative CC) D0 bound

LISHEP 2006 J. Martin22 Excited fermions Fermion substructure  excited fermions For f/  =1/M F*, 95% upper limits: e* 250 GeV (H1) q* 205 GeV (ZEUS) * 135 (f=f’), 158 (f=-f’) GeV (ZEUS) for *, e - p 100x more sensitive than e + p await HERA-II e - p analysis

LISHEP 2006 J. Martin23 Contact interaction HERA-I form factor fit gives R q < m Can also set limits on eqeq contact interactions e-e- e+e+ Parity conserving u quark only APV limits Similar limits from LEP, Tevatron n extra dimensions? Graviton exchange effective coupling Limits close to 1 TeV

LISHEP 2006 J. Martin24 Magnetic monopoles? Dirac monopoles: large magnetic charge, highly ionizing Some BSM models predict light monopoles Could stop in beampipe and stay trapped Cut beampipe into strips passed through superconducting coil system sensitive to 0.1g D

LISHEP 2006 J. Martin25 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