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George LaffertyUniversity of Manchester

Charm 2006: International Workshop on Tau-Charm PhysicsJune 5-7 2006, Beijing

Tau Physics from the B Factories

Combining the strengths of UMIST andThe Victoria University of Manchester

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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

KandK

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

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Tau-pair production in ee 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

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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.

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Hadronic tau decays: and g-2

Muon magnetic moment anomaly given by a = (g-2) / 2

e+

e

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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

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Hadronic tau decays: hh

BF (hh) = (8.56 0.05 0.42) x 10

BaBar study using 232 fb

Phys Rev D72 (2005) 072001

BF (hh) kk2f+Tauola for signal Monte Carlo

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Hadronic tau decays: hh

BF (fh) = (3.9 0.7 0.5) x 10

Resonances in final state include and f1(1285) mesons

Phys Rev D72 (2005) 072001

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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

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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

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Hadronic tau decays: strange spectral functions

The route to world-best measurements of |Vus| and ms

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)

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Hadronic tau decays: K

BaBar preliminary study using 124 fb: evidence for higher mass resonances

BF (K) = (0.438 0.004 0.022) %

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Hadronic tau decays: Ks

Belle study using 351 fb: Fits to mass spectrum need more than K*(892)

BF (Ks) = (0.391 0.004 0.014) %

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Lepton flavour violation in decays

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Lepton flavour violation in decays

BaBar Belle

e

0.7

1.1

3.4

3.8

Creates most interest

Enhanced if m << m ~ m

eee

lll’

2.0

1.9

1 – 3

3.5

2.0

2 – 4

Can expose SUSY Higgs

lhh

lhh

lV0

lKs

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

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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

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Lepton flavour violation: Search for

Belle: BF () < 3.4 x 10

MSSM SUSY

Belle

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Lepton flavour violation: Search for

BaBar: BF () < 8.6 x 10

MSSM SUSY with seesaw

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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 |Vus|, ms (and maybe s)

Important contributions to resolving the muon g 2 problems Structure of non-strange and strange hadronic states CP-violation in decays

20Hadrian’s Wall, built 122-132 AD

And to finish … on behalf of the UK Tourist Board … another great wall …