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Searches and EW physics at HERA. 5 th Rencontres du VietNam 2004 New Views in Particle Physics. Sascha Caron (NIKHEF). (former Aachen). HERA. P(920 GeV). e(27.5 GeV). HERA. HERMES. HERA collides 27.5 GeV e ± with 920 GeV protons at √s=320 (300) GeV. HERA-B.

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Searches and EW physics at HERA


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

    2. HERA HERMES HERA collides 27.5 GeV e± with 920 GeV protons at √s=320 (300) GeV HERA-B HERA2 – luminosity, polarized e beam and detector upgrades Lumi produced by HERA (pb-1) • 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) day of running Sascha Caron (NIKHEF) at Recontres du Vietnam 2004

    3. HERA physics on 1 transparency NC deep inelastic scattering CC deep inelastic scattering Q2 = - squared momentum transfer between e and p W production Multilepton production Sascha Caron (NIKHEF) at Recontres du Vietnam 2004

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

    5. (Deep) inelastic scattering at HERA HERA probes eqinteractions at photon virtualities Q2 from ≈ 0 (photoproduction, γq) up to 4*104 GeV2 NC unique facility CC Test of EW sector with W (CC) and gamma/Z (NC) propagators Unification of weak and e.m. forces at high Q2 (more in HERA QCD talks) Sascha Caron (NIKHEF) at Recontres du Vietnam 2004

    6. Results on: Leptoquarks, general Contact Interactions, Large Extra Dimensions, Quarks Radius Contact Interactions New interactions between e and q can be modeled by 4-fermion contact interactions Parametrized by additional terms in the lagrangian Limits on quark radius (classical form factor): Rq< 10-18 m (ZEUS and H1) or vector contact interaction couplings of up to 5 TeV 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 PT>20 GeV are analyzed • Data is classified to • exclusive channels • Good agreement for • (almost) all channels Event yields are also available for HERA2 data! Sascha Caron (NIKHEF) at Recontres du Vietnam 2004

    8. A general search for new phenomena Mall and ΣPT distributions are systematically investigated using a search algorithm: Find in each channel the region with the greatest deviation 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 ^ ^ Smallest P found in μ-jet-ν, e-jet and e-e channels Repeat the whole analysis with many MC (pseudo data) experiments each with the H1 luminosity About 3% (Σ PT) and 25% (Mall) of MC experiments have a deviation larger than that of μ-j-ν final state Sascha Caron (NIKHEF) at Recontres du Vietnam 2004

    10. Isolated lepton events ep → jet (PT,X)+ PT,miss+ lepton main SM contribution is W production Results from dedicated analysis: HERA 1: e p (observed/expected) Agreement in hadronic channel (with large background) HERA 2: excess of events at H1 no excess in HERA1 ZEUS data clarification needs more lumi 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 Sascha Caron (NIKHEF) at Recontres du Vietnam 2004

    12. Multilepton events Measurement of multilepton events Process: ep → ll (e) mainly via 2-photon collisions Some interesting events at high mass: No excess in muon channels Sascha Caron (NIKHEF) at Recontres du Vietnam 2004

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