Sensitive searches for exotic scalar and tensor couplings in nuclear and neutron decays involve precision measurements of the shape of the
β
-energy spectrum. We have performed a high statistics ...measurement of the
β
-energy spectrum in the allowed Gamow-Teller decay of
6
He with the aim to first find evidence of the contribution due to the weak magnetism form factor. We review here the motivation, describe the principle of the measurement, summarize the theoretical corrections to the allowed phase space, and anticipate the expected statistical precision.
The yield of photons produced by electrons slowing down in CsI and NaI was studied with four electromagnetic physics constructors included in the Geant4 toolkit. The subsequent absorption of photons ...in detector geometries used for measurements of the β spectrum shape was also studied with a focus on the determination of the absorption fraction. For electrons with energies in the range 0.5–4 MeV, the relative photon yields determined with the four Geant4 constructors differ at the level of 10−2 in amplitude and the relative absorption fractions differ at the level of 10−4 in amplitude. The differences among constructors enabled the estimation of the sensitivity to Geant4 simulations for the measurement of the β energy spectrum shape in 6He decay using a calorimetric technique with ions implanted in the active volume of detectors. The size of the effect associated with photons escaping the detectors was quantified in terms of a slope which, on average, is respectively −5.4 %/MeV and −4.8 %/MeV for the CsI and NaI geometries. The corresponding relative uncertainties as determined from the spread of results obtained with the four Geant4 constructors are 0.0067 and 0.0058.
Search for a Neutron Dark Decay in He 6 Le Joubioux, M.; Savajols, H.; Mittig, W. ...
Physical review letters,
3/2024, Letnik:
132, Številka:
13
Journal Article
The electron shakeoff probability of 6Li2+ ions resulting from the β- decay of 6He+ ions has been measured with high precision using a specially designed recoil ion spectrometer. This is the first ...measurement of a pure electron shakeoff following nuclear β decay, not affected by multielectron processes such as Auger cascades. In this ideal textbook case for the application of the sudden approximation, the experimental ionization probability was found to be P(so)(exp)=0.02339(36) in perfect agreement with simple quantum mechanical calculations.
The design of the n2EDM experiment Ayres, N. J.; Ban, G.; Bienstman, L. ...
The European physical journal. C, Particles and fields,
2021/6, Letnik:
81, Številka:
6
Journal Article
Recenzirano
Odprti dostop
We present the design of a next-generation experiment, n2EDM, currently under construction at the ultracold neutron source at the Paul Scherrer Institute (PSI) with the aim of carrying out a ...high-precision search for an electric dipole moment of the neutron. The project builds on experience gained with the previous apparatus operated at PSI until 2017, and is expected to deliver an order of magnitude better sensitivity with provision for further substantial improvements. An overview is of the experimental method and setup is given, the sensitivity requirements for the apparatus are derived, and its technical design is described.
Motivated by the four standard deviations discrepancy between the mean values for the neutron lifetime obtained from beam and bottle experiments, we have searched for a hypothetical neutron dark ...decay in $^6$He nuclei through the channel $^6{\rm He} \rightarrow ^4{\rm He}+n+\chi$. The experiment used a 25~keV high intensity $^6$He$^+$ beam with a high efficiency neutron detector. The search for a signal correlated with the $^6$He activity in the neutron detection rate resulted in a branching ratio ${\rm Br}_\chi \leq 4.0\times10^{-10}$ with a 95% C.L. over the mass window $937.993 < m_\chi < m_n-0.975$ MeV. This result is five orders of magnitude smaller than required to solve the neutron lifetime discrepancy.
Neutron dark decays have been suggested as a solution to the discrepancy between bottle and beam experiments, providing a dark matter candidate that can be searched for in halo nuclei. The free ...neutron in the final state following the decay of 6He into 4He+n+χ provides an exceptionally clean detection signature when combined with a high efficiency neutron detector. Using a high-intensity 6He+ beam at Grand Accélérateur National d’Ions Lourds, a search for a coincident neutron signal resulted in an upper limit on a dark decay branching ratio of Brχ≤4.0×10−10 (95% C.L.). Using the dark neutron decay model proposed originally by Fornal and Grinstein, we translate this into an upper bound on a dark neutron branching ratio of O(10−5), improving over global constraints by one to several orders of magnitude depending on mχ.
The neutron and its hypothetical mirror counterpart, a sterile state degenerate in mass, could spontaneously mix in a process much faster than the neutron β-decay. Two groups have performed a series ...of experiments in search of neutron – mirror-neutron (
n
−
n
′) oscillations. They reported no evidence, thereby setting stringent limits on the oscillation time τ
nn
′
. Later, these data sets have been further analyzed by Berezhiani et al.(2009–2017), and signals, compatible with
n
−
n
′ oscillations in the presence of mirror magnetic fields, have been reported. The Neutron Electric Dipole Moment Collaboration based at the Paul Scherrer Institute performed a new series of experiments to further test these signals. In this paper, we describe and motivate our choice of run configurations with an optimal filling time of 29 s, storage times of 180 s and 380 s, and applied magnetic fields of 10 μT and 20 μT. The choice of these run configurations ensures a reliable overlap in settings with the previous efforts and also improves the sensitivity to test the signals. We also elaborate on the technique of normalizing the neutron counts, making such a counting experiment at the ultra-cold neutron source at the Paul Scherrer Institute possible. Furthermore, the magnetic field characterization to meet the requirements of this
n
−
n
′ oscillation search is demonstrated. Finally, we show that this effort has a statistical sensitivity to
n
−
n
′ oscillations comparable to the current leading constraints for
B
′ = 0.
This article presents a short review of the main progresses achieved at the GANIL facilities during the last thirty years in the field of ion-atom and ion-diatomic molecule collisions. Thanks to the ...wide range of projectile energies and species available on the different beam lines of the facility, elementary processes such as electron capture, ionization and excitation have been extensively studied. Beside primary collision mechanisms, the relaxation processes of the collision partners after the collision have been another specific source of interest. Progresses on other fundamental processes such as Young type interferences induced by ion-molecule collisions or shake off ionization resulting from nuclear beta decay are also presented.
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