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

2. Operation at 200-202 GeV Luminosity on tape:
125.4 pb-1 collected with efficiency ~93%
GeV + GeV
( GeV)
Total collected luminosity in 1999: pb-1
25.9 GeV
76.9 GeV
plus 3.95 pb-1 at Z0 peak
THANKS TO THE LEP GROUP!
LEPC Nov-99
DELPHI Status Report

3. Operation at 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!
LEPC Nov-99
DELPHI Status Report

4. Luminosity
LEPC Nov-99
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%
LEPC Nov-99
DELPHI Status Report

6. VD Resolution Excellent!  intrinsic resolution/layer ~9 m
LEPC Nov-99
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
LEPC Nov-99
DELPHI Status Report

8. Fermion-pair production
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DELPHI Status Report

9. Fermion-pair production
Cross-section
F-B Asymmetry
LEPC Nov-99
DELPHI Status Report

10. Fermion-pair production: mm,tt
cos(qm-)
cos(qt-)
Ms eff.Planck scale
l interference parameter
LEPC Nov-99
DELPHI Status Report

11. Fermion-pair flavour tag
LEPC Nov-99
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)
LEPC Nov-99
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)
LEPC Nov-99
DELPHI Status Report

14. WW cross section WW cross section W hadronic BR DELPHI Status Report
LEPC Nov-99
DELPHI Status Report

15. W mass spectrum Semileptonic channel Fully hadronic channel
LEPC Nov-99
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16. A NICE EVENT jet e+ E=30 GeV g* ? jet DELPHI Status Report
E=29 GeV e+
e+ E=30 GeV
E=42 GeV e-
M(e+e-)=3.8 GeV/c2
g* ?
jet
LEPC Nov-99
DELPHI Status Report

17. A ZZ EVENT e+ E=30 GeV M(e+e-e+)~MZ Interpretation: ZZqq e+e-(+gFSR)
E=29 GeV e+
e+ E=30 GeV
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)
LEPC Nov-99
DELPHI Status Report

18. ZZ analysis ZZ mass region Improved qqqq qqnn I.D.A.
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
LEPC Nov-99
DELPHI Status Report

19. ZZ analysis qqll channel is clean and efficient: “ ZZ+Zg* ”
data MC signal (efficiency)
qqmm %
qqee %
“ ZZ+Zg* ”
“ ZZ+Zg*+Zee ”
LEPC Nov-99
DELPHI Status Report

20. ZZ cross section
LEPC Nov-99
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21. llqq events at LEP2 Mqq (after 4C-fit)
DELPHI has more than 400 pb-1 collected at LEP2
Check of the mass spectrum:
Mqq (after 4C-fit)
LEPC Nov-99
DELPHI Status Report

22. llqq events at LEP2 Mll (with Mqq in Z region)
Excess in eeqq, when Mqq~Mz: check Mee
Mll (with Mqq in Z region)
LEPC Nov-99
DELPHI Status Report

23. eeqq events at LEP2 But... Mll window mmqq eeqq
(GeV/c2) data MC data MC
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
But...
LEPC Nov-99
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.
LEPC Nov-99
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
LEPC Nov-99
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.
LEPC Nov-99
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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
LEPC Nov-99
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28. Squarks Both analyses ( tcc0, bbc0 ) optimized for cases ~ ~ ~ ~
~ ~ ~ ~
Both analyses ( tcc0, bbc0 ) optimized for cases
DM<10 and DM>10
No excess of selected events, limits improved.
LEPC Nov-99
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
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DELPHI Status Report

30. Staus Number of observed events as expected from SM background
Limits for right-handed and minimal mixing stau production
LEPC Nov-99
DELPHI Status Report

31. Asymmetric t pairs mixing caveats at large tanb
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?
LEPC Nov-99
DELPHI Status Report

32. Asymmetric t pairs DELPHI limit at 95% CL:
Use:
Search for a pair of asymmetric t:
10<E1<50, E2/E1<0.15
Acoplanarity > 20o
Analysis at 189 GeV:
DELPHI limit at 95% CL:
in the strip,translates into a lower limit MLSP>45.5 GeV/c2
4 events selected
2.80.7 expected mean eff~17%
LEPC Nov-99
DELPHI Status Report

33. Single Photon Events STIC + FEMC + HPC Check nng cross section and
derive limits on new physics
STIC + FEMC + HPC
LEPC Nov-99
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)
LEPC Nov-99
DELPHI Status Report

35. Two Photons + Missing Energy
After kinematical selection according to final state,
Good agreement data-SM prediction in both cases
LEPC Nov-99
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
LEPC Nov-99
DELPHI Status Report

37. Hll channels Performance: No golden candidate (MH>100 GeV/c2)!
LEPC Nov-99
DELPHI Status Report

38. Hnn channel Preselection improved, likelihood variable used
Efficiency vs background curve Mass plot at 40% efficiency
LEPC Nov-99
DELPHI Status Report

39. Hqq channel
Combined variable (NN output) using b-tag, antiQCD, and mass-compatibility with WW
LEPC Nov-99
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40. HZ mass plots Combined mass plot: 200 + 202 GeV DELPHI Status Report
LEPC Nov-99
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41. HZ mass limit
PRELIMINARY LIMIT (using 2D info: mass-discriminant variable)
Observed limit: mH >106.2 GeV/c2
Expected: mH > GeV/c2 (median) (105.2 GeV/c2 mean)
Discovery sensitivity: 97.2 GeV/c2
LEPC Nov-99
DELPHI Status Report

42. hA search Discriminating likelihood used in the bbbb channel
LEPC Nov-99
DELPHI Status Report

43. MSSM limits Combine hZ + hA search (all LEP2 data)
LEPC Nov-99
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44. Charged Higgs All three channels (cscs, cstn,tntn) analyzed
LEPC Nov-99
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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...
LEPC Nov-99
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!
LEPC Nov-99
DELPHI Status Report