Swagato Banerjee. DESY Seminar, 16 January 2007

Transcription

1 TAU PHYSICS AT BABAR Swagato Banerjee On behalf of the BABAR collaboration DESY Seminar, 16 January 007 (Page: 1)

2 The process: e + e τ + τ Production Decays τ BABAR (Page: )

3 τ Branching Fractions (c.f. A. Stahl) by topology by leptonic/hadronic by resonances by exclusive π modes τ BABAR (Page: 3)

4 τ Physics at BABAR τ -lifetime measurement Tests of CPT, Lepton-universality τ -decays with strange quarks Route to world s best measurements of V us, m s New decay modes via φ resonance observed High Multiplicity hadronic states Rich Resonance sub-structures in 3, 5 prong τ decays Limits on τ decaying into 7/8 pions Direct Searches for New Physics Lepton Flavor, Lepton Number Violation in decays: τ lγ, τ lπ 0 /η/η, τ lll, τ lhh in production: ee lτ Baryon Number Violation τ Λπ/K, τ Λπ/K CP Violation in lepton sector τ BABAR (Page: 4)

5 SLAC-Based B-Factory: PEP II & BABAR The BABAR Detector: τ BABAR (Page: 5)

6 PEP II Records: better than ever 4 design τ BABAR (Page: 6)

7 BABAR: a τ -Factory B-Factories are also τ-factories s = GeV (Υ (4S)): σ(e + e BB) = 1.1 nb σ(e + e τ + τ ) = 0.9 nb Experiment # of τ-pairs LEP CLEO BABAR Precision measurements: systematics limited on-going efforts Ideal for search of rare decays By end of data-taking (Sep 008): L = cm sec 1, L > 900 fb 1 τ BABAR (Page: 7)

8 τ -pair events at BABAR Well separated in space unique signature: Leptonic + Hadronic decay Divide event into hemispheres in CM frame to thrust axis most analyses use leptonic tags τ BABAR (Page: 8)

9 τ -Lifetime BaBar (Preliminary): L = 80 fb 1 (Tau04, Nara) Nucl.Phys. B (Proc.Suppl.) 144 (005) 105 τ τ = (89.40 ± 0.91 stat ± 0.90 syst )fs PDG06: τ τ = (90.6 ± 1.0)fs Test of CPT: τ τ τ τ + τ τ +τ = (0.1±0.3 stat ±X τ + syst )% τ BABAR (Page: 9)

10 τ -Lifetime Lepton Universality Expect: B e = B µ ( ± ) τ = τ (163.1±1.4)fs PDG06: B µ B e = (0.975 ± ) τ BABAR (Page: 10)

11 Lepton Universality Charged Current Universality: A.Pich, Tau06 Ratio of Neutral/Charged Current events in muon (anti)neutrino nucleon scattering measured gl = ± , which is 3σ < SM prediction: gl = NuTev anomaly Loinaz et.al., hep-ph/010193: G F = G µ (1 + ε), ε = τ-decays: most promising place to look for violation O(10 3 ) τ BABAR (Page: 11)

12 Hadronic τ decays R τ Γ(τ ν τ +Hadrons) Γ(τ ν τ e ν e ) = N C + O(α s ) R τ = 1 B e B µ B e = (3.639 ± 0.011) [PDG06] Initial state represents perfect QCD vacuum τ h ν τ probes hadronic V A current: h d θ γ µ (1 γ 5 )u 0, where d θ = cos θ C d + sin θ C s Cabibbo allowed non-strange and suppressed strange decays Ideal for measurements of fundamental quantities: V us, m s, α s Several resonance (sub-)structure waiting to be observed τ BABAR (Page: 1)

13 τ -decays with strange quarks Excellent K/π separation using dedx, Cherenkov angle Inclusive study of strange spectral functions from final states with net strangeness of unity (contributing to 3% of all τ decays) Route to world s best measurements of: V us O(1%) [presently from 3-body leptonic kaon decays], m s 10 MeV [presently from Lattice QCD] Preliminary B(τ K π 0 ν τ ), B(τ K π π + ν τ ) reported with better precision than world average (Tau06, Pisa) τ BABAR (Page: 13)

14 τ K π 0 ν τ events (Tau06, Pisa) 78K e/µ-tagged events: τ + τ mostly; qq, µ + µ small Efficiency:.3%, Purity: 51.9% Backgrounds come from K/π mis-id & additional π 0 (s) in event Dominant systematics come from π 0 reconstruction in-efficiency τ + τ qq µ + µ CLEO 94 (5.1±1.0±0.7) 10-3 ALEPH 99 (4.44±0.6±0.4) 10 OPAL 04 (4.71±0.59±0.3) 10 PDG 06 Average -3 (4.54±0.30) BaBar Preliminary -3 (4.39±0.03±0.1) BF ( 10 ) τ BABAR (Page: 14)

15 1.7M e/µ-tagged τ h h h + ν τ decays ) π π π + Events/(0MeV/c BABAR preliminary ) K π π + Events/(0MeV/c BABAR preliminary ) Events/(0MeV/c M (GeV/c ) K π K + BABAR preliminary ) Events/(5MeV/c M (GeV/c ) K K K + BABAR preliminary M (GeV/c ) MC: M (GeV/c ) τ BABAR (Page: 15)

16 τ h h h + ν τ (Tau06, Pisa) π π π + K π π + CLEO 03 - (9.13±0.05±0.46) 10 PDG 06 Global Fit - (9.0±0.08) 10 1 BaBar Preliminary - (9.11±0.01±0.6) 10 ALEPH 98 (.14±0.37±0.9) 10 CLEO 99 (3.46±0.3±0.56) 10 CLEO 03 (3.84±0.14±0.38) 10 OPAL 04 (4.15±0.53±0.40) 10 PDG 06 Average -3 (3.3±0.5) ALEPH 98 (1.63±0.1±0.17) 10 CLEO 99 (1.45±0.13±0.8) 10 OPAL 00 (0.87±0.56±0.40) 10 CLEO 03 (1.55±0.06±0.09) 10 PDG 06 Average -3 (1.54±0.09) 10 K π K + 1 BaBar Preliminary -3 (1.373±0.011±0.040) BF ( 10 ) -3 BF ( 10 ) 1 BaBar Preliminary -3 (.88±0.0±0.11) ALEPH 98-4 < CLEO 03-5 < %CL BaBar Preliminary K K K + -5 (1.59±0.14±0.11) 10-3 BF ( 10 ) BF ( 10 ) τ BABAR (Page: 16)

17 New decay modes via φ resonance ) Events/(5MeV/c φ K π K + BABAR preliminary ) Entries/(5MeV/c φ K K K + BABAR preliminary MC: (GeV/c M K + - K ) (GeV/c ) M K + - K FIRST MEASUREMENTS of π φ and inclusive K K K + states: B(τ π φν τ ) = (3.49 ± 0.55 ± 0.3) 10 5 (Significance: 5.5σ) B(τ K φν τ ) = (3.48 ± 0.0 ± 0.6) 10 5 (Significance: 10.6σ) τ K φν τ consistent with saturating τ K K K + ν τ channel Consistent with Belle: B(τ K φν τ ) = (4.06 ± 0.5 ± 0.6) 10 5 τ BABAR (Page: 17)

18 3 prong τ -decays via ω resonance BABAR (Preliminary, Tau06): B(τ π π π + π 0 ν τ ) = (4.39 ± 0.01 ± 0.1) 10 Entries π π π + π 0 BABAR preliminary PDG06 Average (Aleph, CLEO): (4.55 ± 0.13) m(4π) (GeV/c ) BABAR (Preliminary, Tau06): B(τ π π } π {{ + π } 0 ν τ ) = ω (1.97 ± 0.01 ± 0.10) 10 PDG06 Average (Aleph, CLEO): (1.9 ± 0.07) 10 Events / ( GeV/c ) 5000 BABAR preliminary π π + π m(3π) (GeV/c ) τ BABAR (Page: 18)

19 3 & 5 prong τ -decays via f 1 resonance BABAR (Preliminary, Tau06): (160 ± 56) η γγ candidates B(τ π π π + ην τ ) = (1.84 ± 0.09 ± 0.13) 10 4 PDG06: (.3 ± 0.5) 10 4 BABAR (Preliminary, Tau06): B(τ π π π + ην }{{} τ ) = f 1 (185) (3.83 ± 0.3 ± 0.0 ± 1.18) 10 4 BABAR, PRD7(005)07001: B(τ π f 1 ν τ ) = (3.9 ± 0.7 ± 0.5) 10 4 using f 1 (185) π π π + π + in 5 prong τ decays Events/0.005 GeV/c Events/0.006 GeV/c f 1 π π + η BABAR preliminary f 1 π π + Mass (GeV/c ) BABAR Mass (GeV/c ) τ BABAR (Page: 19)

20 Rich Resonance Substructure Ratio of Branching Fractions (BABAR Preliminary, Tau06): R ( τ π ω π π π + π 0 ν τ τ π π π + π 0 ν τ ) = ± 0.00 ± R ( τ π f 1 π π π + ην τ τ π π π + ην τ ) = 0.73 ± 0.01 ± 0.04 J P G = 0 + current: τ π π } π {{ + π } 0 ν τ, τ π π π + η }{{} η η nd Class Currents (Weinberg, 1958) waiting to be discovered Suppressed by G-parity conservation Expected at the level of isospin breaking m u m d We see no evidence of π η signal in τ π π π + ην τ BABAR Preliminary, Tau06: B(τ π η ν τ ) < % C.L. CLEO: Upper Limit = % C.L. ν τ τ BABAR (Page: 0)

21 τ decays with 7 or 8 pion final states B(τ 7πν) = dynamics phasespace B(τ 5πν) 6 }{{}}{{} Nussinov-Purohit, PRD65 (00) Resonance sub-structures may enhance multi-pion final states. 1-7 topology simulation Spoilers: Looping tracks BABAR, PRD7 (005) (L = 3. fb 1 ): B(τ 4π 3π + (π 0 )ν τ ) < (CLEO (1997): ) B(τ 4π 3π + ν τ ) < B(τ 4π 3π + π 0 ν τ ) < BABAR, PRD74 (006) (L = 3. fb 1 ): B(τ 3π π + π 0 ν τ ) < (CLEO (1994): ) B(τ π ων τ ) < τ BABAR (Page: 1)

22 Search for New Physics Lepton flavor violation (LFV) not forbidden by SM gauge symmetry most new models naturally include LFV vertex In SM, LF is conserved for zero degenerate ν masses Now we have clear indication that ν s have finite mass Lepton Flavor is violated in Nature: but by how much? SM extended to include finite ν mass and mixing predicts LFV τ ν ν τ µ X W µ γ B(τ ± µ ± γ)[lee-shrock, Phys. Rev. D 16, 1444 (1977)] ( ) m 3 sin θ mix B(τ µ ν µ ν τ ) = 3α 18π M W With 10 3 ev, M W O(10 11 ) ev O(10 54 ) (θ mix : max)... many orders below experimental sensitivity! Observation for LFV unambiguous signature of new physics τ BABAR (Page: )

23 LFV τ decays Mass dependent couplings enhance tau LFV w.r.t. lighter leptons Some models predict LFV upto existing experimental bounds eg. SUSY models: non-diagonal slepton mass matrix LFV Normal (Inverted) hierarchy for slepton τ µγ ( τ eγ) O(10 6 ) (CLEO 00) (J. Ellis, J. Hisano, M. Raidal and Y. Shimizu, Phys. Rev. D 66 (00) ) τ BABAR (Page: 3)

24 LFV τ decays Neutrinoless and 3 body τ decays have different sensitivity B(τ lγ) B(τ lll) SM+ν-mixing (PRL95(005)4180,EPJC8(1999)513) SUSY Higgs (PLB549(00)159, PLB566(003)17) SM+Heavy Majorana ν R (PRD66(00)034008) Non-Universal Z (PLB547(00)5) SUSY SO(10) (NPB649(003)189, PRD68(003)03301) msugra+seesaw (EPJC14(000)319, PRD66(00)115013) MSSM+seesaw (PRD66 (00) ) B(τ µγ): B(τ µµµ): B(τ µη) = 1.5 : 1 : 8.4 ν µ τ Illustrations: χ γ τ µ µ H 0 µ + Search for τ lγ/π 0 /η/η, τ lll, τ lhh (l = e, µ; h = π, K) τ BABAR (Page: 4)

25 Signal Characteristics τ µγ simulation m µγ m τ CM Frame: E = P µ + m µ + E γ s/ 0 τ BABAR (Page: 5)

26 Signal Characteristics (GeV) M EC (Energy, Mass) daughters ( s, m τ ) (upto resolution & radiation) Photon at edge of acceptance Initial State Radiation E (GeV) τ µγ simulation E = E rec s 0 σ( E) 50 MeV M EC (σ 9 MeV) Beam energy constrained mass after vertexing γ at µ POCA(XY) [Inv. mass: σ 4 MeV ] Signal Region: ± σ around ( E, M EC ) τ BABAR (Page: 6)

27 Signal Characteristics (GeV) M EC (Energy, Mass) daughters ( s, m τ ) (upto resolution & radiation) E (GeV) τ µγ simulation E = E rec s 0 σ( E) 50 MeV M EC (σ 9 MeV) Beam energy constrained mass after vertexing γ at µ POCA(XY) [Inv. mass: σ 4 MeV ] Blinded Region: ± 3 σ around ( E, M EC ) τ BABAR (Page: 6)

28 e + e τ + τ (clean environment) τ lγ l 1 or 3 prong γ ν Signal Side Tag Side Backgrounds: τ lll (τ lhh ) l 1 prong l(h) l(h) ν Signal Side Tag Side Backgrounds: τ eγ (τ µγ): τ l l + l : Radiative Bhabha (di-muon) Bhabha, di-muon τ + τ γ(τ lνν) τ l + l l, τ lhh : qq (γ) τ + τ, qq Missing momentum in Signal-side Signal: τ + τ : e + e, µ + µ, qq: Missing momentum in Tag-side Signal: τ + τ : e + e, µ + µ, qq: τ BABAR (Page: 7)

29 Signal vs. Background ln(missing pt/ebeam) Cut-based Selection τ ± e ± γ e + e τ + τ γ Neural Net / tag-side decay Events/ Data µ ± γ τ + τ- + - e-tag µ µ qq eγ-tag µ-tag h-tag 10 e + e e + e γ hγ-tag 3h-tag 10 (Tagside Missing Mass )( GeV ) NN Output τ BABAR (Page: 8)

30 Background estimation: τ lγ/p 0 τ ± l ± γ: Background rate from PDF(m EC ) in ±σ band in E (GeV/c m EC Events/(0.05 GeV/c ) ) 10 5 Data Bhabha e + e - τ + τ - τ ± e ± γ E (GeV) (GeV/c ) m EC τ ± l ± P 0 : Unbinned maximum likelihood fit to (m EC, E) 3σ GSB N data σ = σ PDF tot GSB 3σ PDF N data tot GSB 3σ τ BABAR (Page: 9)

31 τ ± l ± P 0 ) (GeV/c 1.8 hep-ex/ (subm. to PRL) e π 0 (π 0 γγ) e η (η γγ) e η (η π + π - π 0 ) + π - + e η (η π η) e η (η π π - γ) M EC 1.6 BABAR µ π 0 (π 0 γγ) µ η (η γγ) + µ η (η π π - π 0 ) + µ η (η π π - η) + µ η (η π π - γ) E (GeV) N bkg /channel = ( ), Total expected = 3.1, Observed = τ BABAR (Page: 30)

32 Background estimation: τ lll,lhh qq: uniform E (GeV) qq E (GeV) QED QED: E M (GeV) M (GeV) τ + τ : M 0 E 0 E (GeV) ττ E (GeV) data τ lll: after PID & Preselection M (GeV) M (GeV) -dim PDF s: shape from MC/control sample, rate fitted to Data τ BABAR (Page: 31)

33 τ lll PRL9(004)11801 E (GeV) τ e - e + e - - τ - µ + e - e τ - e - µ + µ - BABAR τ - µ - e + e - τ e + µ µ τ - µ - µ + µ M (GeV/c N bkg /channel = (0. 1.5), Total expected = 3.4, Observed = 3 τ BABAR (Page: 3) )

34 τ lhh Lepton Flavor violating modes: τ l h + h Lepton Number violating modes: τ l + h h PRL95(005) E (GeV) e - + τ K K τ - e - K π- - τ- e - π + K τ - e - π + π- BABAR e + - τ K K τ- e + K π- τ - e + π - π τ µ K K τ - µ K π µ π + - τ K τ - µ π + π τ µ K K τ- µ K π- + τ - µ π - π M (GeV/c ) N bkg /channel = ( ), Total expected = 11.3, Observed = 10 τ BABAR (Page: 33)

35 No signal found... Upper Limit: B 90 UL = N 90 UL /(N τ ε) ε: high statistics signal MC simulated for different Data-taking periods ε = Trigger. Reco. Topology. PID. Cuts. Signal Box Cumulative: 90% 70% 70% 50% 50% 50% 90% 63% 44% % 11% ~5% σ τ + τ (10.6 GeV) 0.89 nb, L 339 fb 1 ( BABAR Summer 006) N τ = L σ τ + τ NUL: 90 90% C.L. Upper Limit for (N obs, N bkg ) from Data Naive Sensitivity : N 90 UL =.3 N bkg, N bkg O(1) B 90 UL O(10 7 ) τ BABAR (Page: 34)

36 B-Factories: Status Channel BABAR BELLE BUL 90 ) L ( fb 1 ) BUL 90 ) L ( fb 1 ) τ ± e ± γ PRL96(006)41801 ICHEP06: hep-ex/ τ ± µ ± γ PRL95(005)4180 ICHEP06: hep-ex/ τ ± e ± π TAU06: hep-ex/ ICHEP06: hep-ex/ τ ± µ ± π TAU06: hep-ex/ ICHEP06: hep-ex/ τ ± e ± η TAU06: hep-ex/ ICHEP06: hep-ex/ τ ± µ ± η TAU06: hep-ex/ ICHEP06: hep-ex/ τ lll (1-3) 91.5 (-4) 87.1 PRL9(004)11801 PLB589(004)103 τ lhh (1-5) 1.4 (-16) PRL95(005) NPB(Proc)144(005)173 τ BABAR (Page: 35)

37 B-Factories: Combinations (Tau06, Pisa) Signal and Background PDF parameterizations vary Efficiency combined by weighting with luminosity Observed & background events added (asymmetric errors averaged) 10 6 Toy MC: Poisson distribution with mean (s + b) where signal s = Lσ τ τ B UL (ε ± σ ε ), background (b ± σ b ) are Gaussian PDF s Vary B UL till 10% of toy MCs yield # of events < n obs = # of events observed in the data BUL 90. Average around expected background expected limit. [Ref: Cousins-Highland NIM A30, 331 (199), Barlow CPC 149, 97 (00)] L ε Background events B 90 UL ( 10 8 ) ( fb 1 ) (%) Expected Observed Expected Observed τ ± e ± γ BABAR ± ± BELLE ± BABAR & BELLE ± ± τ ± µ ± γ BABAR ± ± BELLE ± BABAR & BELLE ± ± τ BABAR (Page: 36)

38 B-Factories: Projections B 90 UL = N 90 UL /(N τ ε) τ ± µ ± γ search: Optimize NUL 90 /ε for expected 90% C.L. N 90 UL Baseline: B 90 UL (BaBar 3. fb 1 ) Background free search.3 N obs O(1) Background limited search L B 90 UL 1/L 1/ L BaBar, Belle: 1 ab 1 each (008) L ( ab 1 ) 0.5 (Now) B 90 UL (10 8 ) 10.5 (5) 0.05 (0.7) Super B-Factory: 50 ab 1 B 90 UL < O (10 10 ) / O (10 9 ) no/with Background τ BABAR (Page: 37)

39 LHC expectations N τ / yr (low lumi) W τν Z ττ D S τx B 0 τx B ± τx B S τx More tau s... More backgrounds from ISR/FSR, radiative production... Cleaner Event Signature: 3 prong vertex µ ID m(µµµ) m τ Signal: W τ ν, Backgrounds: Radiation (L. Serin, R. Stroynowski, 1997) For 30 fb 1 data: B(τ µγ) < Signal: Z ττ, Backgrounds: Radiation (E. Barberio, 00) For 30 fb 1 data: B(τ µγ) < Signal: D S τx, Backgrounds: D S µνφ, φ µµ(γ) (A. Stahl, 005) For 100 fb 1 data: B(τ µµµ) < τ BABAR (Page: 38)

40 BABAR Physics Reach Assessment (005) msugra mixing at GUT scale: L = M L L L M ẼẼ Ẽ Model-independent calculation (A.Brignole, A.Rossi, NPB701(004)3) m GUT = GeV µ > 0, A 0 = 0 B(τ µγ) msugra + Seesaw: ν-mixing induces LFV at EW scale via RGE RGE using SPheno B(τ µγ) (W. Porod, CPC153(003)75) Cold Dark Matter: WMAP Data Simulation with micromegas (CPC149(00)103) m νr = GeV, tan β = 55, µ > 0, A 0 = 0, m 0, m 1/, M L, M Ẽ : Diagonal τ BABAR (Page: 39)

41 τ µγ & S φks SUSY SU(5) GUT: Flavor changing right-handed currents Correlations between CP asymmetry in b-s penguins and τ µγ 10 6 B(τ µγ) BABAR BELLE BABAR & BELLE m = 10 3 m 0 m 1/ m g ~ = J. Hisano, Y. Shimizu (PLB565(003)183) tan β = 10, A 0 = 0, m νr = GeV, m ντ = 5 10 ev S φks Current measurement: S(B φk 0 ) = (0.39 ± 0.18) (HFAG, 006) More sensitive B(τ ± µ ± γ) < exclude some regions. τ BABAR (Page: 40)

42 τ lll predictions SUSY + Higgs (A.Brignole, A.Rossi, PLB566(003)17) B(τ 3µ) 10 7 ( tan β 50 )6 ( 100GeV m A ) 4 ( 50 L + 50 R 10 3 ) If Higgs light, s-particles O( TeV), tan β 50 No direct observation, but τ µµµ observable (?) Sensitivity at B-Factories, LHC Non Universal Z (Technicolor) (C.Yue, Y.Zhang, L.Liu, PLB547(00)5) τ lll most sensitive Flavor mixing (k 1 ) = 0., B(τ lll) < 10 8 m Z < 1. TeV τ BABAR (Page: 41)

43 Search for Supersymmetric Higgs Mixing between left-handed smuons and staus with m νr = GeV via seesaw τ ± µ ± η limit translates into exclusion plot in tan β vs. m A plane (M.Sher, PRD66 (00) ) Light and dark shade: m max h and no-mixing stop mixing benchmark models (M. Carena et.al, hep-ph/9913) 95% C.L. from BABAR-BELLE competitive with direct searches at CDF: Higgs τ + τ (310 pb 1 ), D0: Higgs b b (60 pb 1 ), τ + τ (35 pb 1 ); complementary to region excluded by LEP τ BABAR (Page: 4)

44 Summary of Limits on LFV decays B(τ e γ) MARKII CRYSTAL BALL ARGUS DELPHI MARKII B(τ µ γ) ARGUS DELPHI msugra + Seesaw SUSY + SO(10) SUSY + Higgs CLEO BELLE BABAR BELLE BABAR+BELLE Technicolor + Z msugra + Seesaw SUSY + SO(10) SUSY + Higgs CLEO BELLE BABAR BELLE BABAR+BELLE Technicolor + Z Channel BABAR BELLE BABAR & BELLE BUL 90 ) L ( fb 1 ) BUL 90 ) L ( fb 1 ) BUL 90 ) L ( fb 1 ) τ ± e ± γ τ ± µ ± γ τ ± e ± π τ ± µ ± π τ ± e ± η τ ± µ ± η τ ± e ± η τ ± µ ± η τ BABAR (Page: 43)

45 LFV in e + e l + τ production Some theories predict sizeable LFV in e + e l + τ production, even if stringent limits exist on LFV τ -decays J.Bordes, H.-M.Chan, S.T.Tsou, PRD65(00)093006: at s = GeV: σ µτ /σ µµ O(10 4 ) BaBar search: L = 11 fb 1 using τ π ν, τ π π + ν s ( GeV) σµµ σ eτ /σ µµ σ µτ /σ µµ Experiment nb BaBar, PRD75 (031103), nb MARKII, nb OPAL, nb DELPHI, pb OPAL, pb OPAL, pb OPAL, 001 τ BABAR (Page: 44)

46 Baryon Number Violation One of 3 Sakharov s conditions for matter-antimatter asymmetry Angular Momentum conservation B = ± L In lepton baryon + meson decays (B L) = 0 or Many SUSY and superstring inspired models predict B, L violation (B L) gives useful hints to the mechanism of baryon instability Mode (B L) BABAR BELLE hep-ex/ L = 37 fb 1 PLB63(006)51 L = 154 fb 1 τ Λπ conserving τ Λπ violating τ ΛK conserving τ ΛK violating τ BABAR (Page: 45)

47 CP violation in the lepton sector Essential ingredient for matter-antimatter asymmetry CP asymmetry 0.33% expected in τ KS 0π ν τ decays, because of CP impurity in KS 0 (the observed kaons are the mass and not the flavor eigenstates) (Bigi, Sanda: hep-ph/ ) Sources of CP violation in Standard Model are not enough to explain the matter-antimatter asymmetry in the universe τ decays : ideal place to look for new sources of CP violation Expected statistical precision with full BABAR 0.1% Datta, Kiers, London, O Donnell, Szynkman (hep-ph/061016): New Physics can contribute to τ Nπν τ (N = 3, 4) final states τ a 1 π ν τ (polarization-dependent asymmetry) τ ωπ ν τ (triple product asymmetry) Active analyses in BABAR: challenging systematics τ BABAR (Page: 46)

48 Conclusions B-Factories are also τ-factories Dataset expected to be doubled by end of data-taking (Sep 008) On-going effort to better understand systematic errors Expect lots of more τ-physics with inputs also from ISR studies: τ-lifetime, Leptonic Branching Fractions, Lepton Universality High precision tests of QCD Measurements of fundamental quantities: V us, m s, α s, (g ) µ... Structure of non-strange and strange hadronic states Resonance sub-structure of hadronic final states Search for second class currents Search for new Physics are getting significantly closer to theoretical predictions on LFV decays O(10 8 ). Please Stay tuned to update of Experiment vs. Theory plots... Search for CP violation in τ decays τ BABAR (Page: 47)