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DELPHI Status Report

LEPC 9-Nov-1999. DELPHI Status Report. Presented by Jesús Marco IFCA Santander. OPERATION @200-202 GeV. PRELIMINARY RESULTS: SM OVERVIEW & SEARCHES. PROSPECTS FOR 2000. Operation at 200-202 GeV. Luminosity on tape: 125.4 pb -1 collected with efficiency ~93%

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DELPHI Status Report

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  1. LEPC 9-Nov-1999 DELPHI Status Report Presented by Jesús Marco IFCA Santander OPERATION @200-202 GeV PRELIMINARY RESULTS: SM OVERVIEW & SEARCHES PROSPECTS FOR 2000

  2. Operation at 200-202 GeV • Luminosity on tape: • 125.4 pb-1collected withefficiency ~93% • 84.3pb-1 @200 GeV + 41.1pb-1 @202 GeV (+ 0.04 pb-1 @ 204 GeV) • Total collected luminosity in 1999: 232.2 pb-1 • 25.9 pb-1 @192 GeV • 76.9 pb-1 @196 GeV • plus 3.95 pb-1 at Z0 peak THANKS TO THE LEP GROUP! DELPHI Status Report

  3. Operation at 200-202 GeV • Thanks to LEP extremely good background conditions, a gain in efficiency is obtained: • starting before PHYSICS • earlier ramping volts • reduced “run paused” • Major events: • incident with control system of our magnet (only 3 fills lost) • suffered a lot from quality of electricity distribution (broken control card in HV transformer affected electronics...)CLEAR WORRY! DELPHI Status Report

  4. Luminosity DELPHI Status Report

  5. Detector Performance • Detector was not opened during 98/99 shutdown, alignment very good after 2.5 pb-1 at Z0 peak, so since the beginning of high energy data taking! • VD stable and efficient! Average efficiencies: Rf:Closer layer 86% Inner layer 89% Outer layer 96% z: Closer layer 79% Outer layer 85% DELPHI Status Report

  6. VD Resolution • Excellent!  intrinsic resolution/layer ~9 m DELPHI Status Report

  7. SM Overview @192-202 GeV • Fermion-pair production • Coplanar photons • Double radiative return • WW cross section and mass spectrum • Four-fermion events: • ZZ cross section • eeqq events DELPHI Status Report

  8. Fermion-pair production DELPHI Status Report

  9. Fermion-pair production • F-B Asymmetry • Cross-section DELPHI Status Report

  10. Fermion-pair production: mm,tt mm tt cos(qm-) cos(qt-) Ms eff.Planck scale l interference parameter DELPHI Status Report

  11. Fermion-pair flavour tag DELPHI Status Report

  12. Coplanar Photons • Good agreement with QED prediction • Limits on gravity in extra-dimensions: Ms >615 GeV/c2 (l=+1) Ms >703 GeV/c2 (l=-1) DELPHI Status Report

  13. Double radiative return to Z Three cases for symmetric double radiative return • Both photons detected (3o<qg<177o)s=0.270.06 pb • Only one photon seen s=1.030.27 pb • Both photons lost in the beam pipe s=1.590.31 pb (sth=1.29 pb *) *A.B.Arbuzov’s preliminary result (quasi- real electron approximation and ZFITTER) DELPHI Status Report

  14. WW cross section • W hadronic BR • WW cross section DELPHI Status Report

  15. W mass spectrum • Fully hadronic channel • Semileptonic channel DELPHI Status Report

  16. A NICE EVENT jet E=29 GeV e+ e+E=30 GeV E=42 GeV e- M(e+e-)=3.8 GeV/c2 g* ? jet DELPHI Status Report

  17. A ZZEVENT e+E=30 GeV E=29 GeV e+ E=42 GeV e- low energy electron only visible in ID and VD: asymmetric gamma conversion in the beam pipe (FSR) M(e+e-e+)~MZ Interpretation: ZZqq e+e-(+gFSR) DELPHI Status Report

  18. ZZ analysis • ZZ mass region • Improved qqqq • probabilistic analysis based on ideogram techniques • sensitive to all flavours • four or five jet configurations • qqnn I.D.A. • l+l-l+l-: 1 event (4-m event) • llnn • ZZ probability in qqqq analysis DELPHI Status Report

  19. ZZ analysis • qqll channel is clean and efficient: data MC signal (efficiency) qqmm 5 5.6 5.2 87% qqee 6 5.4 4.8 71% “ ZZ+Zg*+Zee ” “ ZZ+Zg* ” DELPHI Status Report

  20. ZZ cross section DELPHI Status Report

  21. llqq events at LEP2 • DELPHI has more than 400 pb-1 collected at LEP2 • Check of the mass spectrum: Mqq(after 4C-fit) DELPHI Status Report

  22. llqq events at LEP2 • Excess in eeqq, when Mqq~Mz: check Mee Mll (with Mqq in Z region) DELPHI Status Report

  23. eeqq events at LEP2 • Resolution in Mee (after 4C-fit) is ~1.7 GeV/c2 • 10 events seen in three neighbouring mass bins ``50-56 GeV/c2(with contribution from different years) • Expected background is 0.790.06 events Mll window mmqq eeqq (GeV/c2) data MC data MC 0-20 15 11.8 7 6.2 20-80 5 6.2 19 9.7 80-120 12 12.4 9 11.6 But... DELPHI Status Report

  24. eeqq events at LEP2 • Angular distribution and charge asymmetry follow expected Standard Model behaviour • Work and cross-checks are going on... DELPHI sees this effect as a good example where a collaborative LEP effort can help to progress, having in mind next year situation. DELPHI Status Report

  25. Searches: preliminary results • Charginos • s-top & s-bottom • s-leptons • Asymmetric t pairs • Photon events with missing energy • Higgs search: • hZ channel and limit on the SM Higgs • hA search • Charged Higgses analysis DELPHI Status Report

  26. Search for Charginos Analysis in stable and unstable neutralino scenarios at Ecm=192, 196, 200 and 202 GeV. No evidence of signal. DELPHI Status Report

  27. Search for Charginos Regions excluded at 95% C.L.in the (m,M2)plane at Ecm=200 GeV under the assumption of a heavy sneutrino DELPHI Status Report

  28. Squarks ~ ~ ~ ~ Both analyses ( tcc0, bbc0 ) optimized for cases DM<10 and DM>10 No excess of selected events, limits improved. DELPHI Status Report

  29. Sleptons Number of selected events in agreement with SM predictions New limits: LSP mass -Slepton mass plane (for tanb=1.5 and m=-200) Me> 91 GeV/c2(for DM>10 GeV/c2)Mm> 85 GeV/c2(for DM>6 GeV/c2) ~ ~ R R DELPHI Status Report

  30. Staus Number of observed events as expected from SM background Limits for right-handed and minimal mixing stau production DELPHI Status Report

  31. Asymmetric t pairs Interpretation in Minimal SUGRA (LEPSUSY WG): ex: tanb=35, m<0 , A0=0 mixing caveats at large tanb If searches for charginos and staus are blind! and if tanb large, selectron cannot help How to cover this unexplored strip at large tanb in mSUGRA? DELPHI Status Report

  32. Asymmetric t pairs DELPHI limit at 95% CL: in the strip,translates into a lower limit MLSP>45.5 GeV/c2 Use: Search for a pair of asymmetric t: 10<E1<50, E2/E1<0.15 Acoplanarity > 20o Analysis at 189 GeV: 4 events selected 2.80.7 expected mean eff~17% DELPHI Status Report

  33. Single Photon Events Check nng cross section and derive limits on new physics STIC + FEMC + HPC DELPHI Status Report

  34. Two Photons + Missing Energy Preselection level: at least two acoplanar g with xg>0.05 (check agreement with SM nngg(g) prediction from KORALZ) DELPHI Status Report

  35. Two Photons + Missing Energy After kinematical selection according to final state, Good agreement data-SM prediction in both cases DELPHI Status Report

  36. Higgs search: SM HZ • Current LEP combined limit: mH>102.6 GeV/c2 • Sensitivity to a 105 GeV/c2 Higgs: • Main background ZZ, but now better mass discrimination DELPHI Status Report

  37. Hll channels • Performance: • No golden candidate (MH>100 GeV/c2)! DELPHI Status Report

  38. Hnn channel • Preselection improved, likelihood variable used Efficiency vs background curve Mass plot at 40% efficiency DELPHI Status Report

  39. Hqq channel • Combined variable (NN output) using b-tag, antiQCD, and mass-compatibility with WW DELPHI Status Report

  40. HZ mass plots • Combined mass plot: 200 + 202 GeV DELPHI Status Report

  41. HZ mass limit • PRELIMINARY LIMIT(using 2D info:mass-discriminant variable) Observed limit: mH >106.2 GeV/c2 Expected: mH > 105.9 GeV/c2 (median) (105.2 GeV/c2 mean) Discovery sensitivity: 97.2 GeV/c2 DELPHI Status Report

  42. hA search • Discriminating likelihood used in the bbbb channel DELPHI Status Report

  43. MSSM limits • Combine hZ + hA search (all LEP2 data) DELPHI Status Report

  44. Charged Higgs All three channels (cscs, cstn,tntn) analyzed DELPHI Status Report

  45. Conclusions: • Excellent year for DELPHI: • Very good detector performance • Large luminosity collected: thanks to the LEP group! • Many interesting physics analysis (including some new) • Good agreement with SM predictions: preliminary estimates for cross sections at high energies, including fermion-pair production, coplanar photons, WW and ZZ • Understanding of excess in eeqq, would like to compare! • Searches analysis updated, new limits on SUSY • Good performance for the Higgs search, but... DELPHI Status Report

  46. Prospects: • ...it may be waiting for the new millenium to appear; joint LEP effort will be needed to discover it ! • Expect highest as possible collision energy for LEP in 2000, with a reasonable luminosity (>150 pb-1) • Should study in detail the possibility of the Higgs fusion • Need additional info on the possibility to run at lower energies if not possible at the maximum one • No major intervention expected during shutdown, DELPHI will be ready! DELPHI Status Report

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