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Search for LFV t decays involving p 0 , h, h ’ at Belle

Search for LFV t decays involving p 0 , h, h ’ at Belle. Y. Enari, Belle collaboration Nagoya University. Motivation. In MSSM at large tan b, t  mh may have a large branching ratio by Higgs mediated process. Comparison other mode.

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Search for LFV t decays involving p 0 , h, h ’ at Belle

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  1. Search for LFV t decays involving p0,h, h’ at Belle Y. Enari, Belle collaboration Nagoya University

  2. Motivation • In MSSM at large tanb, t  mhmay have alarge branching ratio by Higgs mediated process. • Comparison other mode. Mslepton > weak scale, Br(t mg) is not large. M. Sher, Phys.Rev.D66 05731(2002) K.S.Babu PRL,89,241802 (2002) A. Dedes, et.al. PLB 549,2442 (2002) a. (ms/mm)2 b. color factor c. phase space Br(tmh) : Br(t3m) : Br(tmg) =8 : 1.5 : 1 t  mh is important process!! Search for LFV tau decay involving neutral meson at Belle

  3. Status of LFV t decay search CLEO result (PDG2004) Today’s report. Babar t3l tl h 1/ L @ e~3% tl p, 3l. t mg 1/L @ e~3% 1/L @ e~ 9% Belle tmg,3l 110-7 Efficiency e BG level In MSSM, Br of LFV decay may have O(10-7~10-9). Search for LFV tau decay involving neutral meson at Belle

  4. KEKB & Belle detector Lpeak = 13.91033/cm2/sec Ldt = 287.85 fb-1 • Cross section @ s =10.58GeV • t+t- : 0.9 nb • BB : 1.0 nb m-ID eff. = 87.5% fake = 1.4 % e-ID eff. = 92.4% fake = 0.25 % KEKB is t Factory!!!. Search for LFV tau decay involving neutral meson at Belle

  5. Analysis. Invariant mass : Mmh= E2mh - p2mh Energy difference : DE = Emh – Ebeam * Blind region • Modes • t  e p0, m p0 • t  e h , m h • h gg, h p+p-p0 • t  e h’, m h’ • h’ pph h gg • Blind analysis ±10s ±5s ±10s • Evaluation # of signal event • - Low BG level • Counting signal candidates • using elliptical region • Blind region: -0.5< DE < 0.5(GeV), • -5s < Mmh < 5s Search for LFV tau decay involving neutral meson at Belle

  6. Selection criteria (t  l p0, l h, l h’) • p0 gg •  gg ppp0 h’ pph • Signal event reconstruction signal side ( e/m + p0, h, h’) + tag side (1 trk + ng+ missing.) • BG suppression For QED BG. • NOT m(e) (for 1-1prong) • 5 < ECM< 10.GeV For qq and tt BG • p0 veto for h’s g • 0.5 < cosqmh < 0.95 • Mtag < 1.777 GeV/c2 • missing momentum towards tag side. • pmiss vs. mmiss2 2-D cut. (1prong or 3 prong) Br(t1 prong) = 84 % total Search for LFV tau decay involving neutral meson at Belle

  7. Background suppression (1) • Hadronic process (u,d,s,c) • tt generic process •  Opening angle Bhabha, mm, 2photon process  Total energy not-(e or m) in tag side. (Only 1-1 prong modes) sig : 2% loss tt : 67% rej. uds: 65% rej. signal :5% loss mm : 80% reject. Search for LFV tau decay involving neutral meson at Belle

  8. Background suppression(2) • missing particle : pmiss towards detectable regions. signal event : n is in only tag side cosqthrust-miss< -0.55 tt BG event : n are in both sides  Effective missing mass signal : 17% loss tt : 95% reject black: signal MC Blue: tt generic After all kinematical cut applied: (except e/m ID for signal side) eff.(tt) = 3.8  10-6. eff.(uds) = 3.0  10-7. eff.(mm) = 3.4  10-8. eff.(ee) = 3.0  10-7. Search for LFV tau decay involving neutral meson at Belle

  9. Mass distribution (mID; 1.3<Mmh<2.1; with Blind) BG: Fake p/K (80%) • p0, h, h’ mass peak. •  l p0 : true p0 • others : mis-combination data: 77ev. MC:81.6 ± 8.4 data:57ev. MC:48.1±4.0 data:109ev. MC:100±5.9 (mgg– mp0) (mgg– mp0) -3 < < 3 -5 < < 3 0.907 < mh’ < 0.982 (3s region) sgg sgg sgg ~5.2 MeV/c2 sgg ~12 MeV/c2 s ~ 14 MeV/c2 Search for LFV tau decay involving neutral meson at Belle

  10. DE vs Minv. : t  lp0, lh, lh’ Nexp=0.15±0.15 BG estimation Nexp is calculated from the side band events with assuming a flat distribution. Open blind. Nexp=3.1±1.0 Search for LFV tau decay involving neutral meson at Belle

  11. DE vs Minv. : t  lp0, lh, lh’ Nexp=0.15±0.15 BG estimation Nexp is calculated from the side band events with assuming a flat distribution. Open blind. Nexp=3.1±1.0 Systematic uncertainties - eID:1%, mID: 2%, track: 2%, p0 veto 5.5% Beam BG:2.3% Trigger:1.4% 4.5~8.7% - BG estimation:IfNexp<1, assume Nexp=0. Search for LFV tau decay involving neutral meson at Belle

  12. Result Br is obtained from • Upper limit evaluation (POisson Limit Estimator program) • Feldman-Cousins method s0: signal events e : efficiency Ntt: # of t pairs BX : B of sub-decay s0 2(eBX Ntt) B = (140M tt) J. Conrad et al., PRD 012002 (2003) • Systematic uncertainty: using the Gaussian error. Preliminary 10-70 times tighter limit from PDG2004 First search!! Search for LFV tau decay involving neutral meson at Belle

  13. Discussion - t  mh - (1) Comparison with CLEO result • Statistics 4.7fb-1 154fb-1 • Signal efficiency h  gg 7.2%Bh 8.0%Bh h  p+p-p0not use7.2%Bh • Observed events 0 1 CLEO Belle  33  1.7 Keeping BG level low. Upper limit : B (tmh) < 9.6 10-6 B (tmh) < 1.310-7@ 90% C.L. Search for LFV tau decay involving neutral meson at Belle

  14. Discussion - t  mh - (2) Constraint on tanb vs mA B (tmh) < 1.310-7@ 90% C.L. Preliminary • CDF result : measurement (ppA/fbbbbbb) • LEP result : LEP Higgs Working Group, PRL 86,4472 (2002) http://lephiggs.web.cern/LEPHIGGS/paper/Note2001-04 Search for LFV tau decay involving neutral meson at Belle

  15. Summary • Search for tl p0, l h, l h’ meson mode using 154fb-1. • No indication of signal events. B(tl p0, l h, l h’) < 1.3 ~ 1010–7 @ 90%C.L.. • 10-70 times tighter bounds. • First searches in teh’, mh’. Preliminary tl h : e~3% 1/ L @ e~3% tl p, 3l. t mg 1/L @ e~3% 1/L @ e~ 9% Search for LFV tau decay involving neutral meson at Belle

  16. Backup slides Search for LFV tau decay involving neutral meson at Belle

  17. Signal efficiency and BG - muon mode - (153.8, 428, 232, 160 fb-1) side band MC : data : b0 12.5±2.7 13 2.7 ± 0.7 0.8 ± 0.3 2 0.6 ± 0.4 9.2 ± 2.3 9 3.1 ± 1.0 5.5 ± 1.9 5 1.4 ± 0.6 Search for LFV tau decay involving neutral meson at Belle

  18. Signal efficiency and BG - electron modes - side band MC : data : b0 0.7±0.7 0 0 – 0.0 0.0 ± 0.7 1 0.23 ± 0.23 0.0 ± 0.7 1 0.15 ± 0.15 0.8 ± 0.3 1 0.16 ± 0.16 +0.4 Search for LFV tau decay involving neutral meson at Belle

  19. Result: t  lp0, lh, lh’ Preliminary Nobs/Nexp 0ev./0.0+0.4 0ev./0.2±0.2 0ev./0.2±0.2 1ev./0.2±0.2 -0.0 e = 4.7% e = 6.8% e = 5.7% e = 8.5% 5ev./2.7±0.7 0ev./0.6±0.4 0ev./1.4±0.6 1ev./3.1±1.0 e = 6.4% e = 7.2% e = 8.0% e = 8.4% Search for LFV tau decay involving neutral meson at Belle

  20. History of integrated luminosity Ldt = 288fb-1 Continuous injection Ldt = 244fb-1 Ldt = 154fb-1 2003 Summer: SVD/CDC inner part replacement Search for LFV tau decay involving neutral meson at Belle

  21. KEKB performance snap shot (2004.3.1) Continuous injection mode HER: 8.0 GeV e– LER: 3.5 GeV e+ Lpeak = 13.9×1033/cm2/sec Ldt = 287.85 fb-1 HER 1.1A LER 1.6A L ~ 1.1×1034/cm2/sec • Cross section @ s =10.58GeV • t+t- : 0.9 nb • BB : 1.0 nb KEKB is t Factory!!!. Search for LFV tau decay involving neutral meson at Belle

  22. Belle detector m / KL detection 14/15 lyr. RPC+Fe Aerogel Cherenkov cnt. n=1.015~1.030 3.5 GeVe+ CsI(Tl) 16X0 8 GeVe- TOF conter Scinti + FM-PMT Eg resol. E /E = 1.8% @E=1GeV Si vtx. det. 3 lyr. DSSD Central Drift Chamber small cell +He/C2H5 SC solenoid 1.5T m-ID eff. = 87.5% fake = 1.4 % e-ID eff. = 92.4% fake = 0.25 % proton ID eff. ~ 70 % fake ~ 1 % Trk. resol. spt/pt ~ 0.19pt0.30/b % Search for LFV tau decay involving neutral meson at Belle

  23. Status of LFV search in Belle Belle Published Preliminary New result of this summer. CLEO Babar Search for LFV tau decay involving neutral meson at Belle

  24. Summary table of LFV search in Belle Preliminary result B < O(10-7) are obtained New result in this summer. Published results First search result. Search for LFV tau decay involving neutral meson at Belle

  25. Systematic uncertainty • Related sensitivity • Related BG • Using statistical error as systematic error. (30~45%) • If b0 < 1, we set b0=0 in order to obtain conservative limit. In Total : 4.5 ~ 8.7 %  POLE program Search for LFV tau decay involving neutral meson at Belle

  26. 2.1 Selection criteria ( 1-3 prong + h/h’) • 1-3 prong + ng2 Eg > 0.1 GeV , barrel and endcap ptrk>0.06GeV/c barrel. ptrk >0.1GeV/c endcap. net charge=0. dzrms < 1cm, drrms < 1cm  to reject junk track. signal side: m(e)-ID > 0.9 + 2trk(+,–). • Missing momentum towards tag side. • pmiss vs. mmiss2 2-D cut. • 0.5 < cosqmh’ < 0.92 • -3 s < Mh < 3 s e/m h/h’ p0/h using thrust axis, divide 2 hemisphere for tag side, mtag < 1.777 GeV/c2 Search for LFV tau decay involving neutral meson at Belle

  27. 2.2 Selection criteria (1-1 prong + p0/h) • 1-1 prong + ng  2 signal side: m(e)-ID > 0.9 + 2 g. Pm(e)>0.7GeV/c, Eg > 0.22GeV • p0 veto for h’s g tag side: • NOT m(e) • Mtag < 1.777 GeV/c2 Kinematical cut. • Missing momentum towards tag side. • pmiss vs. mmiss2 2-D cut. • 0.5 < cosqmh’ < 0.92 • -5 s < Mh < 3 s e/m p0/h Search for LFV tau decay involving neutral meson at Belle

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