Cosmic Positron Signature from Dark Matter in the Littlest Higgs Model with T-parity

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1 Cosmic Positron Signature from Dark Matter in the Littlest Higgs Model with T-parity Masaki Asano The Graduate University for Advanced Studies Collaborated with Shigeki Matsumoto Nobuchika Okada Yasuhiro Okada hep-ph/

2 WMAP Introduction (Wilkinson microwave anisotropy probe) cold dark matter candidate Neutral Stable Massive (100 GeV 1TeV) WINP (Weakly Interacting Massive Particle) beyond SM No WINP in SM ( WINP ) Supersymmetric Model (neutralino) Little Higgs Model with T-parity (heavy photon) H-C.Cheng and I.Low ( 03)

3 Dark Matter Search indirect direct Dark matter scatter off of a detector Search the positron flux Dark Matter annihilation Gamma rays Neutrino antiprotons positrons from Galactic center halo HEAT ( High Energy Antimatter Telescope ) Energy range (positron) PAMELA (Payload for Antimatter Exploration and Light-nuclei Astrophysics) Future experiments AMS-02 (Alpha Magnetic Spectrometer) ~30 GeV ~270 GeV ~ a TeV

4 Outline 1.Littlest Higgs Model with T-parity 2.Relic abundance of the dark matter 3.Positron signature 4. Summary

5 Littlest Higgs Model with T-parity

6 Low energy cutoff scenario related to quadratic Solve the problem of fine-tuning divergence around Λ1TeV a to the Higgs Constrained by EW Precision Test mass term 2 cutoff scale m 0 +δm 2 Little Higgs Model R.Barbieri and A.Strumia ( 00) Little Hierarchy Problem can also solve Higgs : a pseudo Nambu-Goldstone boson δm 2 Λ 2 cutoff scale W W H h + h h g 2 g 2 Higgs mass : protected at 1-loop quadratic divergence h

7 New particles are constrained by EW Precision Test constraint T-parity (Z 2 symmetry) resolve m Z has to be raised reintroduce fine-tuning SM Particles T-even New Particles T-odd provide Dark matter Candidate

8 Littlest Higgs Model SU(5)/SO(5) non-linear sigma model VEV New triplet Higgs boson SM Higgs doublet SU(5) [SU(2) U(1)] 2 (gauged) [SU(2) U(1)] (SM)

9 Kinetic Term gauge couplings of the SU(2) and U(1)

10 Littlest Higgs Model with T-parity (TeV) 10 1 T-even h T-parity Spectrum T-odd Φ W H, Z H A H B 1 (W 1 ) B 2 (W 2 ) Π ΩΠΩ Ω= diag.(1,1, 1,1,1) Dark matter candidate 0.1 W, Z Lightest T-odd

11 Relic Abundance of Dark Matter

12 Relic density cross section ~g 2 /v ~g 2 ~m h2 /v ~m W2 /v main There are s-channel poles If m AH > m h ~g 2 /v J.Hubisz and P.Meade ( 05) Relic density depends on m AH,m h

13 contour plot of the relic abundance U-branch S-channel pole line m h = 2m AH L-branch Cross section is very large Relic density is very small Allowed region for WMAP at 2σlevel Relic density cross section

14 Indirect Detection of the Dark Matter Using Cosmic Positrons

15 1~2 kpc Sun Annihilation e + Dark Matter Annihilation e + Halo solve the diffusion eq. positron flux Number density of positrons per unit energy Effect of inhomogeneity Boost Factor ( in the inflationary universe ) 2~5 V.Berezinsky et al ( 03)

16 computational procedure In a wide region of the parameter f, m h space 1.Calculate the production rate of e + 2.Solve the diffusion equation Obtain the flux of the signal positrons 3.Think of the Background ( 99) which are obtained by simulations positron fraction E.A.Baltz and J.Edsjo

17 positron fraction in 7 sample points (On the allowed region for WMAP) BF = 5

18 χ2 Analysis the number of positron events observed in the i-th bin χ 2 is proportional to BF 2 the number of events expected from the background contribution in the i-th bin. acceptance of PAMELA 20.5 cm 2 sr AMS cm 2 sr assuming three years of data-taking

19 contour plot of χ 2 In the PAMELA with BF = 5 χ 2 = % confidence level In the AMS-02 with BF = 2

20 χ 2 Plot χ 2 depends on BF and m h χ 2 plot ( along with the U- and L-branch ) within WMAP constraint

21 Possibility to Detect the Signal PAMELA f < 830GeV (m AH < 120GeV ) BF > 5 AMS-02 Wide range of the parameter space including the region BF = 1 95% confidence level contour within WMAP constraint

22 Impact of Higgs Phenomenology Invisible width in the U-branch (m h > 2m AH ) h A H A H up to 5 % LHC and ILC The measurement might be possible at a future muon collider

23 Summary We have studied the possibility to detect the A H dark matter in the littlest Higgs model with T-parity. In the PAMELA experiment, the dark matter signal may be detected when f < 830GeV (m AH < 120GeV ) and BF > 5. In AMS-02 experiments, The dark matter signal may be detected even if there is no enhancement from the boost factor.