1. 1 George Lafferty University of Manchester Charm 2006: International Workshop on Tau-Charm Physics June 5-7 2006, Beijing Tau Physics from the B Factories Combining the strengths of UMIST and The Victoria University of Manchester

2. 2 Topics covered  Tests of the Standard Model  Tau mass and lifetime: lepton universality and CPT  Non-strange hadronic tau decays         and g  -2  5-prong BFs and limits on 7-particle modes  Strange hadronic tau decays  Strange spectral functions      K     and    K     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. 3 Tau-pair production in e  e  collisions at  s = M   The B factories are also  factories  At,  s = M   B B = 1.05 nb and      = 0.89 nb  approximately 1M tau pairs per fb  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. 4 The tau mass and lifetime: test CPT and lepton universality Belle study using 253 fb  Belle: hep-ex/0511038 BaBar: NPPS144(2005)105 BaBar prelim study using 80 fb  BaBar prel.

5. 5 Hadronic tau decays:       and g  -2 Muon magnetic moment anomaly given by a  = (g  -2) / 2 e+e+ ee          

6. 6 Hadronic tau decays:       and g  -2 Belle Belle study using 72 fb  : fits to model of Gounaris and Sakurai BF (       ) = (25.15  0.04  0.31) % hep-ex/0512071

7. 7 Hadronic tau decays:    h   h  BF (    h   h  ) = ( 8.56  0.05  0.42) x 10  BaBar study using 232 fb  Phys Rev D72 (2005) 072001 BF (    h   h  ) kk2f+Tauola for signal Monte Carlo

8. 8 Hadronic tau decays:    h   h  BF (    f  h  ) = ( 3.9  0.7  0.5) x 10  Resonances in final state include   and f 1 (1285) mesons Phys Rev D72 (2005) 072001

9. 9 Hadronic tau decays: Search for         BF (         ) < 3.4 x 10 -6 BF (     ) < 5.4 x 10 -7 at 90% CL BaBar study using 232 fb  Phys Rev D in press  Decay mode allowed, but highly suppressed by phase space  Observation could limit mass of   Interest in multipion decay dynamics  Isobar models predict dominance of  

10. 10 Hadronic tau decays: Search for           BF (          )< 3.0 x 10 -7 BF (       ) < 4.3 x 10 -7 at 90% CL BF (         ) < 2.5 x 10 -7 BaBar study using 232 fb  Phys Rev D72 (2005) 012003

11. 11 Hadronic tau decays: strange spectral functions The route to world-best measurements of |V us | and m s  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 Branching fractions for strange decay modes (from PDG 2005) BaBar and Belle preliminary measurements of  K  are already better than previous world averages … lots more to come (e.g. Tau 2006)  

12. 12 Hadronic tau decays:    K    BaBar preliminary study using 124 fb  : evidence for higher mass resonances BF (    K    ) = (0.438  0.004  0.022) %

13. 13 Hadronic tau decays:    K  s   Belle study using 351 fb  : Fits to mass spectrum need more than K*(892) BF (    K  s   ) = (0.391  0.004  0.014) %

14. 14 Lepton flavour violation in  decays

15. 15 Lepton flavour violation in  decays BaBarBelle          e   0.7 1.1 3.4 3.8 Creates most interest Enhanced if m  << m  ~ m     e  e  e             l  l  l’ 2.0 1.9 1 – 3 3.5 2.0 2 – 4 Can expose SUSY Higgs    l  h  h     l  h  h     l  V 0    l  K  s 1 – 3 0.7 – 5 1.6 – 8 2.0 – 7.7 0.5 Violates lepton number Limits MSSM (small tan  ) Limits R-violating SUSY Limits scale for dim-6 fermionic operators    l     ’ 2 – 10 Limits MSSM (large tan  )      0.7 1.4 Violates B-L Conserves B-L Current BF upper limits for LFV using up to ~ a few x 100 fb  all    

16. 16 Recent Belle results from 158 fb   MSSM with small tan  could give BF(        ~ 10   Also    e    and     constrain models with heavy Dirac neutrinos  Limits also on models with dimension-six effective fermionic operators that induce  –  mixing Lepton flavour violation: Search for  lepton + hh/V

17. 17 Lepton flavour violation: Search for       Belle: BF (       ) < 3.4 x 10  MSSM SUSY Belle

18. 18 Lepton flavour violation: Search for       BaBar: BF (       ) < 8.6 x 10  MSSM SUSY with seesaw

19. 19 The outlook  Current results based on ~ a few x 100 fb   Expected final BaBar and Belle datasets: 2 x > 1 ab   > 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   efficiency)  Potential for lots more  physics:  Improved limits on LFV (down to ~ 10  for some channels)  possible evidence for New Physics  can probe regions that are inaccessible at LHC  Strange spectral functions should give best measurements of |V us |, m s (and maybe  s )  Important contributions to resolving the muon g  2 problems  Structure of non-strange and strange hadronic states  CP-violation in  decays

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