1. Andreas Ringwald, DESY 27 th DESY PRC Closed Session, DESY, Hamburg, 26 October 2011 Towards a comprehensive summary Physics Case for WISP Searches.

2. Andreas Ringwald | Physics Case for WISP Searches | 26 October 2011 | Page 2 Summary of Physics Case > Very Weakly Interacting Slim Particles (WISPs) are strongly motivated from theory, cosmology, and astrophysics  Theory: Axions Axion-Like Particles (ALPs) hidden sector U(1)s (HPs)  Cosmology: Axion, ALP, or HP Cold Dark Matter (CDM) Extra, dark radiation during CMB decoupling  Astrophysics: Photon ALP oscillations as explanation of anomalous transparency of the universe for TeV gamma rays Axion or ALP bremsstrahlung as explanation of non-standard energy loss of white dwarfs > ALPS II can search for them in strongly motivated parameter region

3. Andreas Ringwald | Physics Case for WISP Searches | 26 October 2011 | Page 3 WISPy Cold Dark Matter > Axions, ALPs and HPs can be born in the early universe non-thermally in the form of spatially homogeneous classical field oscillations (misalignment mechanism) > If sufficiently weakly coupled, this CDM component survives until today Arias, Cadamuro, Goodsell, Jaeckel, Redondo, AR, in prep.

4. Andreas Ringwald | Physics Case for WISP Searches | 26 October 2011 | Page 4 WISPy Cold Dark Matter > ALPS II 2012 will reach the parameter range of interest for HP CDM:

5. Andreas Ringwald | Physics Case for WISP Searches | 26 October 2011 | Page 5 WISPy Cold Dark Matter > ALPS II 2017 will reach the parameter range of interest for ALP CDM:

6. Andreas Ringwald | Physics Case for WISP Searches | 26 October 2011 | Page 6 HP Dark Radiation > Global fit to CMB angular power spectrum slightly prefers extra dark radiation beyond three light neutrinos:

7. Andreas Ringwald | Physics Case for WISP Searches | 26 October 2011 | Page 7 HP Dark Radiation > Global fit to CMB angular power spectrum slightly prefers extra dark radiation beyond three light neutrinos:

8. Andreas Ringwald | Physics Case for WISP Searches | 26 October 2011 | Page 8 HP Dark Radiation > For meV scale masses, photon -> HP conversions occur resonantly after BBN, but before CMB decoupling -> HP dark radiation Jaeckel, Redondo, AR > ALPS II 2012 can probe HP explanation of extra dark radiation:

9. Andreas Ringwald | Physics Case for WISP Searches | 26 October 2011 | Page 9 Light Shining through Cosmic Walls > Spectra of distant VHE gamma-ray sources show no strong indications of absorption features due to pair production processes from scattering off photon bath in intergalactic space (Extragalactic Background Light) Horns, Meyer, subm. to JCAP

10. Andreas Ringwald | Physics Case for WISP Searches | 26 October 2011 | Page 10 Light Shining through Cosmic Walls > Photon -> ALP conversions in cosmic magnetic fields may explain this observation, for ALP masses below neV and g ~ 10e-11/GeV De Angelis, Roncadelli, Mansutti; …; Simet, Hooper, Serpico; …; Hochmuth, Sigl; …;Mirizzi, Montanino M Meyer

11. Andreas Ringwald | Physics Case for WISP Searches | 26 October 2011 | Page 11 Light Shining through Cosmic Walls > Photon -> ALP conversions in cosmic magnetic fields may explain this observation, for ALP masses below neV and g ~ 10e-11/GeV De Angelis, Roncadelli, Mansutti; …; Simet, Hooper, Serpico; …; Hochmuth, Sigl; …;Mirizzi, Montanino Meyer

12. Andreas Ringwald | Physics Case for WISP Searches | 26 October 2011 | Page 12 Non-Standard Energy Loss in White Dwarfs > Standard model does not fit to white dwarf luminosity function > Extra energy loss compatible with axion or ALP bremsstrahlung (mass below keV, decay constant ~ 1e9 GeV -> g ~ 1e-11/GeV) Isern et al.

13. Andreas Ringwald | Physics Case for WISP Searches | 26 October 2011 | Page 13 Physics Reach of ALPS II 2017 > ALPS II 2017 will reach the parameter range of interest for VHE light shining through the EBL and WD energy loss (g ~ 10e-11/GeV ):