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The nEDM Experiment at the SNS

The nEDM Experiment at the SNS. Christopher Crawford University of Kentucky for the nEDM Collaboration 77th Annual Meeting of the Southeastern Section of the APS, Baton Rouge, LA 2010-10-23. Outline. Introduction to neutron physics and the SNS EDM properties – scientific motivation

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The nEDM Experiment at the SNS

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  1. The nEDM Experiment at the SNS Christopher Crawford University of Kentucky for the nEDM Collaboration 77th Annual Meeting of the Southeastern Section of the APS, Baton Rouge, LA 2010-10-23

  2. Outline • Introduction to neutron physics and the SNS • EDM properties – scientific motivation • Separated oscillatory fields – ILL experiment • Properties of He – new technique • Experimental setup – expected results

  3. Properties of the Neutron spin 1/2 isospin 1/2 • mn = mp + me + 782 keV • n = 885.7 ± 0.8 s • qn < 2 x 10-21 e • dn < 3 x 10-26 e cm • n= -1.91 N • rm = 0.889 fm • re2 = -0.116 fm2 • 3 valence quarks + sea • exponential magnetization distribution • pion cloud: p n up down uud udd Radial charge distribution – data including BLAST

  4. g 3m Cold and Ultra-Cold Neutrons (UCN) • Cold neutrons: λ ~ 2 – 20 Å • glancing reflections along guides • UCN slow enough to be completely reflected by 58Ni optical potential kinetic: 8 m/s thermal: 4 mK wavelength: 50 nm nuclear: 335 neV (58Ni) magnetic: 60 neV (1 T) gravity: 102 neV (1 m)

  5. Neutron Spin A Electron B Neutrino C Proton d (or t) p (or d) n γ What can we do with neutrons? • Scattering / Bragg diffraction • Complementary to X-ray diffraction • Neutron interferometry • Fundamental symmetry tests of the standard model • Neutron decay lifetime and correlations • PV: NPDGamma, 4He spin rotation • T reversal: electric dipole moment nEDM

  6. Spallation Neutron Source (SNS) Oak Ridge National Laboratory, Tennessee • spallation sources: LANL, SNS • pulsed -> TOF -> energy • LH2 moderator: cold neutrons • thermal equilibrium in ~30 interactions

  7. Spallation Neutron Source (SNS) • spallation sources: LANL, SNS • pulsed -> TOF -> energy • LH2 moderator: cold neutrons • thermal equilibrium in ~30 interactions

  8. Beamline 13 allocated for nuclear physics 7 - Engineering Diffractometer IDT CFI Funded Commission 2008 11A - Powder Diffractometer Commission 2007 9 – VISION 6 - SANS Commission 2007 12 - Single Crystal Diffractometer Commission 2009 5 - Cold Neutron Chopper Spectrometer Commission 2007 13 - Fundamental Physics Beamline Commission 2007 4B - Liquids Reflectometer Commission 2006 14B - Hybrid Spectrometer Commission 2011 4A - Magnetism Reflectometer Commission 2006 15 – Spin Echo 3 - High Pressure Diffractometer Commission 2008 17 - High Resolution Chopper Spectrometer Commission 2008 18 - Wide Angle Chopper Spectrometer Commission 2007 1B - Disordered Mat’ls Commission 2010 2 - Backscattering Spectrometer Commission 2006

  9. SNS Fundamental Neutron Physics Beamline (FNPB) • Experiments • expected to run • Cold neutron beamline • Hadronic PV interaction • b decay correlation • Neutron lifetime • UCN beamline • Neutron EDM

  10. Cold Neutron Beamline – NPDGamma expt.

  11. FnPB neutron flux vs. MC simulation shifted slightly toward longer wavelengths ~ λ-5 2.1 x 1011 neutrons/sat full power (1.4 MW)

  12. + + + - - - Electric Dipole Moment • EDM is a P and T (therefore CP) violating quantity • Standard model value: dn~ 10-32 – 10-31e·cm (Small! Ideal probe for new Physics) • Present limit: dn < 2.8x10-26e·cm (PRL 97, 131801 (2006)) P reversal T reversal

  13. Evolution of EDM Experiments J.M. Pendlebury and E.A. Hinds, NIM A 440, 471 (2000)

  14. W W fL e+i e-i fL f’ SUSY Standard Model CP violation and New Physics • In SM, quark EDM is zero to first order in GF (one loop), and is also zero at the two-loop level (cancellation among diagrams). dn~ 10-32 – 10-31e·cm • Many extension of SM predict an extra set of particles and CP violating phases (eg SUSY, LR symmetric model) • These models predict substantially larger EDMs than SM • Neutron EDM is a very sensitive probe for new sources of CP violation

  15. Cosmic ray contains consistent with secondary production by protons Matter-antimatter symmetry would imply both BBN and CMB anisotropy find: Sakharov conditions: B violating interactions CP and P violation Departure from thermal equilibrium Baryon Asymmetry of the Universe

  16. EDM and CP Violation in QCD • QDC Langrangian can in principle has a P- and T-violating term • The  term can generate a neutron EDM • The current neutron EDM limit gives • One proposed remedy, Peccei-Quinn symmetry, predicts axions. However, axions have not been observed. Strong CP problem

  17. B E n Principle of the Measurement For B ~ 10mG n = 30 Hz For E = 50 kV/cm and dn= 10-28 e·cm Dn= 5 nHz (precesses every 6.5 yr) (corresponds to a change in magnetic field of 2 x10-12 gauss)

  18. Ramsey’s method of separated oscillatory fields — “Traditional” method for nEDM Initial state p/2 pulse Free precession Second p/2 pulse Spin flip oscillator frequency Z component of nuclear spin B field J.H.Smith, E.M.Purcell, and N.F.Ramsey, Phys. Rev. 108, 120 (1957) Spin flip is most efficient when the spin arrives at the 2nd coil with the right phase, i.e. the phase advance of spin rotation is the same as the RF phase advance. Frequency difference between spin flip field and spin’s Larmor precession makes the 2nd pulse be out of phase with the 1st. Slide courtesy of A. Esler and Sussex Neutron EDM group (ILL)

  19. ILL Measurement • Precession measurement: • Ramsey’s separated oscillatory field magnetic resonance method • Magnetometry: • Mercury co-magnetometer • Neutron source: • Ultra-Cold Neutrons from ILL reactor, Grenoble, France • Selected parameters: • E=4.5kV/cm • Tstorage = 130s • N=15000 • Results • dn< 2.8x10-26 ecm (90%CL) P.G. Harris et al., RPL 82, 904 (1999) C. A. Baker et al., PRL 97, 131801 (2006)

  20. 199Hg Co-Magnetometer • Co-magnetometer: • Magnetometer that occupies the same volume over the same precession time interval as the species on which an EDM is sought

  21. Systematic effects due to the interaction of the vE field with B field gradients Particle following roughly circular orbit with orbital frequency r Radial gradient After averaging over rotational direction Need • Pendlebury et al PRA 70 032102 (2004) • Lamoreaux and Golub PRA 71, 032104 (2005) • Barabanov, Golub, Lamoreaux, PRA 74, 052115 (2006) Bv = v x E field changes sign with direction

  22. EDM Experiment at SNS • General strategy: perform experiment in superfluid liquid 4He • Produce UCN in measurement cell via superthermal process • Use polarized 3He as comagnetometer • Use 3He-n interaction as spin precession analyzer • Figure of merit: • Expected gain over the ILL measurement A 2 orders of magnitude overall gain in sensitivity is expected R.Golub and S.K.Lamoreaux Phys. Rep. 237, 1 (1994)

  23. Superthermal Production of UCN R.Golub and J.M.Pendlebury, Phys.Lett.A 62,337,(77) • Expect a production of ~ 0.3 UCN/cc/s • With a 500 second lifetime, UCN~150/cc and NUCN~1.2x106 for an 8 liter volume • 8.9 Å cold neutrons get • down-scattered in superfluid 4He • by exciting elementary excitation • Up-scattering process is • suppressed by a large • Boltzman factor • No nuclear absorption

  24. 3He as comagnetometer A dilute admixture of polarized 3He atoms is introduced to the bath of SF 4He (x = N3/N4 ~ 10-10 or 3He ~ 1012/cc)  B Neutron n~29 Hz 3He 3~32 Hz Measurement cell filled with SF 4He Pickup coils Change in magnetic field due to the rotating magnetization of 3He by SQUID magnetometers

  25. 3He + n  t + p + 760 keV p + n + n n n p p p 3He as spin analyzer / 4He as a Detector J=0 = 5333 b /0 J=1¼ 0 • 3He-n reaction cross section • 3He-UCN reaction rate • Detect Scintillation light from the reaction products traveling in LHe • Convert EUV light to blue light using wavelength shifter • Detect the blue light with PMTs • Signature of EDM would appear as a shift in 3-n corresponding to the reversal of E with respect to B with nochange in 3 4He superfluid filled measurement cell made of acrylic and coated with wavelength shifter

  26. Critical properties of liquid helium p + n + n n n p p p • 4He dispersion curve • 8.9 Å down-scatter to UCNs by emitting phonon • 3He spin 90% from unpaired neutron3He EDM ~0 by Schiff theorem • effective comagnetometer • n + 3He -> p + t + 760 keV • spin-precession analyzer • 4He is an effective scintillator • 4He dielectric constant – HV • 4He is a superfluid (T < 1.7 K) • heat flush purification

  27. B Brf = Brf cos(rf t)e Alternative approach Dressed spin technique • By applying a strong non-resonant RF field, the gyromagnetic ratios can be modified or “dressed” • For a particular value of the dressing field, the neutron and 3He magnetic moments can be made equal (n’=3’) • Can tune the dressing parameter until the relative precession is zero. • Measure this parameter vs. direction of E Brf = 1 gauss, rf = 2x 3 kHz

  28. 6a 7 1b 1a 2 3 5 4 6b 3He System Polarized 3He Collection System Purifiers 3He Atomic Beam Source (ABS) ABS Shutter Purifier isolation Valves Collection Isolation Valve Cell isolation valve Measurement Cell Pressurizer Standoff Valve Measurement Cell Purifier Control Valve Volume Displacement Pressurizer Isolation Valve Pressurizer

  29. T = 1100 - 1110 s p/2 pulse T = 0 - 100 s Fill 4He with 3He Fill Lines n 3He 3He T = 100 - 1100 s UCN from Cold n T = 1110 - 1610 s Precession about E & B Refrigerator L He L He L He L He XUV g Light to PMT Phonon t n 3He XUV g Light to PMT p Deuterated TPB on Walls SQUID E , B E , B E , B E , B E , B T = 1610 - 1710 s Remove 3He 8.9 Å neutrons UCN l ~ 500 Å Emptying Lines r(UCN)=Pt Experiment Cycle

  30. EDM Experiment SchematicVertical Section View 3He Polarized Source Dilution Refrigerator (DR: 1 of 2) Upper Cryostat Services Port Central LHe Volume (300mK, ~1000 Liters) Upper Cryostat DR LHe Volume 450 Liters Re-entrant Insert for Neutron Guide 5.6m 3He Injection Volume Lower Cryostat 4 Layer μ-metal Shield

  31. Magnets and Magnetic Shielding r = 37 cm r = 48 cm r = 65 cm r = 62 cm r = 61 cm B0 field direction Not shown: p/2 spin-flip coil and gradient coils

  32. Lower Cryostat Cutaway View PMTs Gain capacitor Light guides Measurement cells Electrodes Cold neutron beam

  33. Application: new method of designing magnetic coils (from the inside out) Magnetostatic calculation with COMSOL red - transverse field lines blue - end-cap windings • Standard iterative method:Create coils and simulate field. • New technique: start with boundary conditions of the desired B-field, and calculate the winding configuration • Use scalar magnetic potential (currents only on boundaries) • Simulate intermediate region using FEA with Neumann boundary conditions (Hn) • Windings are traced along evenly spaced equipotential lines along the boundary

  34. R&D – nearing completion

  35. Summary • The nEDM is sensitive to new sources of CP-violation • Physics beyond the standard model • To explain the Baryon Asymmetry in the Universe • The SNS experiment based on new concept of measuring the nEDM directly in liquid 4He doped with polarized 3He. • Systematic sensitivity: 3 x 10-28 e cm (limited by geometric phase) • Statistical sensitivity: 8 x 10-28 e cm (prospect of 4.5 x higher flux) • The collaboration is nearing completion of R&D. • CD2 review early next year • Begin operation ~2017

  36. R. Alarcon, S. Balascuta, L. Baron-Palos Arizona State University, Tempe, AZ, USA D. Budker, B. Park University of California at Berkeley, Berkeley, CA 94720, USA G. Seidel Brown University, Providence, RI 02912, USA E. Hazen, A. Kolarkar, V. Logashenko, J. Miller, L. Roberts Boston University, Boston, MA 02215, USA A. Perez-Galvan, J. Boissevain, R. Carr, B. Filippone, M. Mendenhall, R. Schmid California Institute of Technology, Pasadena, CA 91125, USA M. Ahmed, M. Busch, W. Chen, H. Gao, X. Qian, Q. Ye, W.Z. Zheng, X. F. Zhu, X. Zong Duke University, Durham NC 27708, USA F. Mezei Hahn-Meitner Institut, D-14109 Berlin, Germany C.-Y. Liu, J. Long, H.-O. Meyer, M. Snow Indiana University, Bloomington, IN 47405, USA L. Bartoszek, D. Beck, P. Chu, C. Daurer, A. Esler, J.-C. Peng, S. Williamson, J. Yoder University of Illinois, Urbana-Champaign, IL 61801, USA C. Crawford, T. Gorringe, W. Korsch, B. Plaster, H. Yan University of Kentucky, Lexington KY 40506, USA E. Beise, H. Breuer, T. Langford University of Maryland, College Park, MD 20742, USA P. Barnes, S. Clayton, M. Cooper, M. Espy, R. Hennings- Yeomans, T. Ito, M. Makela, A. Matlachov, E. Olivas, J. Ramsey, I. Savukov, W. Sondheim, S. Tajima, J. Torgerson, P. Volegov, S. Wilburn Los Alamos National Laboratory, Los Alamos, NM 87545, USA K. Dow, D. Hassel, E. Ihloff, J. Kelsey, R. Milner, R. Redwine, J. Steele, E. Tsentalovich, C. Vidal Massachusetts Institute of Technology, Cambridge, MA 02139, USA J. Dunne, D. Dutta, E. Leggett Mississippi State University, Starkville, MS 39762, USA F. Dubose, R. Golub, C. Gould, D. Haase, P. Huffman, E. Korobkina, C. Swank, A. Young North Carolina State University, Raleigh, NC 27695, USA R. Allen, V. Cianciolo, S. Penttila Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA M. Hayden Simon-Fraser University, Burnaby, BC, Canada V5A 1S6 N. Fomin, G. Greene University of Tennessee, Knoxville, TN 37996, USA S. Stanislaus Valparaiso University, Valparaiso, IN 46383, USA S. Baessler University of Virgina, Charlottesville, VA 22902, USA S. Lamoreaux, D. McKinsey, A. Sushkov Yale University, New Haven, CT 06520, USA EDM Collaboration

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