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T. Haseyama,
K. Asahi,
J.D. Bowman, P.P.J. Delheij,
H Funahashi,
S Ishimoto,
G. Jones,
A. Masaike,
Y Masuda,
Y Matsuda,
K Morimoto,
S Muto,
S.I. Penttilä,
V. R. Pomeroy,
K Sakai,
E.I. Sharapov,
D. A. Smith,
V.W. Yuan
[show abstract]
[hide abstract]
ABSTRACT: The parity nonconserving spin rotation of neutrons in the 0.734-eV p-wave resonance of $^{139}La$ was measured with the neutron transmission method. Two optically polarized $^3He$ cells were used before and behind a a 5-cm long $^{139}La$ target as a polarizer and an analyzer of neutron spin. The rotation angle was carefully measured by flipping the direction of $^3He$ polarization in the polarizer in sequence. The peak-to-peak value of the spin rotation was found to be $ (7.4 \pm 1.1) \times 10^{-3} $ rad/cm which was consistent with the previous experiments. But the result was statisticallly improved. The s-p mixing model gives the weak matrix element as $xW = (1.71 \pm 0.25)$ meV. The value agrees well with the one deduced from the parity-nonconserving longitudinal asymmetry in the same resonance.
11/2001;
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Y. Matsuda,
J. D. Bowman,
B. E. Crawford, P. P. J. Delheij,
T. Haseyama,
J. N. Knudsen,
L. Y. Lowie,
A. Masaike,
Y. Masuda,
G. E. Mitchell,
S. I. Penttilä,
H. Postma,
N. R. Roberson,
S. J. Seestrom,
E. I. Sharapov,
S. L. Stephenson,
Y.-F. Yen,
V. W. Yuan
[show abstract]
[hide abstract]
ABSTRACT: Parity violation in p-wave neutron resonances of 121Sb, 123Sb, and 127I has been measured by transmission of a longitudinally polarized neutron beam through natural antimony and iodine targets. The measurements were performed at the pulsed spallation neutron source of the Los Alamos Neutron Science Center. Five statistically significant parity violation effects were observed in 121Sb, one effect in 123Sb, and seven effects in 127I. The weak interaction rms matrix elements and the corresponding spreading widths were determined.
Phys. Rev. C. 06/2001; 64(1).
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H. Postma,
J. D. Bowman,
F. Corvi,
B. E. Crawford, P. P. J. Delheij,
C. M. Frankle,
C. A. Grossmann,
F. Gunsing,
T. Haseyama,
J. N. Knudson, [......],
S. I. Penttila,
N. R. Roberson,
S. J. Seestrom,
E. I. Sharapov,
D. A. Smith,
S. L. Stephenson,
Y. -F. Yen,
V. W. Yuan,
L. Zanini,
TRIPLE and Gell collaborations
[show abstract]
[hide abstract]
ABSTRACT: This paper gives a brief overview of parity violation effects at neutron p-wave resonances observed by the TRIPLE collaboration
at Los Alamos together with some information about neutron resonance capture gamma spectroscopy experiments carried out by
the Geel collaboration in relation to these parity violation experiments.
Czechoslovak Journal of Physics 12/2000; 51:A289-A298. · 0.42 Impact Factor
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S. L. Stephenson,
J. D. Bowman,
F. Corvi,
B. E. Crawford, P. P. J. Delheij,
C. M. Frankle,
M. Iinuma,
J. N. Knudson,
L. Y. Lowie,
A. Masaike, [......],
G. E. Mitchell,
S. I. Penttilä,
H. Postma,
N. R. Roberson,
S. J. Seestrom,
E. I. Sharapov,
H. M. Shimizu,
Y.-F. Yen,
V. W. Yuan,
L. Zanini
[show abstract]
[hide abstract]
ABSTRACT: Parity nonconservation (PNC) was studied in p-wave resonances in indium by measuring the helicity dependence of the neutron total cross section in the neutron energy range 6.0–316 eV with the time-of-flight method at LANSCE. A total of 36 p-wave neutron resonances were studied in 115In, and statistically significant asymmetries were observed for nine cases. An analysis treating the PNC matrix elements as random variables yields a weak matrix element of M=(0.67-0.12+0.16) meV and a weak spreading width of Γw=(1.30-0.43+0.76)×10-7 eV.
Phys. Rev. C. 03/2000; 61(4).
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E. I. Sharapov,
J. D. Bowman,
B. E. Crawford, P. P. J. Delheij,
C. M. Frankle,
M. Iinuma,
J. N. Knudson,
L. Y. Lowie,
J. E. Lynch,
A. Masaike,
Y. Matsuda,
G. E. Mitchell,
S. I. Penttilä,
H. Postma,
N. R. Roberson,
S. J. Seestrom,
S. L. Stephenson,
Y.-F. Yen,
V. W. Yuan
[show abstract]
[hide abstract]
ABSTRACT: The analysis of parity nonconservation (PNC) measurements performed on 232Th by the TRIPLE Collaboration has been extended to include the neutron energy range of 250 to 1900 eV. Below 250 eV all ten statistically significant parity violations have the same sign. However, at higher energies PNC effects of both signs were observed in the transmission of longitudinally polarized neutrons through a thick thorium target. Although the limited experimental energy resolution precluded analysis in terms of the longitudinal asymmetry, parity violations were observed and the cross section differences for positive and negative neutron helicities were obtained. For comparison, a similar analysis was performed on the data below 250 eV, for which longitudinal asymmetries were obtained previously. For energies below 250 eV, the p-wave neutron strength functions for the J=1/2 and J=3/2 states were extracted: S1/21=(1.68±0.61)×10-4 and S3/21=(0.75±0.18)×10-4. The data provide constraints on the properties of local doorway states proposed to explain the PNC sign effect in thorium.
Phys. Rev. C. 01/2000; 61(2).
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Yi-Fen Yen,
J D Bowman,
R D Bolton,
B E Crawford, P P J Delheij,
G W Hart,
T Haseyama,
C M Frankle,
M Iinuma,
J N Knudson, [......],
S I Penttilak,
N R Roberson,
S J Seestrom,
E Sharapov,
H M Shimizu,
D A Smith,
S L Stephenson,
J J Szymanski,
S H Yoo,
V W Yuan
[show abstract]
[hide abstract]
ABSTRACT: We have developed a large-area B-loaded liquid scintillation detector for parity-violation studies in neutron resonances with high instantaneous neutron #uxes from the LANSCE short-pulse spallation source. The detector has an e$ciency of 95%, 85% and 71% at neutron energies of 10, 100 and 1000 eV, respectively. The neutron mean capture time in the detector is (416$5) ns. We describe the detector and the current-mode signal processing system, that can handle neutron rates up to 500 MHz. 2000 Elsevier Science B.V. All rights reserved.
Nuclear Instruments and Methods in Physics Research A20.Gd41.Rc30.Hs. 01/2000; 447(29).
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B. E. Crawford,
J. D. Bowman, P. P. J. Delheij,
T. Haseyama,
J. N. Knudson,
L. Y. Lowie,
A. Masaike,
Y. Matsuda,
G. E. Mitchell,
S. I. Penttilä,
H. Postma,
N. R. Roberson,
S. J. Seestrom,
E. I. Sharapov,
S. L. Stephenson,
V. W. Yuan
[show abstract]
[hide abstract]
ABSTRACT: Parity nonconservation (PNC) has been studied in the neutron p-wave resonances of 106Pd and 108Pd in the energy range of 20 to 2000 eV. Longitudinal asymmetries in p-wave capture cross sections are measured using longitudinally polarized neutrons incident on ∼20-g metal-powder targets at LANSCE. A CsI γ-ray detector array measures capture cross section asymmetries as a function of neutron energy which is determined by the neutron time-of-flight method. A total of 21 p-wave resonances in 106Pd and 21 p-wave resonances in 108Pd were studied. One statistically significant PNC effect was observed in 106Pd, and no effects were observed in 108Pd. For 106Pd a weak spreading width of Γw=34-28+47×10-7 eV was obtained. For 108Pd an upper limit on the weak spreading width of Γw<12×10-7 eV was determined at the 68% confidence level.
Phys. Rev. C. 10/1999; 60(5).
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D. R. Rich,
J.D. Bowman,
B.E. Crawford, P.P.J. Delheij,
M. A. Espy,
T. Haseyama,
G. Jones,
C.D. Keith,
J. Knudson,
M. B. Leuschner,
A. Masaike,
Y Masuda,
Y Matsuda,
S. I. Penttila,
V. R. Pomeroy,
D. A. Smith,
W. M. Snow,
S.L. Stephenson,
A. K. Thompson,
V. Yuan
[show abstract]
[hide abstract]
ABSTRACT: The capability of performing accurate measurements of neutron beam polarization opens a number of exciting opportunities in fundamental neutron physics and in neutron scattering. At the LANSCE pulsed neutron source we have measured the neutron beam polarization with absolute accuracy of 0.3% in the neutron energy range from 40 meV to 10 eV using an optically-pumped polarized 3He spin filter and a relative transmission measurement technique. 3He was polarized using the Rb spin-exchange method. We describe the measurement technique, present our results, and discuss some of the systematic effects associated with the method.
09/1999;
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[show abstract]
[hide abstract]
ABSTRACT: A dynamically‐polarized proton target operating at 5 Tesla and 1 K has been built to polarize an epithermal neutron beam for studies of parity violation in compound‐nuclear resonances. Nearly 0.9 proton polarization was obtained in an electron‐beam irradiated ammonia target. This was used to produce a neutron beam polarization of 0.7 at epithermal energies. The combination of the polarized proton target and the LANSCE spallation neutron source produces the most intense pulsed polarized epithermal neutron beam in the world. The neutron‐beam polarizer is described and methods to determine neutron beam polarization are presented. © 1995 American Institute of Physics.
AIP Conference Proceedings. 08/1995; 343(1):532-539.
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Yi‐Fen Yen,
J. D. Bowman,
B. E. Crawford, P. P. J. Delheij,
C. M. Frankle,
K. Fukuda,
C. R. Gould,
A. A. Green,
D. G. Haase,
M. Iinuma, [......],
Y. Matsuda,
G. E. Mitchell,
S. I. Penttilä,
H. Postma,
N. R. Roberson,
S. J. Seestrom,
E. I. Sharapov,
H. M. Shimizu,
S. L. Stephenson,
V. W. Yuan
[show abstract]
[hide abstract]
ABSTRACT: The parity and time‐reversal symmetries can be studied in neutron‐nucleus interactions. Parity non‐conserving asymmetries have been observed for many p‐wave resonances in a compound nucleus and measurements were performed on several nuclei in the mass region of A∼100 and A∼230. The statistical model of the compound nucleus provides a theoretical basis for extracting mean‐squared matrix elements from the experimental asymmetry data, and for interpreting the mean‐squared matrix elements. The constraints on the weak meson‐exchange couplings calculated from the compound‐nucleus asymmetry data agree qualitatively with the results from few‐body and light‐nuclei experiments. The tests of time‐reversal invariance in various experiments using thermal, epithermal, and MeV neutrons are being developed.
AIP Conference Proceedings. 07/1995; 339(1):120-135.
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H. Sato,
Y. Masuda,
K. Sakai,
M. Doi,
K. Asahi,
Z. J. Zheng,
Y. Mori, P. P. J. Delheij,
Y. Matsuda,
M. Iinuma,
H. M. Shimizu,
A. Masaike
[show abstract]
[hide abstract]
ABSTRACT: We have constructed an apparatus to polarize the3He nuclear spin, which will be used as a neutron spin analyzer in T- and P-violation neutron experiments. We report on principles and the present status of the method for the polarization of3He and the determination of its value.
Hyperfine Interactions 01/1994; 84(1):205-209. · 0.21 Impact Factor
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C. M. Frankle,
J. D. Bowman,
J. N. Knudson,
S. I. Penttila,
S. J. Seestrom,
S. H. Yoo,
V. W. Yuan,
C. R. Gould,
D. G. Haase,
G. E. Mitchell,
N. R. Roberson,
Yu. P. Popov,
E. I. Sharapov, P. P. J. Delheij,
H. Postma
[show abstract]
[hide abstract]
ABSTRACT: Polarized neutron transmission experiments show remarkable sensitivity
to the presence of small symmetry violating forces in nuclear
interactions. Parity-nonconserving (PNC) analyzing powers of a percent
or more have been measured on p-wave neutron resonances in nuclei
ranging from 81Br to 238U. A brief summary is
given of the study of PNC effects in neutron resonances. Details of
ongoing polarized neutron transmission experiments are discussed and
some sample data presented. Several development projects are currently
under way, which taken together should improve the sensitivity of these
experiments by a factor of ~ 20. Similar large PNC effects can be
observed in (n, γ) resonances with much smaller samples. A design
for a near 4π gamma ray detector to be constructed of CsI(pure) is
described.
Nuclear Instruments and Methods in Physics Research Section B Beam Interactions with Materials and Atoms 05/1993; 79:306-308. · 1.21 Impact Factor
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C.M. Frankle,
J.D. Bowman,
J.E. Bush, P.P.J. Delheij,
C.R. Gould,
D.G. Haase,
J.N. Knudson,
G.E. Mitchell,
S. Penttilae,
H. Postma,
N.R. Roberson,
S.J. Seestrom,
J.J. Szymanski,
V.W. Yuan,
X. Zhu
[show abstract]
[hide abstract]
ABSTRACT: The parity nonconserving longitudinal analyzing power [ital P] was measured for the [ital E][sub [ital n]]=0.88 eV neutron resonance in [sup 81]Br. The value of [ital P]=+1.77[plus minus]0.33 %; the sign is determined relative to the 0.73-eV resonance in [sup 139]La.
Physical Review, C (Nuclear Physics); (United States). 09/1992; 46:4.
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H. Postma,
J. D. Bowman,
C. D. Bowman,
J. E. Bush, P. P. J. Delheij,
C. M. Frankle,
C. R. Gould,
D. G. Haase,
J. Knudson,
G. E. Mitchell,
S. Penttilä,
N. R. Roberson,
S. J. Seestrom,
J. J. Szymansky,
S. H. Yoo,
V. W. Yuan,
X. Zhu,
TRIPLE Collaboration
[show abstract]
[hide abstract]
ABSTRACT: Parity violation effects have been studied at 40 neutron p-wave resonances of the even-even nuclei238U and232Th. Of these 11 show parity violation effects larger than 2 standard deviations, making parity violation a rather common phenomenon.
Parity mixing up to 10% has been found. The root-mean squared matrix elements for parity violation derived from these resonances
are M=0.58 (+0.50/-0.25) meV for238U, respectively 1.39 (+0.35/-0.38) meV for232Th.
Hyperfine Interactions 01/1992; 75(1):153-163. · 0.21 Impact Factor
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J.D. Bowman,
C.D. Bowman,
J. Knudson,
S. Penttilae,
S.J. Seestrom,
J.J. Szymanski,
V.W. Yuan,
J.E. Bush,
C.M. Frankle,
C.R. Gould,
D.G. Haase,
G.E Mitchell, P.P.J. Delheij,
H. Postma
[show abstract]
[hide abstract]
ABSTRACT: Parity non-conversation was studied for seventeen states in the compound nucleus {sup 239}U by measuring the helicity dependence of the p-wave resonance cross section for epithermal neutrons scattered from {sup 238}U. The root-mean-squared parity-violating matrix element for the mixing of p-wave and s-wave states was determined to be M = 0.58{sub -0.25}{sup +0.50} meV. This corresponds to a parity-violating spreading width of {Gamma}{sup PV} = 1.0 {times} 10{sup {minus}7} eV. This gives a value of 4 {times} 10{sup {minus}7} for {alpha}{sub p}, the ratio of strengths of the P-odd and P-even effective nucleon-nucleon interactions in {sup 239}U. The implications of these results for studies of Time Reversal Symmetry in the compound nucleus is discussed.
12/1989
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C. D. Bowman,
J. D. Bowman,
P. Herczeg,
J. Szymanski,
V. W. Yuan,
J. M. Anaya,
R. Mortensen,
H. Postma, P. P. J. Delheij,
O. K. Baker,
C. R. Gould,
D. G. Haase,
G. E. Mitchell,
N. R. Roberson,
X. Zhu,
A. B. McDonald,
D. Benton,
B. Tippens,
T. E. Chupp
[show abstract]
[hide abstract]
ABSTRACT: A facility for polarized epithermal neutrons of high intensity is set up at the Los Alamos National Laboratory for parityviolation
and time reversal experiments at neutron resonances over a wide range of neutron energies. The beam is polarized with the
aid of a polarized proton target used as a neutronspin filter. Total cross section measurements as well as capture gamma-ray
experiments will be carried out. The main features of this system will be discussed.
Hyperfine Interactions 11/1988; 43(1):117-126. · 0.21 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: Fundamental symmetry studies using intense polarized beams of epithermal neutrons are underway at the LANSCE facility of the Los Alamos National Laboratory. Three classes of symmetry experiments can be explored: parity violation, and time reversal invariance violation for both parity-violating and parity-conserved observables. The experimental apparatus is described and performance illustrated with examples of recent measurements. Possible improvements in the facilities and prospective experiments are discussed. 15 refs., 10 figs.
12/1987
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Frankle,
J.D. Bowman,
J.E. Bush, P.P.J. Delheij,
C. R. Gould,
D.G. Haase,
J.N. Knudson,
G.E. Mitchell,
S. Penttilä,
H. Postma,
N.R. Roberson,
S.J. Seestrom,
J.J. Szymanski,
S.H. Yoo,
V.W. Yuan,
X. Zhu
Physical Review C - Nuclear Physics.
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Frankle,
J.D. Bowman,
J.E Bush, P.P.J. Delheij,
C. R. Gould,
D.G. Haase,
J.N. Knudson,
G.E. Mitchell,
S. Penttilä,
H. Postma,
N.R. Roberson,
S.J. Seestrom,
J.J. Szymanski,
V.W. Yuan,
X. Zhu
Physical Review C - Nuclear Physics 46 (4).
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L.Y. Lowie,
J.D. Bowman,
B.E. Crawford, P.P.J. Delheij,
T. Haseyama,
J.N. Knudson,
A. Masaike,
Y Matsuda,
G.E Mitchell,
S. I. Penttila,
H. Postma,
N.R Roberson,
S.J. Seestrom,
E.I. Sharapov,
S.L. Stephenson,
Y.-F. Yen,
V.W. Yuan
Physical Review C - Nuclear Physics, 56 (1).
