1. Axel Lindner, DESY An experimental Expedition into a new Particle Habitat at smallest Masses Cosmology Meets Particle Physics, DESY Theory Workshop, 28 September 2011

2. Axel Lindner | Cosmology meets Particle Physics | 28 Sept. 2011 | Page 2 The next 40 Minutes … > A collection of open questions  Phenomena in astrophysics  Understanding today‘s Universe > What theory tells  Weakly Interacting Sub-eV Particles: WISPs > Selection of experiments searching for WISPs  Astrophysics  Laboratory  Present Status of WISP seaches and future experiments > Outlook and summary

3. Axel Lindner | Cosmology meets Particle Physics | 28 Sept. 2011 | Page 3 corona 16 MK 5800 K Open Questions: the Sun > Do we understand our Sun?  The solar corona heating http://eo.nso.edu/MrSunspot/solarzoo/coronazoo.html How is energy transferred into the corona? Courtesy of K. Zioutas

4. Axel Lindner | Cosmology meets Particle Physics | 28 Sept. 2011 | Page 4 Open Questions: the Sun > The Sun  X-ray spectra How can one understand the X-ray emission, especially of the quite sun? Is there a new mechanism transporting energy from the core to the surface? Courtesy of K. Zioutas

5. Axel Lindner | Cosmology meets Particle Physics | 28 Sept. 2011 | Page 5 Open Questions: white Dwarfs > White dwarfs  Old burned-out stars.  Final stage of 97% of all stars.  Mass < 1.4 M sun  Thermally cooling down to black dwarfs (takes longer than the age of the Universe). > Most simple star one could think of!  Composition  Physics http://universe-review.ca/I08-25-whitedwarf.jpg http://physics.uoregon.edu/~jimbrau/astr122/Notes/Chapter20.html

6. Axel Lindner | Cosmology meets Particle Physics | 28 Sept. 2011 | Page 6 Open Questions: white Dwarfs > White dwarfs cool too fast!  Observed in individual cases.  Seen in samples. > Is there an unknown energy loss channel at work?  Emission of axions? White dwarfs as physical laboratories: the axion case (J. Isern), 7th Patras Workshop on Axions, WIMPs and WISPs, http://axion-wimp.desy.de

7. Axel Lindner | Cosmology meets Particle Physics | 28 Sept. 2011 | Page 7 Detection of BSM Physics in WD? http://www.indiana.edu/~geol105/images/gaia_chapter_1/white-dwarf.jpg

8. Axel Lindner | Cosmology meets Particle Physics | 28 Sept. 2011 | Page 8 Open Questions: Dark Matter > Dark matter The axion was not invented to solve the Dark Matter problem! H. Baer, presentation at 5th Patras Workshop on Axions, WIMPs and WISPs, 2009 Due to their non-thermal production in the universe light axions would constitute cold dark matter. Such axions couple extremely weakly to matter: the “invisible” axion.

9. Axel Lindner | Cosmology meets Particle Physics | 28 Sept. 2011 | Page 9 Open Questions: TeV  Propagation TeV photons should be absorbed by e + e - pair production due to interaction with the extragalactic background light (EBL):  TeV +  eV → e + + e - However, the TeV spectra of distant galaxies do hardly show any absorption. M. Meyer, 7th Patras Workshop on Axions, WIMPs and WISPs, 2011

10. Axel Lindner | Cosmology meets Particle Physics | 28 Sept. 2011 | Page 10 Open Questions: TeV  Propagation TeV photons should be absorbed by e + e - pair production due to interaction with the extragalactic background light (EBL):  TeV +  eV → e + + e - However, the TeV spectra of distant galaxies do hardly show any absorption. M. Meyer, 7th Patras Workshop on Axions, WIMPs and WISPs, 2011 TeV photons may “hide”

11. Axel Lindner | Cosmology meets Particle Physics | 28 Sept. 2011 | Page 11 Open Questions: TeV  Propagation TeV photons should be absorbed by e + e - pair production due to interaction with the extragalactic background light (EBL):  TeV +  eV → e + + e - However, the TeV spectra of distant galaxies do hardly show any absorption. A new axion-like particle (ALP) could solve this issue. M. Meyer, 7th Patras Workshop on Axions, WIMPs and WISPs, 2011

12. Axel Lindner | Cosmology meets Particle Physics | 28 Sept. 2011 | Page 12 Open Questions: Dark Energy > Dark energy drives the Universe apart. > Is it real?

13. Axel Lindner | Cosmology meets Particle Physics | 28 Sept. 2011 | Page 13 Open Questions: Dark Energy > Dark energy drives the Universe apart. > Is it real? http://www.softcom.net/users/greebo/laugh.htm "Shhhh. That's the theoretical physicists' new particle uniform. If you can't see it, you won't be allowed to graduate."

14. Axel Lindner | Cosmology meets Particle Physics | 28 Sept. 2011 | Page 14 Open Questions: Dark Energy > Dark energy drives the Universe apart. > Is it real? > If yes, it might be attributed to a new kind of scalar field corresponding to very light particles. The cosmological constant problem, S. Weinberg, Rev. Mod. Phys. 61, 1–23 (1989)

15. Axel Lindner | Cosmology meets Particle Physics | 28 Sept. 2011 | Page 15 Understanding the present Universe > LHC probes the very early universe when it was very small, hot and dense. > Dark energy was totally negligible at those times. > Surprisingly, we understand the early universe from fractions of a second to minute scales better than today’s universe. > Dedicated “low energy” experiments are required to get a clue on Dark Energy. LHC L. Verde, 6th PATRAS Workshop, 2010

16. Axel Lindner | Cosmology meets Particle Physics | 28 Sept. 2011 | Page 16 Open Questions: Energy Scales > Neutrinos have masses at the meV scale. > The density of Dark Energy in our Universe is 10 −29 g/cm 3, being equivalent to ρ DE  (2 meV) 4 > Today‘s energy density of the universe is about (meV) 4. > Does this hint at BSM physics at the meV scale? > We should strive for dedicated experiments to solve this issue!

17. Axel Lindner | Cosmology meets Particle Physics | 28 Sept. 2011 | Page 17 Summary on open Questions > Very different phenomena may point at yet unknown particles:  Sun, white dwarfs, TeV transparency, dark matter and dark energy  ν-number excess in CMR data, polarization of light from distant quasars, vanishing electric dipole moment of the neutron, … > None of these observations is really significant yet and / or a real contradiction to Standard Model physics.  However, the number of observations is puzzling! > New experiments (PLANCK, CTA) will improve experimental data, hopefully clarifying the situation. Besides waiting for such new data: > Is there a theoretical scenario combining (most of) the puzzling observations? > How can one search with dedicated experiments for new low mass particles?

18. Axel Lindner | Cosmology meets Particle Physics | 28 Sept. 2011 | Page 18 The next 40 Minutes … > A collection of open questions  Phenomena in astrophysics  Understanding today‘s Universe > What theory tells  Weakly Interacting Sub-eV Particles: WISPs > Selection of experiments searching for WISPs  Astrophysics  Laboratory  Present Status of WISP seaches and future experiments > Outlook and summary

19. Axel Lindner | Cosmology meets Particle Physics | 28 Sept. 2011 | Page 19. What Theory tells … … should not be presented by an experimentalists … … looks like bringing owls to Athens here … So only some very brief remarks! http://www.gutenberg.org/files/20392/20392-h/images/411.png

20. Axel Lindner | Cosmology meets Particle Physics | 28 Sept. 2011 | Page 20 hidden sector A hidden sector of particle physics could exist very well: These particles would be uncharged with respect to electroweak and strong interactions and hence appear to be “dark”. > The unification of forces requires extended gauge structures which led to singlets charged under some new gauge group. Thus GUTs or string theories can‘t avoid a hidden sector. What Theory tells …

21. Axel Lindner | Cosmology meets Particle Physics | 28 Sept. 2011 | Page 21 hidden sector A hidden sector of particle physics could exist very well: These particles would be uncharged with respect to electroweak and strong interactions and hence appear to be dark. > The unification of forces requires extended gauge structures which led to singlets charged under some new gauge group. Thus GUTs or string theories can‘t avoid a hidden sector. > Gauge hierarchy problem: how could one understand the huge difference between the electroweak scale of 10 2 GeV and the Planck scale of 10 19 GeV? A hidden sector introducing a dynamical SUSY breaking could take care for this. > There could be complex physics within the hidden sector with new forces and charges. What Theory tells …

22. Axel Lindner | Cosmology meets Particle Physics | 28 Sept. 2011 | Page 22 hidden sector Particles from a hidden sector could interact in different manners with Standard Model particles: > By gravitation (dark matter in the universe). > By heavy messengers charged under the Standard Model and the hidden sector. > Standard Model particles could be charged also under the hidden sector. This would result in fifth forces. What Theory tells …

23. Axel Lindner | Cosmology meets Particle Physics | 28 Sept. 2011 | Page 23 A new Particle Habitat? > Probably (some / most of ?) the “open question” phenomena point at physics beyond the Standard Model. > There could be a hidden sector of very Weakly Interacting sub-eV Particles (WISPs):  Axion  Axion-like particles ALPs  Hidden photons  Mini-charged particles  Chameleons  … > Such a new habitat is motivated by theory and observations > How to search for such a new particle habitat at low masses?

24. Axel Lindner | Cosmology meets Particle Physics | 28 Sept. 2011 | Page 24 The next 40 Minutes … > A collection of open questions  Phenomena in astrophysics  Understanding today‘s Universe > What theory tells  Weakly Interacting Sub-eV Particles: WISPs > Selection of experiments searching for WISPs  Astrophysics  Laboratory  Present Status of WISP seaches and future experiments > Outlook and summary

25. Axel Lindner | Cosmology meets Particle Physics | 28 Sept. 2011 | Page 25 Seeing the “Invisible”: Primakoff Effect > Axion and axion-like particles (ALPs): exploit the coupling to photons. > photon + photon ↔ ALP photon + ALP → photon > photon + (virtual photon) → ALP ALP + (virtual photon) → photon A virtual photon can be provided by an electromagnetic field. The Search for Axions, Carosi, van Bibber, Pivovaroff, Contemp. Phys. 49, No. 4, 2008

26. Axel Lindner | Cosmology meets Particle Physics | 28 Sept. 2011 | Page 26 Seeing “invisible” WISPs > Neutral scalar or pseudoscalar WISPs: exploit the Primakoff effect > Neutral vectorbosons (“hidden sector photons” HP): exploit mixing with “ordinary” photons.

27. Axel Lindner | Cosmology meets Particle Physics | 28 Sept. 2011 | Page 27 Seeing “invisible” WISPs > Neutral scalar or pseudoscalar WISPs: exploit the Primakoff effect > Neutral vectorbosons (“hidden sector photons” HP): exploit mixing with “ordinary” photons. > Minicharged particles (MCP, about 10 -6 e): “loop effects”.

28. Axel Lindner | Cosmology meets Particle Physics | 28 Sept. 2011 | Page 28 > Neutral scalar or pseudoscalar WISPs: exploit the Primakoff effect > Neutral vectorbosons (“hidden sector photons” HP): exploit mixing with “ordinary” photons. > Minicharged particles (MCP, about 10 -6 e): “loop effects”. Seeing “invisible” WISPs  Axion-Like Particles, Hidden Photons, MiniCharged Particles

29. Axel Lindner | Cosmology meets Particle Physics | 28 Sept. 2011 | Page 29 “Invisible” WISPs in Astrophysics > Indirect: WISPs would open up new energy loss channels for hot dense plasmas  stringent limits on WISP characteristics from the lifetime of stars, length of neutrino pulse from SN and cosmic microwave background radiation for example. > Direct:  Search for axions from the sun (CAST at CERN) The Search for Axions, Carosi, van Bibber, Pivovaroff, Contemp. Phys. 49, No. 4, 2008

30. Axel Lindner | Cosmology meets Particle Physics | 28 Sept. 2011 | Page 30 “Invisible” WISPs in Astrophysics > Indirect: WISPs would open up new energy loss channels for hot dense plasmas  stringent limits on WISP characteristics from the lifetime of stars, length of neutrino pulse from SN and cosmic microwave background radiation for example. > Direct:  Search for hidden photons from the sun (SHIPS in Hamburg)  Search for halo dark matter axions (ADMX in the US) The Search for Axions, Carosi, van Bibber, Pivovaroff, Contemp. Phys. 49, No. 4, 2008

31. Axel Lindner | Cosmology meets Particle Physics | 28 Sept. 2011 | Page 31 > Indirect: WISPs would open up new energy loss channels for hot dense plasmas  stringent limits on WISP characteristics from the lifetime of stars, length of neutrino pulse from SN and cosmic microwave background radiation for example. > Direct:  Search for axions from the sun (CAST at CERN)  Search for halo dark matter axions (ADMX in the US) “Invisible” WISPs in Astrophysics http://www.phys.washington.edu/groups/admx/home.htm lhttp://cast.web.cern.ch

32. Axel Lindner | Cosmology meets Particle Physics | 28 Sept. 2011 | Page 32 Okun 1982, Skivie 1983, Ansel‘m 1985, Van Bibber et al. 1987 “Invisible” WISPs in the Laboratory “Light-shining-through-a-wall” (LSW) G. Ruoso et al. (BFRT Experiment), Z. Phys. C 56 (1992) 505 Note: P  Φ   g 4 g g

33. Axel Lindner | Cosmology meets Particle Physics | 28 Sept. 2011 | Page 33 q = p γ – p Φ l: length of B field Axion Production in a magnetic Field > The production (and re-conversion) of WISPs takes place in a coherent fashion. For ALPs (Φ): With P  Φ = P Φ  = P: g = (P) 1/4 · 2 · / (l·B) / F 1/2 Please take note: P(B field) / P(beam dump) = 10 6 ·(mm/λ abs )·(B/T) 2· (L/m) 2 (A. Ringwald, J. Redondo, arXiv:1011.3741v1 [hep-ph])

34. Axel Lindner | Cosmology meets Particle Physics | 28 Sept. 2011 | Page 34 ALPS @ DESY in Hamburg ALPS PETRA III FLASH European XFEL DORIS III ALPS-II In the HERA tunnel? OLYMPUS PETRA III-Extension FLASH II

35. Axel Lindner | Cosmology meets Particle Physics | 28 Sept. 2011 | Page 35 The ALPS Experiment Any Light Particle Search @ DESY Laser ContainerHERA MagnetDetektor “Light-shining-through-a-wall” (LSW)

36. Axel Lindner | Cosmology meets Particle Physics | 28 Sept. 2011 | Page 36 The ALPS Experiment Any Light Particle Search @ DESY  DESYDESY Max Planck Institute for Gravitational Physics (Albert Einstein Institute), and Institute for Gravitational Physics, Leibniz University HannoverMax Planck Institute for Gravitational Physics (Albert Einstein Institute), and Institute for Gravitational Physics, Leibniz University Hannover Laserzentrum HannoverLaserzentrum Hannover Hamburger SternwarteHamburger Sternwarte

37. Axel Lindner | Cosmology meets Particle Physics | 28 Sept. 2011 | Page 37 The ALPS Experiment > New: realize an optical resonator inside the HERA dipole! Lock by adapting the laser frequency to the distance fluctuations between the mirrors. Lock by adapting the distance between the mirrors to the variations of the laser frequency.

38. Axel Lindner | Cosmology meets Particle Physics | 28 Sept. 2011 | Page 38 ALPS Results (PLB Vol. 689 (2010), 149, or http://arxiv.org/abs/1004.1313) > Unfortunately, no light is shining through the wall! laser hutHERA dipoledetector 3.5·10 21 1/s < 10 -3 1/s

39. Axel Lindner | Cosmology meets Particle Physics | 28 Sept. 2011 | Page 39 ALPS Results (PLB Vol. 689 (2010), 149, or http://arxiv.org/abs/1004.1313) > ALPS is the most sensitive experiment for WISP searches in the laboratory. pseudoscalar and scalar axion-like particles hidden sector photons and minicharged particles Filling a gap remaining from astrophysics and other experiments! PLB 689 (2010), 149

40. Axel Lindner | Cosmology meets Particle Physics | 28 Sept. 2011 | Page 40 Axion-like Particle Status > Present experiments are hardly sensitive enough to probe for the open questions discussed before. > An ALP with a coupling around 10 -11 GeV -1 could be Dark Matter and solve the TeV transparency as well as the white dwarf riddles! Work in progress by P. Arias, M. Goodsell, J. Jaeckel, J. Redondo and A. Ringwald preliminary

41. Axel Lindner | Cosmology meets Particle Physics | 28 Sept. 2011 | Page 41 Hidden Photon Status > Present experiments are only partly sensitive enough to probe for the hidden photon dark matter. > Hidden photons with a mixing around 10 -9 could be interesting! Work in progress by P. Arias, M. Goodsell, J. Jaeckel, J. Redondo and A. Ringwald preliminary

42. Axel Lindner | Cosmology meets Particle Physics | 28 Sept. 2011 | Page 42 An Outlook to future Experiments (my arbitrary selection) > Light-shining-through-a-wall:  ALPS-II  New possibilities at synchrotron radiation sources? > Searching for WISPs from the sun:  Axion and axion-like particles, chameleons  Hidden photons > Novel dark matter searches utilizing HERA dipoles for example (work in progress, not covered here).

43. Axel Lindner | Cosmology meets Particle Physics | 28 Sept. 2011 | Page 43 Prospects for ALPS-II @ DESY > Laser with optical cavity to recycle laser power, switch from 532 nm to 1064 nm, increase effective power from 1 to 150 kW. > Magnet: upgrade to 12+12 straightened HERA dipoles instead of ½+½ used for ALPS-I (LSW with straightened HERA dipoles cannot be surpassed by LSW with LHC dipoles!). > Regeneration Cavity to increase WISP-photon conversions, single photon counter (transition edge sensor?). laser hut HERA dipole detector All set up in a clean environment!

44. Axel Lindner | Cosmology meets Particle Physics | 28 Sept. 2011 | Page 44 > Search for “hidden photons”: The ALPS-II Potential preliminary

45. Axel Lindner | Cosmology meets Particle Physics | 28 Sept. 2011 | Page 45 > Search for axion-like particles: The ALPS-II Potential preliminary

46. Axel Lindner | Cosmology meets Particle Physics | 28 Sept. 2011 | Page 46 LSW at Synchrotron Sources > Light-shining-through-a-wall with X-rays

47. Axel Lindner | Cosmology meets Particle Physics | 28 Sept. 2011 | Page 47 LSW at Synchrotron Sources > Light-shining-through-a-wall with X-rays > Fluxes of up to 10 19 photons per second in dedicated beamlines would allow to probe for Dark Energy chameleons in the laboratory! Work in progress by P. Brax, A.L., K. Zioutas

48. Axel Lindner | Cosmology meets Particle Physics | 28 Sept. 2011 | Page 48 WISPs from the Sun > New Generation Axion Haloscope (CAST successor) I. Irastorza, 7th Patras Workshop on Axions, WIMPs and WISPs, 2011 preliminary

49. Axel Lindner | Cosmology meets Particle Physics | 28 Sept. 2011 | Page 49 WISPs from the Sun > Solar Hidden Photon Search (Toy SHIPS) Tube will be mounted piggyback on an existing telescope at the observatory Bergedorf (east of Hamburg). Courtesy of M. Schwarz

50. Axel Lindner | Cosmology meets Particle Physics | 28 Sept. 2011 | Page 50 WISPs from the Sun > Solar Hidden Photon Search (Toy SHIPS) Courtesy of J. Redondo preliminary

51. Axel Lindner | Cosmology meets Particle Physics | 28 Sept. 2011 | Page 51 WISPs from the Sun > Solar Hidden Photon Search (SHIPS) A future larger version in the HERMES-hall at HERA?

52. Axel Lindner | Cosmology meets Particle Physics | 28 Sept. 2011 | Page 52 Summary I > There is a wealth of phenomena in astrophysics hinting at the existence of a new particle habitat at low masses. > Many extensions of the Standard Model expect such a habitat of WISPs.  Theory is passing the verge of giving detailed guidelines for experiments and relations of WISP searches to unifying theories. > WISPs could solve different phenomena in one go:  Axion(-like) particles: Dark Matter, TeV-transparency, white dwarfs, strong CP problem  Chameleons: Dark Energy, solar corona heating, X-ray spectra of the sun

53. Axel Lindner | Cosmology meets Particle Physics | 28 Sept. 2011 | Page 53 Summary II > There are many different experimental approaches to search for WISPs in astrophysics and the laboratory. > WISP experiments benefit strongly from the infrastructure of labs like DESY:  Re-use of HERA components.  “Parasitic” use of accelerator based light sources. > The next generation of WISP experiments will reach parameter regions predicted by theory.  The next decade will decide on the future of WISP physics. > WISP physics nicely complements physics at the energy frontier.  Understanding the present and the early Universe.

54. Axel Lindner | Cosmology meets Particle Physics | 28 Sept. 2011 | Page 54 Summary II > There are many different experimental approaches to search for WISPs in astrophysics and the laboratory. > WISP experiments benefit strongly from the infrastructure of labs like DESY:  Re-use of HERA components  “Parasitic” use of accelerator based light sources > The next generation of WISP experiments will reach parameter regions predicted by theory.  The next decade will decide on the future of WISP physics. > WISP physics nicely complements physics at the energy frontier.  Understanding the present and early Universe. Expect surprises!