Hadronic Tau Decays at BaBar Swagato Banerjee Joint Meeting of Pacific Region Particle Physics Communities (DPF006+JPS006 Honolulu, Hawaii 9 October - 3 November 006 (Page: 1
Hadronic τ decays Only lepton that decays into hadrons Hadronic Branching Fraction 65% 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 and suppressed decays Ideal for measurements of fundamental quantities like V us, m s, α s Several resonance (sub-structure waiting to be observed Hadronic τ Decays @ (Page:
Strange Spectral Function Inclusive study of strange spectral functions from final states with net strangeness of unity world s best measurement of V us, m s Branching Fractions ( 10 3 [PDG 005] Preliminary B(τ K π 0 ν τ and B(τ K π π + ν τ reported with better precision than the world average (TAU06, Pisa Hadronic τ Decays @ (Page: 3
τ -factory PEP-II B-factory: also a τ-factory At Υ (4S: s = 10.58 GeV σ(e + e BB = 1.05 nb σ(e + e τ + τ = 0.89 nb Experiment # of τ-pairs LEP 3 10 5 CLEO 1 10 7 3 10 8 Hadronic τ Decays @ (Page: 4
The Detector Excellent K/π separation dedx Cherenkov angle Hadronic τ Decays @ (Page: 5
Recent Results from Runs 1-4 Data (L 30 fb 1 τ π π } π {{ + π } 0 ω τ π π π + η }{{} f 1 (185 τ K }{{ π } 0 ν τ K (89 ν τ ν τ Most analyses use leptonic tag Runs 1-5 Data (L 340 fb 1 τ π π π + ν τ τ K π π + ν τ τ π K } {{ K + } φ τ K K } {{ K + } φ ν τ ν τ Hadronic τ Decays @ (Page: 6
τ π π π + π 0 ν τ 411K e-tagged events Background: 10% (τ + τ events with extra π 0 (Preliminary: B(τ π π π + π 0 ν τ = (4.39 ± 0.01 ± 0.1 10 PDG (Aleph, CLEO: (4.46 ± 0.06 10 Entries 35000 30000 5000 0000 15000 10000 5000 0 π π π + π 0 0.8 1 1. 1.4 1.6 1.8 m(4π (GeV/c Fit Breit-Wigner convoluted with 5000 Gaussian (resolution: 6.1 MeV π π + π 0 plus polynomial background 0000 ( 6% from τ + τ with extra π 0 15000 Preliminary: 10000 B(τ π ων τ = 5000 (1.97 ± 0.01 ± 0.10 10 0 Aleph: (1.91 ± 0.07 ± 0.06 10 m(3π (GeV/c Events / ( 0.005 GeV/c 0.7 0.75 0.8 0.85 0.9 Hadronic τ Decays @ (Page: 7
τ π π π + ην τ Fit with Novosibirsk function: (160 ± 56 η candidates qq Background: (54 ± 16 (Preliminary: B(τ π π π + ην τ = (1.84 ± 0.09 ± 0.13 10 4 PDG : (.3 ± 0.5 10 4 Mass (GeV/c Events/0.003 GeV/c 0 00 180 160 140 10 100 80 60 40 0 0 γ γ 0.48 0.5 0.5 0.54 0.56 0.58 0.6 0.6 Fit Breit-Wigner convoluted with Gaussian (resolution: 7 MeV (951 ± 78 f 1 (185 candidates (Preliminary: B(τ π f 1 ν τ = (3.83 ± 0.3 ± 0.0 ± 1.18 10 4 : (4.6 ± 1. ± 0.7 10 4 using f 1 (185 π π π + π + decays Events/0.005 GeV/c 180 160 140 10 100 80 60 40 0 - π π + η 0 1.15 1. 1.5 1.3 1.35 1.4 Mass (GeV/c Hadronic τ Decays @ (Page: 8
Resonant Contributions Ratio of Branching Fractions ( Preliminary: R ( τ π ω π π π + π 0 ν τ τ π π π + π 0 ν τ = 0.400 ± 0.00 ± 0.006 R ( τ π f 1 π π π + ην τ τ π π π + ην τ = 0.73 ± 0.01 ± 0.04 τ π π π + ην }{{} τ decays η Suppressed by G-parity ( nd Class Current Expected at the level of isospin breaking m u m d We fit the region around η (958 and find no signal (Preliminary: B(τ π η ν τ < 1. 10 5 @ 90% C.L. CLEO: Upper Limit = 7.4 10 5 @ 90% C.L. Hadronic τ Decays @ (Page: 9
τ K π 0 ν τ 78K e/µ-tagged events: τ + τ mostly; qq, µ + µ small Background sources: K/π mis-id, π 0 reconstruction in-efficiency 7 6 5 4 3 1 0 ALEPH (5.±0.04±0.05 10 CLEO (5.1±0.10±0.07 10 ALEPH (1991-1995 (4.44±0.06±0.04 10 OPAL (1991-1995 (4.71±0.059±0.03 10 BaBar Preliminary (4.39±0.003±0.01 10 PDG Fit (4.5±0.07 10 0.1 0. 0.3 0.4 0.5 0.6 BR (% Hadronic τ Decays @ (Page: 10
τ π π π + ν τ 1.6M e/µ-tagged events: τ + τ mostly (extra π 0 ; qq < 0.1% Particle-ID component of efficiency migration matrix: π π π + K π π + K π K + K K K + 97.7%.8% 4.8% 1.0% Events/(0MeV/c 90000 80000 70000 60000 3.5 4 3.5 CLEO III (9.13±0.05±0.46 10-50000 40000 30000 0000 10000 0.4 0.6 0.8 1 1. 1.4 1.6 1.8 M (GeV/c 1.5 1 0.5 0 BaBar Preliminary - (9.11±0.01±0.6 10 PDG Fit (9.0±0.08 10-5 6 7 8 9 BR (% Hadronic τ Decays @ (Page: 11
τ K π π + ν τ 69K e/µ-tagged events: non-cross-feed background small Particle-ID component of efficiency migration matrix: π π π + K π π + K π K + K K K + 1.4% 74.7% 16.3% 6.5% 8 Events/(0MeV/c 5000 4000 3000 000 1000 7 6 5 4 3 1 OPAL (1991-1995 (3.60±0.08±0.048 10 ALEPH (.14±0.037±0.09 10 CLEO (3.46±0.03±0.056 10 CLEO (3.84±0.14±0.38 10 OPAL (1991-1995 (4.15±0.53±0.40 10 BaBar Preliminary (.88±0.0±0.11 10 PDG Fit (3.33±0.35 10 0.6 0.8 1 1. 1.4 1.6 1.8 M (GeV/c 0 0 0.05 0.1 0.15 0. 0.5 0.3 0.35 0.4 0.45 BR (% Hadronic τ Decays @ (Page: 1
τ K π K + ν τ 18K e/µ-tagged events: non-cross-feed background negligible Particle-ID component of efficiency migration matrix: π π π + K π π + K π K + K K K + 0.5% 60.1% 5.8% Events/(0MeV/c 000 1800 1600 1400 100 1000 800 600 400 00 1.1 1. 1.3 1.4 1.5 1.6 1.7 1.8 1.9 M (GeV/c 7 6 5 4 3 1 0 ALEPH (1.63±0.1±0.17 10 CLEO (1.45±0.13±0.8 10 OPAL (1990-1995 (0.87±0.56±0.40 10 CLEO III (1.55±0.06±0.09 10 BaBar Preliminary (1.373±0.011±0.040 10 PDG Fit (1.53±0.10 10-0. -0.15-0.1-0.05-0 0.05 0.1 0.15 0. BR (% Hadronic τ Decays @ (Page: 13
τ K K K + ν τ (75 ± 17 e/µ-tagged events: non-cross-feed background < 1% Particle-ID component of efficiency migration matrix: π π π + K π π + K π K + K K K + 0.3% 50.7% Events/(5MeV/c 50 45 40 35 30 5 3 5 5 CLEO III -5 <3.7 10 @ 90%CL 0 15 10 5 5 0 0 1.4 1.45 1.5 1.55 1.6 1.65 1.7 1.75 1.8 1.85 1.9 0.0005 0.001 0.0015 0.00 0.005 0.003 0.0035 M (GeV/c 1 BaBar Preliminary -5 (1.59±0.14±0.11 10 BR (% Hadronic τ Decays @ (Page: 14
New decay modes via φ resonance Events/(5MeV/c 500 400 300 φ Entries/(5MeV/c 10 100 80 φ 60 00 40 100 0 1 1.1 1. 1.3 1.4 1.5 (GeV/c M K + - K 0.95 1 1.05 1.1 1.15 1. 1.5 1.3 1.35 (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 Hadronic τ Decays @ (Page: 15
Conclusions B-Factories are also τ-factories On-going efforts to better understand systematic errors π 0, η reconstruction efficiency uncertainty in production cross-section σ e+ e τ + τ % dataset expected to be doubled by 008 Expect lots of more τ-physics in near future: High precision tests of QCD Measurements of fundamental quantities: V us, m s, α s Resonance sub-structure of hadronic final states Search for second class currents Search for violation of charge-parity symmetry in τ decays Hadronic τ Decays @ (Page: 16