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Determination of Electroweak Parameters at HERA

Determination of Electroweak Parameters at HERA. hep-ex/0507080, submitted to Phys. Lett. B. Z. Zhang LAL, Orsay. On behalf of the H1 Collaboration. Outline Experimental facts Analysis strategies Results Summary & outlook. Experimental Facts.

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Determination of Electroweak Parameters at HERA

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  1. Determination of Electroweak Parameters at HERA hep-ex/0507080, submitted to Phys. Lett. B. Z. Zhang LAL, Orsay On behalf of the H1 Collaboration • Outline • Experimental facts • Analysis strategies • Results • Summary & outlook EPS05, July 21-27, Lisbon

  2. Experimental Facts • The low Q2 precision cross section data + • the high Q2 NC e+p & e-p data + • the high Q2 CC e+p & e-p data constrain 5 sets of PDFs: gluon, up-type quark, down-type quark & their anti-quarks Eur. Phys. J. C30(2003)1, hep-ex/0304003 • NC data at high Q2 also sensitive to • quark couplings to the Z boson aq, vq (q=u, d) • CC data also sensitive to • G, W propagator mass [model independent] • MW, mt [within the SM framework] GF W EPS05, July 21-27, Lisbon

  3. Analysis Strategies • Following the published H1PDF2000 fit procedure: • - Use all H1 NC & CC data (e+p & e-p) for Q2min=3.5GeV2 • - Parameterize 5 PDF sets: with a functional form: • small-x medium-x high-x behavior • at Q20=4GeV2, with 10 free PDF parameters after applying • momentum sum rule and u, d quark flavor counting rule • - Fit in NLO MSbar, massless scheme • Introducing additional EW parameter(s) • in the combined EW+PDF fits  Next slide Eur. Phys. J. C30(2003)1, hep-ex/0304003 EPS05, July 21-27, Lisbon

  4. Combined EW+PDF Analysis Strategies • Model independent fits: • 1) Fit au-vu-ad-vd-PDF • to extract light quark couplings to the Z boson • 2) Fit G-Mprop-PDF • to determine the normalization factor G and W propagator mass Mprop • 3) Fit Mprop-PDF [fix G to GF] • to determine the W propagator mass Mprop • Fits within the SM framework: • 4) Fit MW-PDF [fix mt to 178GeV, MH to 120GeV] • to determine the SM W mass MW • 5) Fit mt-PDF [fix MW to 80.425GeV, MH to 120GeV] • to determine the top quark mass mt Dr contains - quadratic dependence on mt - logarithmic dependence on MH EPS05, July 21-27, Lisbon

  5. First Results on Light Quark Couplings to Z at HERA Tevatron: qqee Drell-Yan, AFB:CDF Collab., Phys. Rev. D71(2005)052002, hep-ex/0411059 LEP: eeqq(g) [a2q+v2q]:http://lepewwg.web.cern.ch/LEPEWWG/plots/winter2005/ EPS05, July 21-27, Lisbon

  6. W Propagator Mass & Coupling G NC @ low Q2: g exchange CC: W exchange  damping NC CC HERA space-like (q2< 0) mass vs. Tevatron/LEP time-like (q2>0) one EPS05, July 21-27, Lisbon

  7. Improved Precision on W Propagator Mass Improvement: mainly due to the full use of all HERA-I data but also due to the coherent treatment of EW-PDF correlation EPS05, July 21-27, Lisbon

  8. Fits Imposing the SM Constraints Introducing SM GF-MW relation in On-Mass-Shell (OMS) scheme Quadratic dependence on mt Logarithmic dependence on MH EPS05, July 21-27, Lisbon

  9. Determination of SM MW and mt Values • W mass value: • MW=80.786 ± 0.205exp GeV • + the world average MZ • indirect determination of • sin2qW=1-M2W/M2Z • =0.2151 ± 0.0040exp • Top quark mass: • mt=104 ± 44exp GeV • First determination in DIS • at EW scale 178±4.3 GeV 80.425±0.038 GeV EPS05, July 21-27, Lisbon

  10. Summary and Outlook • HERA is primarily a QCD machine • but has also sensitivities to EW parameters • - light quark couplings to the Z boson • - W (propagator) mass • - top quark mass through radiative loop effects in DIS • HERA-II [with polarized e± beam and higher L]will • significantly improve the present determinations EPS05, July 21-27, Lisbon

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