M. Kuźniak

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.

Towards a new measurement of the neutron electric dipole moment

The effort towards a new measurement of the neutron electric dipole moment (nEDM) at the Paul Scherrer Instituts (PSI) new high intensity source of ultracold neutrons (UCN) is described. The experimental technique relies on Ramseys method of separated oscillatory fields, using UCN in vacuum with the apparatus at ambient temperature. In the first phase, R&D towards the upgrade of the RAL/Sussex/ILL apparatus is being performed at the Institut Laue-Langevin (ILL). In the second phase the apparatus, moved from ILL to PSI, will allow an improvement in experimental sensitivity by a factor of 5. In the third phase, a new spectrometer should gain another order of magnitude in sensitivity. The improvements will be mainly due to (1) much higher UCN intensity, (2) improved magnetometry and magnetic field control, and (3) a double chamber configuration with opposite electric field directions.

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).

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

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.

SEARCH FOR LORENTZ-INVARIANCE-VIOLATING EFFECTS IN THE DECAY OF FREE NEUTRONS

A. KOZELA,2 G. BAN,4 A. BIAA LEK,2 K. BODEK,1∗ P. GOREL,4,3,1 K. KIRCH,3,7 ST. KISTRYN,1 M. KUŹNIAK,1,2 O. NAVILIAT-CUNCIC,4 N. SEVERIJNS,5 E. STEPHAN,6 and J. ZEJMA1 1Institute of Physics, Jagiellonian University, Cracow, Poland 2Institute of Nuclear Physics, Polish Academy of Sciences, Cracow, Poland 3Paul Scherrer Institute, Villigen, Switzerland 4Universite de Caen Basse-Normandie, CNRS/IN2P3-ENSI, LPC, Caen, France 5Katholieke Universiteit Leuven, Leuven, Belgium 6Institute of Physics, University of Silesia, Katowice, Poland 7Swiss Federal Institute of Technology, Zurich, Switzerland ∗E-mail: ufbodek@if.uj.edu.pl

Search for Time Reversal Violation in Neutron Decay: A Measurement of the Transverse Polarization of Electrons

A non‐zero value of the R‐correlation coefficient due to the e − polarization component, perpendicular to the plane spanned by the spin of the decaying neutron and the electron momentum, would signal a violation of time reversal symmetry and thus physics beyond the Standard Model. The value of the N‐correlation coefficient, given by the transverse e − polarization component within that plane, is expected to be finite. The measurement of N serves as an important systematic check of the apparatus for the R‐measurement. The first phase of data taking has been completed. Preliminary results from a limited data sample show no deviations from the Standard Model predictions.