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First Constraint on P-odd/T-odd Cross Section in Polarized Neutron Transmission through Transversely Polarized $^{139}$La
Authors:
Rintaro Nakabe,
Clayton J. Auton,
Shunsuke Endo,
Hiroyuki Fujioka,
Vladimir Gudkov,
Katsuya Hirota,
Ikuo Ide,
Takashi Ino,
Motoyuki Ishikado,
Wataru Kambara,
Shiori Kawamura,
Atsushi Kimura,
Masaaki Kitaguchi,
Ryuju Kobayashi,
Takahiro Okamura,
Takayuki Oku,
Takuya Okudaira,
Mao Okuizumi,
J. G. Otero Munoz,
Joseph D. Parker,
Kenji Sakai,
Tatsushi Shima,
Hirohiko M. Shimizu,
Takenao Shinohara,
William M. Snow
, et al. (5 additional authors not shown)
Abstract:
We report the first constraint on time-reversal invariance violating (TRIV) effects in polarized neutron transmission through a transversely polarized $^{139}$La target. We formulate the transmission asymmetry within the density matrix formalism, explicitly incorporating the forward scattering amplitude of $^{139}$La including tensor polarization terms up to third-rank. The formalism is applied to…
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We report the first constraint on time-reversal invariance violating (TRIV) effects in polarized neutron transmission through a transversely polarized $^{139}$La target. We formulate the transmission asymmetry within the density matrix formalism, explicitly incorporating the forward scattering amplitude of $^{139}$La including tensor polarization terms up to third-rank. The formalism is applied to existing transmission data originally obtained to measure the spin-dependent cross section near the $0.75$~eV $p$-wave resonance. Since these data were not optimized for P-odd/T-odd observables, the attainable sensitivity is intrinsically limited; nevertheless, they provide a useful test of the formalism on real experimental data. No statistically significant TRIV signal is observed. By analyzing the global $χ^2$ structure in the parameter space, we obtain an upper limit of $|W_T|<15~\mathrm{eV}$ at the 90\% confidence level. This corresponds to an upper limit on the resonance-averaged TRIV cross section of $|Δσ_{\not{T}\not{P}}|<8.3\times10^2~\mathrm{b}$. These results validate the present theoretical framework and provide guidance for future dedicated TRIV searches in polarized neutron transmission experiments.
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Submitted 6 April, 2026; v1 submitted 8 September, 2025;
originally announced September 2025.
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Improved measurements of neutron lifetime with cold neutron beam at J-PARC
Authors:
Y. Fuwa,
T. Hasegawa,
K. Hirota,
T. Hoshino,
R. Hosokawa,
G. Ichikawa,
S. Ieki,
T. Ino,
Y. Iwashita,
M. Kitaguchi,
R. Kitahara,
S. Makise,
K. Mishima,
T. Mogi,
N. Nagakura,
H. Oide,
H. Okabe,
H. Otono,
Y. Seki,
D. Sekiba,
T. Shima,
H. E. Shimizu,
H. M. Shimizu,
N. Sumi,
H. Sumino
, et al. (6 additional authors not shown)
Abstract:
The ``neutron lifetime puzzle'' arises from the discrepancy between neutron lifetime measurements obtained using the beam method, which measures decay products, and the bottle method, which measures the disappearance of neutrons. To resolve this puzzle, we conducted an experiment using a pulsed cold neutron beam at J-PARC. In this experiment, the neutron lifetime is determined from the ratio of ne…
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The ``neutron lifetime puzzle'' arises from the discrepancy between neutron lifetime measurements obtained using the beam method, which measures decay products, and the bottle method, which measures the disappearance of neutrons. To resolve this puzzle, we conducted an experiment using a pulsed cold neutron beam at J-PARC. In this experiment, the neutron lifetime is determined from the ratio of neutron decay counts to $^3$He(n,p)$^3$H reactions in a gas detector. This experiment belongs to the beam method but differs from previous experiments that measured protons, as it instead detects electrons, enabling measurements with distinct systematic uncertainties. By enlarging the beam transport system and reducing systematic uncertainties, we achieved a fivefold improvement in precision. Analysis of all acquired data yielded a neutron lifetime of $τ_{\rm n}=877.2~\pm~1.7_{\rm(stat.)}~^{+4.0}_{-3.6}{}_{\rm (sys.)}$ s. This result is consistent with bottle method measurements but exhibits a 2.3$σ$ tension with the average value obtained from the proton-detection-based beam method.
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Submitted 27 December, 2024;
originally announced December 2024.
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Circular polarization measurement for individual gamma rays in capture reactions with intense pulsed neutrons
Authors:
S. Endo,
R. Abe,
H. Fujioka,
T. Ino,
O. Iwamoto,
N. Iwamoto,
S. Kawamura,
A. Kimura,
M. Kitaguchi,
R. Kobayashi,
S. Nakamura,
T. Oku T. Okudaira,
M. Okuizumi,
M. Omer,
G. Rovira,
T. Shima,
H. M. Shimizu,
T. Shizuma,
Y. Taira,
S. Takada,
S. Takahashi,
H. Yoshikawa,
T. Yoshioka,
H. Zen
Abstract:
Measurements of circular polarization of $γ$-ray emitted from neutron capture reactions provide valuable information for nuclear physics studies. The spin and parity of excited states can be determined by measuring the circular polarization from polarized neutron capture reactions. Furthermore, the $γ$-ray circular polarization in a neutron capture resonance is crucial for studying the enhancement…
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Measurements of circular polarization of $γ$-ray emitted from neutron capture reactions provide valuable information for nuclear physics studies. The spin and parity of excited states can be determined by measuring the circular polarization from polarized neutron capture reactions. Furthermore, the $γ$-ray circular polarization in a neutron capture resonance is crucial for studying the enhancement effect of parity nonconservation in compound nuclei. The $γ$-ray circular polarization can be measured using a polarimeter based on magnetic Compton scattering. A polarimeter was constructed, and its performance indicators were evaluated using a circularly polarized $γ$-ray beam. Furthermore, as a demonstration, the $γ$-ray circular polarization was measured in $^{32}$S($\vec{\textrm{n}}$,$γ$)$^{33}$S reactions with polarized neutrons.
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Submitted 7 May, 2024;
originally announced June 2024.
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Transverse asymmetry of individual $γ$-rays in the $^{139}$La($\vec{n}$, $γ$)$^{140}$La reaction
Authors:
M. Okuizumi,
C. J. Auton,
S. Endo,
H. Fujioka,
K. Hirota,
T. Ino,
K. Ishizaki,
A. Kimura,
M. Kitaguchi,
J. Koga,
S. Makise,
Y. Niinomi,
T. Oku,
T. Okudaira,
K. Sakai,
T. Shima,
H. M. Shimizu,
H. Tada,
S. Takada,
S. Takahashi,
Y. Tani,
T. Yamamoto,
H. Yoshikawa,
T. Yoshioka
Abstract:
The enhancement of the parity-violating asymmetry in the vicinity of $p$-wave compound nuclear resonances was observed for a variety of medium-heavy nuclei. The enhanced parity-violating asymmetry can be understood using the $s$-$p$ mixing model. The $s$-$p$ mixing model predicts several neutron energy-dependent angular correlations between the neutron momentum $\vec k_n$, neutron spin $\vecσ_n$,…
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The enhancement of the parity-violating asymmetry in the vicinity of $p$-wave compound nuclear resonances was observed for a variety of medium-heavy nuclei. The enhanced parity-violating asymmetry can be understood using the $s$-$p$ mixing model. The $s$-$p$ mixing model predicts several neutron energy-dependent angular correlations between the neutron momentum $\vec k_n$, neutron spin $\vecσ_n$, $γ$-ray momentum $\vec k_γ$, and $γ$-ray polarization $\vecσ_γ$ in the $(n,γ)$ reaction. In this paper, the improved value of the transverse asymmetry of $γ$-ray emissions, corresponding to a correlation term $\vecσ_n\cdot(\vec k_n\times\vec k_γ)$ in the $^{139}\mathrm{La}(\vec n,γ)^{140}\mathrm{La}$ reaction, and the transverse asymmetries in the transitions to several low excited states of $^{140}\mathrm{La}$ are reported.
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Submitted 29 February, 2024;
originally announced February 2024.
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Performance of the Fully-equipped Spin Flip Chopper For Neutron Lifetime Experiment at J-PARC
Authors:
K. Mishima,
G. Ichikawa,
Y. Fuwa,
T. Hasegawa,
M. Hino,
R. Hosokawa,
T. Ino,
Y. Iwashita,
M. Kitaguchi,
S. Matsuzaki,
T. Mogi,
H. Okabe,
T. Oku,
T. Okudaira,
Y. Seki,
H. E. Shimizu,
H. M. Shimizu,
S. Takahashi,
M. Tanida,
S. Yamashita,
M. Yokohashi,
T. Yoshioka
Abstract:
To solve the ''neutron lifetime puzzle,'' where measured neutron lifetimes differ depending on the measurement methods, an experiment with pulsed neutron beam at J-PARC is in progress. In this experiment, neutrons are bunched into 40-cm lengths using a spin flip chopper (SFC), where the statistical sensitivity was limited by the aperture size of the SFC. The SFC comprises three sets of magnetic su…
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To solve the ''neutron lifetime puzzle,'' where measured neutron lifetimes differ depending on the measurement methods, an experiment with pulsed neutron beam at J-PARC is in progress. In this experiment, neutrons are bunched into 40-cm lengths using a spin flip chopper (SFC), where the statistical sensitivity was limited by the aperture size of the SFC. The SFC comprises three sets of magnetic supermirrors and two resonant spin flippers. In this paper, we discuss an upgrade to enlarge the apertures of the SFC. With this upgrade, the statistics per unit time of the neutron lifetime experiment increased by a factor of 2.8, while maintaining a signal-to-noise ratio of 250-400 comparable to the previous one. Consequently, the time required to reach a precision of 1 s in the neutron lifetime experiment was reduced from 590 to 170 days, which is a significant reduction in time. This improvement in statistic will also contribute to the reduction of systematic uncertainties, such as background evaluation, fostering further advancements in the neutron lifetime experiments at J-PARC.
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Submitted 31 July, 2024; v1 submitted 20 December, 2023;
originally announced December 2023.
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High sensitivity of a future search for P-odd/T-odd interactions on the 0.75 eV $p$-wave resonance in $\vec{n}+^{139}\vec{\rm La}$ forward transmission determined using pulsed neutron beam
Authors:
R. Nakabe,
C. J. Auton,
S. Endo,
H. Fujioka,
V. Gudkov,
K. Hirota,
I. Ide,
T. Ino,
M. Ishikado,
W. Kambara,
S. Kawamura,
A. Kimura,
M. Kitaguchi,
R. Kobayashi,
T. Okamura,
T. Oku,
T. Okudaira,
M. Okuizumi,
J. G. Otero Munoz,
J. D. Parker,
K. Sakai,
T. Shima,
H. M. Shimizu,
T. Shinohara,
W. M. Snow
, et al. (5 additional authors not shown)
Abstract:
Neutron transmission experiments can offer a new type of highly sensitive search for time-reversal invariance violating (TRIV) effects in nucleon-nucleon interactions via the same enhancement mechanism observed for large parity violating (PV) effects in neutron-induced compound nuclear processes. In these compound processes, the TRIV cross-section is given as the product of the PV cross-section, a…
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Neutron transmission experiments can offer a new type of highly sensitive search for time-reversal invariance violating (TRIV) effects in nucleon-nucleon interactions via the same enhancement mechanism observed for large parity violating (PV) effects in neutron-induced compound nuclear processes. In these compound processes, the TRIV cross-section is given as the product of the PV cross-section, a spin-factor $κ$, and a ratio of TRIV and PV matrix elements. We determined $κ$ to be $0.59\pm0.05$ for $^{139}$La+$n$ using both $(n, γ)$ spectroscopy and ($\vec{n}+^{139}\vec{\rm La}$) transmission. This result quantifies for the first time the high sensitivity of the $^{139}$La 0.75~eV $p$-wave resonance in a future search for P-odd/T-odd interactions in ($\vec{n}+^{139}\vec{\rm La}$) forward transmission.
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Submitted 10 December, 2023;
originally announced December 2023.
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Spin dependence in the $p$-wave resonance of ${^{139}\vec{\rm{La}}+\vec{n}}$
Authors:
T. Okudaira,
R. Nakabe,
S. Endo,
H. Fujioka,
V. Gudkov,
I. Ide,
T. Ino,
M. Ishikado,
W. Kambara,
S. Kawamura,
R. Kobayashi,
M. Kitaguchi,
T. Okamura,
T. Oku,
J. G. Otero Munoz,
J. D. Parker,
K. Sakai,
T. Shima,
H. M. Shimizu,
T. Shinohara,
W. M. Snow,
S. Takada,
Y. Tsuchikawa,
R. Takahashi,
S. Takahashi
, et al. (2 additional authors not shown)
Abstract:
We measured the spin dependence in a neutron-induced $p$-wave resonance by using a polarized epithermal neutron beam and a polarized nuclear target. Our study focuses on the 0.75~eV $p$-wave resonance state of $^{139}$La+$n$, where largely enhanced parity violation has been observed. We determined the partial neutron width of the $p$-wave resonance by measuring the spin dependence of the neutron a…
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We measured the spin dependence in a neutron-induced $p$-wave resonance by using a polarized epithermal neutron beam and a polarized nuclear target. Our study focuses on the 0.75~eV $p$-wave resonance state of $^{139}$La+$n$, where largely enhanced parity violation has been observed. We determined the partial neutron width of the $p$-wave resonance by measuring the spin dependence of the neutron absorption cross section between polarized $^{139}\rm{La}$ and polarized neutrons. Our findings serve as a foundation for the quantitative study of the enhancement effect of the discrete symmetry violations caused by mixing between partial amplitudes in the compound nuclei.
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Submitted 16 September, 2023;
originally announced September 2023.
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Absolute $\rm ^3$He polarimetry for a double-chambered cell using transmission of thermal neutrons
Authors:
A. Watanabe,
K. Sekiguchi,
T. Ino,
M. Inoue,
S. Nakai,
Y. Otake,
A. Taketani,
Y. Wakabayashi
Abstract:
We present an absolute $^3$He polarimetry method based on thermal neutron transmission for a double-chambered cell. This method utilizes the fact that a $^3$He nucleus has a large absorption cross section and a spin dependence for thermal neutrons. The cell had a pumping chamber and a target chamber. Polarized $^3$He gas was produced in the pumping chamber by SEOP and then diffused into the target…
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We present an absolute $^3$He polarimetry method based on thermal neutron transmission for a double-chambered cell. This method utilizes the fact that a $^3$He nucleus has a large absorption cross section and a spin dependence for thermal neutrons. The cell had a pumping chamber and a target chamber. Polarized $^3$He gas was produced in the pumping chamber by SEOP and then diffused into the target chamber. The $^3$He polarization in the target chamber was determined by comparing the neutron transmissions with the polarized and unpolarized targets. The measurement was performed at the RIKEN Accelerator-Driven Compact Neutron Source. The $^3$He polarization in the target chamber was determined with a statistical error of 1.8% and systematic uncertainty of 0.6%. This method can be used to obtain high-precision data of spin observables in few-nucleon scattering for the investigation of nuclear forces.
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Submitted 26 September, 2022;
originally announced September 2022.
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Proton-$\rm ^3He$ elastic scattering at intermediate energies
Authors:
A. Watanabe,
S. Nakai,
Y. Wada,
K. Sekiguchi,
A. Deltuva,
T. Akieda,
D. Etoh,
M. Inoue,
Y. Inoue,
K. Kawahara,
H. Kon,
K. Miki,
T. Mukai,
D. Sakai,
S. Shibuya,
Y. Shiokawa,
T. Taguchi,
H. Umetsu,
Y. Utsuki,
M. Watanabe,
S. Goto,
K. Hatanaka,
Y. Hirai,
T. Ino,
D. Inomoto
, et al. (20 additional authors not shown)
Abstract:
We present a precise measurement of the cross section, proton and $\rm ^3He$ analyzing powers, and spin correlation coefficient $C_{y,y}$ for $p$-$\rm ^3He$ elastic scattering near 65 MeV, and a comparison with rigorous four-nucleon scattering calculations based on realistic nuclear potentials and a model with $Δ$-isobar excitation. Clear discrepancies are seen in some of the measured observables…
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We present a precise measurement of the cross section, proton and $\rm ^3He$ analyzing powers, and spin correlation coefficient $C_{y,y}$ for $p$-$\rm ^3He$ elastic scattering near 65 MeV, and a comparison with rigorous four-nucleon scattering calculations based on realistic nuclear potentials and a model with $Δ$-isobar excitation. Clear discrepancies are seen in some of the measured observables in the regime around the cross section minimum. Theoretical predictions using scaling relations between the calculated cross section and the $\rm ^3 He$ binding energy are not successful in reproducing the data. Large sensitivity to the $NN$ potentials and rather small $Δ$-isobar effects in the calculated cross section are noticed as different features from those in the deuteron-proton elastic scattering. The results obtained above indicate that $p$-$\rm ^3He$ scattering at intermediate energies is an excellent tool to explore nuclear interactions not accessible by three-nucleon scattering.
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Submitted 26 March, 2021;
originally announced March 2021.
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Precise Neutron Lifetime Measurement Using Pulsed Neutron Beams at J-PARC
Authors:
N. Sumi,
K. Hirota,
G. Ichikawa,
T. Ino,
Y. Iwashita,
S. Kajiwara,
Y. Kato,
M. Kitaguchi,
K. Mishima,
K. Morikawa,
T. Mogi,
H. Oide,
H. Okabe,
H. Otono,
T. Shima,
H. M. Shimizu,
Y. Sugisawa,
T. Tanabe,
S. Yamashita,
K. Yano,
T. Yoshioka
Abstract:
A neutron decays into a proton, an electron, and an anti-neutrino through the beta-decay process. The decay lifetime ($\sim$880 s) is an important parameter in the weak interaction. For example, the neutron lifetime is a parameter used to determine the |$V_{\rm ud}$| parameter of the CKM quark mixing matrix. The lifetime is also one of the input parameters for the Big Bang Nucleosynthesis, which p…
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A neutron decays into a proton, an electron, and an anti-neutrino through the beta-decay process. The decay lifetime ($\sim$880 s) is an important parameter in the weak interaction. For example, the neutron lifetime is a parameter used to determine the |$V_{\rm ud}$| parameter of the CKM quark mixing matrix. The lifetime is also one of the input parameters for the Big Bang Nucleosynthesis, which predicts light element synthesis in the early universe. However, experimental measurements of the neutron lifetime today are significantly different (8.4 s or 4.0$σ$) depending on the methods. One is a bottle method measuring surviving neutron in the neutron storage bottle. The other is a beam method measuring neutron beam flux and neutron decay rate in the detector. There is a discussion that the discrepancy comes from unconsidered systematic error or undetectable decay mode, such as dark decay. A new type of beam experiment is performed at the BL05 MLF J-PARC. This experiment measured neutron flux and decay rate simultaneously with a time projection chamber using a pulsed neutron beam. We will present the world situation of neutron lifetime and the latest results at J-PARC.
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Submitted 19 February, 2021;
originally announced February 2021.
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Neutron lifetime measurement with pulsed cold neutrons
Authors:
K. Hirota,
G. Ichikawa,
S. Ieki,
T. Ino,
Y. Iwashita,
M. Kitaguchi,
R. Kitahara,
J. Koga,
K. Mishima,
T. Mogi,
K. Morikawa,
A. Morishita,
N. Nagakura,
H. Oide,
H. Okabe,
H. Otono,
Y. Seki,
D. Sekiba,
T. Shima,
H. M. Shimizu,
N. Sumi,
H. Sumino,
T. Tomita,
H. Uehara,
T. Yamada
, et al. (4 additional authors not shown)
Abstract:
The neutron lifetime has been measured by comparing the decay rate with the reaction rate of $^3$He nuclei of a pulsed neutron beam from the spallation neutron source at the Japan Proton Accelerator Research Complex (J-PARC). The decay rate and the reaction rate were determined by simultaneously detecting electrons from the neutron decay and protons from the $^3$He(n,p)$^3$H reaction using a gas c…
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The neutron lifetime has been measured by comparing the decay rate with the reaction rate of $^3$He nuclei of a pulsed neutron beam from the spallation neutron source at the Japan Proton Accelerator Research Complex (J-PARC). The decay rate and the reaction rate were determined by simultaneously detecting electrons from the neutron decay and protons from the $^3$He(n,p)$^3$H reaction using a gas chamber of which working gas contains diluted $^3$He. The measured neutron lifetime was $898\,\pm\,10\,_{\rm stat}\,^{+15}_{-18}\,_{\rm sys}\,$s.
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Submitted 25 November, 2020; v1 submitted 22 July, 2020;
originally announced July 2020.
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Transverse asymmetry of $γ$ rays from neutron-induced compound states of ${}^{140}{\rm La}$
Authors:
T. Yamamoto,
T. Okudaira,
S. Endo,
H. Fujioka,
K. Hirota,
T. Ino,
K. Ishizaki,
A. Kimura,
M. Kitaguchi,
J. Koga,
S. Makise,
Y. Niinomi,
T. Oku,
K. Sakai,
T. Shima,
H. M. Shimizu,
S. Takada,
Y. Tani,
H. Yoshikawa,
T. Yoshioka
Abstract:
A correlation term ${{ σ}_{n} }\cdot ({ k_{n}\times k_γ}) $ in the ${}^{139}{\rm La}(\vec{n},γ)$ reaction has been studied utilizing epithermal polarized neutrons and germanium detectors. The transverse asymmetry for single $γ$-ray transition was measured to be $0.60\pm0.19$ in the $p$-wave resonance.
A correlation term ${{ σ}_{n} }\cdot ({ k_{n}\times k_γ}) $ in the ${}^{139}{\rm La}(\vec{n},γ)$ reaction has been studied utilizing epithermal polarized neutrons and germanium detectors. The transverse asymmetry for single $γ$-ray transition was measured to be $0.60\pm0.19$ in the $p$-wave resonance.
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Submitted 20 February, 2020;
originally announced February 2020.
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Measurement of 3He analyzing power for p-3He scattering using the polarized 3He target
Authors:
A. Watanabe,
S. Nakai,
K. Sekiguchi,
T. Akieda,
D. Etoh,
M. Inoue,
Y. Inoue,
K. Kawahara,
H. Kon,
K. Miki,
T. Mukai,
D. Sakai,
S. Shibuya,
Y. Shiokawa,
T. Taguchi,
H. Umetsu,
Y. Utsuki,
Y. Wada,
M. Watanabe,
M. Itoh,
T. Ino,
T. Wakui,
K. Hatanaka,
H. Kanda,
H. J. Ong
, et al. (12 additional authors not shown)
Abstract:
Proton-3He scattering is one of the good probes to study the T=3/2 channel of three--nucleon forces. We have measured 3He analyzing powers for p-3He elastic scattering with the polarized 3He target at 70 and 100 MeV. The data are compared with the theoretical predictions based on the modern nucleon--nucleon potentials. Large discrepancies are found between the data and the calculations at the angl…
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Proton-3He scattering is one of the good probes to study the T=3/2 channel of three--nucleon forces. We have measured 3He analyzing powers for p-3He elastic scattering with the polarized 3He target at 70 and 100 MeV. The data are compared with the theoretical predictions based on the modern nucleon--nucleon potentials. Large discrepancies are found between the data and the calculations at the angles where the 3He analyzing power takes the minimum and maximum values, which are not explained by taking into account Delta-isobar degrees of freedom.
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Submitted 1 November, 2019; v1 submitted 23 October, 2019;
originally announced October 2019.
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Measurement of the total neutron scattering cross section ratios of noble gases of natural isotopic composition using a pulsed neutron beam
Authors:
Christopher C. Haddock,
Masayuki Hiromoto,
Katsuya Hirota,
Takashi Ino,
Masaaki Kitaguchi,
Kenji Mishima,
Noriko Oi,
Tatsushi Shima,
Hirohiko M. Shimizu,
W. Michael Snow,
Tamaki Yoshioka
Abstract:
Precision measurements of slow neutron cross sections with atoms have several scientific applications. In particular the n-$^{4}$He s-wave scattering length is important to know both for helping to constrain the nuclear three-body interaction and for the proper interpretation of several ongoing slow neutron experiments searching for other types of neutron-atom interactions. We present new measurem…
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Precision measurements of slow neutron cross sections with atoms have several scientific applications. In particular the n-$^{4}$He s-wave scattering length is important to know both for helping to constrain the nuclear three-body interaction and for the proper interpretation of several ongoing slow neutron experiments searching for other types of neutron-atom interactions. We present new measurements of the ratios of the neutron differential scattering cross sections for natural isotopic-abundance mixtures of the noble gases He, Ar, Kr, and Xe to natural isotopic abundance Ne. These measurements were performed using a recently developed neutron scattering apparatus for gas samples located on a pulsed slow neutron beamline which was designed to search for possible exotic neutron-atom interactions and employs both neutron time of flight information and a position-sensitive neutron detector for scattering event reconstruction. We found agreement with the literature values of scattering cross sections inferred from Ar/Ne, Kr/Ne and Xe/Ne differential cross section ratios over the $q$ range of $1 - 7$ nm$^{-1}$. However for the case of He/Ne we find that the cross section inferred differs by 11.3% (7.6 $σ$) from previously-reported values inferred from neutron phase shift measurements, but is in reasonable agreement with values from other measurements. The very large discrepancy in the He/Ne ratio calls for a new precision measurement of the n-$^{4}$He scattering length using neutron interferometry.
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Submitted 15 November, 2019; v1 submitted 19 June, 2019;
originally announced June 2019.
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Improved determination of thermal cross section of 14N(n,p)14C for the neutron lifetime measurement
Authors:
R. Kitahara,
K. Hirota,
S. Ieki,
T. Ino,
Y. Iwashita,
M. Kitaguchi,
J. Koga,
K. Mishima,
A. Morishita,
N. Nagakura,
H. Oide,
H. Otono,
Y. Seki,
D. Sekiba,
T. Shima,
H. M. Shimizu,
N. Sumi,
H. Sumino,
K. Taketani,
T. Tomita,
T. Yamada,
S. Yamashita,
M. Yokohashi,
T. Yoshioka
Abstract:
In a neutron lifetime measurement at the Japan Proton Accelerator Complex, the neutron lifetime is calculated by the neutron decay rate and the incident neutron flux. The flux is obtained due to counting the protons emitted from the neutron absorption reaction of ${}^{3}{\rm He}$ gas, which is diluted in a mixture of working gas in a detector. Hence, it is crucial to determine the amount of…
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In a neutron lifetime measurement at the Japan Proton Accelerator Complex, the neutron lifetime is calculated by the neutron decay rate and the incident neutron flux. The flux is obtained due to counting the protons emitted from the neutron absorption reaction of ${}^{3}{\rm He}$ gas, which is diluted in a mixture of working gas in a detector. Hence, it is crucial to determine the amount of ${}^{3}{\rm He}$ in the mixture. In order to improve the accuracy of the number density of the ${}^{3}{\rm He}$ nuclei, we suggested to use the ${}^{14}{\rm N}({\rm n},{\rm p}){}^{14}{\rm C}$ reaction as a reference because this reaction involves similar kinetic energy as the ${}^{3}{\rm He}({\rm n},{\rm p}){}^{3}{\rm H}$ reaction and a smaller reaction cross section to introduce reasonable large partial pressure. The uncertainty of the recommended value of the cross section, however, is not satisfied with our requirement.
In this paper, we report the most accurate experimental value of the cross section of the ${}^{14}{\rm N}({\rm n},{\rm p}){}^{14}{\rm C}$ reaction at a neutron velocity of 2200 m/s, measured relative to the ${}^{3}{\rm He}({\rm n},{\rm p}){}^{3}{\rm H}$ reaction. The result was 1.868 $\pm$ 0.003 (stat.) $\pm$ 0.006 (sys.) b. Additionally, the cross section of the ${}^{17}{\rm O}({\rm n},{\rm α}){}^{14}{\rm C}$ reaction at the neutron velocity is also redetermined as 249 $\pm$ 6 mb.
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Submitted 2 August, 2019; v1 submitted 26 April, 2019;
originally announced April 2019.
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A Search for deviations from the inverse square law of gravity at nm range using a pulsed neutron beam
Authors:
Christopher C. Haddock,
Noriko Oi,
Katsuya Hirota,
Takashi Ino,
Masaaki Kitaguchi,
Satoru Matsumoto,
Kenji Mishima,
Tatsushi Shima,
Hirohiko M. Shimizu,
W. Michael Snow,
Tamaki Yoshioka
Abstract:
We describe an experimental search for deviations from the inverse square law of gravity at the nanometer length scale using neutron scattering from noble gases on a pulsed slow neutron beamline. By measuring the neutron momentum transfer ($q$) dependence of the differential cross section for xenon and helium and comparing to their well-known analytical forms, we place an upper bound on the streng…
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We describe an experimental search for deviations from the inverse square law of gravity at the nanometer length scale using neutron scattering from noble gases on a pulsed slow neutron beamline. By measuring the neutron momentum transfer ($q$) dependence of the differential cross section for xenon and helium and comparing to their well-known analytical forms, we place an upper bound on the strength of a new interaction as a function of interaction length $λ$ which improves upon previous results in the region $λ< 0.1\,$nm, and remains competitive in the larger $λ$ region. A pseudoexperimental simulation developed for this experiment and its role in the data analysis described. We conclude with plans for improving sensitivity in the larger $λ$ region.
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Submitted 21 February, 2018; v1 submitted 8 December, 2017;
originally announced December 2017.
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Precise neutron lifetime experiment using pulsed neutron beams at J-PARC
Authors:
Naoki Nagakura,
Katsuya Hirota,
Sei Ieki,
Takashi Ino,
Yoshihisa Iwashita,
Masaaki Kitaguchi,
Ryunosuke Kitahara,
Kenji Mishima,
Aya Morishita,
Hideyuki Oide,
Hidetoshi Otono,
Risa Sakakibara,
Yoshichika Seki,
Tatsushi Shima,
Hirohiko M. Shimizu,
Tomoaki Sugino,
Naoyuki Sumi,
Hiroshima Sumino,
Kaoru Taketani,
Genki Tanaka,
Tatsuhiko Tomita,
Takahito Yamada,
Satoru Yamashita,
Mami Yokohashi,
Tamaki Yoshioka
Abstract:
The neutron lifetime is one of the basic parameters in the weak interaction, and is used for predicting the light element abundance in the early universe. Our group developed a new setup to measure the lifetime with the goal precision of 0.1% at the polarized beam branch BL05 of MLF, J-PARC. The commissioning data was acquired in 2014 and 2015, and the first set of data to evaluate the lifetime in…
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The neutron lifetime is one of the basic parameters in the weak interaction, and is used for predicting the light element abundance in the early universe. Our group developed a new setup to measure the lifetime with the goal precision of 0.1% at the polarized beam branch BL05 of MLF, J-PARC. The commissioning data was acquired in 2014 and 2015, and the first set of data to evaluate the lifetime in 2016, which is expected to yield a statistical uncertainty of O(1)%. This paper presents the current analysis results and the future plans to achieve our goal precision.
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Submitted 10 February, 2017;
originally announced February 2017.
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Development of time projection chamber for precise neutron lifetime measurement using pulsed cold neutron beams
Authors:
Y. Arimoto,
N. Higashi,
Y. Igarashi,
Y. Iwashita,
T. Ino,
R. Katayama,
R. Kitahara,
M. Kitaguchi,
H. Matsumura,
K. Mishima,
H. Oide,
H. Otono,
R. Sakakibara,
T. Shima,
H. M. Shimizu,
T. Sugino,
N. Sumi,
H. Sumino,
K. Taketani,
G. Tanaka,
M. Tanaka,
K. Tauchi,
A. Toyoda,
T. Yamada,
S. Yamashita
, et al. (2 additional authors not shown)
Abstract:
A new time projection chamber (TPC) was developed for neutron lifetime measurement using a pulsed cold neutron spallation source at the Japan Proton Accelerator Research Complex (J-PARC). Managing considerable background events from natural sources and the beam radioactivity is a challenging aspect of this measurement. To overcome this problem, the developed TPC has unprecedented features such as…
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A new time projection chamber (TPC) was developed for neutron lifetime measurement using a pulsed cold neutron spallation source at the Japan Proton Accelerator Research Complex (J-PARC). Managing considerable background events from natural sources and the beam radioactivity is a challenging aspect of this measurement. To overcome this problem, the developed TPC has unprecedented features such as the use of polyether-ether-ketone plates in the support structure and internal surfaces covered with $^6$Li-enriched tiles to absorb outlier neutrons. In this paper, the design and performance of the new TPC are reported in detail.
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Submitted 11 September, 2015; v1 submitted 26 March, 2015;
originally announced March 2015.
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Upper Bounds on Parity Violating Gamma-Ray Asymmetries in Compound Nuclei from Polarized Cold Neutron Capture
Authors:
M. T. Gericke,
J. D. Bowman,
R. D. Carlini,
T. E. Chupp,
K. P. Coulter,
M. Dabaghyan,
M. Dawkins,
D. Desai,
S. J. Freedman,
T. R. Gentile,
R. C. Gillis,
G. L. Greene,
F. W. Hersman,
T. Ino,
G. L. Jones,
M. Kandes,
B. Lauss,
M. Leuschner,
W. R. Lozowski,
R. Mahurin,
M. Mason,
Y. Masuda,
G. S. Mitchell,
S. Muto,
H. Nann
, et al. (11 additional authors not shown)
Abstract:
Parity-odd asymmetries in the electromagnetic decays of compound nuclei can sometimes be amplified above values expected from simple dimensional estimates by the complexity of compound nuclear states. In this work we use a statistical approach to estimate the root mean square (RMS) of the distribution of expected parity-odd correlations $\vec{s_{n}} \cdot \vec{k_γ}$, where $\vec {s_{n}}$ is the…
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Parity-odd asymmetries in the electromagnetic decays of compound nuclei can sometimes be amplified above values expected from simple dimensional estimates by the complexity of compound nuclear states. In this work we use a statistical approach to estimate the root mean square (RMS) of the distribution of expected parity-odd correlations $\vec{s_{n}} \cdot \vec{k_γ}$, where $\vec {s_{n}}$ is the neutron spin and $\vec{k_γ}$ is the momentum of the gamma, in the integrated gamma spectrum from the capture of cold polarized neutrons on Al, Cu, and In and we present measurements of the asymmetries in these and other nuclei. Based on our calculations, large enhancements of asymmetries were not predicted for the studied nuclei and the statistical estimates are consistent with our measured upper bounds on the asymmetries.
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Submitted 3 August, 2006;
originally announced August 2006.
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A Current Mode Detector Array for Gamma-Ray Asymmetry Measurements
Authors:
M. T. Gericke,
C. Blessinger,
J. D. Bowman,
R. C. Gillis,
J. Hartfield,
T. Ino,
M. Leuschner,
Y. Masuda,
G. S. Mitchell,
S. Muto,
H. Nann,
S. A. Page,
S. I. Penttilä,
W. D. Ramsay,
P. -N. Seo,
W. M. Snow,
J. Tasson,
W. S. Wilburn
Abstract:
We have built a CsI(Tl) gamma-ray detector array for the NPDGamma experiment to search for a small parity-violating directional asymmetry in the angular distribution of 2.2 MeV gamma-rays from the capture of polarized cold neutrons by protons with a sensitivity of several ppb. The weak pion-nucleon coupling constant can be determined from this asymmetry. The small size of the asymmetry requires…
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We have built a CsI(Tl) gamma-ray detector array for the NPDGamma experiment to search for a small parity-violating directional asymmetry in the angular distribution of 2.2 MeV gamma-rays from the capture of polarized cold neutrons by protons with a sensitivity of several ppb. The weak pion-nucleon coupling constant can be determined from this asymmetry. The small size of the asymmetry requires a high cold neutron flux, control of systematic errors at the ppb level, and the use of current mode gamma-ray detection with vacuum photo diodes and low-noise solid-state preamplifiers. The average detector photoelectron yield was determined to be 1300 photoelectrons per MeV. The RMS width seen in the measurement is therefore dominated by the fluctuations in the number of gamma rays absorbed in the detector (counting statistics) rather than the intrinsic detector noise. The detectors were tested for noise performance, sensitivity to magnetic fields, pedestal stability and cosmic background. False asymmetries due to gain changes and electronic pickup in the detector system were measured to be consistent with zero to an accuracy of $10^{-9}$ in a few hours. We report on the design, operating criteria, and the results of measurements performed to test the detector array.
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Submitted 10 November, 2004;
originally announced November 2004.