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Tau Physics from the B Factories

Tau Physics from the B Factories. George Lafferty University of Manchester Charm 2006: International Workshop on Tau-Charm Physics June 5-7 2006, Beijing. Combining the strengths of UMIST and The Victoria University of Manchester. Topics covered. Tests of the Standard Model

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Tau Physics from the B Factories

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  1. Tau Physics from the B Factories George Lafferty University of Manchester Charm 2006: International Workshop on Tau-Charm Physics June 5-72006, Beijing Combining the strengths of UMIST and The Victoria University of Manchester

  2. Topics covered • Tests of the Standard Model • Tau mass and lifetime: lepton • universality and CPT • Non-strange hadronic tau decays • t - p-p0n and gm-2 • 5-prong BFs and limits on 7-particle modes • Strange hadronic tau decays • Strange spectral functions • t -K-p0n and t -K0p-n • Lepton-flavour violation in tau production • and decay • Constraints on physics BSM • Outlook for tau physics at the B factories With thanks to Olya Igonkina and everyone else whose slides I have borrowed from

  3. Tau-pair production in e+e- collisions at s = MU • The B factories are also t factories • At , s = MUsB B = 1.05 nb and s t+t- = 0.89 nb  • approximately 1M tau pairs per fb-1 • samples of ~400M (BaBar) and ~600M (Belle) tau pairs • c.f. ~100k pairs for each LEP experiment and 14M at CLEO • Much cleaner event environment at LEP means much lower • systematic errors there: • LEP is better for measuring the large branching fractions • B factories are better for rare and forbidden decays • Ongoing work at B factories to reduce systematic errors • Huge statistics at B factories allow detailed study of the structure • of the hadronic mass spectra

  4. The tau mass and lifetime: test CPT and lepton universality Belle study using 253 fb-1 Belle: hep-ex/0511038 BaBar prelim study using 80 fb-1 BaBar prel. BaBar: NPPS144(2005)105

  5. Hadronic tau decays: t- p-p0n and gm-2 Muon magnetic moment anomaly given by am = (gm-2) / 2 e+ p + n p 0 e- p - t - p -

  6. Hadronic tau decays: t- p-p0n and gm-2 Belle study using 72 fb-1 : fits to model of Gounaris and Sakurai BF (t- p-p0n) = (25.15  0.04  0.31) % Belle hep-ex/0512071

  7. Hadronic tau decays:t- 3h-2h+ n BaBar study using 232 fb-1 kk2f+Tauola for signal Monte Carlo BF (t- 3h-2h+ n) BF (t- 3h-2h+ n) = (8.56  0.05  0.42) x 10-4 Phys Rev D72 (2005) 072001

  8. Hadronic tau decays:t- 3h-2h+ n Resonances in final state include r(770)0 and f1(1285) mesons BF (t-f1h- n) = (3.9  0.7  0.5) x 10-4 Phys Rev D72 (2005) 072001

  9. Hadronic tau decays: Search for t- 3p-2p+ 2p0 n BaBar study using 232 fb-1 • Decay mode allowed, but highly suppressed by phase space • Observation could limit mass of nt • Interest in multipion decay dynamics • Isobar models predict dominance of 2wp-n BF (t- 3p-2p+ 2p 0n) < 3.4 x 10-6 BF (t- 2wp- n) < 5.4 x 10-7 at 90% CL Phys Rev D in press

  10. Hadronic tau decays: Search for t- 4p-3p+ (p0)n BaBar study using 232 fb-1 BF (t- 4p-3p+ (p 0)n) < 3.0 x 10-7 BF (t- 4p-3p+ n) < 4.3 x 10-7 at 90% CL BF (t- 4p-3p+ p 0n) < 2.5 x 10-7 Phys Rev D72 (2005) 012003

  11. Hadronic tau decays: strange spectral functions The route to world-best measurements of |Vus| and ms Branching fractions for strange decay modes (from PDG 2005)  10-3 • All measurements so far are limited by statistics • The total error is important; large errors on small BFs can dominate • Systematic errors are highly correlated (e.g. charged, neutral kaon ID) and scale with BF BaBar and Belle preliminary measurements of t Kpn are already better than previous world averages … lots more to come (e.g. Tau 2006)

  12. Hadronic tau decays: t-K-p0n BaBar preliminary study using 124 fb-1 : evidence for higher mass resonances BF (t-K-p0n) = (0.438  0.004  0.022) %

  13. Hadronic tau decays: t-K0sp-n Belle study using 351 fb-1 : Fits to mass spectrum need more than K*(892) BF (t-K0sp-n) = (0.391  0.004  0.014) %

  14. Lepton flavour violation in t decays

  15. Lepton flavour violation in t decays Current BF upper limits for LFV using up to ~ a few x 100 fb-1 all  10-7 - +

  16. Lepton flavour violation:Search for t  lepton + hh/V Recent Belle results from 158 fb-1 • MSSM with small tanb could • give BF(t - m-r0) ~ 10-8 • Also t - e-r0 and m-r0 constrain • models with heavy Dirac • neutrinos • Limits also on models with • dimension-six effective fermionic • operators that induce t – m mixing

  17. Lepton flavour violation:Search for t- m- h Belle: BF (t- m-h) < 3.4 x 10-7 MSSM SUSY Belle

  18. Lepton flavour violation:Search for t- m- g BaBar: BF (t- m- g) < 8.6 x 10-8 MSSM SUSY with seesaw

  19. The outlook • Current results based on ~ a few x 100 fb-1 • Expected final BaBar and Belle datasets: 2 x > 1 ab-1 •  > 2 billion -pairs by end 2008 • Statistical accuracy will improve by up to ~ 5 • Improvements in muon detection (BaBar), and further work • ongoing to reduce systematic errors (e.g. on p0 efficiency) • Potential for lots more  physics: • Improved limits on LFV (down to ~ 10-8 for some channels) • possible evidence for New Physics • can probe regions that are inaccessible at LHC • Strange spectral functions should give best measurements of |Vus|, ms (and maybe as) • Important contributions to resolving the muon g  2 problems • Structure of non-strange and strange hadronic states • CP-violation in t decays

  20. And to finish … on behalf of the UK Tourist Board … another great wall … Hadrian’s Wall, built 122-132 AD

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