τ Lepton Physics at Belle and BaBar

Transcription

1 τ Lepton Physics at Belle and BaBar Simon Eidelman Budker Institute of Nuclear Physics, Novosibirsk, Russia 1. Lepton universality Outline 2. Two-pion decay and CVC 3. Decays with kaons 4. Second class currents 5. Lepton Flavor Violation (LFV) 6. Conclusions p.1/46

2 General τ lepton is one of the six fundamental leptons As the heaviest lepton, it may decay into both leptons and hadrons: PDG lists more than 200 different τ decays We can study all interactions allowed in the Standard Model and search for effects of New Physics It is a very clean laboratory with no hadrons in the initial and only a few in the final state: 85.36% 1-prong, 14.56% 3-prong, prong events τ leptons will be an important tool at LHC p.2/46

3 τ Lepton Factories Group L dt, fb 1 N ττ, 10 6 LEP (Z-peak) CLEO (10.6 GeV) BaBar (10.6 GeV) Belle (10.6 GeV) τ-c (4.2 GeV) SuperB 50k 45k BaBar ( 557 fb 1 ) and Belle ( 1020 fb 1 ) collected together about 1.5 ab 1 B-factory is also a τ factory producing τ + τ pairs per each fb 1!! Super-c-τ-factory (10 35 cm 2 s 1 ) with Ldt = 10 ab 1 will yield τ + τ pairs!! p.3/46

4 Lepton universality and M τ r = ( G τ eντ νe G µ eν µ νe ) 2 = ( M µ M τ ) 5 ( t µ t τ )B(τ eν τ ν e ) F cor(m µ,m e ) F cor (M τ,m e ) r t τ, fs B(τ eν τ ν e ), % M τ, MeV Comments ± ± PDG, 1992 ± ± ± σ ± ± PDG, 1996 ± ± ± ± σ ± ± PDG, 2004 ± ± ± ± σ p.4/46

5 σ(e + e τ + τ ) Near Threshold σ ττ, nb E beam - m τ, MeV Dotted Born, dashed Coulomb, FSR and VP, dash-dotted ISR, solid beam energy spead p.5/46

6 M τ at KEDR: Observed σ(e + e τ + τ ) σ obs, nb ψ(2s) ψ(3770) E beam , MeV Ldt = 6.7 pb 1, 81 events selected M τ = ( ± 0.15) MeV/c2 V.V. Anashin et al., JETP Lett. 85, 347 (2007) p.6/46

7 M τ at Belle and BaBar I Pseudomass method (ARGUS 1992) uses M p maximum inv. mass of observed hadrons M 2 τ M 2 p = M 2 h + 2(E beam E h )(E h p h ) Events/(2 MeV) Pseudomass (GeV) f(m p ) (p 1 + p 2 M p ) tan 1 (M p p 3 )/p 4 + p 5 + p 6 M p The smearing of the endpoint and tail are caused by ISR/FSR and resolution p.7/46

8 M τ at Belle and BaBar II Both BaBar and Belle use τ π π + π ν τ +c.c, which has a large branching 9% and large statistics in the endpoint region p.8/46

9 M τ at Belle and BaBar III Summary of Belle and BaBar measurements Group BaBar Belle Ldt, fb N ττ, N ev, M τ, MeV ± 0.12 ± ± 0.13 ± 0.35 BaBar: B. Aubert et al., Phys. Rev. D 80, (2009) Belle: K. Belous et al., Phys. Rev. Lett. 99, (2007) p.9/46

10 CPT Test by M τ + vs. M τ I In the pseudomass method M τ + and M τ are measured separately and M = M τ + M τ can be determined Events/(2 MeV) Pseudomass (GeV) Belle: M = 0.05 ± 0.23 ± 0.14 MeV BaBar: M = 0.61 ± 0.23 ± 0.06 MeV p.10/46

11 CPT Test by M τ + vs. M τ II Group OPAL, 2000 Belle, 2007 BaBar, 2009 N τ + τ, M, MeV 0.0 ± ± ± 0.24 M/M τ, ± ± ± 1.4 M/M τ, %CL < 30.0 < 2.8 < 5.5 From MC studies BaBar finds, assuming no CPT violation, that there is a 1.2% chance of obtaining a result as different from zero as that of BaBar. p.11/46

12 τ Lepton Mass Measurements Group M τ, MeV BES, PDG, KEDR, ± 0.15 Belle, ± 0.13 ± 0.35 BaBar, ± 0.12 ± 0.41 PDG, ± 0.16 KEDR, ± 0.15 r = ± (0.99σ) Leptonic universality is OK! The r sensitivity is six times higher than in 1992 (0.004 vs ) This test (G τ /G µ ) is limited by the accuracy of τ τ and B(τ e ν e ν τ ) BES-III can move much further p.12/46

13 Charged Lepton Masses Masses of charged leptons are fundamental constants and should be measured with high precision Particle Mass, MeV σ m /m e ± µ ± τ ± Tests of lepton universality involve m 5 l, tests of new physics m2 l Formula of Y. Koide (1981): ( m e + m µ + m τ ) 2 (m e + m µ + m τ ) = p.13/46

14 Charged Current Universality I G µ /G e B(τ µ)/b(τ e) ± B(π µ)/b(π e) ± B(K µ)/b(k e) ± B(K πµ)/b(k πe) ± B(W µ)/b(w e) ± A. Pich: NPB (Proc. Suppl.) , 300 (2008) p.14/46

15 Charged Current Universality II G τ /G e B(τ µ)τ µ /τ τ ± B(W τ)/b(w e) ± G τ /G µ B(τ e)τ µ /τ τ ± Γ(τ π)/γ(π µ) ± Γ(τ K)/Γ(K µ) ± B(W τ)/b(w µ) ± p.15/46

16 Lepton Universality and Branching Fractions I Three recent measurements at BaBar (467 fb 1 ): Ratio BaBar PDG-08 B(τ µ ν µ ν τ )/B(τ e ν e ν τ ) ± ± ± B(τ π ν τ )/B(τ e ν e ν τ ) ± ± ± B(τ K ν τ )/B(τ e ν e ν τ ) ± ± ± Mode e ν e ν τ µ ν µ ν τ π ν τ K ν τ N ev, Gµ G e «2 = B(τ µ ν µ ν τ ) B(τ e ν e ν τ ) f(m 2 e/m 2 τ) f(m 2 µ/m 2 τ), where f(x) = 1 8x + 8x 3 x 4 12x 2 log x, m ν = 0. G µ /G e = ± , consistent with ± (A. Pich, 2008). B. Aubert et al., arxiv: p.16/46

17 Lepton Universality and Branching Fractions II ( Gτ G µ ) 2 = B(τ π ν τ ) B(π µ ν µ ) 2m π m 2 µτ π δ τ π ν/π µ νm 3 ττ τ ( 1 m 2 µ /m 2 π 1 m 2 π/m 2 τ ) 2, ( Gτ G µ ) 2 = B(τ K ν τ ) B(K µ ν µ ) 2m k m 2 µτ K δ τ K ν/k µ νm 3 ττ τ ( 1 m 2 µ /m 2 K 1 m 2 K /m2 τ ) 2, where the radiative corrections are δ τ π ν/π µ ν = ± and δ τ K ν/k µ ν = ± G τ /G µ = ± ( ± ) with pions (kaons) compared to ± 0.005(0.979 ± 0.017). p.17/46

18 New data on τ π π 0 ν τ from Belle From 64M τ + τ pairs Belle selects 5.4M τ h π 0 ν τ events! 10 1 Belle ALEPH CLEO G&S Fit (ρ (770) + ρ (1450) + ρ (1700) ) F π (M ππ 0) 2 (GeV/c 2 ) 2 For the first time all three ρ mesons are observed! B Belle = (25.24 ± 0.01 ± 0.39)% B ALEPH = ( ± ± 0.085)% The contributions to a had µ are also compatible due to compensation at tails p.18/46

19 CVC. e + e X 0 and τ ν τ X 0.3 ( F π 2 [ee] F π 2 [τ]) / F π 2 [τ] Allowed I G J P = : X = π π 0, (4π), ωπ -0.2, ηπ π 0, K K 0, (6π), τ Average preliminary correcting for m(ρ +/0 ) and Γ(ρ +/0 ) KLOE CMD-2 CMD OLYA DM s (GeV 2 ) Large SU(2) breaking corrections from theory, V.Cirigliano et al., 2002 M(Γ) ρ 0 M(Γ) ρ ± helps, M.Davier, 2003; S.Ghozzi, F.Jegerlehner, 2004 Consistent ρ, ω, φ mixing, M. Benayoun et al., EPJ C 65, 211 (2010) p.19/46

20 New comparison of a exp µ and a th µ after BaBar HMNT 07 (e + e ) 276 ± 51 JN 09 (e + e ) 290 ± 65 Davier et al. 09 (τ) 148 ± 52 Davier et al. 09 (e + e ) 303 ± 51 This work (e + e w/ BABAR) 246 ± 49 BNL-E821 (WA) 0 ± 63 BNL-E a µ a µ exp Reestimation of a had µ after BaBar s ππ and increase of a exp µ by (CODATA changed µ µ /µ p ) 3.2σ, new I/B corrections make τ move to e + e M. Davier et al., EPJ C66, 127 (2010); EPJ C66, 1 (2010) p.20/46

21 Lepton Anomalous Magnetic Moments Lepton Experiment a l /a l e (28) µ (63) τ (0.017) 15 Theory expects a τ = (5) 10 8 SE, M. Passera, Mod. Phys. Lett. A 22, 159 (2007) p.21/46

22 τ Decays with Kaons 1. Decays with 1 or 3 kaons are Cabibbo-suppressed, A sinθ c B(τ S = 1) = (2.87 ± 0.12)%, ALEPH, 1999; (2.81 ± 0.19)%, OPAL, 1999 From strange spectral functions m s, V us Hadronic physics, K 2. Decays with 2 kaons, A cos θ c B(τ (K KX) ν τ ) 0.7% Vector or Axial-vector? Wess-Zumino anomaly CVC tests in τ vs. e + e Hadronic physics, K Knπ, V (ρ, φ)nπ p.22/46

23 τ (Kπ) ν τ at Belle and BaBar I Mode Summary of Belle and BaBar τ (Kπ) ν τ measurements Group R Ldt, fb 1 N ττ, 10 6 N ev, 10 3 B, % K π 0 ν τ BaBar [1] ± ± K 0 Sπ ν τ BaBar [2] ± ± K 0 Sπ ν τ Belle [3] ± ± BaBar [1]: B. Aubert et al., Phys. Rev. D 76, (2007) BaBar [2]: B. Aubert et al., arxiv: Belle [3]: D. Epifanov et al., Phys. Lett. B 654, 65 (2007) p.23/46

24 τ (Kπ) ν τ at Belle and BaBar II Preliminary BABAR 08 0 (K mode) S Belle 07 0 (K mode) S OPAL 00 0 (K mode) ALEPH 99 0 (K mode) L ALEPH 98 0 (K mode) S CLEO 96 0 (K mode) S L (K mode) B BaBar (K π 0 ν τ ) = (0.416 ± ± 0.018)% B PDG (K π 0 ν τ ) = (0.454 ± 0.030)% For both modes new B are consistent with PDG, but lower! PDG B( τ - K π - ) [%] ν τ p.24/46

25 K S π Mass Spectrum at Belle Signal K S K L π K S ππ 0 K S K 3π non-ττ N EVENTS 10 2 N EVENTS s, GeV/c s, GeV/c 2 The M Kπ spectrum is well described by the K (892), K (800) (κ) and K 0(1430) (or K (1410)). p.25/46

26 K (892) 0 Mass and Width Measurement at Belle PDG07 K * (892) K *0 (892) Belle CLEO ALEPH M K * (892), MeV/c 2 M(K (892) ) = ( ± 0.20 ± 0.44 ± 0.59) MeV Γ(K (892) ) = (46.2 ± 0.6 ± 1.0 ± 0.7) MeV p.26/46

27 τ h h + h ν τ from BaBar and Belle I Mode BaBar, 342 fb 1 Belle, 666 fb 1 PDG2006 N ev, B(π π + π ), ± 0.01 ± ± ± 0.08 N ev, B(K π + π ), ± 0.02 ± ± ± 0.35 N ev, B(K K + π ), ± ± ± ± 0.10 N ev B(K K + K ), ± 0.13 ± ± < 3.7 BaBar: B. Aubert et al., Phys. Rev. Lett. 100, (2008) Belle: M.J. Lee et al., arxiv: Results of Belle and BaBar are not very consistent p.27/46

28 τ h h + h ν τ from BaBar and Belle II Branching ratio of τ πππν decay Branching ratio of τ Kππν decay CLEO3 03 (9.13± 0.46) % (PDG 06) (9.02± 0.08) % BABAR 08 (8.83± 0.13) % (This work) (8.42± 0.26) % DELPHI 97 ALEPH 98 CLEO 99 OPAL 00 CLEO3 03 OPAL 04 (PDG 06) BABAR 08 (This work) -3 (4.90±0.80) 10-3 (2.14±0.47) 10 (3.46±0.61) (3.60±0.95) 10-3 (3.84±0.40) 10-3 (4.15±0.66) 10-3 (3.33±0.35) 10-3 (2.73±0.09) 10-3 (3.30±0.17) Branching ratio of τ KKπν decay Branching ratio of τ KKKν decay -3 ALEPH 98 CLEO 99 OPAL 00 CLEO3 03 (PDG 06) BABAR 08 (This work) -3 (1.63±0.27) 10-3 (1.45±0.31) 10-3 (0.87±0.69) 10-3 (1.55±0.11) 10-3 (1.53±0.10) 10-3 (1.35±0.04) 10-3 (1.55±0.06) 10-4 ALEPH 98 < CLEO3 03 < BABAR 08 (This work) -5 (1.58±0.17) 10-5 (3.29±0.26) p.28/46

29 Strange spectral function (v 1 + a 1 ) S (s) τ S ν τ ALEPH K π K 2π K 3π + K η (MC) K 4π (MC) K 5π (MC) pert QCD / parton model (v+a) OPAL (K) from PDG (Kπ+Kη) (Kππ+Kηπ) (Kπππ) naïve parton model s (GeV 2 ) s/gev 2 ALEPH: V us = ± exp ± th ± ms J.Prades from OPAL data: V us = ± , m s = (81 ± 20) MeV m s J.G.Körner,A.Pivovarov, , m s = (130 ± 27) MeV p.29/46

30 V us determination from B(τ K ν τ )/B(τ π ν τ ) B(τ K ν τ ) B(τ π ν τ ) ( ) 2 = f2 K V us 2 1 m2 K m 2 τ fπ V 2 ud 2 ( ) 2 δ τ K ν τ 1 m2 π δ τ π ν tau m 2 τ = ± ± , All non-perturbative effects are in f K /f π = ± from the lattice. One obtains V us = ± consistent with ± from unitarity. Another method, which uses R τ,strange based on PDG plus BaBar/Belle B s, gives V us = ± or 3σ lower than the unitarity value. Might be due to theory problems. p.30/46

31 2nd Class Currents in τ ηπ ν τ I 2nd class currents suppressed in SM: m u m d τ ηπ ν τ has J PG = 0 + Source B 95 (τ ηπ ν τ ), 10 4 Theory prediction: B(τ ηπ ν τ ) Large BG from τ ηπ π 0 ν τ with B = (1.77 ± 0.24) 10 3 CLEO and ALEPH observed τ ηk ν τ : B exp = (2.7 ± 0.6) 10 4 vs. B th HRS, ± 100 ± 120 CLEO, 1987 < 100 ARGUS, 1988 < 90 CLEO, 1992 < 3.4 CLEO, 1996 < 1.4 ALEPH, 1997 < 6.2 p.31/46

32 Decays with η Mesons at Belle Mode Group N ev B exp π π 0 ην τ Belle, ± 111 (1.35 ± 0.03 ± 0.08) 10 3 CLEO, ± 16 (1.7 ± 0.2 ± 0.2) 10 3 K ην τ Belle, ± 51 (1.58 ± 0.05 ± 0.09) 10 4 CLEO, ± 14 (2.6 ± 0.5 ± 0.4) 10 4 K π 0 ην τ Belle, ± 34 (4.6 ± 1.1 ± 0.4) 10 5 CLEO, ± 12 (17.7 ± 5.6 ± 7.1) 10 5 K ην τ Belle, ± 19 (1.30 ± 0.13 ± 0.11) 10 4 CLEO, ± 6 (2.90 ± 0.80 ± 0.42) 10 4 K S π ην τ Belle, ± 8 (4.4 ± 0.7 ± 0.2) 10 4 CLEO, (1.00 ± 0.35 ± 0.11) 10 3 Belle (490 fb 1 ): K. Inami et al., Phys. Lett. B 672, 209 (2009) p.32/46

33 2nd Class Currents in τ ηπ ν τ II B(τ ηπ ν τ ) = (4.4 ± 1.6 ± 0.8) 10 5 or 2.4σ signal, the corresponding upper limit is B < at 95% CL compared to < at CLEO Belle (675 fb 1 ) K.Hayasaka, EPS-2009 p.33/46

34 2nd Class Currents in τ η π ν τ BaBar Events/0.004 GeV/c η π - π Mass (GeV/c ) Group R Ldt, fb 1 B 95 (τ η π ν τ ), 10 6 CLEO, < 74 BaBar, < 7.2 Belle, < 7.0 Theory predicts BaBar: B. Aubert et al., Phys. Rev. D77, (2008) p.34/46

35 2nd Class Currents in τ ωπ ν τ Both currents possible: 1st class current J PG = 1 +, l = 1, B 1.9%. 2nd class current J PG = 1 ++, l = 0, 2. Group B V /B V 95% CL ARGUS, 1987 < 0.5 ALEPH, 1997 < CLEO, 2000 < BaBar, 2009 < F(cosχ) = = N [ 1 2 ǫ (1 ǫ)( 1 cos 2 χ )] BaBar (347 fb 1 ) B. Aubert et al., Phys. Rev. Lett. 103, (2009) p.35/46

36 Searches for New Physics in the Lepton Sector Searches for µ e LFV: µ e conversion, µ e γ (B < ), µ e e + e (B < ) MEG running, PRISM prepared Neutrino oscillations, in particular ν µ ν τ oscillations with a big mixing angle (S/K) searches for large µ τ LFV, e.g., τ µ γ In schemes with inverted hierarchy τ e is also possible, e.g., τ e γ Many models consider extensions of the Standard Model with enhanced LFV. Particularly popular are SUSY models, e.g. MSSM extension of SM, also discussed SUGRA, GUT, Higgs, little Higgs Predicted B(τ µ γ) reach different modes studied. The most stringent limit is B(τ µ + e e ) < The sensitivity is limited by background suppression/statistics. p.36/46

37 How Do We Search for LFV τ Decays I We divide the event space by the plane perpendicular to the thrust axis into two hemispheres tag side, in which some ordinary τ decay (usually 1-prong modes are selected) is observed and signal side, in which we try to completely reconstruct a neutrinoless LFV τ decay. Decays we are searching for are very rare (P < 10 7 ) mostly background (BG) is detected in the signal side. We apply various kinematical, topological and PID cuts to suppress BG. We compare various distributions in data with MC to be sure that we completely understand BG. p.37/46

38 Signal and Tag Sides signal side l l e+ ν(missing) τ τ+ tag side l e- 1-prong decay p.38/46

39 How Do We Search for LFV τ Decays II We calculate an invariant mass of a signal candidate M inv (for BaBar it s M EC using E meas = E beam ) and E = E meas E beam. Signal events should have M inv(ec) M τ, E 0 We blind the signal region (box or ellipse) within ±3σ and optimize all selection criteria based on MC and sideband data We calculate the expected background in signal region We open the signal region and determine the signal yield s 0 from N obs and N exp taking into account systematic errors We calculate the branching ratio or place an upper limit: B = s 0 /2N ττ ǫ, N ττ the number of τ + τ pairs, ǫ acceptance p.39/46

40 Search for τ µ f 0 (980) I Background is well understood! p.40/46

41 Search for τ µ f 0 (980) II BG is suppressed no events in the signal ellipse p.41/46

42 Search for τ µγ (GeV) M EC E (GeV) E (GeV) M inv (GeV/c 2 ) p.42/46

43 τ l γ 90% upper limits on the branching fraction B τ Belle BaBar CLEO mode B, 10 8 N ττ, 10 6 B, 10 8 N ττ, 10 6 B, 10 8 N ττ, 10 6 µ γ e γ Belle: K. Hayasaka et al., Phys. Lett. B 666, 16 (2008) BaBar: B. Aubert et al., Phys. Rev. Lett. 104, (2010) p.43/46

44 Progress of LFV Studies τ µ γ Group Date L, pb 1 N ττ, 10 6 B 90 UL MARK II ARGUS DELPHI CLEO Belle Belle BaBar BaBar & Belle p.44/46

45 Prospects for LFV Studies With τ + τ and ǫ 3%: B < for N ev = 0 Background suppression needed (PID, higher ǫ) τ lγ, µη(γγ), lρ : BG 0, B 1/ N Achievable BR τ lll, µη(π + π π 0 ), Λπ : BG = 0, B 1/N CLEO msugra+seesaw SUSY+SO(10) SUSY+Higgs SM+seesaw B factories (Belle, BaBar) 2006 τ µγ τ µη τ µµµ Super B factory Luminosity (ab -1 ) p.45/46

46 Conclusions We know a lot after CLEO and LEP, Belle and Babar gaining speed Advantages in statistics and searches. Systematic effects? Lepton universality holds, more precise τ τ and B e needed Problems with CVC in the 2π decay smaller, but still exist, a µ Interesting possibilities for QCD, V us Why most B new < B old? Clean laboratory for studies of light mesons, e.g., of various K s Observation of second-class currents feasible Sensitivity of LFV searches approaches 10 8 Hadronic f/f in TAUOLA should be updated B factories are also unique τ factories: high potential for New Physics and precision studies in SM, more expected from SuperB and Super-c τ p.46/46

47 Backup Slides p.47/46

48 Monte Carlo Simulation of τ Decays TAUOLA, KORALB(Z) very important tools for LEP, CLEO, BaBar, Belle, LHC S.Jadach, Z.W as, Comp. Phys. Commun. 36, 191 (1985); S.Jadach, J.H.Kühn,Z.W as, Comp. Phys. Commun. 64, 275 (1990); M.Jeżabek, Z.W as, S.Jadach, J.H.Kühn, Comp. Phys. Commun. 70, 69 (1992) High-statistics experiments more precise description Novosibirsk e + e data for hadronic currents in τ 4πν τ A.Bondar, SE,..., Z.W as, M.Worek, Comp. Phys. Commun. 146, 139 (2002) Events/0.04 GeV/c BABAR Data Signal MC Bkgd MC Mass (GeV/c ) Improvement in J.H.Kühn, Z.W as, Acta Phys. Polon. B39, 147 (2008). p.48/46

49 A Zoo of τ decays p.49/46

50 Lepton Universality and Branchings III From PDG B(τ e ν e ν τ ) = (17.82 ± 0.05)% and previous B(τ µ ν µ ν τ ) the new WA B(τ µ ν µ ν τ ) = ( ± 0.043)%. From this and assuming µ e universality as well as from τ τ /τ µ and assuming τ µ universality, one obtains B(τ e ν e ν τ ) univ = ( ± 0.030)%. The total hadronic branching B had = B(τ e ν e ν τ ) univ = ( ± 0.059)% and the total hadronic width R τ,had = ± p.50/46

51 τ Lifetime Measurements of τ τ, fs Source N ττ, 10 3 τ τ, fs δτ τ sys, % DELPHI, ± 1.4 ± PDG, ± BaBar, ± 0.91 ± Measurement bias 0.220% Background 0.142% Alignment 0.111% τ momentum 0.100% Total 0.310% e,µ) BR(τ PDG BABAR 2004, preliminary τ τ = ± 0.83 fs PDG 2004 BR(τ e,µ) = ± = MeV/c M τ SM: e,µ,τ coupling ratios = (fs) τ τ p.51/46

52 τ Leptonic Branching Measurements of B e, % Source N ττ, 10 3 B, % δb sys, % ALEPH, ± ± CLEO, ± 0.06 ± PDG, ± Systematic uncertainties in CLEO, % N ev N ττ ǫ Trig. PID BG Total p.52/46

53 Alternatives for the pseudomass fit parameterization Two other functions were considered: M p p 1 F 1 (M p ) = (p 3 + p 4 M p ) p2 + (M p p 1 ) + p p 6 M p and 1 F 2 (M p ) = (p 3 + p 4 M p ) 1 + exp M p p 1 + p 5 + p 6 M p. p 2 p.53/46

54 Systematic uncertainties in M τ Source BaBar Belle CM energy and p reconstruction MC Modeling (τ 3πν τ ) MC Statistics Fit Range Parameterization Momentum resolution Negl Background Negl Total Both groups assume M ντ =0 Belle: 10 MeV M τ =-0.1 MeV BaBar: 1 MeV M τ =-0.02 MeV Charge asymmetry from M in D ±, D s ±, Λ ± c : Belle MeV, BaBar MeV p.54/46

55 V us from BaBar and Belle S. Banerjee at KAON 07 combined the recent data on the Kπν τ with older data for the other modes K l3 decays (0.2255±0.0019) K l2 decays (0.2262±0.0014) Hyperon decays (0.2260±0.0050) Unitarity (0.2275±0.0012) τ decays (0.2157±0.0031) τ decays (pred. τ Kν) (0.2171±0.0030) V us p.55/46

56 M(Kπ) from BaBar ) -3 (x Events/0.02 GeV/c Events (log scale) Sample Data Signal - τ K - τ K - - τ π 0 S 0 S π + 0 KL π 0 - π - π - π Other Non τ-events (GeV/c ) M - K π K S π - mass distribution [GeV] τ K π 0 ν τ : B. Aubert et al., Phys. Rev. D76, (2007) τ K 0 S π ν τ : B. Aubert et al., arxiv: Analysis of M(Kπ) spectra is in progress p.56/46

57 Monte Carlo Simulation of τ Decays TAUOLA, KORALB(Z) very important tools for LEP, CLEO, BaBar, Belle, LHC S.Jadach, Z.W as, Comp. Phys. Commun. 36, 191 (1985); S.Jadach, J.H.Kühn,Z.W as, Comp. Phys. Commun. 64, 275 (1990); M.Jeżabek, Z.W as, S.Jadach, J.H.Kühn, Comp. Phys. Commun. 70, 69 (1992) High-statistics experiments more precise description Novosibirsk e + e data for hadronic currents in τ 4πν τ A.Bondar, SE,..., Z.W as, M.Worek, Comp. Phys. Commun. 146, 139 (2002) Events/0.04 GeV/c BABAR Data Signal MC Bkgd MC Mass (GeV/c ) Improvement in J.H.Kühn, Z.W as, Acta Phys. Polon. B39, 147 (2008). p.57/46

58 Conclusions We know a lot after CLEO and LEP, Belle and Babar gaining speed Advantages in statistics and searches. Systematic effects? Lepton universality holds, more precise τ τ and B e needed Problems with CVC in the 2π decay smaller, but still exist, a µ Interesting possibilities for QCD, V us Why most B new < B old? Clean laboratory for studies of light mesons, e.g., of various K s Observation of second-class currents feasible Sensitivity of LFV searches approaches 10 8 Hadronic f/f in TAUOLA should be updated B factories are also unique τ factories: high potential for New Physics and precision studies in SM, more expected from SuperB and Super-c τ p.58/46

59 Backup Slides p.59/46

60 A Zoo of τ decays p.60/46

61 Lepton Universality and Branchings III From PDG B(τ e ν e ν τ ) = (17.82 ± 0.05)% and previous B(τ µ ν µ ν τ ) the new WA B(τ µ ν µ ν τ ) = ( ± 0.043)%. From this and assuming µ e universality as well as from τ τ /τ µ and assuming τ µ universality, one obtains B(τ e ν e ν τ ) univ = ( ± 0.030)%. The total hadronic branching B had = B(τ e ν e ν τ ) univ = ( ± 0.059)% and the total hadronic width R τ,had = ± p.61/46

62 τ Lifetime Measurements of τ τ, fs Source N ττ, 10 3 τ τ, fs δτ τ sys, % DELPHI, ± 1.4 ± PDG, ± BaBar, ± 0.91 ± Measurement bias 0.220% Background 0.142% Alignment 0.111% τ momentum 0.100% Total 0.310% e,µ) BR(τ PDG BABAR 2004, preliminary τ τ = ± 0.83 fs PDG 2004 BR(τ e,µ) = ± = MeV/c M τ SM: e,µ,τ coupling ratios = (fs) τ τ p.62/46

63 τ Leptonic Branching Measurements of B e, % Source N ττ, 10 3 B, % δb sys, % ALEPH, ± ± CLEO, ± 0.06 ± PDG, ± Systematic uncertainties in CLEO, % N ev N ττ ǫ Trig. PID BG Total p.63/46

64 Alternatives for the pseudomass fit parameterization Two other functions were considered: M p p 1 F 1 (M p ) = (p 3 + p 4 M p ) p2 + (M p p 1 ) + p p 6 M p and 1 F 2 (M p ) = (p 3 + p 4 M p ) 1 + exp M p p 1 + p 5 + p 6 M p. p 2 p.64/46

65 Systematic uncertainties in M τ Source BaBar Belle CM energy and p reconstruction MC Modeling (τ 3πν τ ) MC Statistics Fit Range Parameterization Momentum resolution Negl Background Negl Total Both groups assume M ντ =0 Belle: 10 MeV M τ =-0.1 MeV BaBar: 1 MeV M τ =-0.02 MeV Charge asymmetry from M in D ±, D s ±, Λ ± c : Belle MeV, BaBar MeV p.65/46

66 V us from BaBar and Belle S. Banerjee at KAON 07 combined the recent data on the Kπν τ with older data for the other modes K l3 decays (0.2255±0.0019) K l2 decays (0.2262±0.0014) Hyperon decays (0.2260±0.0050) Unitarity (0.2275±0.0012) τ decays (0.2157±0.0031) τ decays (pred. τ Kν) (0.2171±0.0030) V us p.66/46

67 M(Kπ) from BaBar ) -3 (x Events/0.02 GeV/c Events (log scale) Sample Data Signal - τ K - τ K - - τ π 0 S 0 S π + 0 KL π 0 - π - π - π Other Non τ-events (GeV/c ) M - K π K S π - mass distribution [GeV] τ K π 0 ν τ : B. Aubert et al., Phys. Rev. D76, (2007) τ K 0 S π ν τ : B. Aubert et al., arxiv: Analysis of M(Kπ) spectra is in progress p.67/46