Ze-Peng Liu, Yue-Liang Wu and Yu-Feng Zhou Kavli Institute for Theoretical Physics China, Institute of Theoretical Physics, Chinese Academy of Sciences arXiv: , EPJC2011 Dark matter conversions as a source of boost factor

The cosmic-ray lepton anomaly background Nature 458, 607 (2009) Nature, 456, 2008, Phys.Rev.Lett.102:181101,2009 arXiv:

DM annihilation scenario For thermal relic the annihilation cross section at the time of freeze-out is fixed The PAMELA and Fermi data require a much larger annihilation cross section for halo DM Flux Boot factor

Constraints form cosmic gamma-rays Large boost factor B>1000 is in tension with the Fermi results on gamma-rays arXiv: Isotropic diffuse gamma-way Satterllite galaxies

Local clumps Via Lactea II: in sub-halo? B~ 4-15, velocity-dependent ann. cross section Sommerfeld enhancement J. L. Feng, M. Kaplinghat and H. B. Yu, Phys. Rev. Lett. 104, (2010) Resonance enhancement Non-thermal DM: from late-decay of meta-stable particles superWimp ?? Sources of boost factor Diemand, et al, , Nature Sommerfeld, Ann. Phy 403, 257 (1931). J. Hisano, S. Matsumoto and M. M. Nojiri, Phys. Rev. D 67 (2003) Phys. Rev. Lett. 92, (2004) Feldman, Liu, Nath, 09 Ibe, Murayama, Yanagida, 09 Guo, Wu, 09 J.L.Feng 2004

Boost factor in multi-component DM models Large boost requires 1. Large annihilation cross section 2. Still the correct relic density Impossible for one- component thermal DM? Multi-component DM Models with hidden sectors naturally have multi-DM DM may have SUSY partners Neutrinos are already (tiny) part of DM boost from simply mixed thermal multi-DM ? (No) Boost factor from interacting multi-DM ?(Possible) For thermal relic large cross section Always reduces signal Z.P.Liu, Y.L.Wu and YFZ, arXiv: , EPJC2011

Thermal evolution of interacting multi-DM The components can be converted Thermal evolution for interacting DM Use common variable

the DM conversion process Maintain thermal equilibrium between the DM components, after decoupling from the SM thermal bath Convert the heavy DM into the light

Thermal evolution of the total density The total density at equilibrium The total density evolves like an ordinary WIMP at early time effective cross section is temperature-dependent

The effective cross section A interesting limit Approximate form The two-component case

Thermal evolution for two-component DM 1. Thermal equilibrium with SM 2. Decouple from SM, but still in equilibrium with each other 3. Late time DM conversion at large z Slow conversion characterized by r(z) Crossing point 4. Complete decouple (freeze-out) after Freeze-out condition Y1(z) increased eventually

Numerical results Equilibrium Equilibrium density Y2

Numerical results Equilibrium Equilibrium density Y2 Equilibrium density Y1

Numerical results Equilibrium Equilibrium density Y2 Equilibrium density Y1 If no conversion Decoupling of Y2 Decoupling of Y1

Numerical results Equilibrium Equilibrium density Y2 Equilibrium density Y1 If no conversion Decoupling of Y2 Decoupling of Y1 With conversion Evolution of Y2 Evolution of Y1

Numerical results Equilibrium Equilibrium density Y2 Equilibrium density Y1 If no conversion Decoupling of Y2 Decoupling of Y1 With conversion Evolution of Y2 Evolution of Y1 Evolution of Y1+Y2

Conditions for a large boost factor Large internal degree of freedom of Y2: Small mass difference: Cross sections satisfy: Approximate expression for the boost factor Z.P.Liu, Y.L.Wu and YFZ, arXiv: , EPJC2011

Numerical results B vs mass difference B vs relative cross sections

A simple 2dm model Add to the SM

Cross sections

Summary In multi-DM models, DM conversion can significantly modify the thermal evolution of each DM component. The relic density of the DM component may not always inversely proportional to it’s annihilation cross section. Through conversions from heavier DM components, the relic density of light DM can be enhanced, leading to large boost factors. The boost factor is independent of DM relative velocity. For generic models with large conversion rate the boost fact can reach the value required by PAMELA etc. Thank You !

Thanks !

Modern Cosmology Why is there something rather than nothing ? Martin Heidegger Jean-Paul SartreFiredrich Nietzsche from metaphysics to physics

Out of equilibrium: the origin of species Number density highly suppressed at low temperature Predict equal number of baryons and anti-baryons for T=40MeV There will be little left in the Universe ! But the observations give The conditions for baryogenesis 1. B violation 2. C and CP violation 3. Out of equilibrium But how to generate ? no clear answer yet ! Now we know that dark matter density is five times more, why ? Andrei Sakharov

Other possibilities WIMP vs. WIMPless only the ratio matters One component vs. multi- component DM Multi-DM is natural: Neutrinos already part of the whole DM. One heavy (TeV) and one light (GeV) DM can count for both indirect and direct candidate signals Symmetric vs. Asymmetric DM In analogy to the baryon asymmetric Universe. Common origin of both dark and visible matter Elastic vs. Inelastic DM DM inelastic scattering changes the kinematics of collision DAMA results can be made consistent with other experiments

Early Indications of dark matter 1933, Zwicky found a large mass-to-light ratio ~400 from velocity dispersion in the Coma cluster. The first indication of dark matter. 1936, Smith found unexpected high mass in the Virgo cluster. 1939, Babcock found that the outer region of Andromeda galaxy rotates with a high speed. 1959, Kahn and Woltjer inferred from the relative motion between M31 and our Galaxy that the Local Group is much heavier than expected. 1970, Rubin and Ford measured the rotational curve in M31 with unprecedented precision and distance (24kpc), clearly showed the existence of DM or deviation of Newton’s law of gravitation. Fritz Zwicky Vera Rubin

DM as a challenge to the standard model of particle physics (SM) The standard model (SM) Particles: Quarks: u,d,c,s,t,b (charged) Leptons: electron (charged, stable ), muon, tau (charged, unstable) neutrino (neutral, stable) Gauges bosons: W, Z0 (neutral, unstable), gamma (neutral, massless) (Higgs boson): H0 (neutral, unstable ) Interactions : SU(3)xSU(2)xU(1)

Neutrino is not a viable DM candidate Abundance of a hot relic CMB anisotropies: Structure formation neutrino erase fluctuations below ~40 Mpc, imply a top-down structure formation. Neutrino cannot be the main part of DM, We must go beyond the particle Standard Model !

Nonthermal DM ? Thermal: decouple from thermal equilibrium Nonthermal: never reached thermal equilibrium (super weak) Nonthermal generation of DM by gravitational interaction by decay of unstable particles Late decay make affect BBN, CMB DM may get warm by transitions from other particles Thermal DM density enhanced by late decay of unstable states Thermal DM density enhanced by other DMs J.L.Feng 2004 Liu, Wu, YFZ 2011 Zupan, etal, 2009

Strong interacting DM ? DM annihilation interaction is weak at the time of freeze-out, but strong now. Explanation Local cumps ? (unlikely) Temperature-dependent cross section ? Strong: Sommerfeld enhancement Weak: Resonance enhancement The Sommefeld effect Call for long-range force ! Various constraints CMB distortion Subhalo Proto-halo Galactic-center Halo shape

Outline Introduction: evidences of DM from observations DM candidates: WIMPs recent experimental results Thermal evolution of interacting multi-DM Generic case with multiple component DM models Boost factor in two-component DM model Numerical results and a simple model Conclusions

DM revealed from gravitational effects Gravitational curves Strong lensing Weak lensing Large scale structure CMB Bullet clusters

What we know about DM Massive: from gravitational interactions. Stable: lifetime longer than the age of the Universe Electro-magnetic and color neutral: dark, but can annihilate into photons Non-baryonic MACHOs: disfavored by micro-lensing survey MOND: disfavored by bullet clusters D/H from BBN: CMB: Non-relativistic motion ( from N-body simulations ) Cold DM ： substructure, halo core Warm DM ? A big challenge to the standard model of particle physics !

Stability: symmetry + kinematics Symmetries important for keeping particle stable electron: U(1) em. symmetry, lightest charged particle proton: U(1) B-L symmetry, lightest baryon neutrino: Lorentz symmetry, lightest fermion DM protected by symmetries Well-known examples SUSY: R-parity, LSP UED: KK-parity, LKP Little Higgs: T-parity DM stability

DM relic density: The WIMPs miracle Thermal freeze out: the origin of species Weakly Interacting Massive Particles (WIMPs) Particle physics independently predicts WIMPs WIMPs have just the right relic density WIMPs are testable by the current exp.

Search for non-gravitational effects ? Satellite underground Cherenkov telescope balloon collider

Direct searches

CRESST

EDELWEISS-II EDELWEISS-II, arXiv:

Hint of DM? electrons plus positrons ATIC/PPB-BETS Excess in the total flux peak at ~600 GeV rapid drop below 800GeV Fermi LAT Spectrum harder than expected background with power index around ~3. Nature, 456, 2008, Phys.Rev.Lett.102:181101,2009

The boost factor problem The std. WIMP annihilation cross section is too small to account for the PAMELA/Fermi data Positron flux Boost factor Need a large boost factor B~ Bergstrom, Edsjo, Zaharijas, PRL103,031103,09’

DM annihilation scenario For standard thermal relic too small to account for PAMELA and Fermi data ( boost factor needed ) Annihilation rates strongly depend on halo profile Constrained by diffuse gamma rays DM decay scenario No contradiction with relic density Extremely long lifetime required Imply small symmetry breaking induced by high scale (GUT scale) physics Less sensitive to the halo profile Weaker constraints Abdo, et.al, arXiv: Dugger et.al, arXiv:

Numerical results Equilibrium Equilibrium density Y2 Equilibrium density Y1 If no conversion Decoupling of Y2 Decoupling of Y1 With conversion Evolution of Y2

Constraints on the Sommerfeld enhancement Other constraints Halo shape CMB, protohalo Refined analysis at freeze-out Cut-off of resonance, recoupling Force-carrier production & decay rates Kinetic decoupling Self-interaction efficiency, non-thermality J. Zavala, M. Vogelsberger and S. D. M. White, Phys. Rev. D 81, (2010) M. Kamionkowski and S. Profumo, Phys. Rev. Lett. 101, (2008) J. L. Feng, M. Kaplinghat and H. B. Yu, Phys. Rev. Lett. 104, (2010) arXiv:

Numerical results Equilibrium Equilibrium density Y2 Equilibrium density Y1 If no conversion Decoupling of Y2