Showing papers by "S. Roccia published in 2015"
University of Sussex1, Paul Scherrer Institute2, Rutherford Appleton Laboratory3, University of Caen Lower Normandy4, Jagiellonian University5, German National Metrology Institute6, University of Fribourg7, Katholieke Universiteit Leuven8, University of Grenoble9, University of Mainz10, ETH Zurich11, University of Paris-Sud12
TL;DR: In this paper, a detailed and comprehensive analysis of the experimental results that set the current world sensitivity limit on the magnitude of the electric dipole moment (EDM) of the neutron is presented.
Abstract: We present for the first time a detailed and comprehensive analysis of the experimental results that set the current world sensitivity limit on the magnitude of the electric dipole moment (EDM) of the neutron. We have extended and enhanced our earlier analysis to include recent developments in the understanding of the effects of gravity in depolarizing ultracold neutrons; an improved calculation of the spectrum of the neutrons; and conservative estimates of other possible systematic errors, which are also shown to be consistent with more recent measurements undertaken with the apparatus. We obtain a net result of dn=−0.21±1.82×10−26 e cm, which may be interpreted as a slightly revised upper limit on the magnitude of the EDM of 3.0×10−26 e cm (90% C.L.) or 3.6×10−26 e cm (95% C.L.).
492 citations
TL;DR: A magnetometer based on optically pumped Cs atoms that measures the magnitude and direction of a 1 μT magnetic field and achieves a scalar resolution better than 300 fT for integration times ranging from 80 ms to 1000 s.
Abstract: We present a magnetometer based on optically pumped Cs atoms that measures the magnitude and direction of a 1 μT magnetic field. Multiple circularly polarized laser beams were used to probe the free spin precession of the Cs atoms. The design was optimized for long-time stability and achieves a scalar resolution better than 300 fT for integration times ranging from 80 ms to 1000 s. The best scalar resolution of less than 80 fT was reached with integration times of 1.6 to 6 s. We were able to measure the magnetic field direction with a resolution better than 10 μrad for integration times from 10 s up to 2000 s.
40 citations
TL;DR: In this article, a new limit on a possible short range spin-dependent interaction from the precise measurement of the ratio of Larmor precession frequencies of stored ultracold neutrons and Hg-199 atoms confined in the same volume was reported.
35 citations
TL;DR: In this article, the authors report on the design and first tests of a device allowing for measurement of ultracold neutrons polarisation by means of the simultaneous analysis of the two spin components.
Abstract: We report on the design and first tests of a device allowing for measurement of ultracold neutrons polarisation by means of the simultaneous analysis of the two spin components. The device was developed in the framework of the neutron electric dipole moment experiment at the Paul Scherrer Institute. Individual parts and the entire newly built system have been characterised with ultracold neutrons. The gain in statistical sensitivity obtained with the simultaneous spin analyser is $(18.2\pm 6.1)$
% relative to the former sequential analyser under nominal running conditions.
30 citations
TL;DR: The method takes advantage of the relative dephasing of spins arising from a gravitationally induced striation of stored UCNs of different energies, and also permits an improved determination of the vertical magnetic-field gradient with an exceptional accuracy of 1.1 pT/cm.
Abstract: We describe a spin-echo method for ultracold neutrons (UCNs) confined in a precession chamber and exposed to a $|B_0|=1~\text{\mu T}$ magnetic field. We have demonstrated that the analysis of UCN spin-echo resonance signals in combination with knowledge of the ambient magnetic field provides an excellent method by which to reconstruct the energy spectrum of a confined ensemble of neutrons. The method takes advantage of the relative dephasing of spins arising from a gravitationally induced striation of stored UCN of different energies, and also permits an improved determination of the vertical magnetic-field gradient with an exceptional accuracy of $1.1~\text{pT/cm}$. This novel combination of a well-known nuclear resonance method and gravitationally induced vertical striation is unique in the realm of nuclear and particle physics and should prove to be invaluable for the assessment of systematic effects in precision experiments such as searches for an electric dipole moment of the neutron or the measurement of the neutron lifetime.
26 citations
TL;DR: In this paper, the Larmor frequency shift proportional to the electric-field strength for 199Hg atoms contained in a volume permeated with aligned magnetic and electric fields was measured.
Abstract: 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.
24 citations
TL;DR: In this paper, a magnetometer based on optically pumped Cs atoms was used to measure the magnitude and direction of a 1 $\mu$T magnetic field with a scalar resolution better than 300 fT for integration times ranging from 80 ms to 1000 s.
Abstract: We present a magnetometer based on optically pumped Cs atoms that measures the magnitude and direction of a 1 $\mu$T magnetic field. Multiple circularly polarized laser beams were used to probe the free spin precession of the Cs atoms. The design was optimized for long-time stability and achieves a scalar resolution better than 300 fT for integration times ranging from 80 ms to 1000 s. The best scalar resolution of less than 80 fT was reached with integration times of 1.6 to 6 s. We were able to measure the magnetic field direction with a resolution better than 10 $\mu$rad for integration times from 10 s up to 2000 s.
23 citations
TL;DR: In this paper, the Larmor frequency shift proportional to the electric-field strength for atoms contained in a volume permeated with aligned magnetic and electric fields was measured and the results were in good agreement with theoretical expectations.
Abstract: We report on the measurement of a Larmor frequency shift proportional to the electric-field strength for $^{199}{\rm Hg}$ 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.
21 citations
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TL;DR: In this article, the authors report on the design and first tests of a device allowing for measurement of ultracold neutrons polarisation by means of the simultaneous analysis of the two spin components.
Abstract: We report on the design and first tests of a device allowing for measurement of ultracold neutrons polarisation by means of the simultaneous analysis of the two spin components. The device was developed in the framework of the neutron electric dipole moment experiment at the Paul Scherrer Institute. Individual parts and the entire newly built system have been characterised with ultracold neutrons. The gain in statistical sensitivity obtained with the simultaneous spin analyser is $(18.2\pm6.1)\%$ relative to the former sequential analyser under nominal running conditions.
15 citations
University of Jena1, Paul Scherrer Institute2, ETH Zurich3, University of Sussex4, Rutherford Appleton Laboratory5, University of Caen Lower Normandy6, Jagiellonian University7, University of Fribourg8, University of Mainz9, University of Grenoble10, Polish Academy of Sciences11, Katholieke Universiteit Leuven12
TL;DR: In this paper, the expected effects of so-called gravitationally enhanced depolarization of ultracold neutrons were compared to measurements carried out in a spin-precession chamber exposed to a variety of vertical magnetic-field gradients.
Abstract: We compare the expected effects of so-called gravitationally enhanced depolarization of ultracold neutrons to measurements carried out in a spin-precession chamber exposed to a variety of vertical magnetic-field gradients. In particular, we have investigated the dependence upon these field gradients of spin-depolarization rates and also of shifts in the measured neutron Larmor precession frequency. We find excellent qualitative agreement, with gravitationally enhanced depolarization accounting for several previously unexplained features in the data.
15 citations
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TL;DR: In this paper, a spin-echo method for ultracold neutrons (UCNs) confined in a precession chamber and exposed to a |B_0 | = 1uT magnetic field is described.
Abstract: We describe a spin-echo method for ultracold neutrons (UCNs) confined in a precession chamber and exposed to a |B_0 | = 1uT magnetic field. We demonstrate a gravity-dependent spin dephasing by applying small vertical magnetic field gradients. The method gives access to the energy spectrum of stored UCNs, which can be crucial for the assessment of systematic effects in precision experiments such as searches for an electric dipole moment of the neutron.