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The NPD  Experiment David Bowman

The NPDγ Experiment aims to explore the intricacies of hadronic weak interactions and their impact on nuclear forces. Through the collaboration of multiple institutions including JLab, KEK, and LANL, the project focuses on measuring parity-violating admixtures in nuclear wave functions with an unprecedented accuracy of ±0.5 x 10^-7. The updated status indicates that production phases are progressing, and rigorous tests of the apparatus have shown effective performance. This research strives not only to enhance understanding of fundamental particle interactions but also to inform future nuclear physics endeavors.

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The NPD  Experiment David Bowman

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  1. The NPD ExperimentDavid Bowman I Scientific goals II Status

  2. NPD Collaboration • Institutions • Dayton, Dubna, Hamilton, Indiana, Jlab, KEK, LANL, NIST, ORNL, TRIUMF, Berkeley, Manitoba, Michigan, New Hampshire, Tennessee • Sponsors • DoE, NSF, NSERC, LANL, collaborating institutions

  3. Scientific goal of the experiment

  4. Hadronic weak interaction • Weak NN force interferes with the strong NN force. • Changes parity of the NN pair. • Changes INN by 0, 1, or 2. • Produces parity-violating admixtures in nuclear wave functions and PV asymmetries • HWI is described by a meson exchange potential

  5. The value of is controversial • 18F gamma circular polarization experiments give 0. Haxton interprets result to give =0±1.0 10-7. • 133Cs anapole moment gives non-zero value. Flambaum interprets result to give =7±3 10-7. • The goal of the NPDg experiment is to measure with an accuracy of 0.5 10-7. • Goal error is 5% of the DDH reasonable range.

  6. Status of NPD experiment • 04-5 commissioning run complete • 06 production at LANSCE • Measure A to ±10-7 • Move to SNS in 06-7 • Measure A to ±10-8

  7. Apparatus to measure A

  8. Neutron Intensity Monitors

  9. 3He neutron polarizer

  10. Determine 3He polarization • Stable operation for several weeks • 3He polarization = 46±2%

  11. Commissioning the RFSR FP12 neutron guide RF Spin Rotator M2 M1 3He Spin Filter

  12. Preliminary Spin-flipper efficiency

  13. Liquid Para-Hydrogen Target • 20 liter liquid volume, 30 cm diameter • and 30 cm long • Absorbs 65% of neutron beam • 1% neutron depolarized at 17K (0.05% of • LH2 in ortho-state) due to large scattering • cross section • No false asymmetriesfrom target material • Use 6Li to shield CsI from neutrons Ortho (total) Para (total) Capture cross section

  14. CsI detector 48 (15cm)3 modules

  15. noise/counting statistics • Electronic noise << counting statistics • Experiment operates close to counting statistics limit

  16. Electronic asymmetries(beam off) • Time to determine electronic asymmetries << run time • False asymmetries are  10-8

  17. Measured asymmetries • Time to determine background asymmetries << run time • False asymmetries ~ asymmetry  f-bkg are  5 10-8

  18. Spin interactions

  19. Estimated sizes of false asymmetries

  20. Apparatus performance • All components of the apparatus performed as designed • Several physics measurements have been

  21. LH target must be finished, tested, and installed • We request a thorough-going safety review to insure a safe target.

  22. Beam time request • The estimate is based on measured performance • 3He polarization = .55 • Cell diameter = 10 cm • Projected FPNB projected intensity • 7000 MWh for data and systematics • 1000 h at > ,14 MW for tuning and systematics

  23. Schedule • We request that NPD run after the beam line is commissioned • 9/06 Move to SNS • 9/07 Beam line ready • 12/07 Experiment installed • 3/08 Commissioning complete • 6/08 Start production

  24. Geoff’s questions • Technical issues - hydrogen target • Funding $K 2500 already spent for apparatus at LANL • 20 transport to SNS • 160 shielding • 20 supports and stands • 20 Air conditioning • 130 target infrastructure • 30 instrumentation/cabling • Safety - hydrogen target • Complex installation - one block • ~ 40 users • 3 PhD’s to date, trained several undergraduate students, Expect several PhD’s from SNS run

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