1. Searches and EW physics at HERA 5 th Rencontres du VietNam 2004 New Views in Particle Physics Sascha Caron (NIKHEF) (former Aachen) P(920 GeV)e(27.5 GeV) HERA

2. Sascha Caron (NIKHEF) at Recontres du Vietnam 2004 2 HERA Recorded data samples: HERA 1: ≈40pb -1 e+p (300 GeV) ≈15pb -1 e-p (320 GeV) ≈65pb -1 e+p (320) HERA 2: ≈50pb -1 e+p (320) HERA collides 27.5 GeV e ± with 920 GeV protons at √s=320 (300) GeV Lumi produced by HERA (pb -1 ) day of running HERMES HERA-B HERA2 – luminosity, polarized e beam and detector upgrades

3. Sascha Caron (NIKHEF) at Recontres du Vietnam 2004 3 HERA physics on 1 transparency Q 2 = - squared momentum transfer between e and p NC deep inelastic scatteringCC deep inelastic scattering W productionMultilepton production

4. Sascha Caron (NIKHEF) at Recontres du Vietnam 2004 4 Searches and EW physics at HERA oElectroweak tests in deep inelastic scattering oSystematic tests of the SM at high P T oMeasurements of W production and multi-lepton processes oVarious dedicated searches for new physics: SUSY, Contact Interactions, Quark Radius, anomalous top couplings, LQ, H++, magnetic monopoles, large ED, excited fermions and more

5. Sascha Caron (NIKHEF) at Recontres du Vietnam 2004 5 (Deep) inelastic scattering at HERA NC CC HERA probes eq interactions at photon virtualities Q 2 from ≈ 0 (photoproduction, γq) up to 4*10 4 GeV 2 unique facility Test of EW sector with W (CC) and gamma/Z (NC) propagators Unification of weak and e.m. forces at high Q 2 (more in HERA QCD talks)

6. Sascha Caron (NIKHEF) at Recontres du Vietnam 2004 6 Contact Interactions Limits on quark radius (classical form factor): R q < 10 -18 m (ZEUS and H1) or vector contact interaction couplings of up to 5 TeV Results on: Leptoquarks, general Contact Interactions, Large Extra Dimensions, Quarks Radius New interactions between e and q can be modeled by 4-fermion contact interactions Parametrized by additional terms in the lagrangian

7. Sascha Caron (NIKHEF) at Recontres du Vietnam 2004 7 A general Search for new phenomena Systematic search for deviations from the SM All final states are considered in one analysis Objects (e, μ, jet, γ, ν) with P T >20 GeV are analyzed Data is classified to exclusive channels Good agreement for (almost) all channels Event yields are also available for HERA2 data!

8. Sascha Caron (NIKHEF) at Recontres du Vietnam 2004 8 A general search for new phenomena M all and ΣP T distributions are systematically investigated using a search algorithm: Find in each channel the region with the greatest deviation

9. Sascha Caron (NIKHEF) at Recontres du Vietnam 2004 9 A general search for new phenomena Derive for each event class the probability P to observe a deviation anywhere in the spectrum as large as found in the data Repeat the whole analysis with many MC (pseudo data) experiments each with the H1 luminosity Smallest P found in μ-jet-ν, e-jet and e-e channels About 3% (Σ P T ) and 25% (M all ) of MC experiments have a deviation larger than that of μ-j-ν final state ^ ^

10. Sascha Caron (NIKHEF) at Recontres du Vietnam 2004 10 Isolated lepton events Isolated lepton events P Tx >25GeVe channelμΤ H1 e+p (118 pb -1 ) 4/1.48±0.256/1.44±0.250/0.53 ZEUS (130 pb -1 ) 2/2.9±0.55/2.75±0.22/0.12 ep ep → jet (P T,X )+ P T,miss + lepton Results from dedicated analysis: HERA 1: P Tx >25 GeVe channelμ H1 e+p (45 pb -1) 3/0.74±0.150/0.76±0.1 HERA 2: main SM contribution is W production Agreement in hadronic channel (with large background) excess of events at H1 no excess in HERA1 ZEUS data clarification needs more lumi (observed/expected)

11. Sascha Caron (NIKHEF) at Recontres du Vietnam 2004 11 Anomalous top production Compare the l-jet-ν events with models, e.g. single top production with anomalous couplings between tuZ and tuγ Selection cuts optimized for top H1: excess in leptonic channels (3e, 2μ with SM exp. 1.3 ± 0.2) no excess in hadronic channel ZEUS: no excess in hadron or lepton channels Limits on top cross sections and couplings

12. Sascha Caron (NIKHEF) at Recontres du Vietnam 2004 12 Multilepton events M ll >100 GeVee channeleee channel H1 HERA1+2 (165 pb -1 ) 3/0.44±0.13/0.31±0.08 ZEUS (130 pb -1 ) 2/0.77±0.10/0.37±0.04 Measurement of multilepton events Process: ep → ll (e) mainly via 2-photon collisions Some interesting events at high mass: No excess in muon channels

13. Sascha Caron (NIKHEF) at Recontres du Vietnam 2004 13 SUSY@HERA HERA: R P violating SUSY → single production of squarks via couplings Λ’ ijk Also interpretations in terms of MSUGRA model parameters For λ’=0.3 : M squark >275 GeV for all squarks types in nearly full parameter space small couplings: improvement of indirect low-energy limits Large variety of squark decay modes → many final states are considered Example: sbottom production

14. Sascha Caron (NIKHEF) at Recontres du Vietnam 2004 14 Summary High energy ep collisions at HERA are a unique testing ground for the SM Various searches for new physics are performed (model independent and dedicated) Some interesting events are found … and HERA 2 has just started !