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Cosmological mass bounds on hot-dark matter axions

NOW 2008- Neutrino Oscillation Workshop Conca Specchiulla, September 6-13 2008. Cosmological mass bounds on hot-dark matter axions. Alessandro MIRIZZI (MPI, Munich). [based on works in collaboration with S.Hannestad, G.G. Raffelt, Y.Y.Y. Wong]. OUTLINE. Strong CP problem and the axions

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Cosmological mass bounds on hot-dark matter axions

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  1. NOW 2008- Neutrino Oscillation Workshop Conca Specchiulla, September 6-13 2008 Cosmological mass bounds on hot-dark matter axions Alessandro MIRIZZI (MPI, Munich) [based on works in collaboration with S.Hannestad, G.G. Raffelt, Y.Y.Y. Wong]

  2. OUTLINE • Strong CP problem and the axions • Axions and large-scale structures • Cosmological mass limit • Implication for axion search (CAST experiment) • Conclusions Alessandro Mirizzi NOW 2008 Conca Specchiulla, 6-13 September 2008

  3. THE STRONG CP PROBLEM The QCD Lagrangian includes a term which violates CP (and T) where Prediction of an electric dipole moment for the neutron: Present experimental limit : Why so small ? Alessandro Mirizzi NOW 2008 Conca Specchiulla, 6-13 September 2008

  4. THE PECCEI-QUINN MECHANISM Peccei & Quinn 1977, Wilczek 1978, Weinberg 1978 • PQ Symmetry • Introduce a symmetry that results in a term which dynamically minimizeq. Introduction of a new global U(1)PQ simmetry, spontaneously broken at a scale fa. Existence of a massless pseudoscalar fielda(x), the axion, interacting with the gluon field. Re-interpret q as a dynamical variable: Alessandro Mirizzi NOW 2008 Conca Specchiulla, 6-13 September 2008

  5. V(a) Potential (mass term) induced by La drives a(x) to CP-conserving minimum CP-symmetry dynamically restored gluon a a gluon Axions generically couple to gluons and mix with p0 Axions pick up a small mass At low energy (LQCD) the gga vertex generates the potential V(a) which has its minimum at a0=0, restoring dynamically CP-simmetry. Alessandro Mirizzi NOW 2008 Conca Specchiulla, 6-13 September 2008

  6. Gluon coupling (Generic property) G a G Photon coupling g a g Pion coupling p p p a Nucleon coupling (axial vector) N a N Electron coupling (optional absent for hadronic axions) e a e AXION PROPERTIES

  7. This talk COSMOLOGICAL AND ASTROPHYSICAL AXION LIMITS Hadronic axion window ma~ O(eV), fa~106 GeV Alessandro Mirizzi NOW 2008 Conca Specchiulla, 6-13 September 2008

  8. DARK MATTER CANDIDATES Alessandro Mirizzi NOW 2008 Conca Specchiulla, 6-13 September 2008

  9. log(Wa) Non-Thermal Relics Axions Thermal Relics HDM CDM WM log(ma) 100 meV 30 eV log(Wn) Neutrinos Thermal Relics HDM CDM WM log(mn) 30 eV 3 GeV DARK-MATTER AXIONS

  10. Freeze-out temperature THERMAL PRODUCTION OF AXIONS If fa < 1.2 ×1012 GeV there would be a primordial population of axions produced in hot thermal plasma [Turner (1987), Masso’ (2002)] If axions were sufficiently strong interacting (fa < 3 ×107 GeV, ma > 0.2 eV) they decouple after QCD phase transition (T < 200 MeV). The most generic interaction process involves hadrons rather than quarks and gluons that would be relevant at earlier epochs. There would be a background of low-mass (~ eV) relic axions

  11. Low mass thermal relics affect structure formation because they are source of hot dark matter Massive neutrinos affect Large Scale Structures. They smooth out the distribution: no small scale structures. Cold Dark Matter (no neutrino mass) Hot + Cold Dark Matter (non-zero neutrino mass) S. Dodelson, ‘04 Alessandro Mirizzi NOW 2008 Conca Specchiulla, 6-13 September 2008

  12. POWER SPECTRUM OF MATTER DENSITY FLUCTUATIONS Power spectrum Density contrast Alessandro Mirizzi NOW 2008 Conca Specchiulla, 6-13 September 2008

  13. 0 eV 0.3 eV 1 eV Neutrinos affect the Power Spectrum of the 2-point density correlationfunction. Power suppression for lFS≲ 100 Mpc/h P(k)=A kn T2(k) T2(k)= Transfer function Neutrino Free Streaming DP(k)/P(k) = -8 Wn /Wm (Hu et al. 1998) S.Hannestad,hep-ph/0404239 It is possible to obtain constraints on mn. Alessandro Mirizzi NOW 2008 Conca Specchiulla, 6-13 September 2008

  14. NEUTRINO MASS LIMITS [Fogli et al., arXiv: 0805.2517] Alessandro Mirizzi NOW 2008 Conca Specchiulla, 6-13 September 2008

  15. a p p p THERMALIZATION OF HADRONIC AXIONS Choi & Chang, PLB 316, 51(1993); Hannestad, Mirizzi & Raffelt, JCAP 07 (2005) 02 The Lagrangians relevant for axion decoupling processes are the following • Pion-axion interaction Contact interaction Alessandro Mirizzi NOW 2008 Conca Specchiulla, 6-13 September 2008

  16. Freeze-out temperature Cosmic thermal degrees of freedom at axion freeze-out Present-day axion density AXION HOT-DARK MATTER

  17. AXION HOT-DARK MATTER LIMIT FROM PRECISION DATA Credible regions for neutrinos plus axions HDM (WMAP-5, LSS, BAO; SN-Ia) Hannestad, Mirizzi, Raffelt & Wong [arXiV: 0803.1585] Dashed (red) curves: Same with WMAP-3 HMRW [arXiv: 0706.4198] Marginalizing over unknown neutrino hot-dark matter component

  18. New cosmological mass limit Our limit closes the “hadronic axion window” left open by SN1987A arguments NEW AXION MASS LIMIT Our limit ma < 1 eV, corrisponding to fa> 5.7×106 GeV, is comparable with the one obtained with the globular-cluster. However, the globular cluster limit depends on axion-photon coupling that is rather model dependent. Alessandro Mirizzi NOW 2008 Conca Specchiulla, 6-13 September 2008

  19. Laboratory Sun IMPLICATION FOR AXION SEARCHES Searches for solar axions: Axion helioscopes Axion-photon oscillation Primakoff process • Tokyo axion helioscope Results since 1998 • CERN Axion Solar Telescope (CAST) Data since 2003

  20. CAST PHASE II AND OUR COSMOLOGICAL AXION MASS LIMIT PROBABLY CONNECT. LIMITS FROM CAST-I AND CAST-II CAST-II (Preliminary) CAST-I gag < 8.8 x 10-11 GeV-1 at 95% CL for ma < 0.02 eV gag < 2.2 x 10-10 GeV-1 at 95% CL for ma < 0.39 eV

  21. CONCLUSIONS Observations of the cosmological large-scale structure provide well-estabilished neutrino mass limit. We extend this argument to thermal relic axions: • For hadronic axions we find a new mass limit ma < 1 eV (95% CL), corresponding to fa> 5.7×106 GeV. • It is comparable with the (model-dependent) limit obtained with the globular clusters. • It closes the “hadronic axion” window. • It is nicely complementary with the CAST search. • If neutrino masses are detected in laboratory (KATRIN) : Less room for axions in the dark matter inventory. Alessandro Mirizzi NOW 2008 Conca Specchiulla, 6-13 September 2008

  22. Thank you!

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