1. Probing LFV With m – e Conversion Xiao-Gang He (SJTU&NTU) Enkhbat, Deshpande, Fukuyama, He, Trumura and Tsai, PLB703,562(2011) arXiv: 1106.5085 Bo, Tsumura and He, arXive: 1107.5879 (PRD in press) Cai, He, Ramsey-Musolf and Tsai, arXiv:1108.0969

2. 1.Introduction In the minimal SM (without right handed neutrino), lepton flavor number is conserved. Observation of neutrino oscillation tells that lepton number is violated. No other places LFV process has been observed, there are, however, stringent constraints on such processes, the famous ones are m -> e g and e -> e e anti-e. Theoretical models explaining neutrino masses and oscillation usually have LFV interactions. It is important to study LFV processes to understand the laws of Nature. mscatters off a nuclei and changes into an e is a LFV process, m– e conversion. I will show that this processes can provide important information.

3. Current experimental bounds

4. Calculation of m -> e conversion from quark level effective Lagrangian

5. Detailed calculations, Kitano, Koike and Okada, PRD66,096002(2002)

7. 2. m – e Conversion in Fourth Generation Model l m e = V m 4 V e4, V ij quark mixing matrix element with 4 th generation

8. x 1,2,3 = (light neutrino mass)/m W ^2, very small, in SM3, m -> e g, m -> e e anti-e and m – e conversion rates very small!

9. Direct search for the 4 th generation: M 4 > 335 GeV, Tevatron; M t’ > 270 GeV, M b’ > 290 GeV at 95%c.l.( ATLAS), (newer number also larger than 450 GeV) M t’ > 450 GeV, M b’ > 495 GeV at 95% c.l. (CMS) Electroweak precision data: Mass splitting of up and down heavy quark: 60 GeV of so, OK. PMNS matrix 4x4: V i4 < a few x 0.01, OK

10. m – e conversion gives the best bounds! Z-penguin Dominance Current experimental bounds

11. Z-penguin dominance

12. Future experimental sensitivities

13. 3. Radiative Neutrino Mass and Minimal Dark Matter The R n MDM Model Radiatively generate neutrino mass and have dark matter in the model without introducing beyond SM symmetries

15. m -> e g and m – e conversion in R n MDM No Z-penguin contribution to m – e conversion

16. No Z-penguin contribution, m – e conversion is not as strong as that in 4 th generation model

17. 4. Type III Seesaw with Quadruplet

18. Some interesting features of the model

19. m -> e g and m – e conversion in quadruplet model

21. 5. Conclusions m – e conversion can be used to probe LFV interactions If a model with Z-penguin contribution, the current experimental bound on m – e conversion already provides better constraints than those from m -> e g. With Z-penguin contributions, the future experimental sensitivity on m – e conversion can provide better constraints than those from m -> e g.

22. LHC 和暗物质物理研讨会 Workshop on LHC and Dark Matter Physics Web Page: www.physics.sjtu.edu.cn/lhmdwww.physics.sjtu.edu.cn/lhmd 会议时间： 2011 年 11 月 25 日－ 27 日 地点：上海交通大学粒子物理与宇宙学研究所 会议不收注册费。部分参加会议的学生可以获得交通 和住宿资助。 需要资助的学生请与何小刚（ hexg@sjtu.edu.cn ） hexg@sjtu.edu.cn 或廖玮（ liaow@ecust.edu.cn ） 联系。 liaow@ecust.edu.cn