Measurement of Parity Violation in np Capture: the NPDGamma Experiment.
The NPDGamma experiment will measure the parity-violating directional gamma ray asymmetry A γ in the reaction [Formula: see text]. Ultimately, this will constitute the first measurement in the neutron-proton system that is sensitive enough to challenge modern theories of nuclear parity violation, providing a theoretically clean determination of the weak pion-nucleon coupling. A new beam-line at the Los Alamos Neutron Science Center (LANSCE) delivers pulsed cold neutrons to the apparatus, where they are polarized by transmission through a large volume polarized (3)He spin filter and captured in a liquid para-hydrogen target. The 2.2 MeV gamma rays from the capture reaction are detected in an array of CsI(Tl) scintillators read out by vacuum photodiodes operated in current mode. We will complete commissioning of the apparatus and carry out a first measurement at LANSCE in 2004-05, which would provide a statistics-limited result for A γ accurate to a standard uncertainty of ±5 × 10(-8) level or better, improving on existing measurements in the neutron-proton system by a factor of 4. Plans to move the experiment to a reactor facility, where the greater flux would enable us to make a measurement with a standard uncertainty of ±1 × 10(-8), are actively being pursued for the longer term.
University of Manitoba, Winnipeg, MB Canada R3T 2N2.
Shelley A
SA
Page
Los Alamos National Laboratory, Los Alamos, NM 87545.
J D
JD
Bowman
Thomas Jefferson National Accelerator Facility, Newport News VA 23606.
R D
RD
Carlini
University of California, Berkeley, CA 94720-7300.
T
T
Case
University of Michigan, Ann Arbor, MI 48109-1120.
T E
TE
Chupp
University of Michigan, Ann Arbor, MI 48109-1120.
K P
KP
Coulter
University of New Hampshire, Durham, NH 03824.
M
M
Dabaghyan
University of Tennessee, Knoxville, TN 37996-1200.
D
D
Desai
University of California, Berkeley, CA 94720-7300.
S J
SJ
Freedman
National Institute of Standards and Technology, Gaithersburg, MD 20899-0001.
T R
TR
Gentile
Los Alamos National Laboratory, Los Alamos, NM 87545.
M T
MT
Gericke
University of Manitoba, Winnipeg, MB Canada R3T 2N2.
R C
RC
Gillis
University of Tennessee, Knoxville, TN 37996-1200.
G L
GL
Greene
University of New Hampshire, Durham, NH 03824.
F W
FW
Hersman
KEK National Laboratory, Tsukuba, Ibaraki 305-0801 Japan.
T
T
Ino
KEK National Laboratory, Tsukuba, Ibaraki 305-0801 Japan.
S
S
Ishimoto
Hamilton College, Clinton, NY 13323.
G L
GL
Jones
University of California, Berkeley, CA 94720-7300.
B
B
Lauss
Indiana University Cyclotron Facility, Bloomington, IN 47408-1398.
M B
MB
Leuschner
Indiana University Cyclotron Facility, Bloomington, IN 47408-1398.
B
B
Losowski
University of Tennessee, Knoxville, TN 37996-1200.
R
R
Mahurin
KEK National Laboratory, Tsukuba, Ibaraki 305-0801 Japan.
Y
Y
Masuda
Los Alamos National Laboratory, Los Alamos, NM 87545.
G S
GS
Mitchell
Indiana University Cyclotron Facility, Bloomington, IN 47408-1398.
H
H
Nann
Los Alamos National Laboratory, Los Alamos, NM 87545.
S I
SI
Penttila
University of Manitoba, Winnipeg, MB Canada R3T 2N2.
W D
WD
Ramsay
Indiana University Cyclotron Facility, Bloomington, IN 47408-1398.
S
S
Santra
Los Alamos National Laboratory, Los Alamos, NM 87545.
P-N
PN
Seo
Joint Institute for Nuclear Research, Dubna, Russia.
E I
EI
Sharapov
University of Dayton, Dayton OH 45469-1679.
T B
TB
Smith
Indiana University Cyclotron Facility, Bloomington, IN 47408-1398.
W M
WM
Snow
Los Alamos National Laboratory, Los Alamos, NM 87545.
W S
WS
Wilburn
Los Alamos National Laboratory, Los Alamos, NM 87545.
V
V
Yuan
University of New Hampshire, Durham, NH 03824.
H
H
Zhu
hadronic weak interaction; neutron capture; parity violation