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ZEUS Status Report

E. Tassi Calabria Univ. , INFN and Hamburg Univ. ZEUS Status Report. 68 th DESY PRC Meeting 5-6 November 2009. OUTLINE Combined H1 and ZEUS Analyses ZEUS Physics Highlights Concluding Remarks. The combination of H1 and ZEUS data.

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ZEUS Status Report

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  1. E. Tassi Calabria Univ. , INFN and Hamburg Univ. ZEUS Status Report 68th DESY PRC Meeting5-6 November 2009 • OUTLINE • Combined H1 and ZEUS Analyses • ZEUS Physics Highlights • Concluding Remarks

  2. The combination of H1 and ZEUS data Why? To exploit the full potential of the HERA data: Proton Structure: best possible proton PDFs for the LHC Jet/Heavy Flavours: stringent tests of pQCD Diffraction: diffractive PDFs, test Factorization and pQCD BSM: increased sensitivity to new Physics The strong commitment of the experiments to this idea is now bringing the first published(!) results…

  3. First H1-ZEUS Papers and more… NEW for this PRC: first three H1-ZEUS papers 1. “Multi-leptons with High-Transverse Momentum at HERA” - arXiv:0907.3627, published in JHEP 2. “Events with an Isolated lepton and Missing Transverse Momentum and Measurement of W production at HERA” - arXiv: , to be submitted to JHEP 3. “Combined Measurement and QCD Analysis of the inclusive ep Scattering Cross-Sections at HERA” DESY-09-158 , to be submitted to JHEP NEW for this PRC : Preliminary combined F2(Charm)

  4. Inclusive HERA-I DIS Cross Sections Combined are all published HERA-I NC/CC ep cross sections: - 1400 data points that span six orders of magnitude in x/Q2 - 110 syst. error sources - Three “procedural” uncertainties Data show good consistency: - chi2/ndof= 637/656 - small shift of global norms - distributions of pull - Provide a single high-precision data set to use as input in DGLAP Analyses - The combination procedure leads to significantly reduced uncertainties

  5. Inclusive HERA-I DIS Cross Sections • 1-2% precision in the medium Q2region • De facto new standard HERA data inputfor future DGLAP analyses

  6. HERAPDF1.0 Detailed study of the PDFs uncertainties Sea and Gluon: much increased precision LHC Phenomenology

  7. HERAPDF1.0 Comparison to the CTEQ6.6 and MSTW08 PDFS

  8. F2(charm) Heavy Flavour production in DIS: hot topic in pQCD e.g. Treatment of HF in the DGLAP evolution: FFNS vs GMVFNS Combine the H1 and ZEUS F2c results obtained from the published or preliminary HERA-I,-II D-mesons, Lifetime tag and semileptonic analyses Extraction of F2c: Detailed study of the correlations, and additional uncertainties introduced in the extrapolation Combination procedure as in the inclusive case (cross checked with alternative bayesian combination) 6-10% precision ( mostly H1 driven)

  9. F2(charm) GMVFNS FFNS - These results triggered interesting discussions at the last PDF4LHC workshop - Important input to further theoretical developments…

  10. F2(charm) and HERPDF1.0 Further developments soon to come…

  11. New NC DIS inclusive jet cross sections with the anti-kt and SISCone jet algorithms Good description by NLO calculations (DISENT) Larger hadronisation corrections for the SIScone algorithm

  12. New Jet Algorithms: anti-kt and SISCone Good description by NLO calculations (DISENT) Final paper (to be released soon) will also contain αs determinations

  13. Subjets distributions Detailed study of the pattern of QCD radiation from a primary parton and colour coherence effects between initial and final states parton radiation A previous ZEUS publication showed the adequacy of NLO pQCD to describe jets with two subjets • Two resolved subjets (ycut=0.05) • Highest ET subjet closer to jet axis • - Lowest ET subjet towards p-beam direction Study now extended to jets with three resolved subjets using 300 pb-1 of HERA-II data

  14. Three Subjets Measure normalised cross sections as function of the following subjet variables: ETsbj/ETjet , ηsbj- ηjet , |φsbj - φjet| and βsbj, α23 , γ , ηlow- ηjet sbj Higher sensitivity to color factors

  15. Three Subjets

  16. NLO QCD Analysisof ZEUS Diffractive Data RecentlypublishedLargeRapidity Gap (LRG) and protontagged(LPS) data are used, togetherwithdiffractivedijet cross sections in DIS, in a new NLO QCD analysistodeterminedPDFs. Mainobservables, ReducedDiffractiveCross-sections: QCD Factorization: Proton-vertexFactorization: Use DGLAP equationsto evolve dPDFsparametrized at a starting scale: Fits “S”, “SJ”: Bg Cg 0 Fit “C” : Bg=Cg=0

  17. ZEUS DiffractivePDFs zq xg Fit “SJ”: gluonfixedbydijet data Fit “C”: constantgluon at Q02

  18. Diffractive di-jet photo-production Resolved p • NLO predictions(Frixione & Ridolfi) obtainedassumingfactorization • Good data description - no evidenceofsizeablesuppression (c.f.Tevatron)

  19. ZEUS Overall Status Publications: 2008: 18 papers (our best result) 2009: 14 papers done + 5 at EB Level Nr of conference Talks: in line with previous years… Grand Reprocessing of the complete HERA-II data recently completed Detector simulation continue to be worked on and improved Ditto for the analysis software Zarah (our facility for batch analyses) fully mantained till, at least, end of 2011

  20. Long termplans… Data/MC storage: - Root-based Common Ntuples (to replace MDST) (intense validation underway – numbers of users constantly increasing) Preservation: - MC simulation capability - Expert Documentation - Calibration data - Core Analysis Software components Management: - a lighter and more agile organization of the experiment being discussed Share experience with H1 and other experiments (Workshop on preservation in HEP) Support from the Desy Directorate and collaborating institutes remains vital for a successfully completion of our physics program

  21. Summary First H1-ZEUS combined publications released: an important milestone More results soon to come… We’re working in preserving our data and make analyses on the long term possible The ZEUS collaboration is overall in excellent shape and is fully committed to complete its physics program

  22. Extras

  23. New Inclusive DIS NC/CC Measurements 1. “Measurementof the Longitudinal Proton StructureFunction at HERA”  arXiv:0904.1092, to be published by PLB 2. “Measurementof High-Q2 NC DIS e-p cross sectionswithlongitudinallypolarised electron beam at HERA”  arXiv:0901.2385, EPJ C62 (2009) 625 3. “Measurementof CC DIS e-p cross sectionswithlongitudinallypolarised electron beam at HERA”  arXiv:0812.4620, EPJ C61 (2009) 223 4. Preliminary High-Q2 CC e+p cross sections 5. New QCD Analysisof HERA-I and HERA-II data (ZEUS Fit 2009)

  24. NC e+p at low- mid-Q2: “FLruns” Three data setscollectedwithdedicated triggers at the center of mass energies: - 318 GeV (HER) 44.5pb-1 - 251 GeV (MER) 7.1 pb-1 - 225 GeV (LER) 13.9 pb-1 Reduced cross sectionsmeasured in the kinematicregion: 20 < Q2 < 130 GeV2 5 x10-4 < x < 0.007 A precise measurement and an important input to QCD analyses

  25. F2 and FL - Most precise F2from ZEUS in this kinematicregion - Data support non zero FL

  26. NC/CC High-Q2 Cross sections at HERA • Important Electroweak Physics program: • Electroweak unification • Chiral nature of the SM • Determination of light-quarks couplings • Parity violation in DIS at high-Q2 (10-18m) Here will concentrate on their impact on the proton structure

  27. High-Q2 NC e-p cross sections L=170 pb-1 ( HERA-I 16 pb-1) • Improve xuv at high-x

  28. High-Q2 CC e+p cross sections L=136 pb-1 d-flavour sector less well-known  Important input to improve xdv

  29. Zeus 2009 Fit Study the impact of the new HERA-II measured cross section: CC e±p , NC e-p and NC e+p H/M/LER on the ZEUS PDFs • improve unc. on xuv, xdv • slightly steeper gluon

  30. Diffraction and dPDFs at HERA 1. “DIS with Leading Protons or Large Rapidity Gaps at HERA” arXiv:0812.2003, NP B816 (2009) 1 2. “Leading Proton Production in DIS at HERA” arXiv:0812.2416, JHEP 0906:074(2009) 3. “A Measurement of the Q2,W and t dependence of DVCS at HERA” arXiv:0812.2517, JHEP05(2009)108 4. “A QCD Analysis of ZEUS Diffractive Data”  DESY Directorate, soon on SPIRES 5. Combinations of H1 and ZEUS diffractive cross sections and HERA dPDFs

  31. Combination H1ZEUS ofDiffractive Data • Final H1 resultswith HERA-II expectedby the end of the year • Planstodetermine HERA dPDFsfrom the H1-ZEUS combinedmeasurements

  32. HeavyFlavours 1. “MeasurementofJ/psi helicitydistributions in inelasticphotoproduction at HERA”  arXiv:0906.1224, to be published in JHEP 2. “Measurementof charm and beauty production in DIS fromdecaysintomuons at HERA”  arXiv:0904.3487, submitted to EPJC 3. New results on beauty photoproduction 4. Combinationsof H1 and ZEUS F2(charm) measurements

  33. Semileptonic Charm and Beauty HERAII e-p (2004/05) 126 pb-1 Q2 > 20 GeV2 c, b and lf fractions extracted from asimultaneus fit of 3discriminating variables: PTrel, , pTmiss|| Theory : FFNS NLO (HVQDIS) Charm : Good description Beauty: Discrepancy at low Q2 (~2 )

  34. Beauty in Photoproduction Lifetime tagging: Fraction of beauty from decay length significance A precise measurement - Good agreement with NLO QCD

  35. Beauty in Photoproduction

  36. DGLAP Analysis and HERA PDFs • DGLAP equations at NLO in the MS scheme: • QCDNUM17.02 (M. Botje) (NB: Q0 < mc) • Q02 = 1.9 GeV2 ; mc=1.4GeV, mb=4.75 GeV • s(MZ)= 0.1176; r=f=Q • fs=0.31(di-muon production) • PDFs at the starting scale parametrisedas: • xf(x, Q02)= AxB(1-x)C(1+Dx+Ex2) • wherexf=xuv, xdv, xg, xU, xD • Nrofparam. chosen by saturation of 2 • Heavy Quarks coeff. func. calculated in the GM-VFNS of Thorne-Roberts • Results: • 10 parameters for central fit • 2/ndof=574/582

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