Singlet Dark Matter, Type II Seesaw and Cosmic Ray Signals

Nobuchika Okada

Miami 2009 @ Fort Fauderdale, Dec. 15-20, 2009

University of Alabama, Tuscaloosa

In collaboration with Ilia Gogoladze (University of Delaware) Qaisar Shafi (University of Delaware) Toshifumi Yamada (KEK, Japan)

Ref: Gogoladze, N.O. and Shafi, “Type II Seesaw and the PAMELA/ATIC Signals, ” PLB 679 (2009) 237 Gogoladze, N.O. ,Shafi, and Yamada, in preparation

1. Introduction

Existence of Dark Matter has been established!

Wilkinson Microwave Anisotropy Probe (WMAP) satellite has established the energy budget of the present Universe with a great accuracy

Dark Matter particle: non-baryonic electric charge neutral (quasi) stable

The property of the DM is still a prime open question in particle physics and cosmology

Weakly Interacting Massive Particles (WIMPs) are among the best motivated classes of candidates for the dark matter No candidate in the SM New Physics beyond the SM

What is the scale of WIMP?

TeV scale New Physics is suitable for WIMP DM physics!

Solving the Boltzmann Equation,

Investigating the nature of Dark Matter

Collider Physics (LHC, ILC,…)

Producing DM particles at colliders and measure DM properties mass, couplings with SM particles, spin, etc.

Direct detection of DMA variety of experiments has been carried out to directly detect dark matter particle through its elastic scattering off a nucleon

nucleon

detector

DM underground

cosmic rays originating from DM pair annihilations in the halo associated with our galaxy, sun, …

Indirect detection of DM

Sun

Halo

Sun

DM

DM

Earth

Cosmic-ray

Many experiments:

HEAT, PAMELA, ATIC, PPB-BETS, Fermi-LAT

HESS, MAGIC, EGRET, Fermi-GLAST

Super-K, IceCube

Recent hot topic: cosmic-ray e+/e- excesses

(1) The PAMELA experiment has reported a significant positron excess over the expected background without a corresponding increase in the flux of anti-protons! Adriani et al., Nature 458, (2009) 607

Positron excess

Expected

Solar activity

Expected

(2) Fermi satellite experiment also shows an excess of the sum of cosmic-ray e+ and e- flux

PAMELA and Fermi data may constitute the first indirect evidence of dark matter pair annihilations in the halo!

Puzzle: excess of cosmic-ray e+/e- fluxes

no excess of cosmic-ray anti-proton flux

DM

DM

leptons

DM

DM

quarks

favored? disfavored?

In normal dark matter models, there is no significant difference

This implies a leptophilic nature of DM

Plan of this talk

1. Introduction 2. Propose a simple model of leptophilic DM

3. Numerical analysis Fitting to PAMELA and Fermi data and implication to neutrino

physics

4. Summary

2. Simple model of leptophilic dark matter

What’s missing in the SM?

1. Dark Matter particle we’ve already discussed

2. Neutrino masses and mixings

Oscillation data

Very small mass scaleLarge mixing angle

Simplest extension of the SM to incorporate Dark Matter particle & Neutrino Masses

Introduce 2 scalars

Gogolzdze, N.O. & Shafi, PLB 679 (2009) 237

Neutrino mass via Type II seesaw

DM relic abundance

When , we get the right DM abundance

Leptophilic nature of DM

If is small, dominates

When DM pair annihilations happen in the halo, they produce mostly lepton flux

The flavor structure of the primary lepton fluxes are determined by the Yukawa coupling and hence, there is a correlation with neutrino oscillation data

Interesting Implications

Flavor structure of lepton flux carry the information of neutrino mass matrix:

Cosmic-ray neutrino flux

would be detected in future experiments

(ex: IceCube)

3. Numerical Analysis

We will show the proposed model can fit PAMELA and Fermi data with a suitable choice of parameters

For data fitting, it is necessary to introduce a boost factor (BF~1000) to enhance the annihilation cross section of DMs in the halo

DM relic abundance:

Typical scale to fit PAMELA data:

BF could either have astrophysical origin: large inhomogeneities in DM distribution a particle physics origin: Breit-Wigner enhancement

New scalar S Arrange

Gogolzadze, N.O., Shafi, and Yamada in preparation

In our analysis, free parameters in the model are: DM mass Annihilation cross section (with BF) Triplet scalar mass Yukawa coupling

For simplicity, we consider two cases for triplet scalar mass

(1) triplets from DM annihilation almost at rest

(2) highly boosted triplets

Energy distribution of primary leptons from triplet decay

(1)

(2)

In type II seesaw,

For simplicity, we assume hierarchical neutrino mass spectrum

From the formula of partial decay width and the neutrino oscillation data, we find the flavor structure of primary leptons as

(i) Normal hierarchical case e : mu : tau = 0.02 : 1 : 1 e : mu : tau = 2 : 1 : 1 (ii) Inverted hierarchical case

We calculate cosmic-ray e+/e- flux from DM pair annihilation for various values of DM mass with the annihilation cross section with the boost factor being a free parameter and fit the PAMELA and Fermi data

Positron and electron propagation in the galaxy is determined by the static diffusion equation

Diffusion coef. Energy loss rate Source term

Background flux:

Best fits to PAMELA and Fermi data

(A) NH &

(B) NH &

(C) IH &

Upper bound on neutrino flux from galactic center by Super-K

DM pair annihilations produce neutrino flux directly or via the decay of mu and tau

SuperK measured the up-ward muon flux induced by cosmic-ray muon neutrinos gives us the upper bound on neutrino flux from galactic center

Earth

SK

Neutrinos from GC

Neutrino flux vs. SK upper bound

Flux highly depend on DM density profile around the GC

We consider two typical DM density profiles: NFW profile & isothermal profile with 4 kps core

(A) NH & (B) NH &

Too much flux Too much flux

(C) IH &

Inverted hierarchical case is consistent with SK bound

IceCube+DeepCore experiment can significantly improve the SK bound in the near future

Mandal et al., arXiv:0911.5188 [hep-ph]

5. Summary

We have proposed a very simple extension of the SM to incorporate the DM particle and neutrino masses in the SM, where only one gauge singlet scalar and one SU(2) triplet scalar with a unit hypercharge are introduced.

Neutrino masses are obtained by type II seesaw

The type II seesaw structure naturally induces a leptophilic nature for the DM

The flavor structure of the primary lepton fluxes are related to neutrino oscillation data because of type II seesaw

We have calculated cosmic-ray e+/e- fluxes for two typical masses, and , and for NH and IH neutrino mass spectrum

We have shown that a suitable choice of mass and annihilation cross section (with the boost factor) can fit both PAMELA and Fermi data

We have also calculated neutrino flux form GC and found that NH cases predict too much flux which is severely constrained by Super-K up-ward muon flux

On the other hand, IH case with DM mass 1 TeV and can give a very nice fits to both the PAMELA and Fermi data without tension with the SK bound, and IH neutrino mass spectrum is favored