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Physics Highlights from ALEPH (Winter Conferences 2002)

Physics Highlights from ALEPH (Winter Conferences 2002). Paschal Coyle. Centre de Physique des Particules de Marseille On behalf of the ALEPH Collaboration LEP Physics Jamboree, Feb 28 th 2002. Preliminaries. All results shown are final i.e. recently published or about to be published

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Physics Highlights from ALEPH (Winter Conferences 2002)

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  1. Physics Highlights from ALEPH(Winter Conferences 2002) Paschal Coyle Centre de Physique des Particules de Marseille On behalf of the ALEPH Collaboration LEP Physics Jamboree, Feb 28th 2002

  2. Preliminaries • All results shown are final i.e. recently published or about to be published • The WW analyses are still ongoing, will not give preliminary numbers- results anticipated for the summer • All LEP I results profit from reprocessing of the data -improved lepton ID, charged particle tracking and dE/dX • All limits given at 95% confidence level LEP Physics Jamboree, Feb 28th, 2002

  3. R-parity beauty GMSB sleptons charm squarks Asymmetries SUSY Higgs charged Bsoscillations exclusive ? MSSM Ds-lepton Standard Model inclusive-lepton LEP Physics Jamboree, Feb 28th, 2002

  4. New Heavy Flavour Results at LEP I - Bs Oscillations - AFB LEP Physics Jamboree, Feb 28th, 2002

  5. Bs Oscillations B 0 s n “topological” c meson _ _ _ W s(d) b - - Bs(d) Bs(d) t t W s(d) b Vts(td) Final state Topology: Initial state B 0 s K Initial state Mistag(NN) ~24% IP Kf l + NEW Improved Exclusive Bs Inclusive lepton Ds-lepton l + l + B 0 s B p+ 0 s n Ds- Ds- More details: CERN-EP 2002/016 better Bs purity, better resolution, less events LEP Physics Jamboree, Feb 28th, 2002

  6. Bs Oscillations: Exclusive Bs ALEPH • Bs decay chain: BsDs-+, BsDs-a1+ • (with fully reconstructed Ds- -, K*K-) • Events with photons and º’srecovered e.g. BsDs*--(a1-) with Ds*-Ds • Statistics low: Ds-a1+ 36 events Ds-+ 44 events • High Bs purity (e.g.  ~80% ) • Very good proper time resolution as no  (factor 3 better than inclusive analysis) • Final state tag is perfect LEP Physics Jamboree, Feb 28th, 2002

  7. Bs Oscillations: Ds-lepton • 297 Ds-lepton candidates reconstructed in: 8 channels (hadronic and semileptonic) • Bs purity~40%. Discriminating variables used to identify subsamples with higher Bs fraction • Careful parametrization of momentum and decay length resolutions • Proper time resolution reasonable (despite ) hadronic decays LEP Physics Jamboree, Feb 28th, 2002

  8. Bs Oscillations: Inclusive Lepton • New vertexing algorithm: estimate of B • direction included as ‘track’ in the fit • (typically 10% better resolution) • Neural net for bl tagging based on: • lepton p, pT, energy, lepton i.p. wrt to c vertex • New selection: *2.2 more events (~74k), with • same resolution as old analysis • Subclasses for decay length resolution, each • with separate correction for the estimate of • event-by-event decay length uncertainty • Event-by-event Bs fraction from neural net • based on: • charge estimators of charm vertex (B0 vs B+) • presence of decay K+, K0s, , (Bs vs B0) • presence of fragmentation K+ bl tagging NN Bs fraction NN LEP Physics Jamboree, Feb 28th, 2002

  9. Bs Oscillations: The Amplitude Plots w=ms A=1 W<ms A=0 A Inclusive lepton Ds-lepton Exclusive Obs. limit: ms>2.4 ps-1 Exp. limit: ms>0.3 ps-1 ms>7.2 ps-1 ms>7.4 ps-1(was 6.6 ps-1) ms>11.4 ps-1(was 9.5 ps-1) ms>14.0 ps-1(was 9.8 ps-1) 1.645A@15ps-1: 2.5 1.645A@15ps-1: 1.2 1.645A@15ps-1: 2.1 LEP Physics Jamboree, Feb 28th, 2002

  10. Bs Oscillations: ALEPH Combination Observed limit: ms > 10.8 ps-1(was 9.6 ps-1 ) Expected limit: ms > 15.6 ps-1 (was 10.6 ps-1 ) Consistent with expectations for a signal around ms=16-18 ps-1 LEP Physics Jamboree, Feb 28th, 2002

  11. Bs Oscillations: WORLD Combination Observed limit: ms > 14.9 ps-1 Expected limit: ms > 19.3 ps-1 Can not claim a measurement LEP Physics Jamboree, Feb 28th, 2002

  12. AFBb and AFBc using Leptons b l- b l+ - e- e- AFBb  e+ e+ b b sin2 W Sample of inclusive semileptonic decays is binned in variables (NN outputs) which discriminate: b versus c versus uds bl versus bcl in b events LEP Physics Jamboree, Feb 28th, 2002

  13. AFBb and AFBc using Leptons b enriched c enriched 70 angular distributions of signed thrust axis are simultaneously fitted with AFBb and AFBc as free parameters Off peak points also measured More details: CERN EP/2001-097 AFB0,b = 0.0998  0.0040  0.0017 AFB0,c = 0.0732  0.0053  0.0037 LEP Physics Jamboree, Feb 28th, 2002

  14. AFB0,b –ALEPH and LEP Combination ALEPH has also published a measurement of AFBb using an inclusive jet charge method EPJ C22 (2001) 201: AFB0,b = 0.1017  0.0027  0.0012 New ALEPH only Combination: AFB0,b = 0.1011  0.0026 (sin2 W = 0.231880.00047) LEP Physics Jamboree, Feb 28th, 2002

  15. ALEPH Measurements of Sin2eff All Results Are Final comparable precision to the most precise determination from SLD: sin2eff = 0.23098  0.00026 LEP Physics Jamboree, Feb 28th, 2002

  16. Searches for Higgs bosons at LEP II • SM • MSSM • Invisible • Charged LEP Physics Jamboree, Feb 28th, 2002

  17. Final Results for SM Higgs Search • Preliminary results published in PLB 495 (2000) 1: 3s excess - 2 independent analysis streams (NN, Cuts) -fixed before data taking • Final results recently published in PLB 526 (2002)191 - Additional MCmore precise shapes and efficiencies - All Y2K data reprocessed- gaining 1pb-1 most significant candidates already reprocessed for the preliminary publication - New LEP ECM- about 140 MeV lower - Further systematic studies Impact of uncertainties on (1-CLb)from b-tagging, correlations in discriminating variables, jet smearing, gluon splitting, as, MC description of selection variables - Improved treatment ofbeam-induced background Studied on random triggers, “dirty MC” generated, cleaning procedure implemented LEP Physics Jamboree, Feb 28th, 2002

  18. Candidate (b) 4 b cand. HZ hyp. mH= 112.8GeV NN = 0.997 jet b-tag: Z 1 0.994 2 0.78 H 3 0.993 4 0.999 Evis= 252 GeV ! very bad kin. fit! ELEP=206.7 22 GeV in SICAL LEP Physics Jamboree, Feb 28th, 2002

  19. SM Higgs: Treatment of Beam Induced Backgrounds min{2(norm)- 2(ISR)} R= 2(beam) Events with an energetic, isolated, low angle cluster are fitted to three hypotheses: 1)Cluster- part of event  standard four-jet fit [2(norm)] 2) Cluster- ISR photon  fit rest of event to four-jets taking into account momentum imbalance caused hypothetical ISR photon [2(ISR)] 3) Cluster- beam induced background  remove from event and fit rest of event to four-jets [2(beam)] R>2  beam contamination candidate (b) MC (no Beam bkg) MC with Beam bkg M(Higgs) of candidate (b): 112.8 GeV114.4 GeV LEP Physics Jamboree, Feb 28th, 2002

  20. SM Higgs: Results Expected (bkg only) Expected (bkg only) observed observed 0.24% Expected (sig+bkg) Expected (sig+bkg) NN stream Preliminary result confirmed: Excess observed and consistent with Higgs mass ~115 GeV LEP Physics Jamboree, Feb 28th, 2002

  21. SM Higgs: Significance of Excess Observed Limit on M(higgs)>111.5 GeV Expected Limit on M(higgs)>114.2 GeV LEP Physics Jamboree, Feb 28th, 2002

  22. SM Higgs: systematics studies If added in quadrature: 0.17 0.15 LEP Physics Jamboree, Feb 28th, 2002

  23. Higgs bosons in the MSSM sin(-) cos(-) e- Z Z* hZ:SM topologies hA:4b, bb N exp. N obs. (year 2000) 4b 5.5 10 bb3.0 3 e+ h small tan large tan No mixing scenario Combined vs. tan mh> 89.8 GeV mA> 90.1 GeV 0.7<tan < 2.3 excluded (mh max scenario) mh max scenario More details: PLB 526 (2002)191 LEP Physics Jamboree, Feb 28th, 2002

  24. Invisible Higgs mh > 114.1 GeVfor 2=1 In some parameter regions Higgs can decay invisibly e.g. h Nobs. Nexp. Acoplanar leptons 7 6.7 Acoplanar jets 42 48.6 year 2000 More details: PLB 526 (2002)191 LEP Physics Jamboree, Feb 28th, 2002

  25. Charged Higgs 3 different topologies: N obs. N exp. (year 2000) H+ H-    9 14.0 H+ H-   cs 127 108.9 H+ H-  cs cs 950963.2 cs cs channel mH+ > 79.3 GeV(any BR) LEP Physics Jamboree, Feb 28th, 2002

  26. Searches for SUSY particles at LEP II • Sleptons • Squarks • GMSB • R-parity violation LEP Physics Jamboree, Feb 28th, 2002

  27. MSSM: Scalar Leptons ~ l l   Pair of oppositely charged, same flavour leptons (e,,) Nobs./Nexp. 39/35.5 Nobs./Nexp. 54/63.0 Nobs./Nexp. 39/38.1 year 2000: ~ ~ ~ M(R)> 76 GeV M(R)> 88 GeV M(eR)> 95 GeV tan=2, =-200 GeV more details: CERN EP/2001-086 Only valid for m>15 GeV LEP Physics Jamboree, Feb 28th, 2002

  28. MSSM: Scalar Leptons-absolute mass limit ~ ~ Use eReL production in small M region: 2<M<4 GeV: eReL -1 soft, 1 hard electron  cuts on P(esoft) as f(M(),M(eR)) M<2 GeV: eReL -1 hard electron single electron selection ~ ~ ~ ~ Gaps in chargino selections (‘corridor’), filled using production of 13 Problems when 2 is light use 2B/3B chargino selections ~ lRl  1l  2(1ll)l  2(1)l ~ ~ ~ M(eR)> 73 GeV, M(eL)> 107 GeV, M() > 84 GeV LEP Physics Jamboree, Feb 28th, 2002

  29. MSSM: Scalar Leptons-effect of Higgs mass limit For a given m0: limit on Mh gives limit on M1/2 as function of tan Use Higgs results: Mh >111 GeV for small tan ~ ~ ~ M(eL)> 115(115) GeV M()> 84 (84) GeV M(eR)> 77(75) GeV For mtop=175(180) GeV and assuming no stau mixing LEP Physics Jamboree, Feb 28th, 2002

  30. MSSM: Scalar Quarks ~ t c/u1 Acoplanar jets (36/34.5) longed lived hadrons (1/2.8) Size of mixing proportional to mass of SM partner stop the lightest squark ~ ~ ~ t b l  Acoplanar jets+leptons 11/7.2 (all years) t b 1 f f’ Multi-jets 6/5.8 NEW W* BR ~ ~ ~ ~ M(t)>97 GeV, M>8 GeV M(t)>78 GeV, M>10 GeV M(t)>92 GeV, M>8 GeV ~ M(t)>63 GeV, any M, any decay LEP Physics Jamboree, Feb 28th, 2002

  31. Gauge Mediated SUSY Breaking Topologies ~ ~ G is the Lightest Supersymmetric Particle (LSP) ~ ~ ~ ~ ~ ~ ~ ~ LEP Physics Jamboree, Feb 28th, 2002

  32. Gauge Mediated SUSY Breaking Topologies ~ ~ ~ Stau NLSP (l  l G) Neutralino NLSP (G) Kinks & i.p: 1/1.1 Acoplanar Photons (4/4.9) + Non-pointing Photons (2/1.0) Stable heavy charged 1/2.3 Acoplanar leptons M(stau) > 77 GeV (any lifetime) M(1) > 52 GeV (any lifetime) MNLSP> 52 (77) GeV universal mass scale - > 10 (16) TeV M(G) > 0.024 (0.061) eV (Using Higgs constraint) For no. messenger pairs<6 ~ LEP Physics Jamboree, Feb 28th, 2002

  33. R-Parity Violation: Single Sneutrino Production Production: Decay: direct- 3 leptons - 7 out of 9 (LLE) couplings accessible - Masses up to s via neutralino- 3 leptons+ Emiss e.g. (132) e e ~ (132) ~ more details: CERN EP/2001-094 similar limits for other s LEP Physics Jamboree, Feb 28th, 2002

  34. Summary Many ALEPH physics analyses completed…. Bs oscillation analyses (exclusive, Ds-lepton, semi-inclusive) - sensitivity significantly improved b and c asymmetries (leptons, inclusive) Searches for SM Higgs -confirms conclusions of preliminary publication Searches for SUSY Charged and invisible Higgs Absolute mass limits on scalar leptons and quarks Complete study within the GMSB framework R-Parity single sneutrino production LEP Physics Jamboree, Feb 28th, 2002

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