1. New constraints on light bosons from the high energy universe Denis WOUTERS Service de Physique des Particules Supervisor: Pierre BRUN D. Wouters and P. Brun, PRD, 2012, Irregularity in  -ray source spectra as a signature of axion-like particles D. Wouters and P. Brun, ApJ, 2013, Constraints on axion-like particles from X-ray observations of Hydra galaxy cluster HESS Collaboration (contact author), A&A, 2013, Discovery of very high energy  -ray emission from the BL Lac object PKS 0301-243 with H.E.S.S.» HESS Collaboration (contact author), submission to PRD, Constraints on axion-like particles with H.E.S.S. from the irregularity of the PKS 2155-304 energy spectrum Results presented at international conferences: 8 th Patras Workshop, Chicago, July 2012 5 th Symposium on High-Energy Gamma-Ray Astronomy, Heidelberg, July 2012 Rencontres de Moriond, La Thuile, March 2013 9 th Patras Workshop, Mayence, June 2013

2. 100 K 10 6 K10 9 K10 15 K ? Energy Temperature TeV energies and beyond require acceleration of particles What is the high energy universe? 10 12 K 1

3. Radio IR Optical UV X-rays  -rays Very High Energy  -rays HESS Collaboration (contact author), A&A, 2013 SynchrotronInverse Compton scattering The example of an Active Galactic Nucleus (AGN): Ideal targets for tests of fundamental physics Super-massive black hole Accretion disc jet PKS 0301-243 Electrons 2

4. Hypothetical particle theoretically well-motivated Axion: Hypothetical light pseudo-scalar particle Solves strong CP problem Possible explanation for Dark Matter Coupling g  a  Mass m Axion-like particles (ALPs) Coupling and mass unrelated Does not necessarily solve strong CP problem Possible explanation for Dark Matter Prediction from string theory models gaga m Axions ALPs The Search for Axion-Like Particles: 3

5. ALP / Photon oscillations in magnetic field ALPs have a vertex with two photons Energy threshold for oscillations:  a  gaga a   Mixing for g a   8x10  GeV -1 (CAST limit) B  G (galaxy cluster) m a = 30 neV    TeV a Primakoff effect 4

6. Magnetic fields involved: 1 G = 10 -4 T Lobe  G, 10 kpc Galaxy cluster  G, 1 Mpc Jet  mG, 1 parsec (pc) Intergalactic medium < 1nG, 1 Gpc Milky Way  G, 20 kpc Magnetic fields all along the line of sight 5

7. Magnetic fields in astrophysics usually turbulent Modeling of turbulence (eg: Kolmogorov spectrum) Original signature: Signature of ALPs Strong irregularities in the spectrum Homogeneous magnetic domains D. Wouters & P. Brun, PRD, 2012 P  1 23 4 1+21+21+2+31+2+31+2+3+41+2+3+4 1 2 34 No ALP 6

8. Gamma Muons Hadron h The H.E.S.S. experiment Angular resolution  0.1° Energy resolution  15% Effective area  10 5 -10 6 m 2 7

9. H.E.S.S. Observations of PKS 2155-304: Brightest active galactic nucleus observed by H.E.S.S. 45505  -rays observed during the flare of July 2006 Spectrum constructed with new unfolding method No anomalous irregularities in the observed spectrum HESS internal note, 2012, D. Wouters and P. Brun Example of ALP signal: HESS smeared 8 HESS Collaboration (contact author), 2013, to be submitted.

10. Constraints from H.E.S.S. observations: Constraints on irregularities from  /ALP conversion in: Galaxy cluster magnetic field 1 µG Intergalactic magnetic field 1 nG (optimistic) First constraints on ALPs from  -ray astronomy HESS Collaboration (contact author), 2013, to be submitted. 9

11. Constraints from X-ray observations: Chandra observations of Hydra A galaxy cluster (0.5-10 keV) Bright X-ray point-like source, non-thermal synchrotron emission Thermal component of hot electrons all around (T = 3 keV) Magnetic field profile and electron density measured Hydra A, AGN 1’ = 34 kpc VLA image: Search for irregularities in spectrum of bright central source 10

12. Spectrum of central source exclude strong irregularities D. Wouters & P. Brun, ApJ, 2013 Constraints from X-ray observations: Stringent constraints on all ALPs with masses < 10 -11 eV 11

13. Outlook: Spatial anisotropies of  -ray spectral indexes TeV  -rays absorbed in the intergalactic medium Claims for anomalous transparencies Anomaly explained by ALPs Test proposed: anomaly correlates with Galactic Magnetic Field Not enough sources detected. Need CTA (500 AGN expected) D. Wouters, P. Brun and P. Serpico, in prep. New observable, CTA required  TeV  GeV P a  No ALPs 12

14. CTA transparency HESS X-ray / Hydra A CAST Microwave cavities QCD Axions 13 ALP CDM

15. Study of new HESS source, constraint on EBL New ALP signature: irregularities in spectra Constraints from HESS observations of PKS 2155-304 Constraints from X-ray observations of Hydra A Constraints extend to light pseudo-Goldstone bosons coupled to photons Prospective for CTA: elucidate transparency anomaly Projects in collaboration with IPhT: – Philippe Brax: Constraints on disformal couplings (dark energy) – Chiara Caprini: Models of cosmological magnetic fields for  /ALP coupling HESS Collaboration, A&A, 2013 Wouters & Brun, PRD, 2012 Wouters & Brun, ApJ, 2012 HESS Collaboration, to be submitted, 2013 On-going work: Summary: 14 D. Wouters, P. Brun and P. Serpico, in prep.