Photoregeneration Experiment Axion search

Laboratoire pour l Utilisation des Lasers Intenses, Palaiseau A.-M. Sautivet, F. Amiranoff Photoregeneration Experiment Axion search Laboratoire Collisions Agrégats Réactivité, Toulouse C. Robilliard, M. Fouché, C. Rizzo Laboratoire National Champs Magnétiques Pulsés, Toulouse J. Mauchain, R. Battesti

Reasons for prediction : Strong CP problem CP symmetry in Quantum ChromoDynamics : In standard model : CP violated θ = strong CP violating term = fundamental constant θ 1 Strong CP problem : Large electric dipole moment for the neutron Problem : not observed experimentally ( θ < 10-10 )

Possible solution Peccei Quinn solution to restore CP symmetry : θ fundamental constant = field particle = AXION Challenge : Detect this particle Implication of detecting this new particle : For QCD theory Cosmological implications : Constitutive of dark matter

Outline 1) Axion??? Properties Axion-Magnetic field interaction 2) Experimental searches ADMX : cosmological axions CAST : solar axions BFRT : production on earth PVLAS ; first detection of axion? 3) Our experiment Setup Key elements : laser, B, detector Synchronization 4) Results Conclusion

Beyond the standard model Pseudoscalar Boson Neutral Very low mass Properties Weak and strong forces : very low cross section Hardly interact with ordinary matter Axion = extremely difficult to detect Coupling to photon : Axion production by photon in a static magnetic field (and vice versa) : Primakoff effect

Axion coupling to photon Wave equation : C i ψ ( z) = C ψ ( z) z = ω 0 0 0 ω B / 2M with 0 B / 2M ω m / 2ω a ψ ( z) = c ( z) + c ( z II photon II ) + c Oscillation between two states : photon (polarisation // B) axion a a axion Parameters : m a axion mass g aγ = 1/M coupling constant ω photon energy

Conversion probability : p Conversion probability ( z) ( z' ) z 2 B m ' ' exp 2 2 = a z dz i M 0 ω In a constant magnetic field over a length L : 2Bω p( L) = 2 Mma 2 2 sin 2 2 m a L 4ω m a 2 L 4 ω << 1

ADMX (Axion Dark Matter experiment) Axion from the halo dark matter of our galaxy Tunable resonant micro wave cavity Superconducting magnet : 8 T over 0.6 m RF detector with small noise Sensitive experiment Model dependent No EFFECT ADMX S. J. Asztalos et al., Phys. Rev. D 69, 011101 (2004)

CAST (CERN Axion Solar Telescope) Solar axion Superconducting magnet : 9 T over 10 m X rays detector CAST prospects CAST 2003 Sensitive experiment Model dependent No EFFECT ADMX G. G. Raffelt, arxiv:hep-ph/0611118)

BFRT (Brookhaven-Fermilab-Rochester-Trieste) Ligth shining through the wall experiment 2 superconducting magnets : 3.7 T over 4.4 m Continuous laser, λ = 514 nm m a max = 8 10-4 Multi-pass cavity in the generation area Photomultiplier, quantum efficiency = 0.1 CAST prospects CAST 2003 ADMX Production and detection in terrestrial lab Model independent Less sensitive No EFFECT BFRT photoregeneration R. Cameron et al., Phys. Rev. D 47, 3707 (1993)

PVLAS (Polarizzazione del Vuoto con LASer ) QED test Superconducting magnet : 5 T over 1 m Continuous laser, λ = 1064 or 532 nm Resonant cavity, F ~ 10 5, L = 6 m Dichroïsm not predicted by QED!!! x E E perp E par B 0 Production and detection in terrestrial lab Model independant Less sensitive PVLAS interpretation : Production of axion E. Zavattini et al., Phys. Rev. Lett. 96, 110406 (2006) ; E. Zavattini et al., arxiv:0706.3419 [hep-ex] y

axion of PVLAS (2006) Problem : Seriously inconsistent with other limits Crucial need for an independent experimental test CAST prospects CAST 2003 Excluded by BFRT PVLAS Experimental projects : ADMX ALPS at DESY OSQAR at CERN LIPSS at Jefferson Laboratory BMV in France GammeV at Fermilab. BFRT photoregeneration PVLAS

Principle of the experiment Number of regenerated photon : N RP =η N i 4 4 BL sin ( y) 4 2M y N i Number of incident photons with y = 2 ma L ω L magnet length η detection efficiency

The three key elements Number of regenerated photon : N RP =η η N i 4 4 BL sin ( y) 4 2M y with y = 2 ma L ω 1. Laser : High N i N RP as high as possible 2. Coils : high BxL 3. Photon detector : high detection efficiency η

1. Nano 2000 Laser Chain (LULI) 1 to 1.5 kj / pulse λ = 1053 nm N i = 5 to 8 10 21 / pulse Pulse duration = 5 ns 5 pulses / day

2. Coils Development (LNCMP) X coil geometry high transverse magnetic field I N i Length = 45 cm I Aperture = 12 mm B 1 B 2 B Coils originally developed for the BMV experiment by S. Batut & O. Portugall.

2. Coils test (LNCMP) B 0 > 12.2 T over 36 cm B.L = 4,5 T.m Time duration : 5 ms B 0 reached within 1.75 ms B 0 (+/- 0.3 %) during 150 μs

2. Coils cryostats (LNCMP) Immersion in liquid nitrogen

3. Detection Single photon Detector : Commercially available from Princeton Lightwave Instruments - 80x80 mm 2 APD optimizes at 1064 nm - Geiger mode with detection gate = 5 ns - Coupling through a fibre Fibre link : - 30 m long avoid electronic noise due to XCoils

3. Detector Test (LCAR) Goals : - High detection efficiency - low dark count rate Adjustments : - Temperature -Biasvoltage - Discriminator threshold Tests performed with cw Nd:YAG monomode laser. Working point Dark count rate = 5 10-4 / Pulse η = 0.5

Performance Expected results : After5 pulses : test PVLAS results (2σ confidence level) With100 pulses: improve BFRT limits for all masses Characteristics of our experiment : Pulsed experiment background not limiting Limited number of pulses / year

General set-up (LCAR)

Inplementation at LULI Vacuum : To avoid air ionization

Inplementation at LULI Focalisation Lens : f = 20 m

Implementation at LULI Coils and their cryostats

Implementation at LULI Generator originally developed for experiments at ESRF by P. Frings. For the Pulsed magnetic field : Transportable generator V max = 16 kv 3 x 1 m 3 ~ 3 tons

Implementation at LULI Fibre and coupler Fibre injection : 80 to 90 %

Synchronization Laser-XCoils B0 (+/- 0.3 %) during 150 μs Magnetic pulse trigger : from the laser chain Ensure laser pulse happens during these 150 μs

Synchronization Laser-Detector Laser pulse : 5 ns Detector gate : 5 ns Trigger = same fast signal as laser with delay lines Jitter = 150 ps Working point

Final tests Optical shielding : no count Electromagnetic noise : count Detector in shielding bay : no count Alignment procedure : with the unchopped pilot beam aligned with the high energy pulse

Final tests How can we be sure that the high energy pulse follows exactly the same optical path? Image recorded for each pulse. Estimation of losses

Ready to take data Strength of our experiment : - high laser energy + high B L - laser + B + detector pulsed Ready : end of May Small integration time to test PVLAS claims Background of detection not limiting Efficient experiment : - to test PVLAS results 2 to 2500 regenerated photons / pulse - not to detect standard axion 10-21 to 10-30 regenerated photons / pulse

Measurements 2 weeks in July and September Number of pulses : 24 Total incident energy : 29.5 kj Effective number of incident photon : 1.15 10 23 Result : No regenerated photon detected How to be sure that detection works correctly?

Detection checking High energy optical path : image recorded for each pulse Synchronization : 2 oscilloscopes - Laser trigger - Magnetic field magnetic field - laser synchronization checking B 0 measurement - Laser trigger - Detector trigger - Detector monitor - Photon TTL detector - laser synchronization checking checking of the APD polarisation

Our limits? : p ( L) ( z' ) L 2 B m ' ' exp 2 2 = a z dz i M 0 ω p Limits? No regenerated photon detected If PVLAS limits confirmed : 2 to 2500 regenerated photons / pulse For a : - detection efficiency η - Confidence level (Ex. : CL = 0.95 2σ) Number n of missed regenerated photon Numerical integration of with 2 ( L) N n 2 i Limits in the (m a, M) plane

Our present limits BFRT 3σ PVLAS 3σ 2006

C. Robilliard et al., Phys. Rev. Lett. 99, 190403 (5 nov. 2007) Our present limits BFRT 3σ PVLAS 3σ 2006 Our limits 3σ Our limits 5σ PVLAS excluded

C. Robilliard et al., Phys. Rev. Lett. 99, 190403 (5 nov. 2007) Our present limits BFRT 3σ PVLAS 3σ 2006 Our limits 3σ Our limits 5σ FermiLab 3σ PVLAS 3σ 2007

Conclusion PVLAS results not confirmed Axion is still running Prospects : 2 weeks of measurements in 2008 Improvement of our limits compared to other terrestrial experiments To test standard axion : far more difficult Different design

Collaborators LCAR Carlo Rizzo Cécile Robilliard Rémy Battesti Julien Mauchain LNCMP LULI Anne-Marie Sautivet François Amiranoff