Measurement of the Parity Violating Neutron Spin Rotation in 4He

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Measurement of the Parity- Violating Neutron Spin
Rotation in 4He
http//www.iucf.indiana.edu/Experiments/WEAK/spinr
ot.html

• IUCFW.M.Snow, C.D.Bass, J.M.Dawkins,
• D.Luo, A. Micherdzinska, M.
  Sarsour
• NIST H.P.Mumm, J.S.Nico
• NC State Univ P.R.Huffman, D. Haase
• TUNL D.M.Markoff
• Univ of Washington B.R.Heckel, E.Swanson
• Gettysburg College Bret Crawford

Da Luo, DNP 04
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Motivations
Compared to strong interaction, the magnitude of
weak interaction is very small.
N
N
Mesons
In Nucleon-Nucleon interactions, the weak
interaction couplings are not well understood.
DDH model (Desplanques et al, 1980) and new EFT
model(Zhu et al, 2004) 6 weak NN couplings
N
N
Holstein. Weak Interactions in Nuclei
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Expression for spin rotation in termsof weak
couplings(10-6rad/m, Dmitriev 83)sensitivity
goal rad/m
Experimental Constraints
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How Spin Rotation Works
Incoming spin along
Neutron optical phase shift due to strong and
weak interaction
Parity-odd phase shift is opposite for zgt and
-zgt
Parity-odd phase shift for length , density
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Basic Idea of the Apparatus
-coil
4He
Front
-coil
Back
4He
Parity-Violating
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Apparatus Layout
C.D.Bass
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Output Coil and Analyzer
N-N-
sin

NN-
Output coil adiabatically rotates neutron spin by
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The 4-Chamber Target
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Cryostat Layout
C.D.Bass
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Magnetic Shielding
Anna Micherdzinska
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Diamagnetism of 4He
Size of diamagnetism in 4He
For
get
This systematic effect
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4He slows down the neutron beam
Fermi potential of 4He 10neV
K of Neutron 5meV
The N velocity change
When B field is , this causes
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Small-Angle Scattering
The velocity, pathlength and travel time in
B-field all change. Different solid angle of 2
targets causes systematic
This systematic effect
simulations by Murad Sarsour
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• The previous experiment at NIST got a
  measurement consistent with zero
• New experiment at NISTSuperfluid He target,
  additional magnetic shielding (Cryoperm).
• Sensitivity goal
• Diane M. Markoff, PhD Thesis, U.Washington, 1997

Expectations
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