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Sanjay K Swain, SLAC BABAR Collaboration 27 th July 2007

t -decays in B-factories. Sanjay K Swain, SLAC BABAR Collaboration 27 th July 2007. SUSY07 @ Karlsruhe. Outline. Introduction t  l g ( l = e, m ) t  l K s t  l P 0 (P 0 = p 0 ,h,h ’) t  lll / l hh (h = K, p ) t  L h Conclusion.

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Sanjay K Swain, SLAC BABAR Collaboration 27 th July 2007

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  1. t-decays in B-factories Sanjay K Swain, SLAC BABAR Collaboration 27th July 2007 SUSY07 @ Karlsruhe Outline • Introduction • t lg (l = e, m) • t  lKs • t lP0 (P0 = p0,h,h’) • t lll / lhh (h = K, p) • t  L h • Conclusion

  2. Lepton Flavor Violation (LFV) in t-decays • In the minimal Standard Model, the lepton flavor is conserved • for each generation • e.g t -> mg is not allowed • Lt =1 Lt =0 => DLt= 1 • Lm=0 Lm=1 => DLt = -1 but L = 0 ne nm nt e- m- t- L = Le + Lm + Lt Lt =1 Lm =1 Le =1 • But neutrino oscillation implies: nm ne => Lepton Flavor is violated • The LFV in neutral sector induces LFV in charged lepton sector 2 DMn2   DMn2 ~ 10-3 eV2 But B(t->mg)  Mw2 Mw ~ 1011 eV ~ 10-54 Lee-Shrock, Phys. Rev. D 16, 1444 (1977)

  3. New physics phenomena in t-decays 1. Things would be completely if we replace The slepton have same lepton numbers and do have mixing 2 2 DMn   ~ DM n and Mx have different (higher) mass scale ~ ~ Now B(t->mg)  2 ~ Mx 2. • The branching fraction can be enhanced significantly

  4. Two asymmetric energy B-factories PEP-II at SLAC KEKB at KEK 9GeV (e-)  3.1GeV (e+) peak luminosity: 1.121034cm-2s-1 8GeV (e-)3.5GeV (e+) peak luminosity: 1.711034cm-2s-1 B-factories BaBar Belle

  5. Integrated Luminosity KEKB + PEP-II Cross Section sBB1.05 nb stt 0.92 nb July 2006 710/fb (Jan 07) >1000/fb !! KEKB for Belle more than 1 billion (109) t-pairs 391/fb (Jan 07) PEP-II for BaBar

  6. t-decay topology electron/muon • Two hemispheres  thrust (separated in space) • Signal side: neutrino-less 1-prong decay • -> electron / muon • (all the particles are fully reconstructed) • Tag side: 1-prong or 3-prong • enn , mnn, pn, rt g Signal side t- e- e+ t+ Tag side tag missing MEC : beam energy constrained t mass DE: energy difference Et- Ebeam t mg Signal MC Sometimes, variables used are DEand DM = Mrec – Mt

  7. Analysis methodology 2.0 ±3s blinded region ±2s signal region Mec (Gev/c2) We look for the expected and observed background in the neighboring regions to validate the fit GSB: DE[-1.0, 0.5] and MEC[1.5,2.0] For t->lP0: -0.8 1.5 -1.0 0.0 0.5 DE (Gev) For t->lg, the expected background in the signal box is obtained by fitting the sidebands of MEC distribution from the ±2s band in DE where as for t->lP0, the background is obtained by 2D un-binned maximum likelihood fit to un-blinded region in MEC and DE.

  8. Results from tlg Efficiency=(4.7±0.3)% BF (t -e- g) < 11 x10-8 PRL 96, 041801 (2006) Efficiency=(7.42±0.65)% BF (t - m- g) < 6.8 x 10-8 PRL 95, 041802 (2006) Signal MC Efficiency=2.99% BF (t -e- g) < 12 x10-8 Data Efficiency=5.07% BF (t - m- g) < 4.5 x 10-8 ar-Xiv:0705.0650 [hep-ex]

  9. Results from tlg and impact on new physics S. Banerjee (Tau06) Nucl. Phys. Proc. Suppl. 169, 199 (2007) MSSM with seesaw: <vu> tanb = <vd> Vu,d are VEVs of neutral higgs coupled to up-type or down-type fermion fields

  10. tlKs (l= e or m) BELLE used 281 fb-1 data B (t - m-Ks ) < 4.9 x 10-8 B (t -e-Ks ) < 5.6 x 10-8 @90% CL Signal MC Data PLB 639, 159 (2006) 1. In R-parity violating SUSY scenario -> l, l’, l’’ ( with 45 couplings)  t decays lKs via tree level scalar neutrino exchange by ll’ coupling • This result can be used to constrain new physics scale in dimension-six • fermionic effective operator involving t-m flavor violation motivated by • neutrino oscillations • lower bounds on axial-vector and pseudo-scalar operators: 36.2TeV and 37.2 TeV

  11. t lP0 (P0 = p0, h, h’) Data Using 339 fb-1 data, the upper limit is (1 - 6 ) x 10-7 Signal box (±2 in DE and MEC) Total expected events = 3.1 Total observed events = 2 Shaded region covers 68% of signal MC PRL 98, 061803 (2007)

  12. t lP0 (P0 = p0, h, h’) 401 fb-1 data PLB 648, 341 (2007) These improved upper limit can be used to constrain the parameters of Heavy Dirac neutrino model. Branching fractions of different modes are evaluated in terms of Model Parameters: yte and ytm  [ 0, 1] Using t -> lp0 , yte< 0.17 and ytm < 0.47 @ 90% C.L

  13. Constraining new physics using tmh result M.Sher, PRD 66, 057301 (2002) The left plot shows the Exclusion regions in the mA and tanb plane by different experiments (@ 95% C.L.) New result from BABAR Competitive with the direct Higgs searches at CDF and D0 _ CDF: pp -> H -> t+t- (310 fb-1) _ _ D0: pp -> H -> bb(260 fb-1) -> t+t-(325 fb-1) S.Banerjee (Tau 06) Nucl. Phys. Proc. Suppl. 169, 199 (2007)]

  14. t  lll ( l = e or m) 376 fb-1 BABAR data used Total expected events = 4.2 Total observed events = 6 Signal box 90% of the selected MC events Upper limits ~ ( 4 – 8) x 10-8

  15. t lhh’and tlV0 h (h’) -> K or p V0-> K*(892), r0, f Belle used 158 fb-1 data PLB 640, 138 (2006) Vector Decay modes used: [ e, m ] x [ p+p-, p-p-, p+K-,K+p-,K-p-,K-K+,K-K-, r0, k*0, K*0, f ] _ 22 decay modes (including modes violating total lepton number) The upper limit varies (1.6 - 8.0) X 10-7 1. These improved upper limit can be used to constrain the parameters of Heavy Dirac neutrino model. Signal Box Using t -> lr0 , yte2 < 0.24 and ytm2 < 0.38 @ 90% C.L 2 Constraint the energy scale of dimension-six fermionic effective operator Luu,dd> 29.4TeV, Lss> 24.8 TeV and Lds> 26.8 TeV

  16. Lepton and baryon number violating t-decay • The baryon asymmetry of the universe -> Baryon number violation • (Sakharov condition) • For lepton -> baryon + meson decays, the angular momentum conservation • requires, D(B-L) = 0 or 2 The following decays modes used in this analysis: (237 fb-1) t- ->L0p- t- ->L0p- (hep-ex: 0607040) t- ->L0K- t- ->L0K-

  17. Summary • None of the lepton flavor violating processes has been observed yet. • For t lg, the best upper limit is ~ 4.5 X 10-8 • For t lP0, the best upper limits are ~ (1-9) X 10-8 • For t lKS, the upper limits are ~ 5 X 10-8 • For t lll (hh’), the upper limits are ~ (1 - 8) X 10-8 • Further probe into the LFV using more data can put constraint • on different theoretical models. • If LFV is discovered in near future, it is possible that LFV-inducing • particles will be produced directly at high energy. The LFV effects from • real particles production may then also be seen at colliders STAY TUNED !

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