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Ultracold neutron energy spectrum and storage properties from magnetically induced spin depolarization
Authors:
N. J. Ayres,
G. Ban,
G. Bison,
K. Bodek,
V. Bondar,
T. Bouillaud,
D. Bowles,
G. L. Caratsch,
E. Chanel,
W. Chen,
P. -J. Chiu,
C. B. Crawford,
V. Czamler,
M. Daum,
C. B. Doorenbos,
M. Ferry,
M. Fertl,
A. Fratangelo,
D. Galbinski,
W. C. Griffith,
Z. D. Grujic,
K. Kirch,
V. Kletzl,
B. Lauss,
T. Lefort
, et al. (31 additional authors not shown)
Abstract:
We present a novel method for extracting the energy spectrum of ultracold neutrons from magnetically induced spin depolarization measurements using the n2EDM apparatus. This method is also sensitive to the storage properties of the materials used to trap ultracold neutrons, specifically, whether collisions are specular or diffuse. We highlight the sensitivity of this new technique by comparing the…
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We present a novel method for extracting the energy spectrum of ultracold neutrons from magnetically induced spin depolarization measurements using the n2EDM apparatus. This method is also sensitive to the storage properties of the materials used to trap ultracold neutrons, specifically, whether collisions are specular or diffuse. We highlight the sensitivity of this new technique by comparing the two different storage chambers of the n2EDM experiment. We validate the extraction by comparing to an independent measurement for how this energy spectrum is polarized through a magnetic-filter, and finally, we calculate the neutron center-of-mass offset, an important systematic effect for measurements of the neutron electric dipole moment.
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Submitted 10 November, 2025;
originally announced November 2025.
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Improved search for neutron to mirror-neutron oscillations in the presence of mirror magnetic fields with a dedicated apparatus at the PSI UCN source
Authors:
N. J. Ayres,
Z. Berezhiani,
R. Biondi,
G. Bison,
K. Bodek,
V. Bondar,
P. -J. Chiu,
M. Daum,
R. T. Dinani,
C. B. Doorenbos,
S. Emmenegger,
K. Kirch,
V. Kletzl,
J. Krempel,
B. Lauss,
D. Pais,
I. Rienaecker,
D. Ries,
N. Rossi,
D. Rozpedzik,
P. Schmidt-Wellenburg,
K. S. Tanaka,
J. Zejma,
N. Ziehl,
G. Zsigmond
Abstract:
While the international nEDM collaboration at the Paul Scherrer Institut (PSI) took data in 2017 that covered a considerable fraction of the parameter space of claimed potential signals of hypothetical neutron ($n$) to mirror-neutron ($n'$) transitions, it could not test all claimed signal regions at various mirror magnetic fields. Therefore, a new study of $n-n'$ oscillations using stored ultraco…
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While the international nEDM collaboration at the Paul Scherrer Institut (PSI) took data in 2017 that covered a considerable fraction of the parameter space of claimed potential signals of hypothetical neutron ($n$) to mirror-neutron ($n'$) transitions, it could not test all claimed signal regions at various mirror magnetic fields. Therefore, a new study of $n-n'$ oscillations using stored ultracold neutrons (UCNs)is underway at PSI, considerably expanding the reach in parameter space of mirror magnetic fields ($B'$) and oscillation time constants ($τ_{nn'}$). The new apparatus is designed to test for the anomalous loss of stored ultracold neutrons as a function of an applied magnetic field. The experiment is distinguished from its predecessors by its very large storage vessel (1.47\,m$^3$), enhancing its statistical sensitivity. In a test experiment in 2020 we have demonstrated the capabilities of our apparatus. However, the full analysis of our recent data is still pending. Based on already demonstrated performance, we will reach a sensitivity to oscillation times $τ_{nn'}/\sqrt{\cos(β)}$ well above hundred seconds, with $β$ being the angle between $B'$ and the applied magnetic field $B$. The scan of $B$ will allow the finding or the comprehensive exclusion of potential signals reported in the analysis of previous experiments and suggested to be consistent with neutron to mirror-neutron oscillations.
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Submitted 31 October, 2021;
originally announced November 2021.
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Development of microwave cavities for measurement of muonium hyperfine structure at J-PARC
Authors:
K. S. Tanaka,
M. Iwasaki,
O. Kamigaito,
S. Kanda,
N. Kawamura,
Y. Matsuda,
T. Mibe,
S. Nishimura,
N. Saito,
N. Sakamoto,
S. Seo,
K. Shimomura,
P. Strasser,
K. Suda,
T. Tanaka,
H. A. Torii,
A. Toyoda,
Y. Ueno,
M. Yoshida
Abstract:
The MuSEUM collaboration is planning measurements of the ground-state hyperfine structure (HFS) of muonium at the Japan Proton Accelerator Research Complex (J-PARC), Materials and Life Science Experimental Facility. The high-intensity beam that will soon be available at H-line allows for more precise measurements by one order of magnitude. We plan to conduct two staged measurements. First, we will…
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The MuSEUM collaboration is planning measurements of the ground-state hyperfine structure (HFS) of muonium at the Japan Proton Accelerator Research Complex (J-PARC), Materials and Life Science Experimental Facility. The high-intensity beam that will soon be available at H-line allows for more precise measurements by one order of magnitude. We plan to conduct two staged measurements. First, we will measure the Mu-HFS in a near-zero magnetic field, and thereafter we will measure it in a strong magnetic field. We have developed two microwave cavities for this purpose. Furthermore, we evaluated systematic uncertainties from such a fluctuation of microwave fields and confirm the requirement of the microwave system, we use a microwave field distribution calculated from the finite element method.
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Submitted 3 January, 2022; v1 submitted 14 April, 2021;
originally announced April 2021.
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Rabi-Oscillation Spectroscopy of the Hyperfine Structure of Muonium Atoms
Authors:
S. Nishimura,
H. A. Torii,
Y. Fukao,
T. U. Ito,
M. Iwasaki,
S. Kanda,
K. Kawagoe,
D. Kawall,
N. Kawamura,
N. Kurosawa,
Y. Matsuda,
T. Mibe,
Y. Miyake,
N. Saito,
K. Sasaki,
Y. Sato,
S. Seo,
P. Strasser,
T. Suehara,
K. S. Tanaka,
T. Tanaka,
J. Tojo,
A. Toyoda,
Y. Ueno,
T. Yamanaka
, et al. (4 additional authors not shown)
Abstract:
As a new method to determine the resonance frequency, Rabi-oscillation spectroscopy has been developed. In contrast to the conventional spectroscopy which draws the resonance curve, Rabi-oscillation spectroscopy fits the time evolution of the Rabi oscillation. By selecting the optimized frequency, it is shown that the precision is twice as good as the conventional spectroscopy with a frequency swe…
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As a new method to determine the resonance frequency, Rabi-oscillation spectroscopy has been developed. In contrast to the conventional spectroscopy which draws the resonance curve, Rabi-oscillation spectroscopy fits the time evolution of the Rabi oscillation. By selecting the optimized frequency, it is shown that the precision is twice as good as the conventional spectroscopy with a frequency sweep. Furthermore, the data under different conditions can be treated in a unified manner, allowing more efficient measurements for systems consisting of a limited number of short-lived particles produced by accelerators such as muons. We have developed a fitting function that takes into account the spatial distribution of muonium and the spatial distribution of the microwave intensity to apply the new method to ground-state muonium hyperfine structure measurements at zero field. This was applied to the actual measurement data and the resonance frequencies were determined under various conditions. The result of our analysis gives $ν_{\rm HFS}=4\ 463\ 301.61 \pm 0.71\ {\rm kHz}$, which is the world's highest precision under zero field conditions.
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Submitted 12 February, 2021; v1 submitted 24 July, 2020;
originally announced July 2020.
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New precise spectroscopy of the hyperfine structure in muonium with a high-intensity pulsed muon beam
Authors:
S. Kanda,
Y. Fukao,
Y. Ikedo,
K. Ishida,
M. Iwasaki,
D. Kawall,
N. Kawamura,
K. M. Kojima,
N. Kurosawa,
Y. Matsuda,
T. Mibe,
Y. Miyake,
S. Nishimura,
N. Saito,
Y. Sato,
S. Seo,
K. Shimomura,
P. Strasser,
K. S. Tanaka,
T. Tanaka,
H. A. Torii,
A. Toyoda,
Y. Ueno
Abstract:
A hydrogen-like atom consisting of a positive muon and an electron is known as muonium. It is a near-ideal two-body system for a precision test of bound-state theory and fundamental symmetries. The MuSEUM collaboration performed a new precision measurement of the muonium ground-state hyperfine structure at J-PARC using a high-intensity pulsed muon beam and a high-rate capable positron counter. The…
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A hydrogen-like atom consisting of a positive muon and an electron is known as muonium. It is a near-ideal two-body system for a precision test of bound-state theory and fundamental symmetries. The MuSEUM collaboration performed a new precision measurement of the muonium ground-state hyperfine structure at J-PARC using a high-intensity pulsed muon beam and a high-rate capable positron counter. The resonance of hyperfine transition was successfully observed at a near-zero magnetic field, and the muonium hyperfine structure interval of $ν_{\text{HFS}}$ = 4.463302(4) GHz was obtained with a relative precision of 0.9 ppm. The result was consistent with the previous ones obtained at Los Alamos National Laboratory and the current theoretical calculation. We present a demonstration of the microwave spectroscopy of muonium for future experiments to achieve the highest precision.
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Submitted 2 March, 2021; v1 submitted 13 April, 2020;
originally announced April 2020.