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A new mechanism for large boost factor from DM conversions Yu-Feng Zhou collaborators: Ze-Peng Liu, Yue-Liang Wu Institute of theoretical physics (ITP), Chinese Academy of Sciences (CAS). work in progress

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Outline Introduction The recent DM search results and implications The stability of DM and the CP symmetry The boost factor problem A new source of boost factor from late time DM conversions Numerical results and simple models Summary

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Evidences of DM from gravitational effects Gravitational curves Strong lensing Weak lensing Large scale structure CMB Bullet cluster

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Searching for non-gravitational effects Satellite underground Cherenkov telescope balloon collider

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Hint of DM ? Positron fraction if interpreted as DM signal Large annihilation cross section now, boost factor problem. Sommerfeld enhancement ? Resonance enhancement ? Non-thermal DM ? DM may slightly decay ? Mainly annihilation/decay into leptons, not quarks Light final states <1GeV ? Leptophilic interaction ? background PAMELA Nature 458, 607 (2009)

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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. Large boost factor still needed Nature, 456, 2008, Phys.Rev.Lett.102:181101,2009

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Under ground experiments J. Li’s Talk CDMS-II, arXiv: CoGeNT, arXiv: , Xenon100, arXiv: DAMA CDMS-II CoGent Hint on light DM ?

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Symmetries important for keeping particle stable electron:U(1) em. symmetry, lightest charged particle proton: U(1) B-L symmetry, lightest baryon DM are often protected by symmetries Well known examples SUSY: R-parity, UED: KK-parity, Little Higgs: T-parity Symmetries for DM stability

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DM in minimal extensions of the SM SMScalar DM Simplest extension to SM: scalar DM Silveira, Zee, 1985 McDondald, 1994, Burgess, Pospelov & Veldhuis, 2001 Barger,Langacker, KcCaskey, 2007 Shafi, Okada, 2009 He,Li, Tsai, 2007,2009 Left-Right ModelScalar DM P and CP symmetry Extension to LRM with scalar DM P and CP broken auto stable ! Guo, Wang, Wu, YFZ, Zhuang,PRD79,055015(2009);

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A LR model with spontaneous P and CP violation Gauge interaction: P- and CP-transformations Flavor contents Two bi-doublet required for spontaneous CP violation. Only one bi-doublet cannot give the correct CP phase

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If P and CP are only broken spontaneously After EWSB S_D does not participate gauge Interactions, as it is gauge singlet Require that S_D does not develop a nonzero VEV S_D a DM particle

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Relic density and direct detection Parameter space from relic density Prediction for direct detection rate one bi-doublet case two bi-doublet case Guo, Wang, Wu, YFZ, Zhuang,PRD79,055015(2009);

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A special case: large Yukawa couplings to light quarks Relic density is dominated by heavy quark, not light ones DM-nucleus scattering is sensitive to light quark Yukawa couplings

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DM decay through soft C-breaking terms Including soft C-breaking term Guo, Wu, YFZ, PRD81, (2010) dominant part: C- and P-even tiny part: C-odd

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Explain PAMELA data well. for all type of lepton final states. mu/tau final states favored by Fermi tau-lepton final states predict High neutrino-induced muon flux. PAMELA Fermi Guo, Wu, YFZ, PRD81, (2010) mass parameters Consider 3 cases with final states dominated by different lepton flavor

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Predictions for up-going muon flux Triplets couple to neutrinos and charged-leptons with the same strength up-going muon flux can reach the current SK bound Guo, Wu, YFZ, PRD81, (2010)

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Inverse Compton scattering (ICS) Final state radiation (FSI) Virtual internal bremsstrahlung (VIB) ICS FSI VIB ICS FSI VIB Diffuse gamma-rays SH-III caseLH-III case Guo, Wu, YFZ, PRD81, (2010) ICS FSI VIB

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

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Boot factor for DM annihilation Local clumps Via Lactea II: in subhalo? B~ 4-15, Temperature-dependent ann. cross section Sommerfeld enhancement Resonance enhancement Possible origins 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 Other mechanism: DM decay, non-thermal DM ….

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Constraints from relic density 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:

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Boost factor in multi-component DM models (with temperature independent ann. cross sections) 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

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

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Nature of the DM conversion The role of large Keep the components in chemical equilibrium for a long time Convert the heavy DM into the light

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The total density The total density at equilibrium The total density evolves like an ordinary WIMP at early time Nontrivial z-dependence in effective cross section

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The effective cross section A interesting limit Approximate form Two component case

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Thermal evolution for two-component DM 1. Thermal equilibrium 2. Departure from thermal equilibrium but still in chemical Equilibrium 3. Late time DM conversion at large z Slow conversion characterized by r(z) Crossing point 4. Freeze-out after Freeze-out condition Y1(z) increased eventually

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The condition for a large boost factor Large internal degree of freedom of Y2: Small mass difference: Cross sections satisfy: Approximate expression for the boost factor

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Numerical results Equilibrium Equilibrium density Y2

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Numerical results Equilibrium Equilibrium density Y2 Equilibrium density Y1

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

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

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

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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

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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

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Numerical results B vs mass difference B vs relative cross sections

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A generic model Add to the SM

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Cross sections

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Parameters and boost factor Parameter set (off resonance) Cross sections Boost factors Parameter set (near resonance)

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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 is mostly temperature independent. For generic models with large conversion rate the boost fact can reach ~ Thank You !

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backups

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Positron signals Diffusion eq. Background Sources from DM decay

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The Sommerfeld enhancement Sommerfeld enhancement factor S: N. Arkani-Hamed, et al, Phys. Rev. D 79, (2009)

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KITPC 2011 program Dark matter and new physics Sept. 21-Nov. 06, 2011 (7-week) International Coordinators: Shafi, Qaisar (Delaware), Aprile, Elena (Columbia U.) Wang, Tsz-king Henry(IOP,) Wefel, John (Louisiana State U.) Matsumoto, Shigeki (IPMU), Su, Shu-Fang (Arizona U.) Geng, Chao-Qiang ( NCTS ), Local Coordinators: Bi, Xiao-Jun (IHEP) Ni, Kai-Xuan (SJTU) Yang, Chang-Geng (IHEP) Yue, Qian (Tsinghua U.) Zhou, Yu-Feng (ITP )

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Numerical results B~150 B~1000 no conversion With conversion Large boost factor if mass diff. is small

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The Sommerfeld effect A. Sommerfeld, Annalen der Physik 403, 257 (1931). J. Hisano, S. Matsumoto and M. M. Nojiri, Phys. Rev. D 67 (2003) Phys. Rev. Lett. 92, (2004)

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Constraints from relic density J. L. Feng, M. Kaplinghat and H. B. Yu, Phys. Rev. Lett. 104, (2010) Irreducible process

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Symmetries for hidden sector DM Hidden sector U(1) symmetry exact U(1) Broken U(1): a massive Z’, a scalar Hidden custodial symmetry vector DM Custodial symmetry SU(2)_C keep vector bosons stable Ackerman,buckley,Carroll, Kamonkowski 08’ Feng, Tu, Yu 08’, Feng, Kaplinghat, Tu, Yu 09’ Foot etal. 10’ Pospelov, Ritz, voloshin 07’ Gpoalakrishnal,Jung,Wells 08’ Gpoalakrishnal,Lee,Wells 08’ Mambrini 10’ Higgs portal kinetic mixing Hambye 08’ SMHidden sector DM Symmetry not shared wiht SM sector

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