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HERA-II results on inclusive cross-sections

HERA-II results on inclusive cross-sections. A .M. Cooper-Sarkar Oxford On behalf of ZEUS and H1 at the low-x workshop, Lisbon 2006. Neutral Current (NC) and Charged Current (CC) single and double differential cross sections from ’03-’05 running with polarised e+ and e- beams

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HERA-II results on inclusive cross-sections

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  1. HERA-II results on inclusive cross-sections A .M. Cooper-Sarkar Oxford On behalf of ZEUS and H1 at the low-x workshop, Lisbon 2006 • Neutral Current (NC) and Charged Current (CC) single and double differential cross sections from ’03-’05 running with polarised e+ and e- beams • Polarisation dependence of cross-sections • Limits on MWR • Extraction of xF3 • New PDF fit- reduced high-x uncertainties • Fits for electroweak parameters: • MW, GF,, g • au,vu,ad,vd, • T3u,T3d, sin2θW, T3uR,T3dR

  2. New data with polarised lepton beams for both Neutral Current (NC) and Charged Current (CC) processes Kinematic variables : virtuality of exchanged boson: Bjorken x: inelasiticity

  3. New data with polarised beams -- e+p cross sections have been published. ZEUS hep-ex 0602026: H1 Phys Lett B634 (2006) 173 -- e–p analyses (preliminary)

  4. The data has been used for new fits to improve our knowledge of parton distributions (PDFs) and electroweak parameters First Charged Current results (At leading order LO)

  5. ZEUS: polarisation dependence of e+ and e- e+p CC cross section (hep-ex 0602026) e–p CC cross section (ZEUS preliminary) Both for e+p and e–p, measured cross sections from different polarisations have the same shape.Only their scales are different.Consistent with SM prediction =>

  6. H1: dependence of cross-section on charge of lepton

  7. (Q2 > 200 GeV2) H1 (Q2 > 400 GeV2) <Pe>=–0.27±0.01 <Pe>=–0.27±0.01 бe-p = 70.4 ± 1.2(stat.) ± 3.1(sys) pb <Pe>=+0.37±0.02 <Pe>=+0.33±0.02 бe-p = 34.5 ± 1.4(stat.) ± 1.5(sys) pb Consistent with SM – the limit on RHCC cross-section corresponds to95% CL on mass of WR boson, MWR>180 GeV ZEUS: MWR>186 GeV H1

  8. ZEUS preliminary Cross sections were meausured as a function of Pe. Linear relation between cross section and polarisation is clearly shown.

  9. Now Neutral Current Results -y2FLo/p At leading order (LO)

  10. Positron single differential cross-sections H1 dб/dQ2 e+p RH,LH and RH/LH

  11. Electron single differential cross-sections H1 dб/dQ2 e- p RH,LH and RH/LH

  12. H1 б(Unpolarised) H1 xF3

  13. ZEUS also has preliminary results on polarised double differential cross-sections for both CC and NC processes- these are shown with a new PDF fit ZEUS-pol.

  14. ZEUS also has preliminary results on polarised double differential cross-section for both CC and NC processes- these are shown with a new PDF fit ZEUS-pol

  15. So what is this new PDF fit? ZEUS-pol It is done with exactly the same formalism as the published ZEUS-JETS fit (Eur.Phys.J.C42(2005)1) -but adding in the double differential cross-sections for NC and CC data from 121 pb-1 of the new HERA-II e-p ‘05 polarised data Precision of xuv now approaches that of global fits using fixed target data Expected since NC and CC e- are dominantly sensitive to u quark

  16. ZEUS have also made an analysis varying the electroweak parameters simultaneously with the PDF parameters within the same fit formalism -y2WL(x,Q2) This was from the shape of CC dб/dQ2 This was from a similar PDF+EW analysis on HERA-I H1 data

  17. Let the neutral current axial vector and vector couplings au,vu,ad,vd be free

  18. These results are best displayed as contour plots Compare to the red contours determined in the same way – BUT without polarised data Improvement in the vector couplings as expected from polarised F2 data

  19. Compare the result with those from other experiments H1 analysis of HERA-I data LEP and CDFanalyses

  20. In fact for DIS data the sensitivity to the couplings is through γ/Z interference to the axial vector couplings (from xF30) and vector couplings (from F2P) separately – not to the combinations ( a2+ v2) which LEP and CDF data access through the Z - so we plot the axial and vector contours separately The improvement in the vector couplings with polarised data is striking

  21. We can also make fits within the standard model formalism OR we can extend the standard model formalism with right handed isospin

  22. Summary • New data on Neutral Current (NC) and Charged Current (CC) single and double differential cross sections from ’03-’05 running with polarised e+ and e- beams • Polarisation dependence of cross-sections in agreement with Standard Model • Limits on MWR: MWR>180 GeV ZEUS: MWR>186 GeV H1 • Extraction of xF3 • New PDF fit- reduced high-x uncertainties- particularly for xuv • Fits for electroweak parameters: MW – best measurement for space-like process • GF,, - at high scale Q2 ~400 GeV2 • vector and axial vector NC couplings: au,vu,ad,vd, • T3u,T3d, sin2θW, T3uR,T3dR • In agreement with Standard Model – best measurements using light quarks

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