Process Characterization: Lifetime of Magnetically Trapped
Ultra Cold Neutrons
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Introduction
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In collaboration with a team from the Ionizing
Radiation Division of NIST, Harvard, Los Alamos and Berlin, SED
staff played a major role in the stochastic modeling, planning
and analysis associated with a highly acclaimed neutron lifetime
experiment. In this experiment, for the first time, ultra cold
neutrons were produced and confined in a magnetic trap. Since
systematic errors are much lower than in alternative approaches,
a planned second generation version of the experiment should
yield a neutron lifetime estimate more accurate
than the currently accepted best value. Since knowledge of the
mean lifetime of the neutron allows one to test the consistency
of the standard model of electroweak interactions, the experiment
is of great fundamental importance. Further, the mean lifetime
of the neutron is an important parameter in astrophysical
theories which predict the evolution of the early universe after
the Big Bang. Thus, SED has made a major contribution to
fundamental physics and measurement science.
Background/Impetus
Customers
Goals
Impact
SED Milestones
R&D Team
Achievements
Publications
Presentations
Additional technical information on this project is available at:
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Background/
Impetus
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A high precision measurement of the neutron lifetime yields a test
of the consistency of the standard model of electro-weak
interactions. Also, the mean lifetime of the neutron is an
important parameter in astrophysical models. Ultra low temperature
confinement technology will facilitate a new generation of
fundamental
physics experiments.
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Customers
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The customers for the neutron lifetime project are the
scientific community.
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Goals
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The goals for the neutron lifetime project are:
- Develop technology to confine polarized ultra cold neutrons
in a magnetic trap.
- Determine the mean lifetime of the neutron to high precision.
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Impact
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The impact of this work is that it leads to a dramatic reduction
in systematic error in neutron lifetime estimate compared to
previous experiments. It also tests the standard model of
radioactive decay, refines the predictions of Big Bang
Nucleosynthesis theory predictions, and develops new technology
for trapping polarized neutrons.
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Milestones for the neutron lifetime project are:
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FY03 Milestones
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- Design and analyze third generation experiment (dependent
on funding).
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FY02 Milestones
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- Perform the analysis of data from second generation
experiment.
- Complete the manuscript on systematic error in lifetime
estimate due to imperfect background correction.
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FY01 Milestones
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- Compare performance of various neutron lifetime estimation
algorithms which account for background.
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FY00 Milestones
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- Develop statistical plan to select best way to redesign
the experimental apparatus for second generation experiment.
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FY99 Milestones
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- Develop likelihood models for observed data and compare
performance of neutron lifetime estimation algorithms for
first generation planning study.
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FY98 Milestones
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- Development optimal data collection strategy for
background correction planning study.
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FY97 Milestones
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- Construct stochastic model of neutron trapping
process and experimental data.
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FY98 Milestones
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- Development optimal data collection strategy for
background correction planning study.
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R&D Team
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Kevin
Coakley, Statistical Engineering Division, ITL
P. R. Huffman, Ionizing Radiation Division, PL
M. S. Dewey, Ionizing Radiation Division, PL
J. Doyle, Harvard University
G. L. Greene, Los Alamos National Laboratory
S. K. Lamoreaux, Los Alamos National Laboratory
R. Golub, Hahn-Meitner Institut, Berlin
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Achievements
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Achievements of the neutron lifetime project include:
- Experimental design of second generation experiment (now
running).
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Publications
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Publications resulting from the neutron lifetime project
include:
- K. J. Coakley and G. L. Yang, "Estimation of the Neutron
Lifetime: Comparison of Methods which Account for
Background," submitted to Physical Review C.
- C. R. Brome, J. S. Butterworth, K. J. Coakley, M. S. Dewey,
S. N. Dzhosyuk, R. Golub, G. L. Greene, K. Habicht,
P. R. Huffman, S. K. Lamoreaux, C. E. H. Mattoni,
D. N. McKinsey, F. E. Wietfeldt, and J. M. Doyle,
"Magnetic Trapping of Ultracold Neutrons," Physical
Review C, 63, 055502, 1-15 (2001).
- K. J. Coakley, "Optimal Background Correction Schemes for
Neutron Lifetime Experiments Using Magnetically Trapped
Neutrons," Nuclear Instruments and Methods in Physics
Research A, 469, 454-363 (2001).
- G. Yang and K. J. Coakley, "Likelihood Models for Two-Stage
Neutron Lifetime Experiments," Physical Review C,
63, 014602 (2001).
- P. R. Huffman, A. K. Thompson, F. E. Wietfeldt, G. L. Yang,
K. J. Alvine, C. R. Brome, S. N. Dzhosyuk, C. E. H. Mattoni,
R. A. Michniak, D. N. McKinsey, L. Yang, J. M. Doyle,
R. Golub, S. K. Lamoreaux, and K. J. Coakley, "Magnetic
Trapping of Ultracold Neutrons: Prospects for an Improved
Measurement of the Neutron Lifetime," Proceedings of the
Conference on Fundamental Physics with Pulsed Neutron
Beams (2000).
- P. R. Huffman, C. R. Brome, J. S. Butterworth, K. J. Coakley,
M. S. Dewey, S. N. Dzhosyuk, D. M. Gilliam, R. Golub,
G. L. Greene, K. Habicht, S. K. Lamoreaux, C. E. Mattoni,
D. N. McKinsey, F. E. Wietfeldt, and J. M. Doyle, "Progress
Towards Magnetic Trapping of Ultracold Neutrons," Nuclear
Instruments and Methods A, 440, 522-527 (2000).
- P. R. Huffman, C. R. Brome, J. S. Butterworth, K. J. Coakley,
M. S. Dewey, S. N. Dzhosyuk, R. Golub, G. L. Greene,
K. Habicht, S. K. Lamoreaux, C. E. Mattoni, D. N. McKinsey,
F. E. Wietfeldt, and J. M. Doyle, "Magnetic Trapping of
Ultracold Neutrons," Nature, 403, 62-64 (2000).
- C. R. Brome, J. S. Butterworth, K. J. Coakley, M. S. Dewey,
S. N. Dzhosyuk, D. M. Gilliam, R.Golub, G. L. Greene, K. Habicht,
P. R. Huffman, S. K. Lamoreaux, C. E. Mattoni, D. N. McKinsey,
F. E. Wietfeldt, and J. M. Doyle, "Magnetic Trapping of Ultracold
Neutrons," Bulletin of the American Physical Society,
44, 16 (1999). Abstract
- P. R. Huffman, K. J. Coakley, M. S. Dewey, D. M. Gilliam,
G. L. Jones, F. E. Wietfeldt, J. S. Butterworth,
S. N. Dzhosyuk, C. E. H. Mattoni, D. N. McKinsey, J. M. Doyle,
R. Golub, K. Habicht, M. D. Cooper, G. L. Greene, and
S. K. Lamoreaux, "Progress Towards Magnetic Trapping of
Ultracold Neutrons," 1999 Sigma Xi poster session,
NIST, Gaithersburg, MD (1999). Abstract
- C. R. Brome, J. S. Butterworth, S. N. Dzhosyuk, P. R. Huffman,
C. E. H. Mattoni, D. N. McKinsey, J. M. Doyle, K. J. Coakley,
M. S. Dewey, D. M. Gilliam, G. L. Jones, F. E. Wietfeldt,
R. Golub, K. Habicht, M. D. Cooper, G. L. Greene, and
S. K. Lamoreaux, "Progress Towards Magnetic Trapping of
Ultracold Neutrons," Bulletin of the American Physical
Society, 44, 989 (1999). Abstract
- K. J. Coakley, "Statistical Planning for a Neutron Lifetime
Experiment Using Magnetically Trapped Neutrons," Nuclear
Instruments and Methods in Physics Research A, 406,
pp. 451-463 (1998).
- J. S. Butterworth, C. R. Brome, P. R. Huffman,
C. E. H. Mattoni, D. N. McKinsey, J. M. Doyle, K. J. Coakley,
M. S. Dewey, D. M. Gilliam, F. Wietfeldt, G. L. Greene,
S. K. Lamoreaux, R. Golub, and K. Habicht, "Magnetic Trapping
of Ultra-Cold Neutrons," Bulletin of the American Physical
Society, 42, 1628 (1997). Abstract
- P. R. Huffman, C. R. Brome, J. S. Butterworth,
C. E. H. Mattoni, D. N. McKinsey, J. M. Doyle, M. S. Dewey,
K. J. Coakley, D. M. Gilliam, R. Golub, K. Habicht,
S. K. Lamoreaux, and G. L. Greene, "Determination of the
Neutron Lifetime Using Magnetically Trapped Neutrons,"
Bulletin of the American Physical Society, 42,
938 (1997). Abstract
- J. S. Butterworth, C. R. Brome, P. R. Huffman,
C. E. H. Mattoni, D. N. McKinsey, J. M. Doyle, M. S. Dewey,
K. J. Coakley, D. M. Gilliam, R. Golub, K. Habicht, and
S. K. Lamoreaux, "Determination of the Neutron Lifetime
Using Magnetically Trapped Neutrons," Bulletin of the
American Physical Society, 41, 1217 (1996). Abstract
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Presentations
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Presentations resulting from the neutron lifetime project include:
- K. C. Coakley, "Optimal Background Correction Strategies for
a Neutron Lifetime Experiment," presented at technical
collaboration meeting at NIST Center for Cold Neutron
Research, Gaithersburg, MD, September 1999.
- K. C. Coakley, "Statistical Planning for a Neutron Lifetime
Experiment," 1997 Joint Meetings of the American Statistical
Association and the Institute of Mathematical Statistics,
Anaheim, CA, August 1997. (Also at NIST, Boulder, CO,
April 1997.)
- K. C. Coakley, "Optimal Design of a Neutron Lifetime
Experiment and Chaotic Behavior of Magnetically Trapped
Neutrons," presented at technical collaboration meeting at
Physics Department, Harvard University, September 1996.
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Date created: 2/6/2002
Last updated: 2/6/2002
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sedwww@nist.gov.
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