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Neutrons and

Neutrons and

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Neutrons and

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  1. Neutrons and Fundamental Symmetries σ Brad Plaster, University of Kentucky θp θe τ P p n e + e – T DNP 2010: Neutrinos and Fundamental Symmetries Santa Fe November 2, 2010 B. Plaster 1

  2. Tool:Neutrons 7 m/s thermal ~350 neV ~50 μeV ~25 meV ~500 keV Kinetic Energy very cold cold epithermal fast ultracold UCN “turbine”, “superthermal” source cold moderation R. Golub and J.M. Pendlebury, PLA 53, 133 (1975) R. Golub and J.M. Pendlebury, PLA 62, 337 (1977) C.L. Morris et al., PRL 89, 272501 (2002) F. Atchinson et al., PRL 95, 182502 (2005) C.M. Lavelle et al., PRC 82, 015502 (2010) B. Plaster 2

  3. Physics: Fundamental symmetries T  CP P β-decay : gA, τn, Vud Neutron EDM Physics Beyond SM Robust Consistency Test of SM Baryon Asymmetry NN weak interaction β-decay ΔB n-n : ΔB = 2, ΔL = 0 Bias : Recent, Near-Term U.S.-Experiments Physics Beyond SM B. Plaster 3

  4. Neutron β-decay σ Precise measurements probe the extent to which the weak interaction description is complete and consistent θp θe p n e Lifetime Correlation Coefficients e gA , gV GF , Vud gA , gV consistent ? consistent ? Robust test of consistency of Standard Model B. Plaster 4

  5. Correlation coefficients Jackson, Treiman, and Wyld, PR 106, 517 (1957) Distribution in momenta and energyfrompolarized neutrons Correlation coefficients σ e –  correlation spin neutrino asymmetry beta asymmetry θ −0.103(4) −0.1173(13) 0.983(4) e n greatest sensitivity to  =gA/gV B. Plaster 5 J.S. Nico, J. Phys. G 36, 104001 (2009)

  6. New “A” result: UCNA at LANL β-decay rate ~5 Hz (2007)  ~60 Hz (2010) • First measurement of any correlation coefficient with UCN • Nearly 100% polarization via μ∙ B interaction • Stored UCN, smaller neutron-generated backgrounds B. Plaster 6

  7. New “A” result: UCNA at LANL UCNA Proof-of-Principle Pre-UCNA R.W. Pattie et al., PRL 102, 012301 (2009) Expt’s ΔA/A [%] PERKEO II 0.6 ILL-TPC 1.3 IAE-PNPI 1.2 PDG Average 1.1 PERKEO I 1.7 PERKEO II: H. Abele et al., PRL 88, 211801 (2002) UCNA New Result −0.1189 ± 0.0008 J. Liu et al., arXiv: 1007.3790 [in press, PRL] UCNA: + 0.00123 Invited Talk: J. Liu, Thurs, FA.00003 −0.11966 ± 0.00089 − 0.00140 B. Plaster 7

  8. Comparison of “A” experiments Systematic Corrections [ % ] Polarization / Spin-Flip Backgrounds Others PERKEO I (1986) 2.6 ~ 3 ~13 magnetic mirroring ILL (1997) 2.9 ~ 3 ~15  cos θ  PNPI (1997) 23 small ~3  cosθ  PERKEO II (2002) 1.4 0.5 ~0.1  cosθ  UCNA (New) 0.0 0.015 ~0.5 – ~1.0 backscattering + cosθ B. Plaster 8

  9. “a”: aCORN at NCNR Figures courtesy of F. Wietfeldt Current PDG Precision: 3.9% Novel aCORN Concept : “Classic Technique” Recoil Energy [keV] aSPECT (ILL): Retardation Spectrometer Yerozolimsky and Mostovoy (1993, 1994) B. Plaster 9 F.E. Wietfeldt et al., NIM A 545, 181 (2005)

  10. “a”: aCORN at NCNR Figures courtesy of F. Wietfeldt  1% (aCORN & aSPECT) : aCORN Status: • Competitive value for gA • Currently running on NG-6, < 4% on “a” by April 2011 • Coupling constants in recoil-order ~2x those in “A” (weak magnetism, SCC) • 2012, move to high-flux NG-C, < 1% on “a” S. Gardner and C. Zhang, PRL 86, 5666 (2001) B. Plaster 10

  11. β-decay new physics constraints PDG Values: 0.0050 ± 0.0052 SM: Left-handed S and T currents G. Konrad, W. Heil, S. Baeβler, D. Pocanic, and F. Gluck, arXiv:1007.3027 Current: a, A, B Future: a, b, A, B, C B. Plaster 11

  12. β-decay new physics constraints Right-handed S and T currents G. Konrad, W. Heil, S. Baeβler, D. Pocanic, and F. Gluck, arXiv:1007.3027 Current: a, A, B Future: a, b, A, B, C Neutrino Mass Constraints: T.M. Ito and G. Prezeau, PRL 94, 161802 (2005) B. Plaster 12

  13. T- & CP-violation: Neutron EDM spin-1/2 spin-1/2 P T + – + – spin-1/2 spin-1/2 CP + + – – SM value highly suppressed NOT detectable in-flight cold neutron w/ current methods CKM: ~10−32 e-cm Positive signal = NEW physics !! free of SM backgrounds stored UCN or QCD θ-term B. Plaster 13 Pospelov and Ritz, Ann. Phys. 318, 119 (2005)

  14. EDMs and the baryon asymmetry Beyond-the-SM CP Violation ? YB = nB/s ~ 9  1011  Baryon Asymmetry of the Universe WMAP, BBN Sakharov Criteria B-Violation SM CP-violating interactions too small to generate YB C- and CP-Violation Departure from Equilibrium MSSM Baryogenesis V. Cirigliano, Y. Li, S. Profumo, and M.J. Ramsey-Musolf, JHEP 1001:002 (2010) Lower limits ? But also see : Y. Li, S. Profumo, and M.J. Ramsey-Musolf, JHEP 1008:062 (2010) B. Plaster 14

  15. B, E τB= μх B τE= d х E μ, d How to “measure” an EDM Apply an electric field, look for electric Zeeman effect ! Reverse E relative to B h = −2μB − 2dE H= −[ μ• B ± d • E ] h = −2μB + 2dE hΔ d = − 4E B. Plaster 15

  16. Challenges B = 10 mGauss dn ~ 1  1027 e-cm μ = 29.2 Hz E ~ 50 kV/cm d ~ 5  108Hz Figure-of-Merit (UCN storage) H= −[ μ• B ± d • E ] B-field must be well-known E-field large as possible number neutrons coherence time E-field-correlated B-fields B. Plaster 16

  17. Co-magnetometers B(t) monitoring crucial Typical laboratory magnetic field environment … (day vs. night) May (will !?) vary differently in different locations T. Brys et al., NIM A 554, 527 (2005) In-situ “co-magnetometer” atoms measure B-field experienced by UCN ! UCN Atoms with“no” EDM ! Subtleties: Averaging for UCN vs. co-magnetometer ? Gravitational sagging Temperature gradients “Pseudo-magnetic field” effects S.K. Lamoreaux and R. Golub, J. Phys. G 36, 104002 (2009) B. Plaster 17

  18. ILL: |dn|  2.9  1026 e-cm C.A. Baker et al., PRL 97, 131801 (2006) Ramsey’s separated oscillatory fields  Accumulated phase 199Hg co-magnetometer Room temperature experiment B. Plaster 18 Figures from: P.G. Harris, arXiv:0709.3100

  19. New “geometric phase” systematic Pendlebury et al., PRA 70, 032102 (2004) z y Bxy components from x ∂B/∂z gradients E  v motional fields B E Consider ~circular UCN orbits: False EDM  10-27 e-cm Direction of Bxy rotates ! Gradients  10-7 G/cm False EDM frequency shift: Affects UCN and Co-Magnetometer Δωn~ [∂B/∂z]  E / B2 Golub and Lamoreaux, PRA 71, 032104 (2005) B. Plaster 19 Barabanov, Golub, and Lamoreaux, PRA 74, 02115 (2006)

  20. Future neutron EDM program New intense SD2 UCN source (Fall 2010) Sussex/RAL/ILL apparatus: 300K Ramsey method Hg co-magnetometer + ext. Cs (gradient control) Operate thru 2012 Goal ~5 x 10–27 e-cm “n2EDM” concept (2012 – ) ~5 x 10–28 e-cm CryoEDM experiment UCN production in superfluid4He Cryogenic Ramsey method SQUID monitoring of B-field Goal ~3 x 10–27 e-cm, ~2013 Move to new beamline 2013/2014 As presented at Lepton Moments 2010 Symposium K. Kirch, P.G. Harris B. Plaster 20

  21. Future neutron EDM program nEDM Experiment at the SNS Superfluid4He, 3He, UCN “bath” In-situ UCN production 3He co-magnetometer “Real-time” measurement of frequency Construction/Assembly 2011 – 2016 Start Commissioning 2017 Goal 8 x 10–28 e-cm [90% C.L.] B • Simultaneous measurement of  and  in two UCN storage cells E R. Golub and S.K. Lamoreaux, Phys. Rep. 237, 1 (1994) B. Plaster 21 S.K. Lamoreaux and R. Golub, J. Phys. G 36, 104002 (2009)

  22. B, E “Real-time” frequency measurement (3He) ~ 11% greater than (n) n + 3He  p + T spin dependent UCN (n) = 29.2 Hz σ() ~ 11000 b (3He) = 32.4 Hz σ() ~ 0 3He While spins precessing N(t) 1 – |P3Pncos[(3 – n)t]| scintillation light (EUV) in the superfluid4He fit frequency in both cells B. Plaster 22

  23. n-n oscillations • Search for ΔB = 2, ΔL = 0  B-L broken by 2 units • Neutrinoless double β-decay breaks B-L by 2 units Free :  8.6 x 107 s Bound :  1.3 x 108 s In-flight n  n Transitions in nuclei Annihilation into ~5 π’s Suppression factor due to nuclear environment Fe: TR ~ 1023 s-1 M. Baldo-Ceolin et al., Z Phys C 63, 409 (1994) Soudan 2: PRD 66, 032004 (2002) R.N. Mohapatra, J. Phys. G 36, 104006 (2009) B. Plaster 23 W.M. Snow, NIM A 611, 144 (2009)

  24. n-n: Cold neutrons ILL : Flight times ~ 0.1 s DUSEL : Intensity ~ 1011 s-1 Few MW reactor, vertical shaft Running Time ~ 2.4 x 107 s Improved focusing, longer time Factor of  30 improvement B. Plaster 24 W.M. Snow, NIM A 611, 144 (2009)

  25. n-n: UCN ?? Idea would be : Longer flight times + Repeated observation g Offset lower brightness of UCN sources Flight times ~ 2v0/g ~ 1 s Observations/UCN ~ ~ 885 What could the reach be ? TRIUMF UCN source ~ 107/s [maybe 109/s with upgrades ??]  ~8 x 109 stored UCN, ~885 obsverations/UCN/cycle  With ~ 1 x 104 cycles/year  FOM ~ [8 x 109 x 885] x [1 x 104]x t2 ~ 7 x 1016 Previous ILL: FOM ~ 1018 x t2 ~ 2 x 1016 B. Plaster 25 Discussions of TRIUMF UCN numbers/potential with J. Martin

  26. Summary Fundamental symmetry tests with neutrons diverse Neutron β-decay program Recent progress on ~8 year-old disagreement in “A” values Exciting program of neutron EDM searches next 5–10 years Probe beyond-the-Standard Model CP-violation Interesting to think about reviving n-nbar search(es) B. Plaster 26

  27. Acknowledgments Thanks to all of my collaborators on the UCNA and nEDM experiments. Thanks to C. Crawford, S. Gardner, J. Martin, and F. Wietfeldt for slide contributions and interesting discussions. Funded by DOE Grant No. DE-FG02-08ER41557. B. Plaster 27

  28. Technical progress: Scintillation Work by LANL, Indiana B. Plaster

  29. W.C. Griffith et al., PRL 102, 101601 (2009)