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Status of ALEPH physics analyses

Status of ALEPH physics analyses. LEP Physics Jamboree, February 27, 2001 Frederic Teubert, CERN on behalf of the ALEPH collaboration Heavy flavour results Searches for SUSY Searches for Higgs Difermion production W results. LEP I LEP II. Preliminaries.

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Status of ALEPH physics analyses

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  1. Status of ALEPH physics analyses LEP Physics Jamboree, February 27, 2001 Frederic Teubert, CERN on behalf of the ALEPH collaboration Heavy flavour results Searches for SUSY Searches for Higgs Difermion production W results LEP I LEP II Frederic Teubert

  2. Preliminaries • Results are preliminary and not exhaustive. • The results on Z physics, take profit of the significant improvements on lepton ID and charged particle tracking from the reprocessing of LEPI data made in 1998. • Most of the physics results shown are based on 217 pb-1 collected at energies between 200 GeV and 209 GeV in the year 2000. • The reprocessing of the year 2000 data was finalized successfully in December. Frederic Teubert

  3. New calibration constants • Reprocessing of 2000 data. New calibration and alignment constants included. Improved tracking at low polar angles. Effects are very small, but... always looking for perfection. (Z1 - Z2) * sign(cos) 50 m before reprocessing -50 m 0.2 0.4 0.6 0.8 50 m after reprocessing -50 m 0.2 0.4 0.6 0.8 abs(cos ) Frederic Teubert

  4. New Heavy Flavour Results at LEP I Frederic Teubert

  5. AFB (b) using jet charge • New inclusive measurement using jet charge. 30% overall increase in the size of the data sample using a NN to tag b-events. Improved jet charge estimator, using fast Kaon tagging and separated primary and secondary vertex charge estimators. Systematic uncertainties reduced thanks to a lower mistag rate and the use of double tag methods. A0,bFB = 0.1004  0.0033 sin2eff = 0.23201  0.00058 Frederic Teubert

  6. Measurement of sin2eff final preliminary final To be compared with the most precise determination from SLD: sin2eff = 0.23098  0.00026 Frederic Teubert

  7. Bs Oscillations Final state Initial state IP S.V. K Kf l + B 0 s n “topological” c meson • Improved limit with a new study of inclusive lepton events. Most sensitive analysis with better error on the measured amplitude. Improved event selection and vertex reconstruction allows to increase by a factor 2 the data sample. Improved initial state tag and Bs enrichment. Careful treatment of the event-by-event error on the secondary vertex. Significance improved by a factor 2 at high frequencies. Frederic Teubert

  8. Bs Oscillations Inclusive lepton only ALEPH average ms > 11.1 ps-1 (observed) @ 95% c.l. 11.9 ps-1 (sensitivity) ms > 10.7 ps-1 (observed) @ 95% c.l. 13.1 ps-1 (sensitivity) A ~2 deviation from A=0 is observed @ 17 ps-1 Frederic Teubert

  9. Searches for SUSY particles at LEP II Frederic Teubert

  10. MSSM: missing energy channels • Large variety of experimental topologies: SLEPTONS (2000 data):#obs. #exp. bkg. m > 15 GeV 39 38.7(me > 94 GeV @95% c.l.) 39 34.7(m > 86 GeV @95% c.l.) 17 20.1(m > 75 GeV @95% c.l.) SQUARKS (2000 data): #obs. #exp. bkg. (high m) 11 8.6 3 1.6 0 1.2 CHARGINOS/NEUTRALINOS (2000 data): #obs. #exp. bkg. 35 32.0 11 8.5 any tan , m0  500 ~ ~ ~ m LSP > 39.6 GeV @ 95% c.l. Frederic Teubert

  11. Charginos nearly mass-degenerate with Neutralino • New analysis searching for  nearly mass-degenerate with the lightest neutralino. For m < m: chargino will be stable in the detector and leave strong ionization signal. For m < m < 3 GeV: e+e-   + - ISR photon to ensure the trigger. EXAMPLE (m() = 86 GeV): #obs. #exp. bkg. m=0.3 GeV 1 2.9 m=2.0 GeV 1 3.0 in the Higgsino region, with m0 = 500 GeV m  > 89.5 GeV @ 95% c.l. Frederic Teubert

  12. GMSB: acoplanar photons/taus ~ ~ ~ • LSP = G ( massless) NLSP   :   GG acoplanar photons + missing Energy #obs. #exp. 4 4.9 (E>37GeV) NLSP   :    GG acoplanar taus + missing Energy lifetime independent mass limit, #obs. 161 #exp. 157.7 m  > 99 GeV @ 95% c.l. cut #obs. 1 #exp. 2.3 stable heavy leptons ~ ~ ~ ~ ~ acoplanar leptons #obs. 1 #exp. 1.1 m  > 75 GeV @ 95% c.l. Kinks, large impact parameter ~ Frederic Teubert

  13. RPV: large multiplicity • ijkLi Lj Ek + ’ijkLi Qj Dk + ’’ijkUi Dj Dk Many topologies searched… For large m0, the chargino mass limit is given by the kinematic limit, as for the RPC case. m  > 103 GeV @ 95% c.l. Frederic Teubert

  14. Searches for Higgs bosons at LEP II Frederic Teubert

  15. Higgs bosons in the MSSM No mixing scenario sin( - ) cos( - ) hZ: SM topologies hA: 4b, bb #bkg. #obs. 4b 5.5 10 bb3.0 3 small tan  large tan  Combined vs tan  Maximal mixing scenario sin2( - ) = 0: m h > 91.2 GeV @ 95% c.l. m A > 91.6 GeV @ 95% c.l. 0.7 < tan  < 2.1 (excluded) Frederic Teubert

  16. Charged Higgs 3 different topologies: #obs. #exp. bkg. H+ H-    11 14.2 H+ H-   cs 127 118.0 H+ H-  cs cs 1066 1083.3 cs cs channel (2000 data) m H+ > 77.9 GeV @ 95% c.l. (any BR) Frederic Teubert

  17. Charged Higgs Simple cut analysis common to the 4 LEP experiments: • nch > 15 • thrust < 0.9 • 0.6 < Evis/s < 1.4 • E < 25 GeV • El < 50 GeV • Etmiss < 0.3 s • Elmiss < 0.5 (Mvis-MZ) • ln(Y34) > -4.5 • |cos| < 0.9 Similar conclusion than ALEPH standard analysis, but less sensitive. Cut analysis Standard analysis Frederic Teubert

  18. Status of the SM Higgs search • Results published, PLB 495(2000) 1-17 (received 10 November 2000) Much of the excess seen in the 4-jet analysis. New calibration constants check on the most significant candidatesno effect. Expected (bkg only) 3.2  (LEP WG convention) Observed 0.1% Expected (signal +bkg) mH > 111.1 GeV(observed) @ 95% c.l. mH > 114.2 GeV(expected) Frederic Teubert

  19. Status of the SM Higgs search • Changes w.r.t. LEPC November 3 (3.3 LEP WG convention): - added the last 7 pb-1 of data collected, (-0.1). total luminosity >200 GeV: 216.1 pb-1. • Status today  PLB 495 1-17, (3.2 LEP WG convention): - Reprocessing of all 2000 data shows no significant change. - Several systematic uncertainties have been evaluated: - b-tagging - jet energy and angle reconstruction - MC statistics ... + several x-checks already described in previous ALEPH talks. - Work going on to finalize the study of systematic effects… largest effect maychange the significance of the excess by 0.2. Frederic Teubert

  20. ZZ production channel ZZ bkg. #exp. #obs.(2000 data) llxx 15.1 1.4 16.5 16 ll 2.0 1.9 3.8 3 qq 26.1 21.7 47.7 53 4q(b) 16.1 7.1 23.1 25 4q(non-b) 27.1 49.8 76.9 75 ZZ (205 GeV) = 1.21  0.25 pb ZZ (207 GeV) = 1.01  0.18 pb Frederic Teubert

  21. Difermion production at LEP II Frederic Teubert

  22. Difermion production e+e- qq  (s’/s) > 0.9 statistics  systematics  theoretical uncertainty e+e- +-, +- Frederic Teubert

  23. QCD event shapes and jet rates # jets Thrust Heavy jet mass Wide jet broadening Good agreement with MCpredictions tuned at the Z. Frederic Teubert

  24. W physics at LEP II Frederic Teubert

  25. Single W production channel We bkg. #exp. #obs.(2000 data) W qq’ 46.5 79.1 125.6 138 W l 26.0 10.2 36.2 32 Common LEP definition: We (205 GeV) = 0.78  0.27 pb We (207 GeV) = 1.19  0.25 pb Frederic Teubert

  26. WW production lqq ll W pair production in agreement with most up-to-date calculations (RACOONWW, YFSWW). Branching ratios (%): (Data/YFSWW - 1 ) = (-1.31.1)% (Data/RACOONWW - 1) = (-1.0 1.1) % total qqqq B(We) = 10.95  0.27  0.16 B(W) = 11.11  0.25  0.15 B(W) = 10.57  0.32  0.20 B(Wqq) = 67.33  0.38  0.28 |Vcs| = 0.967  0.018  0.014 Frederic Teubert

  27. Gauge Boson Couplings • Triple Gauge Boson Couplings. Probe non-abelian structure of SU(2)  U(1). Anomalous contribution grow with energy and affect cross-section and angular distributions. New O() calculations have been taken into account in the cross-section prediction and have been taken as systematic uncertainties in the angular distribution. Frederic Teubert

  28. Gauge Boson Couplings Using WW events only: adding single-W and single-: (stat+syst) O() g1Z = 0.015 0.032 0.013  = 0.018 0.124 0.037  = 0.006 0.034 0.015 (stat+syst) g1Z = 0.015  0.034  = -0.021  0.077  = -0.001  0.033 Frederic Teubert

  29. W mass • Last ALEPH update using data collected from 1997 to 1999: • ALEPH (172 GeV - 202 GeV): • Main systematic uncertainties: • Fragmentation: correlated between channels and years (MW=34 MeV) • LEP energy: correlated between channels and years (MW=17 MeV) • Final state interactions: only 4q channel (MW=42 MeV) Mw = 80.449  0.045(stat)  0.048(syst) GeV Frederic Teubert

  30. Improvements on the tau channel Resolution on the invariant mass reconstructed is improved using a specific -jet finder. Selection also improved using a NN. Expected error on mW from W reduced by 30% Previous analysis New analysis Frederic Teubert

  31. Systematic uncertainties: fragmentation Discrepancies in MC description of the parton shower evolution + hadronizationFragmentation uncertainty . Several methods to evaluate this uncertainty: - Variation of tuning QCD parameters in JETSET: Mw < 10 MeV • Comparison data vs MC, Mw(4q)  10 MeV, Mw(non-4q)  15 MeV - Comparison of different QCD hadronization models: Mw(4q) = 30 MeV, Mw(non-4q) = 40 MeV Hard gluon emission in HERWIG found to be not appropriate for W physics. Reevaluation of systematic uncertainties: Mw(4q) = 10 MeV , Mw(non-4q) = 15 MeV Frederic Teubert

  32. Systematic uncertainties: FSI CR BE Current estimation: 30  22 = 37 MeV Bose-Einstein correlations Colour-Reconnection Frederic Teubert

  33. W mass results 2/d.o.f. = 9.3/8 Mw(non-4q)=80.456  0.051(stat)  0.032(syst) GeV Mw(4q)=80.507  0.054(stat)  0.026(syst)  0.037(CR/BE) GeV Mw(4q) - Mw(non-4q) =0.051  0.075 GeV Frederic Teubert

  34. W mass results 2/d.o.f. = 9.3/9 2/d.o.f. = 0.9/1 MW =80.471  0.038(stat)  0.023(syst)  0.015(CR/BE) GeV  0.017(LEP) GeV Frederic Teubert

  35. W mass and width summary (previous average) ALEPH: MW =80.471  0.038(stat)  0.032(syst) GeV W =2.13  0.11(stat)  0.09(syst) GeV (SM: 2.09 GeV) Frederic Teubert

  36. Conclusions • Plenty of (preliminary) physics results using the last data collected by ALEPH. • No evidence for physics beyond the SM has been found. • Observation of an excess(~3) in the search for the SM Higgs, at mH ~ 114 GeV. • Precision measurements are in good agreement with the SM as long as the Higgs is not far away… • For more details, http://alephwww.cern.ch/ALPUB/oldconf/conferences.html Frederic Teubert

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