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The facts: First look to the excess Studies going on … Perspectives for 2000 run

Status report from the LEPSUSYwg: “The stau excess” F Cerutti, G.Ganis, F.Holldorfer, K.Jakobs and M.Maggi. The facts: First look to the excess Studies going on … Perspectives for 2000 run Signal hypothesis Fluctuation hypothesis Possible strategy Conclusions ?!?.

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The facts: First look to the excess Studies going on … Perspectives for 2000 run

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  1. Status report from the LEPSUSYwg: “The stau excess”F Cerutti, G.Ganis, F.Holldorfer, K.Jakobs and M.Maggi • The facts: • First look to the excess • Studies going on … • Perspectives for 2000 run • Signal hypothesis • Fluctuation hypothesis • Possible strategy • Conclusions ?!? F.Cerutti

  2. The facts: combined excess • stau ADLO 189-202 GeV combined • Exchanged matrixes in the Mstau-Mchi plane : Cand, Bkg, Eff

  3. The facts: excess probability • Estimator used to quantify the excess

  4. The facts: excess probability

  5. The facts: excess probability • E fraction of point with CLexcess<2% • Gedanken experiments (bkg only) • Pexcess= N(E>Edata)/Ntot =10-3 (6.8% A)

  6. Mstau from xs • Find the stau mass comparingstRvs data excess (Mc<30): • MtR = (86.7 ± 1.4) GeV (Mc~15-35)

  7. The reference point • Take as “reference point” Mt=85 GeV Mc=20 GeV: • Cand = 226 • Bkg = 179.5 • P(Bkg,NNcand) = 5 x 10-4

  8. Compatibility with signal in the reference point : ALEPH only

  9. Bkg composit. and systematics • Background composition in 85-20: • Systematics on bkg: ~2-4% dominated by MC statistics • If we add 4% to bkg in 85-20: P(Bkg,NNcand) = 3 x 10-3 • Gedanken experiment full plane with bkg sys (+1s): Pexcess=N(E>Edata)/Ntot=1.2%

  10. Comparison Data vs Bkg • Decided to exchange more info within ADLO to allow additional checks • For each event (Data, MC Bkg and MC signal) exchange: Pt1 Pt2 Pmiss Weight(bkg) Bin-position, ... • For the 85-20 point check variables [Bkg vs Data] ADL(189-202)O(189) DT=184 MC=146. Excess = 38±14 (2.7 s)

  11. Comparison Data vs Bkg • Emax • Emin • Mtt • Ptmiss • Acollinearity • Emax vs Emin • Mt1 vs Mt2 • Tau ID1 vs Tau ID2

  12. ALEPH: H+ vs stau (B.Fabbro) • H+ vs stau Large-dM (L-dM.OR.S-dM): can bkg can bkg 189 20 15.520 15.5 192-202 36 35.530(46) 21.7(34.2) e(M=85) 38%39% • The two analyses are NOT incompatible • cand=16 bkg=17 dif=-1±4 H+ only • cand=10 bkg=4 dif=6±3 stau only • cand=20 bkg=18 dif=2±4 H+.AND.stau • Warning: 9 events(5 large-dm)selected by stau and NOT by H+ have a NOT identifiedenergetic lepton -> to be checked !

  13. Perspective for y2k run • Patrick performance for LEP y2k

  14. Perspective for y2k run • Studied 18configurations: • 1 22 weeks at 192 GeV • 2 “ 196 GeV • 3 “ 198 GeV • 4 “ 200 GeV • 5 “ 202 GeV • 6 “ 203 GeV • 7 “ 204 GeV • 8 “ 204.6 GeV • 9 “ 205.2 GeV • 10 “ 206 GeV • 11 22 w 206.8 GeV

  15. Perspective for y2k run • 12 22 w MiniRamp 1-step 4-bun. • 13 22 w MR + 24 w extens. MR • 14 22 w + 24 w extens. 200 GeV • 15 Status at LEPC in July MR • 16 MR up to LEPC+200 GeV 22+24 • 17 MR up to LEPC+200 GeV 22+2 • 18 Status before 2000 run • Results for signal hypothesis in the given for three stau masses: 85,87 and 89 GeV (mild dependence from Mc=20 GeV)

  16. Mt=87 GeV

  17. Mt=85 GeV Mt=89 GeV

  18. Significance for Mstau = 89-85 GeV • 1 22 weeks at 192 GeV 3.1-3.9 sigma • 2 “ 196 GeV 3.4-4.3 sigma • 3 “ 198 GeV 3.5-4.3 sigma • 4 “ 200 GeV 3.6-4.3 sigma • 5 “ 202 GeV 3.6-4.2 sigma • 6 “ 203 GeV 3.6-4.1 sigma • 7 “ 204 GeV 3.6-4.0 sigma • 8 “ 204.6 GeV 3.5-4.0 sigma • 9 “ 205.2 GeV 3.5-3.9 sigma • 10 “ 206 GeV 3.1-3.3 sigma • 11 22 w 206.8 GeV 3.1-3.3 sigma • 12 22 w MiniRamp 1-step 3.4-3.8 sigma • 13 22+24 w MR 3.8-4.5 sigma • 14 22+24 w 200 GeV 4.1-5.3 sigma • 15 Status at LEPC in July mr 3.2-3.5 sigma • 16 MR up to LEPC+200 GeV (22+24) 4.1-5.2 sigma • 17 MR up to LEPC+200 GeV (22+2) 3.5-4.2 sigma • 18 Status before 2000 run 2.9 sigma

  19. Perspective for y2k run:No signal hypothesis • Question: can we exclude at 95% CL 85<Mt<89 with next year data alone ? • Answer: YES but for configurations 10, 11, 15 and 17(89 GeV only) ! • 10 Ecm=103 • 11 Elep=103.6 • 15 Status at LEPC with MR • 17 MR up LEPC then 198 GeV

  20. Conclusions ?!? • The facts: • An excess in the ADLO combined LEP data has been found • This excess corresponds to a probability ~10-3 without any bkg systematics • With the bkg systematics included it goes up to ~0.5-1% (not a discovery !) • To be better understood background systematics (A lepton ID) • Y2K run: signal hypothesis: • 4-5 sigma significance still reachable if emphasis toL is given and6 months extension is obtained

  21. Conclusions ?!? • At the July LEPC significance could increase from the actual 2.9 to [3.3-3.5] sigma (assuming a successful MR run) • Significance [3.8-5] sigma could still be reached if, after LEPC, run is optimized for L (run at ~200 GeV) .AND. the 6 months extension is given • Y2K run: no signal hypothesis: • A [85-89] GeV stau mass can be excluded at 95% CL by next year run alone in all the run configurations but the run at the highest energy (103 GeV)

  22. Y2K optimal stau strategy ?!? • Run with MR up to LEPC ~ 120pb-1 than: • Higgs exclusion (Kinematic limit ?) • Stau excess significance (+ or - ?) • If+ indication for stau AND- for H (and c+): switch from MR to optimal stau run (large L at Elep~200) • Final decision on 6 months extensionshould be taken later (and/or as soon as the 4 sigma are reached): August-September ? • Ongoing work: • Careful review of bkg systematics • Provide signal files and fit for Mstau-Mchi (xs plus shapes) • Schedule regular meetings during y2k run

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