International workshop ee collisions from phi to psi

International workshop e+e- collisions from phi to psi Search for Lepton Flavor Violating Tau decays at B-factory - Introduction - Experimental results - Future prospects - Summary 2006/2/27 -3/2 International workshop e+ecollisions from phi to psi at BINP 2006/2/27 -3/2 K. Inami Nagoya university, Belle

Introduction n n Lepton flavor violating decays have a very small probability in the Standard Model (even with neutrino oscillation). New physics effects (SUSY, Extra-D, etc. ) may allow us to observe LFV with the present experimental sensitivity. Previous results from CLEO were sensitive to Br~O(10 -6). The B factories (Belle and Ba. Bar) have sensitivities of O(10 -7~10 -8). 2006/2/27 -3/2 International workshop e+e- collisions from phi to psi at BINP 2

B-factories n Asymmetric-energy e+ecollider at Upsilon(4 S) n n 500 fb-1 Very high luminosity n n For CPV search with B 0 Integrated luminosity -1 for Belle n >500 fb -1 for Ba. Bar n >300 fb-1 Tau factory! n s(tt)~0. 9 nb, s(BB)~1. 1 nb 2006/2/27 -3/2 International workshop e+e- collisions from phi to psi at BINP 3

Detectors at B-factories n F/B asymmetric detectors n n Good vertex resolution and particle ID ability Accumulated data: 8 n >4. 5 x 10 t-pairs at Belle, >3. 0 x 108 t-pairs at Ba. Bar Br~O(10 -8) sensitivity! 2006/2/27 -3/2 International workshop e+e- collisions from phi to psi at BINP 4

Analysis method n Event Selection n n Low multiplicity events Separate into hemispheres n n Missing momentum n n n Signal and tag sides Low missing mass Small Ng Lepton tag etc. 2006/2/27 -3/2 International workshop e+e- collisions from phi to psi at BINP 5

Analysis method (2) n Signal extraction n Calc. Minv and DE n n Blinded signal region n n DE=Erec-Ebeam Event selection study Estimate background Signal MC of t mg Signal region using sideband data n Open blind and estimate signal yield n n Estimate upper limits BG reduction is important to improve the sensitivity. Background 2006/2/27 -3/2 International workshop e+e- collisions from phi to psi at BINP 6

t mg Belle n n Ba. Bar n 86. 3 fb-1 data n 232 fb-1 data n Br<3. 1 x 10 -7 at 90%C. L. n Br<0. 68 x 10 -7 PRL 92, 171892 (2005). n PRL 95, 041802 (2005). Background: t mnn + ISR n Small contamination of mm BG in DE>0 2006/2/27 -3/2 International workshop e+e- collisions from phi to psi at BINP 7

t mg : Belle vs Ba. Bar n Belle : Br<3. 1 x 10 -7 / 86. 3 fb-1 n n n e = 11. 1% 2 D EML fit with 5 s signal box Nsignal= 0, NBG= 54 n n Belle : 5 s box Nsignal is constrained to be 0. Ba. Bar : Br<0. 68 x 10 -7 / 232 fb-1 n n n e = 9. 4% 1 D EML fit with 2 s DE band Nsignal= -2. 2, NBG= 143 n n Ba. Bar : 2 s band N is allowed to be negative. Negative yield gives lower U. L. than expected. 2006/2/27 -3/2 International workshop e+e- collisions from phi to psi at BINP 8

t eg n Belle n Ba. Bar n 86. 7 fb-1 data n 232 fb-1 data n Br<3. 9 x 10 -7 at 90%C. L. n Br<1. 1 x 10 -7 PLB 613, 20 (2005). n PRL 96, 041801 (2006). Background: t enn + ISR 2006/2/27 -3/2 International workshop e+e- collisions from phi to psi at BINP 9

t 3 l n Belle: 87. 1 fb-1, Ba. Bar: 91. 5 fb-1 PLB 598, 103 (2004), PRL 92, 121801 (2004). n Br<(1. 1~3. 5)x 10 -7 at 90%C. L. Belle’s results Signal region n Background: low level n qq around DE<0, QED(mm or Bhabha) around DE>0 2006/2/27 -3/2 International workshop e+e- collisions from phi to psi at BINP 10

t lhh n n Belle: 158 fb-1, Ba. Bar: 221 fb-1 Br<(1. 6~8. 0)x 10 -7 by Belle (preliminary) Br<(0. 7~4. 8)x 10 -7 by Ba. Bar, PRL 95, 191801 (2005). Background: qq(flat) and tt(corner) n t ehh: negligible BG level 2006/2/27 -3/2 International workshop e+e- collisions from phi to psi at BINP Ba. Bar’s results 11

t lp 0/h/h’ n n t ep 0 t mp 0 t eh ’ t mh ’ qq Lepton + Pseudoscalar meson 154 fb-1 Belle: Br(t mh)<1. 5 x 10 -7 Br < (1. 5~10)x 10 -7 PLB 622, 218 (2005). n t eh Data tt t mh Background n n Signal region m: tt + qq e: negligible 2006/2/27 -3/2 International workshop e+e- collisions from phi to psi at BINP 12

t l. Ks n n n Belle preliminary Belle: 281 fb-1 t m. Ks Br(t m. Ks)<0. 52 x 10 -7 Br(t e. Ks)<0. 60 x 10 -7 (Preliminary, hep-ex/0509014) n n n Most stringent U. L. among tau LFV searches High efficiency (14%, 12%) and Low BG t e. Ks Background: negligible n D± l±Ksn, p±Ks 2006/2/27 -3/2 International workshop e+e- collisions from phi to psi at BINP 13

t l. V 0 n Lepton+Vector meson Belle: 158 fb-1 n Br<(2. 0~7. 7)x 10 -7 n Belle preliminary t er 0 t e. K* t mr 0 t m. K* t ef t m. K* t mf (Preliminary) n Background: tt n n t m. V 0: + qq t e. V 0: +2 photon (ee eeuu, eess etc. ) 2006/2/27 -3/2 International workshop e+e- collisions from phi to psi at BINP Signal region 14

t Baryons n t pg, pp 0 n n Belle (preliminary) B(t pg)<3. 0 x 10 -7 (87 fb-1) B(t pp 0)<6. 5 x 10 -7 (154 fb-1) Background: many tt, qq n n p/p misidentification t Lp n n n t- Lp- Belle: 154 fb-1 B(t Lp)<1. 4 x 10 -7 B(t Lp)<0. 72 x 10 -7 PLB 632, 51 (2006). n Background: tt(a 1 n), qq 2006/2/27 -3/2 International workshop e+e- collisions from phi to psi at BINP 15

B. R. summary New Physics n n Br < O(10 -6) in PDG (by CLEO) Br < O(10 -7) by Belle and Ba. Bar 2006/2/27 -3/2 International workshop e+e- collisions from phi to psi at BINP 16

For Future n B-factories are accumulating data stably. n n Currently, >7. 5 x 108 t-pairs in two B-factories. However, improvement of LFV sensitivity will be slow. n Non-negligible backgrounds m/p n n Need better m/p separation Low energy t-factory may have an advantage. n Effects of ISR and qq may be reduced. 2006/2/27 -3/2 International workshop e+e- collisions from phi to psi at BINP 17

Future prospect n Super B-factory : >10 times more data n B. R. sensitivity: ~1/n for negligible BG case ~1/ n for BG dominated modes 2006/2/27 -3/2 International workshop e+e- collisions from phi to psi at BINP 18

Future prospect (2) n Possible sensitivity with Super B-factory n Red band for 5~10 ab-1 Super B-factory 2006/2/27 -3/2 International workshop e+e- collisions from phi to psi at BINP 19

Summary n n A data sample of >7. 5 x 108 t-pairs has been successfully obtained by the B-factories. LFV sensitivities are Br~1 x 10 -7. n n For some modes, it will be hard to improve the sensitivity due to backgrounds. n n n Exploring possible parameter space of New Physics Better muon identification Tau-factory at around energy threshold may be better to reduce ISR effects. ? Super B-factory will produce 1010 t-pairs at 10 ab-1. LFV sensitivity will reach Br~O(10 -9). 2006/2/27 -3/2 International workshop e+e- collisions from phi to psi at BINP 20

Effect to physics parameter n MSSM with Seesaw PRD 60, 055008 (1999). n Higgs mediated in MSSM PRD 66, 057301 (2002). n Heavy Dirac neutrino model PRD 62, 0306010 (2000). n B(t l. V 0) constrain y 2 te and y 2 tm. 2006/2/27 -3/2 International workshop e+e- collisions from phi to psi at BINP 21