PRINCIPLE OF THE EXPERIMENT

1. PASSIVE AMPLIFICATION Polarisation Magnifier at cell output : Passive Amplification of the Polarisation Tilt dichroic component with axes x (transmission 1) and y (transmission Ty << 1) Polarimeter imbalance  left-right asymmetry ALR(PV)(SX-SY)/(SX+SY) = 2 k PV  y ty = 1/3 tx = 1  x 3 x Calibration: rotating ex by cal probe rotationkcalALR(cal)=2 k cal But… 9 x less photons detected : photon shot noise also increased X 3 ! To gain in S/N we increase the probe intensity PV = [ALR(PV)/ALR(cal)] . cal  How to make a polarisation magnifier ? 6 brewster plates... with no two surfaces parallel ! (interference + linear dichroism  birefringence) ACTIVE AMPLIFICATION ...by the atomic medium itself! 6 wedged silica plates see Ref. (6) • Exploiting further ALR 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 Excited vapour  anisotropic amplifier (: gain anisotropy)  exponential growth of both probe intensity and left-right asymmetry vs. optical density ALR 2PV x [exp(hA) -1] = 2 ( E1PV/bEz) x[exp(hA) -1] where A = Ln( Iout/ Iin) : optical density, Ez2  Increase Ez at will? ... Not in practice : high endcap potentials discharges at Ez > 2 kV/cm 0 -V1 V1 -V2 V2 0 V1 -V1 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 E1PV within 2x10-13 eao 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! PRINCIPLE OF THE EXPERIMENT PRESENT RESULTS see Ref.(5) HOW TO AMPLIFY THE PV EFFECTS? EXCITATION AND DETECTION EVOLUTION OF THE RESULTS (7 different cells) 1 point: 400 PV data 1 point: 200 PV data 2002 August 2004 2002 2003 2004 8 months 7 weeks - q PVexp (µrad)    E1PV: : PV E1 6S-7S amplitude interferes with bEz : Stark inducedE1 amplitude Since first 9% result (cell # 1, Ref. 1), S/N improved by 3.5  acquisition time for S/N = 1 reduced by 12   Excited vapour gain axes are // (and ),not toeexcbut to eexc+ qPV eexc^z :rotated fromeexcby an angle 10-6 rad,odd in Ez  output probe polarneprout= eprin + k qPVeprin^z atomic factor (Cs density, HFS,..) cells Noise reduction OUR GOAL: measurement of E1PV with 1% precision as a cross check of the Boulder 1999 result A new independent measur’ of QW 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..) and increased rep. rate 160Hz Updated average result : qPV= 0.950  0.025 µrad together with a 1% accurate Ez field in-situ determination from atomic signals agrees with PV= 0.962  0.005µrad, at 1.62 kV/cm expected from Boulder result for E1PV//b see Ref.(4) POLARIMETRIC METHOD OF MEASUREMENT ... and CALIBRATION Input probe polarisationparallel toex, rotates during propagation by an anglekPV(k : atomic factor) We extract a new determination of E1PV E1PV = (- 80.8  2.1) x 10 -13 eao for the 6S ,F=3 – 7S, F=4 hyperfine transition probe polarimeter S/N now adequate to reach 1% precision by lengthening the acquisition time, using last improved cesium cell (conductive windows, ref.7) Selection criteria of the PV rotational invariant 0,4s 0,8s 6s 12s 2 mn 4Polarization configurations : 0°, 45°, 90°, 135° 1 PV data cell input IMPLEMENTATION of the EXPERIMENT excitation beam Dichroic mirror probe beam