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Axions

Axions. Georg G. Raffelt, Max-Planck-Institut f ür Physik, München. Axions. Motivation, Limits and Searches. PONT d’Avignon, 21-25 April 2008, Avignon, France. Axion Physics in a Nut Shell. Particle-Physics Motivation. Solar and Stellar Axions. CP conservation in QCD by

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Axions

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  1. Axions Georg G. Raffelt, Max-Planck-Institut für Physik, München Axions Motivation, Limits and Searches PONT d’Avignon, 21-25 April 2008, Avignon, France

  2. Axion Physics in a Nut Shell Particle-Physics Motivation Solar and Stellar Axions CP conservation in QCD by Peccei-Quinn mechanism Axions thermally produced in stars, e.g. by Primakoff production a g g  Axions a ~ p0 a mpfp mafa • Limits from avoiding excessive • energy drain • Searchforsolaraxions(CAST, Sumico) g For fa≫ fp axions are “invisible” and very light Cosmology Search for Axion Dark Matter In spite of small mass, axions are born non-relativistically (“non-thermal relics”) Microwave resonator (1 GHz = 4 meV) N g a  “Cold dark matter” candidate ma ~ 1-1000 meV Primakoff conversion S Cosmic String Bext

  3. The CP Problem of Strong Interactions Standard QCD Lagrangian contains a CP violating term Induces a neutron electric dipole moment (EDM) much in excess of experimental limits ≲ Why so small? Characterizes degenerate QCD ground state (Q vacuum) Phase of Quark Mass Matrix

  4. Dynamical Solution Peccei & Quinn 1977 - Wilczek 1978 - Weinberg 1978 Re-interpret as a dynamical variable (scalar field) Pseudo-scalar axion field Peccei-Quinn scale, Axion decay constant V(a) Potential (mass term) induced by LCP drives a(x) to CP-conserving minimum CP-symmetry dynamically restored gluon a a gluon Axions generically couple to gluons and mix with p0 Pion decay constant

  5. Peccei-Quinn Mechanism Proposed in 1977

  6. The Pool Table Analogy Axis Symmetry broken Floor inclined fa _ New degree of freedom  Axion Q Symmetry dynamically restored (Weinberg 1978, Wilczek 1978) (Peccei & Quinn 1977) P.Sikivie, Physics Today, Dec. 1996, pg. 22 Gravity Pool table Symmetric relative to gravity

  7. 30 Years of Axions

  8. The Cleansing Axion Frank Wilczek “I named them after a laundry detergent, since they clean up a problem with an axial current.” (Nobel lecture 2004, written version)

  9. Windows of Opportunity Axions Alternatives Solve strong CP problem by Peccei-Quinn dynamical symmetry restoration • Massless up-quark • Spontaneous CP violation • set at some high energy scale • (no radiative corrections) • Cosmic cold dark matter candidate • Direct detection possible • Supersymmetric particles • Superheavy particles • Sterile Neutrinos • Many others … • (but usually not experimentally • accessible) Search for new physics at E ≫ TeV in low-energy experiments (Axions Nambu-Goldstone boson of spontaneously broken symmetry) • Neutrino masses (see-saw) • Proton decay • Neutron electric dipole moment • Deviation from Newton’s Law • (e.g. large extra dimensions)

  10. Axions as a Research Topic Papers in SPIRES that cite one of the two original Peccei and Quinn papers or Weinberg’s or Wilczek’s paper or with “axion” or “axino” in their title (total of 3186 papers up to 2007)

  11. Axions as Pseudo Nambu-Goldstone Bosons E  fa V(a) • UPQ(1) spontaneously broken • Higgs field settles in • “Mexican hat” V(a) a E  LQCD ≪ fa a • UPQ(1) explicitly broken • by instanton effects • Mexican hat tilts • Axions acquire a mass _ Q=0 • The realization of the Peccei-Quinn mechanism involves a new chiral • U(1) symmetry, spontaneously broken at a scale fa • Axions are the corresponding Nambu-Goldstone mode

  12. From Standard to Invisible Axions Standard Model Standard Axion Weinberg 1978, Wilczek 1978 Invisible Axion Kim 1979, Shifman, Vainshtein, Zakharov 1980, Dine,Fischler,Srednicki1981 Zhitnitsky 1980 All Higgs degrees of freedom are used up • Peccei-Quinn scale fa = • electroweak scale few • Two Higgs fields, • separately giving mass • to up-type quarks and • down-type quarks • Additional Higgs with • fa≫ few • Axions very light and • and very weakly • interacting No room for axions Axions quickly ruled out experimentally and astrophysically • New scale required • Axions can be • cold dark matter • Can be detected

  13. Axion Properties Gluon coupling (Generic property) G a G Mass Photon coupling g a g Pion coupling p p p a Nucleon coupling (axial vector) N a N Electron coupling (optional) e a e

  14. Supernova 1987A Energy-Loss Argument SN 1987A neutrino signal Volume emission of novel particles Emission of very weakly interacting particles would “steal” energy from the neutrino burst and shorten it. (Early neutrino burst powered by accretion, not sensitive to volume energy loss.) Neutrino diffusion Late-time signal most sensitive observable Neutrino sphere

  15. Axions as Pseudo Nambu-Goldstone Bosons E  fa V(a) • UPQ(1) spontaneously broken • Higgs field settles in • “Mexican hat” V(a) a E  LQCD ≪ fa a • UPQ(1) explicitly broken • by instanton effects • Mexican hat tilts • Axions acquire a mass _ Q=0 • The realization of the Peccei-Quinn mechanism involves a new chiral • U(1) symmetry, spontaneously broken at a scale fa • Axions are the corresponding Nambu-Goldstone mode

  16. Series of Papers on Axion Cosmology in PLB 120 (1983) Page 127

  17. Series of Papers on Axion Cosmology in PLB 120 (1983) Page 133

  18. Series of Papers on Axion Cosmology in PLB 120 (1983) Page 137

  19. Killing Two Birds with One Stone • Peccei-Quinn mechanism • Solves strong CP problem • May provide dark matter • in the form of axions

  20. Production of Cold Axion Population in the Early Universe Inflation after PQ symmetry breaking Reheating restores PQ symmetry Homogeneous mode oscillates after T ≲ LQCD Dependence on initial misalignment angle • Cosmic strings of broken UPQ(1) • form by Kibble mechanism • Radiate long-wavelength axions • Wa independent of initial conditions Approximate axion cold dark matter density • Isocurvature fluctuations from large • quantum fluctuations of massless • axion field created during inflation • Strong CMBR bounds on isocurvature • fluctuations • Scale of inflation required to be • very small LI≲ 1013 GeV • [Beltrán, García-Bellido & Lesgourgues • hep-ph/0606107] • Inhomogeneities of axion field large, • self-couplings lead to formation of • mini-clusters • Typical properties • Mass ~ 10-12 Msun • Radius ~ 1010 cm • Mass fraction up to several 10%

  21. Axions from Cosmic Strings Strings form by Kibble mechanism after break-down of UPQ(1) Small loops form by self-intersection Paul Shellard

  22. Axion Mini Clusters The inhomogeneities of the axion field are large, leading to bound objects, “axion mini clusters”. [Hogan & Rees, PLB 205 (1988) 228.] Self-coupling of axion field crucial for dynamics. Typical mini cluster properties: Mass ~ 10-12 Msun Radius ~ 1010 cm Mass fraction up to several 10% Potentially detectable with gravitational femtolensing Distribution of axion energy density. 2-dim slice of comoving length 0.25 pc [Kolb & Tkachev, ApJ 460 (1996) L25]

  23. Inflation, Axions, and the Anthropic Principle • Late inflation scenario of axion cosmology • Initial misalignment angle constant in our patch of the universe • Dark matter density determined by the initial random number Qi • Is different in different patches of the universe • Dark matter fraction not calculable from first principles • Random number chosen by process of spontaneous symmetry breaking • Natural case for applying anthropic reasoning for the observed dark • matter density relative to baryons • Linde, “Inflation and Axion Cosmology,” PLB 201:437, 1988 • Tegmark, Aguirre, Rees & Wilczek, • “Dimensionless constants, cosmology and other dark matters,” • PRD 73, 023505 (2006) [arXiv:astro-ph/0511774]

  24. Axion Hot Dark Matter from Thermalization after LQCD p p p a Freeze-out temperature Cosmic thermal degrees of freedom 104 105 106 107 fa (GeV) Cosmic thermal degrees of freedom at axion freeze-out Chang & Choi, PLB 316 (1993) 51 104 105 106 107 fa (GeV)

  25. Lee-Weinberg Curve for Neutrinos and Axions log(Wa) Non-Thermal Relics Axions Thermal Relics HDM CDM WM log(ma) 10 meV 10 eV log(Wn) Neutrinos & WIMPs Thermal Relics HDM CDM WM log(mn) 10 eV 10 GeV

  26. Axion Hot Dark Matter Limits from Precision Data Credible regions for neutrino plus axion hot dark matter (WMAP-5, LSS, BAO, SNIa) Hannestad, Mirizzi, Raffelt & Wong [arXiv:0803.1585] Marginalizing over unknown neutrino hot dark matter component ma < 1.0 eV (95% CL) WMAP-5, LSS, BAO, SNIa Hannestad, Mirizzi, Raffelt & Wong [arXiv:0803.1585] ma < 0.4 eV (95% CL) WMAP-3, small-scale CMB, HST, BBN, LSS, Ly-a Melchiorri, Mena & Slosar [arXiv:0705.2695]

  27. Axion Bounds [GeV] fa 103 106 109 1012 ma keV eV meV meV Experiments Tele scope CAST Direct search ADMX Too much hot dark matter Too much cold dark matter Globular clusters (a-g-coupling) Too many events Too much energy loss SN 1987A (a-N-coupling)

  28. Experimental Tests of the Invisible Axion Primakoff effect: Axions-photon transitions in external static E or B field (Originally discussed for p0 by Henri Primakoff 1951) • Pierre Sikivie: • Macroscopic B-field can provide a • large coherent transition rate over • a big volume (low-mass axions) • Axion helioscope: • Look at the Sun through a dipole • magnet • Axion haloscope: • Look for dark-matter axions with • A microwave resonant cavity

  29. Search for Galactic Axions (Cold Dark Matter) DM axions Velocities in galaxy Energies therefore ma = 1-1000 meV va 10-3 c Ea (110-6) ma Microwave Energies (1 GHz  4 meV) Axion Haloscope(Sikivie1983) Axion Signal Bext 8 Tesla Thermal noise of cavity & detector Microwave Resonator Q  105 Power Primakoff Conversion Power of galactic axion signal g a Cavity overcomes momentum mismatch ma Frequency Bext

  30. Axion Dark Matter Searches 1. Rochester-Brookhaven- Fermilab PRD 40 (1989) 3153 2. University of Florida PRD 42 (1990) 1297 4 3. US Axion Search (Livermore) ApJL 571 (2002) L27 5 4. CARRACK I (Kyoto) preliminary hep-ph/0101200 5. ADMX (Livermore) foreseen e.g. Rev. Mod. Phys. 75 (2003) 777 Limits/sensitivities, assuming axions are the galactic dark matter 3 2 1

  31. ADMX (G.Carosi, Fermilab, May 2007)

  32. ADMX (G.Carosi, Fermilab, May 2007)

  33. ADMX (G.Carosi, Fermilab, May 2007)

  34. Renewed ADMX data taking has begun on 28 March 2008 (Same day as CAST He-3 began) ADMX (G.Carosi, Fermilab, May 2007)

  35. ADMX (G.Carosi, Fermilab, May 2007)

  36. Fine Structure in Axion Spectrum • Axion distribution on a 3-dim sheet in 6-dim phase space • Is “folded up” by galaxy formation • Velocity distribution shows narrow peaks that can be resolved • More detectable information than local dark matter density P.Sikivie & collaborators

  37. Search for Solar Axions Axion Helioscope (Sikivie 1983) Axion-Photon-Oscillation N a g Magnet S Primakoff production Axion flux a g Sun • Tokyo Axion Helioscope (“Sumico”) (Results since 1998, up again 2008) • CERN Axion Solar Telescope (CAST) (Data since 2003) Alternative technique: Bragg conversion in crystal Experimental limits on solar axion flux from dark-matter experiments (SOLAX, COSME, DAMA, ...)

  38. Tokyo Axion Helioscope (“Sumico”) ~ 3 m S.Moriyama, M.Minowa, T.Namba, Y.Inoue, Y.Takasu & A.Yamamoto, PLB 434 (1998) 147

  39. Results and Plans of Tokyo Axion Helioscope (“Sumico”) S. Inoue at TAUP 07

  40. Extending to higher mass values with gas filling Axion-photon transition probability Axion-photon momentum transfer Transition suppressed for qL ≳1 Gas filling: Give photons a refractive mass to restore full transition strength (~ MSW effect) (ne electron density) He4 vapour pressure at 1.8 K

  41. LHC Magnet Mounted as a Telescope to Follow the Sun

  42. CAST at CERN

  43. CAST Focussing X-Ray Telescope • From 43 mm  (LHC magnet aperture) to ~3 mm  • Signal/background improvement > 100 • Signal and background simultaneously measured One spare mirror system from the failed Abrixas x-ray satellite

  44. Sun Spot on CCD with X-Ray Telescope

  45. Limits from CAST-I and CAST-II CAST-I results: PRL 94:121301 (2005) and JCAP 0704 (2007) 010 CAST-II results (He-4 filling): preliminary

  46. Limits on Axion-Photon-Coupling 10-4 PVLAS Signature Laser 10-6 Telescope PVLAS expected PVLAS expected PVLAS expected Helio seis mology 10-8 Tokyo Helioscope Tokyo Helioscope HB Stars CAST Sensitivity CAST Sensitivity +Gas 10-10 Axion-photon-coupling gag[GeV-1] DM Search DFSZ model 10-12 KSVZ model Axion Line 10-14 Future 10-16 +Gas 10-7 10-6 10-5 10-4 10-3 10-2 10-1 1 10 100 Axion mass ma [eV]

  47. Alps Axion-like particles (ALPs) (Pseudo)-scalar particles with a two-photon vertex

  48. Particles with Two-Photon Coupling • Particles with two-photon vertex: • Neutral pions (0), Gravitons • Axions (a) and similar hypothetical particles Two-photon decay Photon Coalescence Primakoff Effect Conversion of photons into pions, gravitons or axions, or the reverse Magnetically induced vacuum birefringence In addition to QED Cotton-Mouton-effect PVLAS experiment recently measured an effect ~ 104 larger than QED expectation (Signal now disproved)

  49. Dimming of Supernovae without Cosmic Acceleration? Axion-photon-oscillations in intergalactic B-field domains dim photon flux  Effect grows linearly with distance  Saturates at equipartition between photons and axions (unlike grey dust) Mixing matrix Domain size ~ 1 Mpc Field strength ~ 1 nG a-g-coupling ~ 10-10 GeV-1 Axion mass < 10-16 eV Photon energy ~ 1 eV Electron density ~ 10-7 cm-3 (average baryon density) Chromaticity depends sensitively on assumed values and distribution of ne and B Csáki, Kaloper & Terning (hep-ph/0111311, hep-ph/0112212, astro-ph/0409596). Erlich & Grojean (hep-ph/0111335). Deffayet, et al. (hep-ph/0112118). Christensson & Fairbairn (astro-ph/0207525). Mörtsell et al. (astro-ph/0202153). Mörtsell & Goobar (astro-ph/0303081). Bassett (astro-ph/ 0311495). Ostman & Mörtsell (astro-ph/0410501). Mirizzi, Raffelt & Serpico (astro-ph/0506078).

  50. Cantatore 12

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