The current status of precision measurements in allowed nuclear beta decay is reviewed, including neutron decay, with emphasis on their potential to look for new physics beyond the standard ...electroweak model. Experimental results are interpreted in the framework of phenomenological model-independent descriptions of nuclear beta decay as well as in some specific extensions of the standard model. The values of the standard couplings and the constraints on the exotic couplings of the general beta decay Hamiltonian are updated. The ratio between the axial and vector couplings obtained is CA/CV=-1.269 9269 under standard model assumptions. Particular attention is devoted to the discussion of the sensitivity and complementarity of different precision experiments in direct beta decay. The prospects and impact of precision tools and of high intensity low-energy beams are also addressed.
We present the result of an experiment to measure the electric dipole moment (EDM) of the neutron at the Paul Scherrer Institute using Ramsey's method of separated oscillating magnetic fields with ...ultracold neutrons. Our measurement stands in the long history of EDM experiments probing physics violating time-reversal invariance. The salient features of this experiment were the use of a ^{199}Hg comagnetometer and an array of optically pumped cesium vapor magnetometers to cancel and correct for magnetic-field changes. The statistical analysis was performed on blinded datasets by two separate groups, while the estimation of systematic effects profited from an unprecedented knowledge of the magnetic field. The measured value of the neutron EDM is d_{n}=(0.0±1.1_{stat}±0.2_{sys})×10^{-26} e.cm.
Magnetic storage of UCN for a measurement of the neutron lifetime Ezhov, V.F.; Andreev, A.Z.; Ban, G. ...
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment,
12/2009, Letnik:
611, Številka:
2
Journal Article, Conference Proceeding
Recenzirano
We present the status of an experimental setup designed and built for the measurement of the neutron lifetime and we describe also details about the measuring sequence. The central element of the ...setup is a magnetic trap made of permanent magnets. Neutrons surviving in the trap after fixed storage times are counted after their extraction and the trap losses are continuously monitored during the storage periods. The technique has achieved a statistical sensitivity of about 2
s on the storage time what constitutes the most sensitive magnetic trapping technique for ultra-cold neutrons developed so far.
Performance of a micro-channel plates position sensitive detector Liénard, E.; Herbane, M.; Ban, G. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
10/2005, Letnik:
551, Številka:
2
Journal Article
Recenzirano
The absolute detection efficiency of large area micro-channel plates (MCPs) detectors has been measured with
6Li
+ and
23Na
+ ions in the 0.5–7.5
keV energy range. Two detectors of 47
mm and 83
mm ...active diameter have been tested. They consist in a pair of MCPs mounted in a chevron configuration with delay line anodes for position readout. The efficiency saturates above 3000
eV, reaching a value of 52.3(3)%, consistent with the MCPs geometry. The behaviour of the efficiency with respect to the ion kinetic energy is ascribed to the electronic threshold, through a detailed analysis of the collected charge distribution. The efficiency dependence on the ions impact position and incidence angle has also been studied. A loss of efficiency has been observed in the vicinity of the MCPs bias angle, which can be avoided if a large post-acceleration field is created in front of the MCPs. Finally the study of a position calibration is presented. A position resolution of 110(26)
μm has been achieved.
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 (UCN); 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 $d_\mathrm{n} = -0.21 \pm 1.82 \times10^{-26}$ $e$cm, which may be interpreted as a slightly revised upper limit on the magnitude of the EDM of $3.0 \times10^{-26}$ $e$cm (90% CL) or $ 3.6 \times10^{-26}$ $e$cm (95% CL). This paper is dedicated by the remaining authors to the memory of Prof. J. Michael Pendlebury.
Precision correlation measurements in nuclear beta decay using atom and ion traps have made significant progress since the last
ENAM2004 Conference
. We review here the achievements and plans of ...different projects and discuss for each of them their potential to contribute to the determination of the V
ud
element of the Cabibbo-Kobayashi-Maskawa quark mixing matrix. This matrix element has traditionally been determined from the analysis of data in nuclear superallowed 0
+
0
+
transitions, neutron decay and pion beta decay but can also independently be determined from data in nuclear mirror transitions. This requires the measurement of correlation parameters in such decays to determine the Gamow-Teller to Fermi mixing ratio which, in most cases, dominates the error on the extracted value of |
V
ud
| .
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