APV-Avril05.ppt

PRINCIPLE OF THE EXPERIMENT PRESENT RESULTS see Ref.(5) E 1 PV: : PV E 1 6S-7S amplitude interferes with E z : Stark induced E 1 amplitude POLARIMETRIC METHOD OF MEASUREMENT ... and CALIBRATION Input probe polarisation parallel to ex , rotates during propagation by an angle k PV (k : atomic factor) Polarimeter imbalance left-right asymmetry A LR ( PV ) (S X -S Y )/(S X +S Y ) = 2 k PV Calibration: rotating ex by cal probe rotation k cal A LR ( cal ) = 2 k cal PV = [A LR ( PV ) / A LR ( cal )] . cal IMPLEMENTATION of the EXPERIMENT EXCITATION AND DETECTION 4 Polarization configurations : 0°, 45°, 90°, 135° Selection criteria of the PV rotational invariant 1 PV data 0,4s 0,8s 6s 2 mn 12s PV exp (µrad) 2002 2004 2003 1 point: 400 PV data 1 point: 200 PV data Excited vapour gain axes are // (and ), not to exc but to exc + PV exc ^ z : rotated from exc by an angle 10 -6 rad, odd in E z output probe polar n pr out = pr in + k PV pr in ^ z atomic factor (Cs density, HFS,..) z pv pv E E / 1 OUR GOAL: measurement of E 1 PV with 1% precision as a cross check of the Boulder 1999 result A new independent measur’ of Q W the weak charge of Cs nucleus as a precise test of the electroweak theories (Standard Model and extensions, e.g. extra dimensions, additional gauge bosons..) 8 month s 7 weeks cells 2002 EVOLUTION OF THE RESULTS (7 different cells) August 2004 probe beam excitatio n beam REFERENCES (1) "A New Manifestation of Atomic Parity Violation in Cesium: a Chiral Optical Gain induced by linearly polarized 6S-7S Excitation" , J. Guéna & al., Phys. Rev. Lett. 90, 143001 (2003). (2) "Cylindrical symmetry discrimination of magnetoelectric optical systematic effects in a pump- probe atomic parity violation experiment’’ , M-A. Bouchiat & al., Eur. Phys. J. D28, 331 (2004). (3) "Prospects for forbidden-transition spectroscopy and parity violation measurements using a beam of cold stable or radioactive atoms’’, S. Sanguinetti & al., Eur. Phys. J. D25, 3 (2003). (4) "Proposal for high-precision Atomic Parity Violation measurements using amplification of the asymmetry by stimulated emission in a transverse E and B fields pump-probe experiment “, J. Guéna & al., JOSA B 22, 21 (2005). (5) “Measurement of the parity violating 6S-7S transition amplitude in cesium within 2x10 -13 atomic unit accuracy by stimulated emission”, J. Guéna, M. Lintz, and M- A. Bouchiat, Phys. Rev. A.71, 042108 (2005). ArXiv:physics/0412017. (6) “Demonstration of an optical polarization magnifier with low birefringence”, M. Lintz & al., Rev Sci. Instr. 76, 4, 043102 (2005), arXiv:physics/0410044 . (7) “An alkali vapor cell with metal coated windows for efficient application of an electric field”, D. Sarkisyan & al., Rev. Sci. Instr., 76, 053108. ArXiv:physics/0504020 (8) Review Article: “ Atomic Parity Violation: Principles, Recent Results, Present Motivations”, J. Guéna, M. Lintz, and M-A. Bouchiat, Mod. Phys. Lett. A 20,6, 375 (2005). ArXiv:physics/0503143 THE CESIUM PARITY VIOLATION EXPERIMENT IN PARIS: Determination of E 1 PV within 2x10 -13 ea o J. Guéna, M. Lintz and M.-A. Bouchiat, Département de Physique de l'ENS, 24 rue Lhomond, 75 231 Paris cedex 05, FRANCE Particle physics... ...without accelerator! HOW TO AMPLIFY THE PV EFFECTS? cell input S/N now adequate to reach 1% precision by lengthening the acquisition time, using last improved cesium cell (conductive windows, ref.7) Updated average result : PV = 0.950 0.025 µrad together with a 1% accurate E z field in-situ determination from atomic signals agrees with PV = 0.962 0.005 µrad, at 1.62 kV/cm expected from Boulder result for E 1 PV/ / We extract a new determination of E 1 PV E 1 PV = (- 80.8 2.1) x 10 -13 ea o for the 6S ,F=3 – 7S, F=4 hyperfine transition PASSIVE AMPLIFICATION How to make a polarisation magnifier ? 6 brewster plates... with no two surfaces parallel ! (interference + linear dichroism birefringence) Polarisation Magnifier at cell output : Passive Amplification of the Polarisation Tilt x 3 y x t y = 1/3 t x = 1 But… 9 x less photons detected : photon shot noise also increased X 3 ! To gain in S/N we increase the probe intensity dichroic component with axes x (transmission 1) and y (transmission T y << 1) 6 wedged silica plates see Ref. (6) Excited vapour anisotropic amplifier (: gain anisotropy) exponential growth of both probe intensity and left-right asymmetry vs. optical density A LR 2 PV x [exp(A) -1] = 2 ( E 1 PV /E z ) x [exp(A) -1] where A = Ln( I out / I in ) : optical density, E z 2 Increase E z at will? ... Not in practice : high endcap potentials discharges at E z > 2 kV/cm ...by the atomic medium itself! Exploiting further A LR amplification: a new PV proposal in transverse E and B fields Advantages in transverse field configuration: • Larger excitation rate (involves scalar polarisability =10x), • Longer interaction length possible without discharges New cell design to restore cylindrical symmetry by rotating E and B fields by 45° steps New observable = PV excited-state orientation probe circular dichroism, detected using circular analyser Predicted quantum-noise limit is reduced by a factor of 10, or even more in the triggered superradiant regime ! possible design for a 0.1% statistical precision ACTIVE AMPLIFICATION -V1 V1 V1 -V1 -V2 V2 0 0 Noise reduction and increased rep. rate 160Hz Dichro ic mirror Since first 9% result (cell # 1, Ref. 1), S/N improved by 3.5 acquisition time for S/N = 1 reduced by 12 probe polarimete r see Ref.(4)

APV-Avril05.ppt

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