Probing LFV With – e Conversion

Xiao-Gang He(SJTU&NTU)

Enkhbat, Deshpande, Fukuyama, He, Trumura and Tsai, PLB703,562(2011) arXiv: 1106.5085Bo, Tsumura and He, arXive: 1107.5879 (PRD in press)

Cai, He, Ramsey-Musolf and Tsai, arXiv:1108.0969

1. IntroductionIn 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 -> e 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.

scatters off a nuclei and changes into an e is a LFV process, – e conversion. I will show that this processes can provide important information.

Current experimental bounds

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

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

– e Conversion in Fourth Generation Model

eV4Ve4,

Vij quark mixing matrix element with 4th generation

x1,2,3 = (light neutrino mass)/mW^2, very small, in SM3, -> e , -> e e anti-e and – e conversion rates very small!

Direct search for the 4th generation:M4 > 335 GeV, Tevatron; Mt’> 270 GeV, Mb’ > 290 GeV at 95%c.l.( ATLAS),(newer number also larger than 450 GeV) Mt’ > 450 GeV, Mb’ > 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: Vi4 < a few x 0.01, OK

– e conversion gives the best bounds!Z-penguin Dominance

Current experimental bounds

Z-penguin dominance

Future experimental sensitivities

3. Radiative Neutrino Mass and Minimal Dark Matter The RMDM Model

Radiatively generate neutrino mass and have dark matter in the model without introducing beyond SM symmetries

-> e and – e conversion in RMDM

No Z-penguin contribution to – e conversion

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

4. Type III Seesaw with Quadruplet

Some interesting features of the model

-> e g and – e conversion in quadruplet model

5. Conclusions

• – e conversion can be used to probe LFV interactions

• If a model with Z-penguin contribution, the current experimental bound on – e conversion already provides better constraints than those from -> e .

• With Z-penguin contributions, the future experimental sensitivity on – e conversion can provide better constraints than those from -> e .

LHC和暗物质物理研讨会Workshop on LHC and Dark Matter Physics

Web Page: www.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

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