Optical Search for QED vacuum magnetic birefringence, Axion & photon Regeneration Laser-based Particle/Astroparticle Physics Experiments at CERN To Test QED & probe the Low Energy Frontier… 2010 Status Report, from P. Pugnat on the behalf of the OSQAR Collaboration 99 th Meeting of the SPSC (CERN), 16 November 2010

► 26 Members from 11 Institutes (CERN, Cz, Fr & Po) The OSQAR CERN For Low Energy Laser-based Particle/Astroparticle Physics2 CERN, Geneva, Switzerland G. Deferne, P. Pugnat (now at LNCMI-CNRS), M. Schott, A. Siemko Charles University, Faculty of Mathematics & Physics, Prague, Czech Republic M. Finger Jr., M. Finger, M. Slunecka Czech Technical University, Faculty of Mechanical Engineering, Prague, Czech Republic J. Hošek, M. Kràl, K. Macuchova, M. Virius, J. Zicha ISI, ASCR, Brno, Czech Republic A. Srnka IMEP/LAHC - INPG, Grenoble Cédex-1, France L. Duvillaret, G. Vitrant, J.M. Duchamp IN, CNRS – UJF & INPG, BP 166, Grenoble Cédex-9, France B. Barbara, R. Ballou LASIM, UCB Lyon1 & CNRS, Villeurbannes, France M. Durand (now at NIST, Gaithersburg), J. Morville LSP, UJF & CNRS, Saint-Martin d'Hères, France R. Jost, S. Kassi, D. Romanini TUL, Czech Republic M. Šulc Warsaw University, Physics Department, Poland A. Hryczuk, K. A. Meissner

Outline Introduction Scientific Motivations Reminder of the OSQAR Experiments –VMB Measurement –Photon Regeneration (PR) Experiment Progress achieved in 2010 & Expected for 2011/12 Short & Long Time Perspectives Summary, Perspectives & Requirements for 2011 The OSQAR CERN For Low Energy Laser-based Particle/Astroparticle Physics3

Scientific Motivations ► Complementary to the LHC The OSQAR CERN For Low Energy Laser-based Particle/Astroparticle Physics Physics at the Sub-eV scale to search WISPs (Weakly Interacting Sub-eV Particles) Physics at the TeV scale to search WIMPs (Weakly Interacting Massive Particles) Many extensions of the Standard Model, like those based on supergravity or superstrings, predict not only WIMPS but also WISPs… 4

xxxx Delbrück scattering Scientific Motivations in a Nutshell To measure for the 1 st time the Vacuum Magnetic Birefringence predicted by the QED (Heisenberg & Euler, Weisskopf, 1936) i.e. the vacuum magnetic “anomaly” of the refraction index “ n-1” ~ in 9.5 T To explore the Physics at the Low Energy Frontier (sub-eV) –Axion & Axion Like Particles i.e. solution to the strong CP problem (Weinberg, Wilczek, 1978) & Non-SUSY Dark Matter candidates (Abbott & Sikivie; Preskill, Wise & Wilczek, 1983) –Paraphotons (Georgi, Glashow & Ginsparg, 1983), Milli-charged Fermions –Chameleons (Khoury & Weltman, 2003) –The unknown … A New Way of doing Particle Physics based on Laser beam(s) Spin-offs in the domain of the metrology of electric & magnetic fields The OSQAR CERN For Low Energy Laser-based Particle/Astroparticle Physics5

Principles of the Experiments ► In one aperture of dipole-1, measurement of the Vacuum Magnetic Birefringence & Dichroïsm ► In the 2 nd aperture of dipole-1 & one aperture of dipole-2, Photon Regeneration Experiment x a  9.5 T x  ~ 53 m The OSQAR CERN For Low Energy Laser-based Particle/Astroparticle Physics LN 2 cooled CCD Use of 2 LHC cryo-dipoles (double apertures) for Phase-1 & 2 6

The OSQAR CERN For Low Energy Laser-based Particle/Astroparticle Physics7 Axions  Change of the linear polarisation of a laser beam after propagation in the vacuum with B transverse : –Elliptical –“Pseudo”-rotation Background for the ellipticity coming from the QED VMB  Physics is guaranteed Very small effects ~ rad / T 2 km 3  optical cavity to increase the path in B P. Pugnat, L. Duvillaret, M. Finger, M. Kral, A. Siemko, J. Zicha Czechoslovak Journal of Physics, Vol.55 (2005), A389 ; Optical scheme with inputs from D. Romanini. L. Maiani, R. Petronzio, and E. Zavattini, Phys. Lett. 175B (1986) 359 Field Modulation at 1-10 mHz & dedicated filtering techniques Phase 1 VMB & Linear Dichroism measurements to test QED & Search Axion/ALP: Principle & Proposed Optical Scheme VMB ~ rad / T 2 km

VMB measurement – The key problem to solve : How to get rid of the birefringence & dichroism of the optical cavity ? A new approach was proposed by a team from OSQAR & presented in 2009 (SPSC-SR ; ) The OSQAR CERN For Low Energy Laser-based Particle/Astroparticle Physics8

9 x  in  out y  in  out B Maintain the high finesse of the cavity during the synchronous rotation of the mirrors around their optical axis VMB & Linear Dichroism measurements - (R)evolution of the optical scheme Use residual mirrors birefringence as an optical bias for homodyne detection From SPSC-SR-053 Expected sensitivity 10 hours of time integration rad Cavity in transmission instead of reflection 2∙ rad Optimized mirrors in the long cavity 2∙ rad Optimized electronics rad VMB ~ rad An update for the OSQAR-VMB is in preparation

Photon Regeneration runs in 2010 “An invisible light shining through a wall” K. van Bibber et al. PRL 59 (1987) 759 The Boss Borrowed from Aaron S. Chou, SLAC HEP seminar, Jan. 14, 2008

The OSQAR CERN For Low Energy Laser-based Particle/Astroparticle Physics Photon Regeneration ► 1 st operation in 2010 with 2 aligned LHC dipoles A B C A B C D E F D E F B1 E1 53 m 11

Safety Issues – Operation of a Class IV laser Additional constraints coming from the open access of the SM18 hall to visitors Safety audit of March 8 th -Strict Procedure for operation (EDMS doc v.3) - Improvements of the beam shielding - Modification of the water circuit for the laser cooling The OSQAR CERN For Low Energy Laser-based Particle/Astroparticle Physics12

Overview of the experimental runs in 2010 The OSQAR CERN For Low Energy Laser-based Particle/Astroparticle Physics13 PeriodOSQAR configurationData acquisition runs February Photon Regeneration ► 2 LHC dipoles temporary used/available ► 18 W Ar+ laser with linear polarization // B Cumulative time integration of ► 0.83 h for scalar search ► 0.67 h for paraphoton search Breakdown of the Laser 15 March - 9 June Shutdown of the cryogenics 19 June - 7 July ► 1 LHC dipole temporary used/available ► 14 W Ar+ laser (new one provided by ESPCI-Paris) Background study & long term stability runs AugustPhoton Regeneration ► 2 LHC dipoles temporary used/available ► 14 W Ar+ laser (new one provided by ESPCI-Paris) with linear polarization  B Cumulative time integration of ► 85 h for pseudo-scalar search ► 18.5 h for scalar search ► 72 h for background

Exemple of raw & filtered data Filtering of raw data to supress cosmic signals from each frame before accumulation The OSQAR CERN For Low Energy Laser-based Particle/Astroparticle Physics14 Statistical analysis to built exclusion limits Preliminary

Preliminary Results for 2010 Runs Detailed analysis is undergoing CCD background stability makes difficult the combined analysis between all data sets 1 st analysis (conservative) of best data sets –12.7h/6.5W for pseudoscalar –7.37h/6.7W for scalar The OSQAR CERN For Low Energy Laser-based Particle/Astroparticle Physics15 Preliminary ► The expected sensitivity in 2009 (SPSC-M-770) has been reached

Sensitivity of the Photon Regeneration Experiment Exclusion limit forg A  B (T)B -1 Magnetic Length (m)L -1 Optical power (W)P -1/4 Detection threshold (  /s) dN  /dt 1/4 Time integration  t -1/8 The OSQAR CERN For Low Energy Laser-based Particle/Astroparticle Physics16 P. Sikivie, PRL 51 (1983) K. van Bibber et al. PRL 59 (1987) 759

Expected exclusion limits for 2011/12 Assumptions - 24 h of time integration - Optical power x 50 - New CCD allowing a background reduction by 50 ► Target = to improve the ALPs limit by x5 The OSQAR CERN For Low Energy Laser-based Particle/Astroparticle Physics17 Expectation

How to increase the optical power ? ► By extending the laser cavity The OSQAR CERN For Low Energy Laser-based Particle/Astroparticle Physics18 A laser cavity extended up to 5 m inside the magnet aperture was already built ► With an intra-cavity CW power larger than few 100 W Need to be repeated with the new laser & a mirror with a larger radius to extend the cavity up to 20 m…

The OSQAR CERN For Low Energy Laser-based Particle/Astroparticle Physics Experiments - Expected results - Short & “Long” Term Perspectives PVLAS, PRL 96 (2006) CAST-2003, PRL 94 (2005) ALPs 2010 Expectation for 2011/12 OSQAR-PR From C. Hagmann, K. van Bibber, L.J. Rosenberg, Physics Lett. B, vol.592, 2004 Photon regeneration Experiment - Preliminary Phase to test PVLAS results; 1 dipole with/without gas (done) * * - Phase-1 : 2 dipoles, CW laser beam, extra & intra cavity to improve BFRT/GammeV results ( ) and ALPs ( ) - Phase-2 : 2 dipoles, CW laser beam & High Finesse FP cavity ( ) - Phase-3 : more than 2 dipoles to be competitive with CAST (long term) “n-1 Experiment” i.e. VMB & Linear Dichroism - Phase-1 & 2 : Measurements of QED prediction in O(  2 ) & O(  3 ) respectively within 1 dipole (2013 & 2014 at the earliest…) *P. Pugnat, et al. Czech Journal of Physics, Vol.55 (2005), A389; Czech Journal of Physics, Vol.56 (2006), C193; * * 1 st results in Phys. Rev. D 78, (2008) Axion Search 19

The OSQAR CERN For Low Energy Laser-based Particle/Astroparticle Physics For the longer term: Toward the “axionic” laser With LHC Dipoles, i.e. Experiment of ~150 m long,… Phys. Rev. Lett. 98, (2007) 20

Summary, Perspectives & Requirements The potential discovery of the OSQAR-PR was significantly improved in 2010 with the simultaneous use of 2 LHC dipoles The sensitivity obtained for pseudoscalar & scalar search has reached the foreseen target and is only surpassed today by the new results of the ALPs experiment OSQAR-PR limitations due to the : - Less than expected availability of the LHe cooling capacity at SM18 - Reduced optical power of the laser - Poor performances of the CCD detector Perspectives for 2011 & To break the OSQAR-PR limitations ► Increase the time integration ► Extend the laser cavity up to 20 m ► New CCD - This, to improve the exclusion limits for pseudoscalar & scalar search by about one order of magnitude - To develop a first prototype of a rotating Fabry perot cavity for the VMB measurement Requests for LHC dipoles at cold condition for at least 1 period of 2 weeks and 4 periods of 1 week each The OSQAR CERN For Low Energy Laser-based Particle/Astroparticle Physics21

Acknowledgements The OSQAR collaboration would like to thank - Gilles Tessier from ESPCI-Paris (Ecole Supérieure de Physique & de Chimie Industrielles de la ville de Paris) to have provided the new 14 W Ar+ laser, - The CERN teams of the SM18-test hall (MSC-TF, CRG-OD, RF-KS) for their valuable technical contributions, inputs and advices, as well as - The management of CERN-TE department for continuous support. The OSQAR CERN For Low Energy Laser-based Particle/Astroparticle Physics22