Relating Radiative Seesaw Neutrino Relating Radiative Seesaw Neutrino And Dark Matter Mass ScalesAnd Dark Matter Mass Scales

Xiao-Gang HeXiao-Gang He

1.1. IntroductionIntroduction

2.2. Radiative seesaw and dark matter MassesRadiative seesaw and dark matter Masses

3.3. Dark matter with SM symmetry onlyDark matter with SM symmetry only

4.4. A model of radiative seesaw and DM with SM symmetryA model of radiative seesaw and DM with SM symmetry

Work with Yi Cai, M. Ramesy-Musolf and Lu-Hsing TsaiWork with Yi Cai, M. Ramesy-Musolf and Lu-Hsing Tsai

1. Introduction1. Introduction

There is about 20% of the energy come from dark matter in our universe. There is about 20% of the energy come from dark matter in our universe. What is the nature of DM is not known: WIMP, Axion, …What is the nature of DM is not known: WIMP, Axion, …What is DM mass, not known, a big range is allowed.What is DM mass, not known, a big range is allowed.DM must be stable, usually impose DM must be stable, usually impose additional symmetryadditional symmetry beyond SM symmetry, beyond SM symmetry, such as R-parity in susy, Zsuch as R-parity in susy, Z2 2 symmetry in darkon modelsymmetry in darkon model, …, …

Neutrinos have non-zero masses. In minimal SM, neutrinos do not have masses. Neutrinos have non-zero masses. In minimal SM, neutrinos do not have masses. Need to go beyond SM to explain why neutrinos have small but non-zero masses.Need to go beyond SM to explain why neutrinos have small but non-zero masses.

Loop generation of neutrino masses, like Zee model…Loop generation of neutrino masses, like Zee model…Also the Seesaw models, Type I, Type II and Type III, and other variations.Also the Seesaw models, Type I, Type II and Type III, and other variations.

All need to introduce new particles in the model. In general these new particles do All need to introduce new particles in the model. In general these new particles do not play a role of DM. not play a role of DM. It would be good to relate them. It would be good to relate them.

2. Radiative seesaw and dark matter Masses2. Radiative seesaw and dark matter MassesE. Ma, PRD73:077301,2006 introduce right handed neutrinos NE. Ma, PRD73:077301,2006 introduce right handed neutrinos NRR and a new Higgs doublet and a new Higgs doublet

under Zunder Z22

NNRR -> - N -> - NRR

-> - -> -

no vev, Zno vev, Z22 not broken. No usual seesaw not broken. No usual seesaw neutrino masses. One loop will generate them.neutrino masses. One loop will generate them.

If neutral If neutral is the lightest particle, it can be DM is the lightest particle, it can be DM

If one of the N is the lightest, it is the DMIf one of the N is the lightest, it is the DM

DM mass related to radiative seesaw neutrino mass scale.DM mass related to radiative seesaw neutrino mass scale.

Can one get rid off the additional ZCan one get rid off the additional Z22 symmetry? Just SM gauge symmetry can do the job? symmetry? Just SM gauge symmetry can do the job?

3. Dark matter with SM symmetry only3. Dark matter with SM symmetry only

M. Cirelli, N. Fornengo and A. Strumia, NP B753,178(2006)M. Cirelli, N. Fornengo and A. Strumia, NP B753,178(2006)

Choose large SM representation with no color which cannot couple to SM Choose large SM representation with no color which cannot couple to SM

fermions and Higgs with renormalizable terms. The neutral component stable, fermions and Higgs with renormalizable terms. The neutral component stable,

plays the role of DM. ---- Minimal Dark Matterplays the role of DM. ---- Minimal Dark Matter

Smallest representations: n = (1, 5, 0)Smallest representations: n = (1, 5, 0)

Why? If n fermion, L: (1,2,-1/2), H: (1,2,1/2) -> L H: (1 + 3, 0), Why? If n fermion, L: (1,2,-1/2), H: (1,2,1/2) -> L H: (1 + 3, 0),

Smallest n: (1, 4, ½) or (1,5,0). Smallest n: (1, 4, ½) or (1,5,0).

If want Majorana mass term, not good to have (1,4,1/2).If want Majorana mass term, not good to have (1,4,1/2).

If n scalar, HH*H: (2 + 3 + 4, ½), to avoid n to couple to this term, If n scalar, HH*H: (2 + 3 + 4, ½), to avoid n to couple to this term,

The minimal should be (1,5,0)The minimal should be (1,5,0)

The lightest n does not decay. Can be candidate for DM.The lightest n does not decay. Can be candidate for DM.

Co-annihilation produce the right relic DM densityCo-annihilation produce the right relic DM density

Coupling is SU(2) coupling, known, the DM relic density will fix the DM massCoupling is SU(2) coupling, known, the DM relic density will fix the DM mass

Require n to produce the DM relic density, the mass can be determined.Require n to produce the DM relic density, the mass can be determined.

4. A model of radiative seesaw and DM with SM symmetry4. A model of radiative seesaw and DM with SM symmetry

Ma model + MDM Ma model + MDM

A new model:A new model: No additional symmetries other than SM gauge symmetry! No additional symmetries other than SM gauge symmetry!

Radiative seesaw at one loop levelRadiative seesaw at one loop level

Needs more than one NNeeds more than one NRR to get phenomenologically consistent neutrino masses. to get phenomenologically consistent neutrino masses.

Dark matter, assuming NDark matter, assuming NRR11 is the lightest is the lightest

From: M. Cirelli and A. Strumia, New J Phys. 11, 105005(2009)From: M. Cirelli and A. Strumia, New J Phys. 11, 105005(2009)

Relic density: DM mass is about 9.6 TeV.Relic density: DM mass is about 9.6 TeV.

DM direct detectionDM direct detection

DiscussionsDiscussions

Since DM mass of order 10 TeV, not much can be done at LHC.Since DM mass of order 10 TeV, not much can be done at LHC.

Flavour physics, like mu to e gamma may constrain the neutrino mass parameters.Flavour physics, like mu to e gamma may constrain the neutrino mass parameters.

With appropriate choices of new fields in the SM, without additional symmetries other With appropriate choices of new fields in the SM, without additional symmetries other

than the SM gauge symmetry, it is possible to have WIMP DM. The DM mass is than the SM gauge symmetry, it is possible to have WIMP DM. The DM mass is

determined by DM relic density. This mass scale also determines the radiative seesaw determined by DM relic density. This mass scale also determines the radiative seesaw

scale for generating non-zero neutrino masses.scale for generating non-zero neutrino masses.

Dark matter mass scale is naturally related to the radiative seesaw neutrino mass scale.Dark matter mass scale is naturally related to the radiative seesaw neutrino mass scale.

Relating Radiative Seesaw Neutrino And Dark Matter Mass ScalesRelating Radiative Seesaw Neutrino And Dark Matter Mass Scales

Mission accomplished! But does Nature choose to do so?........................................Mission accomplished! But does Nature choose to do so?........................................

A meeting may be of interesting to youA meeting may be of interesting to you

Welcome to Shanghai Particle Physics and Cosmology SymposiumWelcome to Shanghai Particle Physics and Cosmology Symposium

SPCS2011: 1 – 3, June in SJTUSPCS2011: 1 – 3, June in SJTU

Web page: Web page: www.physics.sjtu.edu.cn/spcs

Postdocs and students are encouraged to submit talksPostdocs and students are encouraged to submit talks