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Physics results from ALEPH (Summer Conferences 2002)

Physics results from ALEPH (Summer Conferences 2002). Andrea Venturi INFN Pisa and CERN On behalf of the ALEPH Collaboration LEP Physics Jamboree Jul 22 nd 2002. LEP II. Outline. Standard Two photons ee  Zee  mm ee Colour reconnection studies. LEP I. t ’s branching ratios.

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Physics results from ALEPH (Summer Conferences 2002)

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  1. Physics results from ALEPH(Summer Conferences 2002) Andrea Venturi INFN Pisa and CERN On behalf of the ALEPH Collaboration LEP Physics Jamboree Jul 22nd 2002

  2. LEP II Outline • Standard • Two photons • ee  Zee  mmee • Colour reconnection studies LEP I t’s branching ratios Charm gluon splitting Only g’s final states asfrom event shape • Searches for new physics • single top production • LSP limits • stop into gluino LSP • non-standard Higgs • “Complete” LEP II or LEP I datasets used for (almost) all the results • Results are preliminary unless published • Exclusion limits at 95% CL Physics results from ALEPH - Andrea Venturi - INFN Pisa / CERN

  3. New results with the full LEPI statistics: ~330k tt pairs Classification of each t decay according to number of tracks, p0’s and particle id: 13 classes (e,m,h,hp0,h2p0,…,3h,3hp0,…) Improved treatment of MC corrections and systematic evaluation, especially g’s and p0’s Results corrected for the t decays into K’s,w’s and h’s using previous analyses (ALEPH and CLEO) LEP I: t Branching Ratios Physics results from ALEPH - Andrea Venturi - INFN Pisa / CERN

  4. Lepton universality tested within 2-3 per mille LEP I: t Branching Ratios Lepton universality: Bm and Bp translated into electron BR WA t, m and p lifetimes and t mass used Physics results from ALEPH - Andrea Venturi - INFN Pisa / CERN

  5. Vector spectral functions from pp0, 3pp0, p3p0 BR’s and mass distributions LEP I: t Branching Ratios Hadronic contribution to g-2 radiative corrections An example: ee p+p- cross section from BR(pp0) Physics results from ALEPH - Andrea Venturi - INFN Pisa / CERN

  6. 3 jets events with a lepton in the least energetic jet NN with 6 variables to increase signal purity: ~25% e, ~18% m Main systematics: Lepton id Charm jet simulation BR(c  l) gcc(e)=(2.990.280.41) %gcc(m)=(2.900.380.74) % LEP I: gluon splitting into charm gcc=(2.98  0.48) %WA: (2.96  0.38)% Physics results from ALEPH - Andrea Venturi - INFN Pisa / CERN

  7. Results from the full LEP I+LEP II ALEPH data set 6 event-shape variables used:T, MH2, BW, BT, C, -log y3 Fit with O(as2) + NLLA Good agreement with as running LEP I + LEP II: as from event-shape variables running to MZ and combining:as(MZ)=0.12110.0047 Physics results from ALEPH - Andrea Venturi - INFN Pisa / CERN

  8. Measurements with LEP II data LEP II: gg  p+p-and gg  K+K- Prediction Rescaled x2 Angular distributions pp pp Wgg distributions KK KK Physics results from ALEPH - Andrea Venturi - INFN Pisa / CERN

  9. D* from D0 + soft pion Measurement “direct” and “single-resolved” contributions D* cross sections vs pt and h s(ee  ee cc) LEP II: gg  D* X Single-resolved direct Rapidity Frixione et al. (2000) Physics results from ALEPH - Andrea Venturi - INFN Pisa / CERN

  10. gg  D* X and s(eeeecc) Transverse momentum Physics results from ALEPH - Andrea Venturi - INFN Pisa / CERN

  11. New results: AbFB, QudscFBand Rc LEP II: 2 fermions production: HF results all: 2.3 s 207: 3.5 s Physics results from ALEPH - Andrea Venturi - INFN Pisa / CERN

  12. New analysis Signal definition according to LEP WG (phase space cuts): Mmm > 60 GeV Forw electron q < 12o bckw elect: E>3 GeV, 12o<q<168o Selection efficiency: (362)% 16 events selected (183-207 GeV) (1.9 expected bkg) LEP II (4f): ee Zee  eemm cross section s(ee Zee  eemm)=57  14  4 fb (average from 183 to 207 GeV) Physics results from ALEPH - Andrea Venturi - INFN Pisa / CERN

  13. Looking for Colour Reconnection in WW4q events: preliminary results • Colour singlets can be created across decay products of different W’s: we cannot ask ourselves which W a particle comes from. • Interesting to better understand non-perturbative QCD, worrying for the W mass measurement • Larger effects at the end of the parton shower and in the non-perturbative part  MC models • ALEPH preliminary results from: • Charged particle multiplicity and momentum spectrum analysis • Real data are compared to different MC models using WW4q and WW lnqq events • Particle flow analysis in WW4q (started by L3) • Particle multiplicity between jets from the same and different W’s are compared to MC models with and without Colour Reconnection • Variation of the W mass measurement when soft particle (momentum cut) are discarded from jet reconstruction Physics results from ALEPH - Andrea Venturi - INFN Pisa / CERN

  14. DMW with CR models SKI model predictions Mass shift in MeV % of reconnected events In SKI model Preco is controlled by the parameter Ki Physics results from ALEPH - Andrea Venturi - INFN Pisa / CERN

  15. CR: Charged Particle spectra JETSET vs others Xp=p/Ebeam 10 GeV 1GeV Physics results from ALEPH - Andrea Venturi - INFN Pisa / CERN

  16. In WW 4q events particles are projected to the closest inter-jet plane and angles w.r.t. jet are measured Inter-jet angles are normalized to 1 Distribution is folded and binned ratio is done: Rn = one bin from 0.2 to 0.8 Rn=1.0950.014(stat) 0.006(syst) 0.006(extrap) extrapolated to 189 GeV CR: Particle flow between W’s 3 0=4 1 2 (A+B)/ (C+D) Physics results from ALEPH - Andrea Venturi - INFN Pisa / CERN

  17. Rn measured in data is compared with MC predictions from different models with and without CR Rn(data)= 1.0950.014(stat) 0.006(syst) 0.006(extrap) Background, BE and detector systematics are included. Fragmentation is not included CR: Particle flow between W’s SKI model DR/stot Model parameter Ki ki=2.3 Bias induced by MC tuning has not been evaluated yet Physics results from ALEPH - Andrea Venturi - INFN Pisa / CERN

  18. CR is expected to affect mainly low momentum particles and particles away from the jet core CR from the W mass • Measure the variation of the W mass obtained removing progressively low momentum particles (pcut analysis) or “far away” particles (cone analysis) • The following results have been obtained with the pcut analysis • The slope of the W mass measurement is compared to the MC predictions. Mass shift Momentum cut Physics results from ALEPH - Andrea Venturi - INFN Pisa / CERN

  19. Ariadne2 (CR) model predicts a fairly large mass shift (~70-80 MeV) but quite insensitive to momentum and cone cuts CR from the W mass • Very preliminary results: • conservative systematics and bias • improved “calibration” studies to be done Semileptonic events control sample Fully hadronic events Physics results from ALEPH - Andrea Venturi - INFN Pisa / CERN

  20. VERY preliminary study Relative error variation wrt no Pcut analysis It is sensitive to CR It can differentiate models In particular AR2 CR from the W mass statistical error Physics results from ALEPH - Andrea Venturi - INFN Pisa / CERN

  21. Final results(CERN-EP/2002-033): From SM to new physics: g’s final states • Acoplanar photons • ee  XX  YYgg: s < 0.1 – 0.04 pb • ee co1co1 gg: Mc > 98.8 GeV • Single photon • Nn = 2.86  0.09 • ee  XY  YYg: s < 0.25 – 0.05 pb • Super-light gravitino > 1.3 10-5 eV • Gravity with extra dimension: graviton mass limit: MD > 1.26 – 0.57 TeV (d=2-6) • Collinear photons • Gravity with extra dimension: string scale • Contact interactions:L6 > 1.35 TeV, L7 > 0.74 TeV , L8 > 21.4 GeV • Excited electron: M > 213 GeV (fg = 1) Physics results from ALEPH - Andrea Venturi - INFN Pisa / CERN

  22. Final results with full LEPII data CERN-EP/2002-042 Multijet (with one b) final state (with or without leptons) e ~ 3% (lepton) , ~ 13.5% (hadron) including BR’s Single top production limits ALEPH limits • 24 candidates in data (20.1 expected) • BR(tZc)+BR(tZu)<14% (95% CL) • (no g coupling, mtop=174 GeV) Physics results from ALEPH - Andrea Venturi - INFN Pisa / CERN

  23. Small mass differences with mass unification only if M2 very large More “natural” with AMSB Dedicated analysis to cover the hole between: Long-lived charginos: search for heavy stable charged particles Chargino’s decay products can trigger DAQ Search for ISR g plus soft tracks compatible with gc+c- production and decay Charginos nearly degenerate with neutralino Gaugino region Higgsino region • Mc> 88 GeV (heavy sfermions) • (Phys. Lett B533 (2002) 223) Physics results from ALEPH - Andrea Venturi - INFN Pisa / CERN

  24. Physics results from ALEPH - Andrea Venturi - INFN Pisa / CERN

  25. Framework : MSSM LSP = c01 Mass unification “Standard” analyses: Chargino and Neutralino searches Squarks and sleptons Higgs Boson If stau mixing ft is let free c  ,c0  can be dominating Dm( - c0) can be small: soft t’s in final state Additional searches: eec+ c-  tnc0tnc0 acoplanar t’s pairs (large Dm), ISR g+soft tracks (small Dm) ee c01c02  c0  tc0tc0single t(small Dm) ee c02c02   ttc0ttc02-4 t’s final state LSP mass: toward an absolute limit Physics results from ALEPH - Andrea Venturi - INFN Pisa / CERN

  26. LSP limit m1/2 vs m0 An example:m=-1000 GeV tanb=35: ft = 0 - 40 I – chargino 3-bodies Standard analyses New t analyses ISR g analysis II – chargino 2 - bodies tanb=35 ft = 0 III - t’s final states Charginos + ISR Selectrons MLSP > 41.6 GeV tanb=35 ft = 40 Physics results from ALEPH - Andrea Venturi - INFN Pisa / CERN

  27. Very preliminary Y2K data only Gluino is LSP can be produced at LEP II R-parity conserved  R-hadrons s-top decays into gluino LSP • MC simulation • gluino parton shower in PYTHIA • R-hadrons interact as heavy pions • Missing energy is not always present • Selection of acoplanar jets • depends on DM • efficiencies: 10-22 % • 4f background is subtracted Physics results from ALEPH - Andrea Venturi - INFN Pisa / CERN

  28. Flavour-independent Higgs boson search (CERN-EP/2002-027) Only HZ  qqqq analysis has been modified with respect to the standard Higgs boson search No b-tagging + estimators of WW and HZ hypothesis Search of Higgs boson with non-standard decays BR(had)+ BR(tt)= 1 :MH > 109.1 GeV MH > 110.6 GeV MH > 112.4 GeV BR(had)*s/sSM BR(tt)*s/sSM Hadronic final state limits tt final state limits MH GeV MH GeV Physics results from ALEPH - Andrea Venturi - INFN Pisa / CERN

  29. Search for gg decays of a Higgs boson (CERN-EP/2002-044): LEP I + LEP II Looking for events with two g’s +: Missing energy (Hnn) 2-4 charged tracks (Hll) > 5 tracks (Hqq) Search of Higgs boson with non-standard decays Fermiophobic Higgs: M>105.4 GeV Physics results from ALEPH - Andrea Venturi - INFN Pisa / CERN

  30. Summary and conclusions • ALEPH is still obtaining interesting results from LEP I data • Exclusion limits from searches are becoming more and more general • More exotic models have been explored • Progress in understanding the main systematics of the W mass measurement (LEP-wide joint effort) • See you in Winter 2003 with other (final) results: 4f cross sections, searches, W mass, … Physics results from ALEPH - Andrea Venturi - INFN Pisa / CERN

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