23 Septemberl 2008Tau081         decay at Belle Tau08; Novosibirsk, 22-25, September, 2008 Hisaki Hayashii Nara women’s University

8 April Introduction Hadronic decays of tau lepton provide clean environment for studying the dynamics of hadronic states.  s (s), a , V us, m s         has the largest Br CVC relation with e + e - →     Plays an important role for the h. v. p. term in the a=(g  -2)/2 muon anomalous magnetic moment. a  =(g  -2)/2 hadron +CVC

8 April Introduction （ cont. ） Recent data indicate that there is a systematic difference between the 2  system in e + e － reaction and  -decays, even after applying known iso-spin violation correction. Main difference btw and is from 2  mode. not yet published preliminary a  (exp)-a  (th) is ICHEP-2006(M.Davier et al.): A hint to New Physics beyond the SM!

8 April In this talk, We present update results from Belle experiment based on 5.6x 10 6         decays (72.2/fb). spectral function What should be measured Branching Fraction Mass Spectrum B-factory exp. : final state particles are separated well. c.f. LEP exp.

8 April Analysis Procedure e + e    +   selection         selection Background subtraction Unfolding Br measurement Extract pion form factor |F  (s)| 2 Fit with Breit-Wigner Form Evaluation of a  distribution event selection unfolded distribution 72.2/fb unfolding （ correct the detector effect ） Extract pion form factor evaluation of the DATA Unfolded     distribution

8 April e + e    +   Selection Event Selection Low multiplicity: Number of charged tracks ： 2 or 4, net charge=0 Rejection of Bhabha and     ;  |P|*< 9 GeV Physics background rejection: Use Missing Mass and Missing Angle information.(Bhabha,2photon) Low track and gamma multiplicity. (qq continuum)  charged track         Selection one charged track in the event hemisphere. one  0 in the event hemisphere. No additional g with Eg≥200MeV Tag-side condition: 1, 3 prong+ any  For Br measurement  1 prong + no  : For mass spectrum

8 April e + e -     - Selection Particle multiplicity Bhabha m+m- Two photon

8 April  0 Signal Signal region right ： left ： Sideband region Sideband region is used to estimate the non-  0 background 5.6M events         Generally background free, but non- negligible BK In the low M  0 region. - Ｓｉｄｅ ｂａｎｄ ｒｅｇｉｏｎ： Ｄｏｍｉｎ ａｔｅｄ ｂｙ ｔｈｅ ｔａｉｌ from ｔｒｕ ｅ “  0 ” -Reproducing the signal shape by MC is important.

8 April Background non-  B.G. feed down B.G. m 2  distribution Tau mass limit (0)(0) The signal level is different more than 4th order of magnitude between  (770) and  ’’(1700). BG is important at threshold and  ’’ region.

8 April New MC set New  MC (include  ” to TAUOLA MC) More reliable estimate of continuum BG Estimate continuum using BG enriched sample. Require stronger cut for tag side 1 charged track + no  More reliable estimate of feed-down BG. some modes have small Br but dominate in the special region. i.e. threshold region        (    0  )       0 K L  etc. Systematic study  0 side band, efficiency check Some important features

8 April Acceptance (including tagging eff.) Data are Unfolded with the Singular Value Decomposition (SVD) method. Acceptance

8 April Results Br Mass Spectrum Pion form factor Extract resonance Parameters Comparison with previous exp. Evaluation of a  and iso-spin violation correction.

8 April Result (1) Branching Fraction Normalized to the number of  -pairs Tau-pair selection  acceptance : % : background : %  0 selection Acceptance: % Background feed down: % qq-conti. : % Br 2  = ( （ stat) 0.39(sys))% Belle

8 April Systematic on Br Measurement Source Tracking efficiency 0.47  0 efficiency 1.3 Background in  -pair 0.59 Feed down background 0.16 Continuum background 0.20  veto 0.20 Trigger 0.32 MC statistics 0.08 Total 1.52 Systematic is dominated by the uncertainty of the  0 efficiency and the BG in  -pair  0 Calibrated by  signals ( ). Checked by using electron tracks.

8 April Result (2): Mass spectrum Mass spectra  ＝  Phase space  Form Factor  umber of entries /0.05 (GeV/c 2 ) 2 Unfolded Results

8 April Result (3) Pion Form Factor |F π | 2 From 64M      pairs, Belle selects 5.5M        events! Error bars include both statistical and systematic Interference between  ’ and  ” Fit with BW |Fπ|2|Fπ|2 2  F

8 April Systematic on the mass distribution (1) Unfolding procedure Reproducibility of the signal. （ UNF ①） Unfolding condition : value±5 （ UNF ②） Acceptance (Accept.)  0 efficiency uncertainty Effect of  -track isolation Change a cut on the cluster-track distance （ default and tighter one(30cm ） ) Momentum or energy scale (ENS) Change E  by it’s uncertainty estimated from the   mass peak position.  ±0.2 ％ )

8 April Systematic on the mass distribution (2) Background Continuum BG (BKG ① ) estimate at the mass region higher than m  uncertainty is estimated to be 10% Feed down BG (BKG ② ) dominated by         systematic is estimated by changing the Br in PDG by 1  non-  0 BG (BKG ③ ) dominated in the low (M  0 ) 2 region. In this region, the size of the non-  0 background in the lower M  side is different between data and MC. This differences is corrected and the difference is included as a systematic.

8 April Non-  0 background( details). 0.10<(M  0 ) 2 <0.15 F=1.375 F=1 0.55<(M  0 ) 2 <0.60 M   00

8 April Systematic on the Mass Spectrum/Form Factor M 2  threshold  region  ’ region  ” region Unfolding (MC) Unfolding (cond) BKG (continuum) BKG (feed-down ) BKG(non-  0 ) Acceptance Energy scale Total ( %) Systematic Region Dominant Factor %   ’ Energy scale/Unfolding 5% threshold Background (  0, feed down) 10%  ’’ Continuum BG by Toy MC

8 April fit parameters Gounaris-Sakurai (GS) parameterization  (770),  ’(1400),  ’’(1700) Result(4) Resonance parameters The normalization of the GS form is given by Fit with BW form

8 April Fit Results Fit parameter Norm fixed Norm [1.0 ] 774.6±0.2± ±0.4± ±7±28 434±16± ±17±89 80/52 All  ’  ’’ resonance parameters are determined at the same time! PDG2006 , e + e - Hadron reaction ± ± ± ± fit with  ’’ x 2 /ndf=80/(90-10) fit w/o  ’’ x 2 /ndf=135/(90-6) Significance of  ’’ : 6.5  Most precise

8 April Comparison with previous exp. BELLE & ALEPHBELLE & CLEO Ref: Phys. Rep.421 (2005) 191 Ref: Phys. Rev. D61, (2000) 1 Agree with previous exp. of data. Our result is more precise especially in high mass region. 2  F 2  F

8 April Effect on a   ? i Detailed Comparison:  ’ region Fit: Fit to Belle Data Belle-CLEO consistent, ALEPH is higher at (M   2 > 0.8 GeV 2 ;

8 April Evaluation of a   2  ItemValue ± ± ± ±0.42 (17.84±0.06)% ±1.82 (25.42±0.11)% ±2.30 Total ± ３．０ World average is calculated combining our new result

8 April a  （２  ）  contribution from each mass range range (GeV 2 ) BelleALEPH Belle> ALEPH Belle<ALEPH No iso-spin violation correction is applied X Total

8 April Iso-spin Violation Correction Ref. V. Cirgliano et al., J. High Energy Phys. 08, 002(2002) A.Flores-Tlalpa et al., Phys. Rev. D 74, (2006) Source Correction Uncertainty Short distance rad. Cor (S EW ) ± 0.2 Long distance rad. Cor.(G EM ) m  - = m  0 (in phase space)  -  interference ± 0.6 m  - = m  0 (in decay width) +4.2 Electromagnetic decays -1.4 ± 1.4 m  0 = m  – - ± 2.0 Total ± 2.5 X FSR correction in e + e -  V  ->      : +4.2  Total+FSR = ±

8 April Results (5) a  （２  ） Belle(  ) ALEPH, CLEO, OPAL (  ) CMD2,SND (e + e  ) After applying the known iso-spin violation correction. Integrated region:  results are higher than those from e + e -. Ref. Eur. Phys. J. C27, 497 (2003) Ref. Nucl. Phys. Proc. Suppl. 169, 288 (2007)

8 April Summary We have studied          using high statistics Belle data Br measurement: (1.6% accuracy) Precise 2  mass spectrum and the pion form factor are determined. We can provide them by a table. In addition to  (700),  ’(1400),  the production of  ’’(1700) is unambiguously identified and its parameters are determined. Our results for agree with the previous  based results but are higher than those from e + e -. The results are accepted by PRD, will appear in Oct. issue. The paper is accepted by PRD and will appear in Oct. issue.

8 April Backup Slide

8 April Comparison :   - >  -  0  and e + e - - >     by F. Jegerlehner (private commun.)

8 April Internal Systematic Error source Background estimation ・ non-  （ ee->hadron ） ・ feed-down h≥2  0 ・ feed-down K －  0 ±0.11 ±0.09 ±0.15  0 /  selection efficiency/shape cuts ±0.35 Energy scale ±0.10 Gamma veto ±0.93  /track overlap 0.24 Tagging Dependence <0.1 Smearing/Migration effect Total ±1.04

8 April  interference  -  interference effects are estimated using following form for the amplitude.

8 April Pion Form Factor |F π | 2 Low mass region  mass region (linear scale) Error bars include both statistical and systematic

8 April Systematic of resonance parameters Source of systematics  ’  ’   ’’  ’’  Fit bias Unfold B.G Acceptance Momentum scale total (MeV) (MeV) (MeV)(MeV) (deg.) (MeV) (MeV) (deg.)

8 April e + source Ares RF cavity Belle detector World record: L = x /cm 2 /sec SCC RF(HER) ARES(LER) 8 x 3.5 GeV 22 mrad crossing ~ 1 km in diameter Mt. Tsukuba KEKB Belle since 1999 First successful op. of Crab cavities The KEKB Collider

8 April  / K L detection 14/15lyr. RPC+Fe Central Drift Chamber Tracking +dE/dx Small cell +He/C 2 H ６ CsI(Tl) 16X 0 Si vtx. det. 3 lyr. DSSD TOF counter SC solenoid 1.5T 8 GeV e  3.5 GeV e  Good tracking and particle identification Belle detector  0 mass resolution ;   ~ 5 -8MeV Aerogel Cherenkov cnt. n=1.015~1.030