1 / 38

Tau Physics

Tau Physics. Flavor Physics and CP Violation May 5-9, 2008, National Taiwan University, Taiwan Hisaki Hayashii Nara Women’s University. Contents. Lepton Flavor Violation in t decays Tau decays to strange particles 2 p decay and muon anomalous magnetic moment.

jesse
Download Presentation

Tau Physics

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. TauPhysics Flavor Physics and CP Violation May 5-9, 2008, National Taiwan University, Taiwan Hisaki Hayashii Nara Women’s University National Taiwan University, Taipei, Taiwan

  2. Contents • Lepton Flavor Violationin t decays • Tau decays to strange particles • 2p decay and muon anomalous magnetic moment National Taiwan University, Taipei, Taiwan

  3. Lepton Flavor Violation (LFV) • Standard Model (SM) exactly forbids LFV. • Extended SM including neutrino mixing term includes LFV. • Charged Lepton Flavor Violation can occur through loop diagram. But, extremely tiny branching ratio below experimental sensitivity (Marciano and Sanda, Phys.Lett. B67 (1977), Pham, EPJ C8(1999)513) • Many NP models include LFV vertex naturally. • Observation of charged LFV •  Clear signal of new physics! • Tau lepton has many possible LFV decay modes. •  Wide window to probe New Physics effects. National Taiwan University, Taipei, Taiwan

  4. LFV tau decays • Predicted by many new physics models • Normal NP models enhance t  mg. • For some NP parameters, other modes may be enhanced instead. National Taiwan University, Taipei, Taiwan

  5. Status of LFV search at spring 2007 • Current accumulated luminosity; >700fb-1 at Belle and >500fb-1 at BaBar. • Searches for 3l, lhh modes should be updated. V0=r, w, f, K* National Taiwan University, Taipei, Taiwan

  6. LFV analysis • Signal extraction • Calc. Minv and DE • DE=Erec-Ebeam • Blinded signal region •  Event selection study • Estimate background using sideband data • Open blind and estimate signal yield • Estimate upper limits by Likelihood fit or number of events in signal region • BG reduction is important to improve the sensitivity. • Find effective ways to use all information Signal MC Signal region Background National Taiwan University, Taipei, Taiwan Minv

  7. t3 leptons; BG reduction • Optimized event selection for each mode separately because the BG processes are different. BG events eemm(eeee) Bhabha(mm) Signal topology • g conversion veto • (e-e+e- and m-e+e-) • Electron-veto on the tag-side • (e-e+e- and e-m+m-) National Taiwan University, Taipei, Taiwan

  8. data signal t-ge-e+e- signal region t-gm-m+m- tlll search; Belle • Data; 535fb-1 • Efficiency; (6.0-12.5)% • NBG; 0.0-0.4 events • Nobs; 0 events for all modes • Br<(2.0-4.1)×10-8 at 90%C.L. (Y.Miyazaki et. al., PLB 660 (2008) 154) National Taiwan University, Taipei, Taiwan

  9. tlll search; BaBar • Data; 376fb-1 • Efficiency; (5.5-12.4)% • NBG; 0.3-1.3 events • Total BG; 4.2±0.8 • Nobs; 6 events in total • Br<(3.7-8.0)×10-8at 90%C.L. (B.Aubert et. al.,PRL 99 (2007) 251803) =Minv-Mt National Taiwan University, Taipei, Taiwan

  10. tlV0 search data signal • Belle; 543fb-1 data • Ten modes are investigated, l=e,m and V0=r,K*0,K*0,f,w • Main BG: SM t decay;tpwn,tpppn • Signal Efficiency; 2.5 - 4.9 % • Expected NBG;0.0 - 1.0 events • Observed number of events; 1 event for tmf, ew, eK*0 0 events for others • Br<(5.9-18)×10-8 (Y.Nishio et. al., arXiv:0801.2475) • BaBar; 384fb-1 data • Searched for mw, ew Br<(10-11)×10-8 (B.Aubert et. al., PRL 100;071802 2008) National Taiwan University, Taipei, Taiwan

  11. mf0 ef0 ● data signal MC tlf0(980) search Br(t→mf0): Br(t→mmm): Br (t→mh) =1.3: 0.54 :1 (C.H.Chen et.al, PRD74:035010,2006 ) • Scalar Higgs mediation • No search yet. • Belle; 671fb-1 • Use f0(980)p+p- (4s) • No event is observed. • Preliminary result Br(t→l f0(980) )xBr(f0(980)→p+p-) m f0(980) : <3.3X10-8, e f0(980) : <3.4X10-8 National Taiwan University, Taipei, Taiwan

  12. Current status of LFV search • Sensitivity is improved by factors of 3-10. It comes from the luminosity increase and successful BG reduction. • t3leptons sets most stringent upper limit. V0=r, w, f, K* National Taiwan University, Taipei, Taiwan

  13. LFV Searches Prospects • B-factories improved LFV tau Br limit by factor 10-100 • Limits can be improved by factor 2-4 analyzing all planned B-factories yield. • Super B-factories expected to improve search region again by factor 10-100 dep. on bkg. • tlg; scale as ~1/L • e+e-t+t-g is irreducible BG. • ~10-8 level at super B-factory • tlll, lX0; scale as ~1/L • BG can be reduced by lepton-ID or mass requirement for X0 • O(10-9) level at super B-factory National Taiwan University, Taipei, Taiwan

  14. Taudecays to strange particles • B-factory detectors have a good p/K separation, useful to discriminate Cabibbo-suppressed ts decays • Inclusive ts can potentially achieve most precise/clean Vus measurement (0.7%): by Pich • In ts decays the uncertainty on Vus is dominated by experimental uncertainties. • For 3-body K decays, the uncertainty on Vus is limited by theory determination of the form-factor :f(0)+ (1%->0.5%?). • If spectral functions are also measured, Vus and ms can be determined by a simultaneous fit. National Taiwan University, Taipei, Taiwan

  15. Approaches to Vus Inclusive measurement by summing up all decay modes. National Taiwan University, Taipei, Taiwan

  16. Before B factories: Br(ts ) Precision: 4-10% National Taiwan University, Taipei, Taiwan

  17. Before B factories: Vus and ms Hadronic Width: Flavour SU(3) Breaking: where Vus Ｍａｌｔｍａｎ，　ｈｅｐ-ph/061１1８０ National Taiwan University, Taipei, Taiwan Ms (GeV)

  18. Strength at B-factories Good K-p Separation High Statistics Well separated in space National Taiwan University, Taipei, Taiwan

  19. Br(t-Kpnt) t-K-p0nt • 230 fb-1 data • 78K e/m tagged events PRD 76 (2007) 051104(R) t-Ksp-nt • 351 fb-1 data • 53K e/m tagged events PL B654 (2007) 65 National Taiwan University, Taipei, Taiwan

  20. Exclusive Br(t-h-h+h-nt) PRL 100 (2008) 011801 National Taiwan University, Taipei, Taiwan

  21. Update on Vus using B Factor Results [1] [1] M. Palutan, Kaon’07 By Pich [2] hep-ex/0707.3058 Updated Results [2] • Babar: • t-K-p0nt PRD 76 (2007) 051104(R) • t-K-p+p-ntPRL 100 (2008) 011801 Belle: • t- Ksp-nt PLB 654 (2007) 65 Theory prediction assuming m-t universality • Br(t- K-nt) from Br(K-m-nt ) 3.3s [2] M. Jamin, Moriond EW ‘07 S.Banerjee, arXiv:0707.3054v4 National Taiwan University, Taipei, Taiwan

  22. hadron +CVC t-p-p0ntand am • t-p-p0nt • has the largest Br • CVCrelation with e+e-→p+ p- • Plays an important role for the h. v. p. term in the muon anomalous magnetic moment. am=(gm-2)/2 National Taiwan University, Taipei, Taiwan

  23. not yet published not yet published preliminary Status of am • Recent data indicate that there is a systematic difference between the 2psystem in e+e－reaction and t-decays, even after applying knownisospin violation correction. Main difference btw and is from 2p mode. ICHEP-2006(M.Davier et al.): am(exp)-am(th) is Ahint to New Physics beyond the SM!? How about t ? National Taiwan University, Taipei, Taiwan

  24. 2 F p Pion Form Factor |Fπ|2 From 23M t+t-pairs, Belle selects 5.4M t-p-p0nt events! |Fπ|2 • Unfolded by Singular Value Decomposition Method. • Error bars include both statistical and systematic • Fit with BW • Interference between r’ and r”: r”signal significance 6.5s National Taiwan University, Taipei, Taiwan

  25. Belle 25.12 0.04 0.38 Br(t-p-p0nt ) • Normalized to the number of t-pairs • Tau-pair selection acceptance : 32.6 0.05% : 1.1120.003 background : 7.4 0.03% • pp0 selection Acceptance: 41.0 0.1 % Background feed down: 7.02 0.08 % qq-conti. : 2.22 0.05 % • Br= (25.12 0.04（stat) 0.38(sys))% Preliminary National Taiwan University, Taipei, Taiwan

  26. Systematic on Br Measurement • Source Tracking efficiency 0.47 p0 efficiency 1.4 Background in t-pair 0.36 Feed down background 0.16 Continuum background 0.20 g veto 0.20 Trigger 0.32 MC statistics 0.08 Total 1.6 • Systematic is dominated by the uncertainty of the p0 efficiency • Calibrated by h signals ( ). • Checked by using electron tracks. • (gg →p0p0can use to improve p0 efficiency in near future.) National Taiwan University, Taipei, Taiwan

  27. Systematic on the Mass Spectrum/Form Factor ( %) Check by known MC distribution Systematic Region Dominant Factor 0.7-1.8% r,r’ Energy scale/Unfolding 5% threshold Background (p0, feed down) 10% r’’ Continuum BG/Unfolding National Taiwan University, Taipei, Taiwan

  28. Comparison with previous exp. Fit: Fit to Belle Data • Belle-CLEO consistent, • ALEPH is higher • at (Mpp)2 > 0.8 GeV2 Effect on am2p? i National Taiwan University, Taipei, Taiwan

  29. Results am （２p） X 10 -10 Belle> ALEPH Belle<ALEPH No iso-spin violation correction is applied National Taiwan University, Taipei, Taiwan Total

  30. Isospin Violation Correction • Ref. V. Cirigliano et al., J. High Energy Phys. 08, 002(2002) A.Flores-Tlalpa et al., Phys. Rev. D 74, 071301 (2006) Source Correction Uncertainty Short distance rad. Cor (SEW) -12.0 0.2 Long distance rad. Cor.(GEM) -1.0 mp- mp0(in phase space) -7.0 r-w interference +3.5 0.6 mp- mp0(in decay width) +4.2 Electromagnetic decays -1.4 mr0 mr– - 1.4 Total -13.7 2.0 X10-10 National Taiwan University, Taipei, Taiwan

  31. am （２p）: comparison t and e+e- • Integrated region: • After applying the known iso-spin violation correction. • Belle(t) • ALEPH, CLEO, OPAL (t) Ref. Eur. Phys. J. C27, 497 (2003) • CMD2,SND (e+e-) Ref. Nucl. Phys. Proc. Suppl. 169, 288 (2007) t results are higher than those from e+ e-. National Taiwan University, Taipei, Taiwan

  32. Conclusions/Summary • LFV Searches • Good experimental coverage • New searches for 3-prong final state • t3l, lV0, lf0 using 400~700 fb-1 of data • Better sensitivity than previous analysis • LFV sensitivities are Br~O(10-8) • LFV are Super B-factory Golden channels  Sensitivity will reach Br~O(10-9). • Vus fromtsinclusive • Results on several Br, Vus are updated. • 3.3 s discrepancy w.r.t Kaons and unitarity • Spectrum measurement: cross check + determine Vus and ms, simultaneously. • High statistics study on t-p-p0nt • Br and mass spectrum are updated. • Inaddition to r(700), r’(1400),the production of r’’(1700) is unambiguously identified and its parameters are determined. • Belle results for agree with the previous t based results but are higher than those from e+ e-. National Taiwan University, Taipei, Taiwan

  33. r-w-f int. based on the Hidden Local Symmetry can explain the difference of 2p spec. between e+e- and t (M. Benayoun et al. arxiv:0711.4482) National Taiwan University, Taipei, Taiwan

  34. Backup Slide National Taiwan University, Taipei, Taiwan

  35. External parameters World average is calculated combining our new result and the preceding measurements of other experiments. National Taiwan University, Taipei, Taiwan

  36. Davier et al. Mod. Phys. 78,1043 (2007) National Taiwan University, Taipei, Taiwan

  37. National Taiwan University, Taipei, Taiwan

  38. National Taiwan University, Taipei, Taiwan

More Related