Low-frequency nuclear spin maser and search for atomic EDM of 129 Xe A. Yoshimi RIKEN SPIN /10/11-16 Trieste, ITALY Collaborator : K. Asahi (Professor, Tokyo Inst. of Tech./RIKEN) S. Emori (Tokyo Inst. of Tech.) S. Oshima (Tokyo Inst. of Tech.)

Electric Dipole Moment d  0 T-violation CP-violation Non-zero EDM associated with spin Direct evidence of violation of time reversal symmetry s s Time reversal Time : t -t Spin : s -s EDM : d d CPT theorem Standard Model (SM) : Predicted EDM is about 10 5 smaller than the present experimental upper limit Beyond the SM : Detectable EDM Detection of non-zero EDM CP-violation beyond the standard model

Recent EDM experiment of diamagnetic atoms Vold et. al., Phys. Rev. Lett. 52 (1984) Rosenberry and Chupp, Phys. Rev. Lett. 86 (2001) Lamoreaux et. al., Phys. Rev. Lett. 59 (1987) Romalis et. al., Phys. Rev. Lett. 86 (2001) Operation of continuous spin maser One shot measurement … 2000 sec. Repetition of FID measurement …. 300 – 500 sec/1run

Supersymmetric modelStandard model EDM theory Present experimental upper limit T. Falk et al., hep-ph/ Upper limit of CP-violating complex phases in Supersymmetric model M=250GeV M=500GeV (O.P. Sushkov et al., JETP 60 (1984) 873) Energy scale of superpartner (T. Falk et al., hep-ph/ )

Project of atomic EDM experiment of 129 Xe at RIKEN-TIT Continuous nuclear spin maser Free Induction DecayContinuous oscillation Large polarization of Xe nucleus Spin exchange with optical pumped Rb atom Nuclear polarization O(10) 100 torr (10 18 /cc) 129 Xe Rb Rapid decrease of frequency precision Spin maser at low frequency Low static field experiment (  mG )  Small field fluctuation Use of the ultra high sensitive magnetometer

Spin MASER Polarization vector : M Feedback field : B fb B0B0 Feedback torque Relaxation, pumping T2 relaxation Polarization’s growing (pumping effect) Feedback torque pump Feedback system Zeeman level Transverse magnetic field - synchronism with spin precession - Phase : perpendicular to the transverse polarization Amplitude : proportional to the transverse polarization Population inversion Feedback EM-field synchronism with emitted photon Polarization

Induced current C B0B0 L I  nPQ B FB Pumping light Spin maser with the tuned coil of tank circuit NMR-based spin maser > kHz (B 0 = 1 G) Oscillation threshold Artificial feedback through the optical spin detection Operation at low magnetic field Small field fluctuation High-sensitive magnetometer Long intrinsic T 2 Optical-detection-feedback spin maser B 0  mG Probe laser beam Pumping laser beam Lock-in detection Phase shifter Photo diode Feedback coil Nuclear spin M. Richards et al., J. Phys. B 21 (1988) 665. T. Chupp et al., PRL 72 (1994) A. Yoshimi et al., PLA 304 (2002) 13.

Experimental apparatus Enriched 129 Xe : 230 torr Rb : ~ 1 mg P xe ~ 10 % 18 mm Xe gas cell Pyrex spherical grass cell SurfaSil coated Magnetic shield (3 layers ) Parmalloy Size : l = 100 cm, d = 36, 42, 48 cm Shielding factor : S = 10 3 Pumping LASER Tunable diode laser = nm ( Rb D1 line ),  = 3 nm Output: 18 W Probe LASER tunable diode laser with external cavity  = nm ( Rb D1 line ),  = nm Output: 15 mW Solenoid coil (for static field) B 0 = 28.3 mG ( I = 3.58 mA) PEM Mod. Freq. 50 kHz Si photo diode Freq. band width: 0 – 500 kHz NEP: 8  W/Hz Heater T cell = 60 ~ 70 ℃

Typical maser oscillation signal B 0 = 28.3 mG, ref = Hz, feedback gain : 18  G/0.1mV Feedback system ON Steady state oscillation Measured frequency : Signal (mV) Time (s) (  84 hours) Signal (V) Time (s)

Frequency characteristics Fourie spectrum ( 1 hr. run ) Conventional spin maser ( = 3.56 kHz ) Low-frequency spin maser ( = 33.5 Hz ) t (sec)  (rad)  = 0.96  Hz =  mHz    -3/2 Frequency precision (  Hz) Time (s) Precession angle

On-going developments 1 – magnetometer - Fluctuation of magnetic field  Main source of frequency noise in spin maser operation Neutron EDM experiment….. Hg atomic magnetometer Xe EDM Michigan Gr. ….. 3 He co-magnetometer k Linear polarized light Alkali vapor Faraday rotation B 1×10 4 rad/G, 4× G/  Hz (B < 0.1G) Atomic magnetometer with Rb using magneto-optical rotation D. Budker et al., PRA 62 (2000) calibration run

On-going developments 2 – magnetic shield - Construction of 4-layer shield l = 1600 mm, R =  400 mm Transverse: S ≈10 6 Longitudinal: S ≈10 4 Estimated shielding factor Measured residual field z (cm) Field (  G) longitudinal transverse Shielding factor : S ≈10 4

Installation of atomic magnetometer into low frequency spin oscillator sensitivity :  G/  Hz   B  G (  (Xe)  0.1 nHz ) Main source of frequency noise interaction with Rb atomic spins (10 9 /cc) P(Rb)  0.01 % ( re-polarization from Xe )   (Xe)  0.2 nHz (  T  0.01˚C) Estimation of experimental EDM-sensitivity  Probe light (Magnetometer) (E=10kV/cm) Conceptual setup Estimation of frequency precision Precision (  Hz ) Time (s)

Summary and Future Construction of the nuclear spin maser with an artificial feedback system, and operated it at low frequency 33 Hz ( under B = 28 mG ). Frequency precision of 1 contiguous measurement presently reaches to 1  Hz. (without magnetometer/free-running) Construction of 4-layer magnetic shield. Installing the Rb magnetometer with magneto-optical rotation. Aiming at search for the atomic electric dipole moment in Xe ; d(Xe) =  ecm.