1 RECENT RESULTS AND FUTURE PROSPECTS IN TAU PHYSICS: HIGHLIGHTS OF THE 10th WORKSHOP ON TAU PHYSICS AT NOVOSIBIRSK Martin Perl

2 The final excellent summary talk by W. Marciano is not posted yet, but one of the excellent summary talks by G. Lafferty is posted. by

3 WORKSHOPS ON TAU PHYSICS A Bit of History: 10 th Workshop: Novosibirsk Budker Institute for Nuclear Research Chaired by Simon Eidelman 1 st Workshop organized by Michael Davier in th Workshop in Manchester, 2010

4 Budker Institute 0f Nuclear Research : Gersh Itskovich Budker present: Alexander N. Skrinsky VEPP-2000 VEPP-4M

5 6 hours flying time

6 Alwyn, Kim E.Alwyn, Kim E. MANCHESTER U Davier, MichelDavier, Michel ORSAY, LAL Giorgi, MarcelloGiorgi, Marcello INFN, PISA Lund, ParkerLund, Parker UC, IRVINE Mazur, Michael Mazur, Michael UC, SANTA BARBARA Nugent, IanNugent, Ian VICTORIA U Roney, MichaelRoney, Michael VICTORIA U Schenk, StefanSchenk, Stefan HEIDELBERG U., PHYS. INST West, TimothyWest, Timothy MANCHESTER U. Wren, AdamWren, Adam ROYAL HOLLOWAY - BEDFORD COLL BABAR colleagues who spoke on tau physics at Workshop Lafferty, George (Manchester) gave two superb summary talks.

7 Some Tau Physics Topics Branching fractions and leptonic universality Lepton-flavor violation

8 Branching fractions and leptonic universality B (     )/B  e    e  g  /g e =1.0036± B    /B(  →   ) g  /g  =0.9859± ? from Ian Nugent

9 Have reached down to few x From Y.Miyazaki (Nagoya) Lepton-flavor violation

10 LFV prediction by model Some predictions are already excluded by the present results. ? ? Some can be tested soon by combined statistics of Babar and Belle From Marcello Giorgi

11 Search for   l - l + l -  U in units of No signal observed

12 Related Muon Physics Muon lifetime Lepton-flavor violation (g-2) 

13 from Kevin Lynch The MuLan Experiment at PSI Measuring the muon lifetime to 1ppm Muon lifetime

14 SUSY SU(5) predictions: BR(   e  )   A  eA  Long history of searches. 1.2  Last result: MEGA (1999) BR < 1.2  Lepton-flavor violation  e 

15 MEG Experiment at PSI From Oleg Kiselev Looking for  e  at level !

16 New Considerations on Theoretical Calculation of a  = (g  -2)/2 From reports by S. Eidelman and M. Davier

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18 Hadrnic Vacuum Polarization and Muon (g –2)     had 

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21  BaBar analysis of  and  ISR processes completed  Absolute  cross section agrees with NLO QED within 1.2%  Preliminary results available for  in the range GeV  Comparison with results from earlier experiments  discrepancy with CMD-2 and SND mostly below   Large disagreement with KLOE  Better agreement with  results, especially Belle   Contribution to a  from BaBar agrees better with  results   Deviation between BNL measurement and theory prediction significantly reduced using BaBar  data a  [exp ] – a  [SM ]=(27.5 ± 8.4)  10 –10  (14.0  8.4)  10  10 Davier Conclusions from BABAR

22 Facilities Presently Or Soon Contributing To Tau Physics: VEPP- 4M PEP-2 KEKB BESIII LHC

23 From A. Shamov VEPP- 4M, E beam =1 to 5 GeV L = 2 x 10 31

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25 From A.Zhemchugov(JINR) BESIII (Beijing)

26 BESIII

27 LHC Tau very useful as tool in elucidating but no obvious advantage for studying tau properties at least in early years.

28 Proposed New Facilities That Will Contribute To Tau Physics: Super B Factories (L can reach ) Super Tau-Charm Factory (Novosibirsk) (L can reach )

29 Tau Physics at Tau-Charm Factory and Super B Factory (from George Lafferty summary talks) At or Close to Tau Pair Threshold: Precise mass measurement Strong kinematic constraints on decays of taus produced at rest. Non-tau backgrounds well known from running just below threshold Small radiative corrections Low systematic errors but low cross section

30 Few GeV Above Tau Pair Threshold: Increased cross section but not competitive with Super B Factory for statistics Low systematic errors

31 At Upsilon(4S) High luminosity and high statistics Large backgrounds for hadronic decays

32 Super B Factory Proposal for facility near Rome discussed by M. Giorgi. The proposal is well known at SLAC. Luminosity goal is No report at this Workshop on proposal for facility in Japan. From Babar and Belle we know a great deal about the potential for tau physics at a B factory

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35 Super Tau-Charm Factory also called Super C  Factory New proposal from BINP A.BlinovA.Bogomyagkov A.BondarV.Kiselev I.KoopG.Kurkin E.LevichevP.Logachev S.NikitinI.Okunev V.M.PetrovP.Piminov Yu.Pupkov S.Sinyatkin A.Skrinsky D.Shatilov V.Smaluk P.Vobly

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37 BINP Summary by Levichev C-tau factory with L = cm -2 s -1 seems to be an extremely attractive facility for HEP experiments Crab-waist approach allows us to obtain such luminosity with achievable machine parameters: required beam intensity, low emittance, injection efficiency, polarization features have been already obtained in B- and Phi-factories, light sources, etc. We are in the beginning now and there are many things have to be done (further optimization of the FF design, the DA optimization, Touschek lifetime increase, etc.). But at the same time we have an advantage-ground to start the project: injection facility is under commissioning, tunnels for linac and injection lines are ready, a lot of the facility solutions are based on existing wares and technologies.