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The Neutron Beta-Decay Exploring the properties of fundamental interactions

The Neutron Beta-Decay Exploring the properties of fundamental interactions. A,B,C,D ,… t. The Neutron Alphabet. Hartmut Abele Bar Harbor. 1. Standard Model and Neutron Decay. Neutron -decay lifetime  ~ 15 min -endpoint: E max = 782 keV

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The Neutron Beta-Decay Exploring the properties of fundamental interactions

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  1. The Neutron Beta-Decay Exploring the properties of fundamental interactions A,B,C,D,…t The Neutron Alphabet Hartmut Abele Bar Harbor

  2. 1. Standard Model and Neutron Decay Neutron -decay • lifetime  ~ 15 min • -endpoint: Emax = 782 keV V-A Theory: Vector coupling: gV = GF Vudf1(q2→0) Axial vector coupling: gA = GF Vud g1(q2→0) • ratio  = gA/ gV = -1.276 • Standard Model: Vud, 

  3. The Neutron Alphabet, Observables A: P-odd Dr. Mund (2007) B: P-odd Schumann et al., PRL 99, 191803 (2007) C: P-odd Schumann et al., PRL 100, 151801 (2008) a Stratowa et al. (1975) D: T-odd TRINE, emiT G A. Kozela et al., PRL 102, 172301 (2009) N A. Kozela et al., PRL 102, 172301 (2009) R: T-odd A. Kozela et al., PRL 102, 172301 (2009)  A Neutron Spin  Electron B Neutrino C Proton a D R N see review: The neutron. Its properties and basic interactions, Prog. Part. Nucl. Phys. 60 (2008) 1-81

  4. Neutrons alphabetize the Standard Model • a or A  = gA/ gV

  5. aSPECT, correlation a, University Mz/TUM/ILL Proton spectroscopy

  6. p+ e- θ n νe Decay rate w(E) response function Ftr(E)=Ftr(E; U,BA/ B0) @ U=375V Spectrum for a = + 0.3 … for a = - 0.103 (PDG 2008) 0 200 400 600 Proton kinetic energy E [eV] UMZ, TUM, ILL: Neutron decay spectrometer aSPECT Setup at the ILL-Grenoble, 2008 Sensitivity of the proton spectrum to the neutrino electron correlation coefficient a Proton detector Magnetic field U BA Analyzing Plane Electrode … for a = - 0.103 (PDG 2008) Protons B0 Neutron decay Present best experiments: Δa/a = 5% Present status of aSPECT: (Δa/a)stat = 2% per day Anti-magnetic screen

  7. e- p n aCORN p p v v Slow group Fast group p e Tulane (F. Wietfeldt), Indiana, NIST, et al.

  8. Principle: momentum space diagram • Typical momentum vector for pe • p lie in a second cylinder, kinematically distinct groups • a will cause an asymmetry between coincidence events between I and II. • Groups I and II can be experimentally distinguished by TOF. B

  9. Electron and neutrino momenta from electron energy cose from proton momentum and electron energy using 4T  1T TOF between electron and proton Nab Bowman, Pocanic et al.

  10. Characteristics of Experiments Using Magnetic Fields(Dubbers 1980s)  PERKEO I A, B, C

  11. Results A: 2004 - 2006 PERKEO II Collaboration • New beam position PF1B@ILL • New polarizer system 99.7% • New analyzer system 100% A Neutron Spin Electron

  12. 2002: result: A = -0.1189(8)  = -1.2739(19)2006: result: A = -0.1198(5)  = -1.2762(13) 12

  13. B. Maerkisch, PERKEO III : Neutron Decay Measurements PERKEO III: Impressions from the Installation at ILL Plastic Scintillator Detector Spectrometer PERKEO III LiF Chopper

  14. Time of Flight Spectrum countsin detectors boron beamdump homogeneous magnetic field region background measurement chopper open neutron time of flight [ms] B. Maerkisch, PERKEO III : Neutron Decay Measurements

  15. June 2009: Fermi Spectrum Spectrum after background subtraction, downstream detector: preliminary Spectra for both spin states preliminary it works! B. Maerkisch, PERKEO III : Neutron Decay Measurements

  16. June 2009: Beta Asymmetry Spectrum 18h of data, downstream detector: preliminary Statistical precision ~1% / day B. Maerkisch, PERKEO III : Neutron Decay Measurements

  17. a bit history:l from neutron b-decay • -1.1900(200), PDG (1960) • -1.2500(200), PDG (1975) • -1.2610(40), PDG (1990) • -1.2594(38), Gatchina (1997) • -1.2660(40), M, ILL (1997) • -1.2740(30), HD, ILL (1997) • -1.2686(47), Gatchina, ILL (2001) • -1.2739(19), HD, ILL (2002) • -1.2762(13), HD, ILL (2006)

  18. Hartmut Abele, Technische Universität München 18

  19. UCNA (ultracold neutrons) Superconducting solenoidal magnet (1.0 T) Be coated mylar foil MWPC Detector housing Plastic scintillator PMT Polarizer / Spin flipper Decay volume Light guide Field Expansion Region Neutron absorber Diamond-coated quartz tube UCN source Short test run: A0=-0.1138(46)(21) A. Young (NCSU), A. Saunders (LANL), et al.

  20. Why ratio= gA/ gV from Neutrons? • Processes with the same Feynman-Diagram Courtesy of D. Dubbers

  21. Letters and SM spelling • a,A  = gA/ gV • A + t Vud from CKM matrix Quark mixing is rotation in flavor space CKM-Matrix is unitary

  22. Situation 1995 - 2004 Baseline from Vus

  23. Present status lifetime 2 types of experiments: • Beam experiments • Storage experiments • Storage losses

  24. New experiments • World average 885.2 ± 0.8 s without 878.5 ± 0.8 s •  = 878.2 ±1.9 Ezhov, UCN09 St. Petersburg • New plans: • PENELOPE • UCN in permanet magnets • UCN in He • cold neutrons in beam

  25. Letters and SM spelling • a,A  = gA/ gV • A + t Vud from CKM matrix • A + B + t  Right Handed Currents (RHC)? WL WR

  26. Origin of nature’s lefthandedness Standard Model: Elektroweak interaction 100% lefthanded Grand unified theories: Universe was left-right symmetric at the beginning Parity violation = 'emergent' Order parameter <100% Neutron decay: Correlation B + A: Mass right handed W-Boson: mR > 280 GeV/c2 Phase: -0.20 < zeta <0.07 WL WR 26

  27. Result PERKEOII: AsymmetryB & AsymmetryCThesis: M. Schumann 2007 •  result is virtually independent from detector calibration • result limited by statistics and error ( magnetic mirror effect) Background Bn Displacement Our Result: New mean Value:Bmean = 0.9807(30) B = 0.9802(50) C = -0.2377(26) Schumann et al., Phys. Rev. Lett. 100, 151801 (2008), arXiv:0706.3788. Schumann et al., Phys. Rev. Lett. 99, 191803 (2007), arXiv:0706.3788.

  28. Letters and SM spelling • C = xcA + B • A + B + C Scalar Interactions  Tensor Interactions • A + B + C  Right Handed Currents (RHC)? V-A S, T WL WR

  29. A + B + C Scalar Interactions  Tensor Interactions Letters and SM spelling S, T V-A Schumann et al., PRL 100, 151801 (2008) gT/gA gT/gA World average 2007 A + B + C + , Neutrons 29

  30. Letters and SM spelling: Times Reversal Tests • D, R ? T-odd  CP-violation CP • Candidate models for scalar couplings (at tree-level): • Charged Higgs exchange • Slepton exchange (R-parity violating super symmetric models) • Vector and scalar leptoquark exchange • The only candidate model for tree-level tensor contribution (in renormalizable gauge theories) is: • Scalar leptoquark exchange See P. Herczeg, Prog. Part. Nucl. Phys. 46 (2001) 413. Courtesy of K. Bodek

  31. Mott polarimeter Pb-foil Pb-foil scintillator scintillator MWPC • Measure polarization of e in polarized n-decay • Analyzer: Mott scattering of e on lead • Measure e-track twice • Precision: 210-2 • R = 0.008 ± 0.015 ± 0.005 • For details : Bodek et al. • PRL 102 172301 (2009) Analyzingpower • <SMott>0.2 K. Bodek, PSI Users' Meeting No. 40, 2009

  32. Limits on S and T coupling constants Bodek, PSI Users' Meeting No. 40, 2009

  33. Low energy studies in the LHC era • Low energy = • High precision

  34. B-coefficient Effect large: g-2 neutron-beta-decy Super symmetry effects: 10-5 See Ramsey-Musolf, Physics Reports 456 (2008) 1–88 Low-energy precision tests of supersymmetry

  35. Can we get there? • New experiments • New source for beta-decay products: PERC

  36. Cold Neutrons @ PF1B (ILL), MEPHISTO (FRM2) High Flux:  = 2 x 1010 cm-2s-1  Decay rate of 1 MHz / metre Polarizer: 99.7 ± 0.1 % Spin Flipper: 100.05 ± 0.1 % Analyzer: 100 % 3He-cells Spectrometer Hartmut Abele, Technische Universität München 36

  37. Summary • a, A, B, C, D… • In standard model: a and A are related to • Sensitivity to S, V, A, T, P interaction • Sensitivity to symmetries • P-violating: A, B , C, R • T-violating: D, R • If T-invariance holds, coupling constantsare real

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