R. Henneck

Test of Lorentz invariance with spin precession of ultracold neutrons

A clock comparison experiment, analyzing the ratio of spin precession frequencies of stored ultracold neutrons and 199Hg atoms, is reported. No daily variation of this ratio could be found, from which is set an upper limit on the Lorentz invariance violating cosmic anisotropy field b perpendicular < 2 x 10(-20) eV (95% C.L.). This is the first limit for the free neutron. This result is also interpreted as a direct limit on the gravitational dipole moment of the neutron |gn| < 0.3 eV/c2 m from a spin-dependent interaction with the Sun. Analyzing the gravitational interaction with the Earth, based on previous data, yields a more stringent limit |gn| < 3 x 10(-4) eV/c2 m.

A measurement of the neutron to 199Hg magnetic moment ratio

The neutron gyromagnetic ratio has been measured relative to that of the 199Hg atom with an uncertainty of 0.8 ppm. We employed an apparatus where ultracold neutrons and mercury atoms are stored in the same volume and report the result γn/γHg=3.8424574(30).

Analyzing power in n+d elastic scattering at 67 MeV

The analyzing power Ay of 2H(n, n)2H elastic scattering at En = 67 MeV has been measured in the angular range 30° < θ c.m. < 165°. The data are in good agreement with the results of our rigorous three-nucleon calculations employing the PARIS and the BONN B potential.

Dynamic stabilization of the magnetic field surrounding the neutron electric dipole moment spectrometer at the Paul Scherrer Institute

The Surrounding Field Compensation (SFC) system described in this work is installed around the four-layer Mu-metal magnetic shield of the neutron electric dipole moment spectrometer located at the Paul Scherrer Institute. The SFC system reduces the DC component of the external magnetic field by a factor of about 20. Within a control volume of approximately 2.5m x 2.5m x 3m disturbances of the magnetic field are attenuated by factors of 5 to 50 at a bandwidth from

Spin-dependent np total cross section

10^{-3}

Measurement of a false electric dipole moment signal from 199Hg atoms exposed to an inhomogeneous magnetic field

Hz up to 0.5 Hz, which corresponds to integration times longer than several hundreds of seconds and represent the important timescale for the nEDM measurement. These shielding factors apply to random environmental noise from arbitrary sources. This is achieved via a proportional-integral feedback stabilization system that includes a regularized pseudoinverse matrix of proportionality factors which correlates magnetic field changes at all sensor positions to current changes in the SFC coils.

Analyzing power of the 2H(n, np)n breakup reaction at 67 MeV in selected kinematical configurations

Abstract We have measured the spin-dependent total cross-section difference Δσ L in neutron-proton scattering at 66 MeV which is highly sensitive to the 3 S 1 - 3 D 1 mixing parameter e 1 . The result Δσ L = −(26.5 ± 1.2 ± 1.6) mb is in good agreement with recent phase-shift analyses that require a large e 1 (a stronger tensor force).

Production of ultracold neutrons from cryogenic 2H2, O2, and C2H4 converters

We report on the measurement of a Larmor frequency shift proportional to the electric-field strength for 199Hg atoms contained in a volume permeated with aligned magnetic and electric fields. This shift arises from the interplay between the inevitable magnetic field gradients and the motional magnetic field. The proportionality to electric-field strength makes it apparently similar to an electric dipole moment (EDM) signal, although unlike an EDM this effect is P- and T-conserving. We have used a neutron magnetic resonance EDM spectrometer, featuring a mercury co-magnetometer and an array of external cesium magnetometers, to measure the shift as a function of the applied magnetic field gradient. Our results are in good agreement with theoretical expectations.Graphical abstract

Differential cross section for elastic n+d scattering and n+d break-up quasi free-scattering at 67 MeV

Abstract The angular distribution of the analyzing power A y for the 2 H( n , np)n breakup reaction at 67 MeV was measured in two kinematical regions: np quasi-free scattering and np final-state interaction. The results are compared with rigorous three-nucleon calculations using the Paris potential and allowing for charge dependence in the 1 S 0 state. According to the actual experimental conditions energy averaging was simulated in the theoretical calculations. In both configurations agreement between experimental and calculated values is found.

Testing isotropy of the universe using the Ramsey resonance technique on ultracold neutron spins

Ultracold neutrons (UCN) have been produced using the cold neutron (CN) beam FUNSPIN at SINQ on cryogenic oxygen (O2), tetradeuteromethane (C2H4), and deuterium (2H2) targets. The target cell (40 mm long, fiducial volume about 45 cm3) was operated between room temperature and 8 K and UCN were produced from gaseous, liquid and solid targets. UCN rates have been measured as a convolution of UCN production and transport out of the target and to the detector. At least within the accessible temperature range of this experiment, deuterium outperforms the other materials.