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Particle Physics with Slow Neutrons

I: Neutrons in the Standard Model II: Neutrons beyond the Standard Model Right-handed currents CP violation Baryon number violation Valery Nesvizhevsky: Gravitationally bound quantum states of neutrons: applications and perspectives. Particle Physics with Slow Neutrons.

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Particle Physics with Slow Neutrons

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  1. I: Neutrons in the Standard Model II: Neutrons beyond the Standard Model Right-handed currents CP violation Baryon number violation Valery Nesvizhevsky: Gravitationally bound quantum states of neutrons: applications and perspectives Particle Physics with Slow Neutrons Particle Physics with Slow Neutrons I LNGS Summer Institute, September 2005 Torsten Soldner

  2. Introduction The neutron and its interactions Cold and ultracold neutrons Neutron decay in the Standard Model Theoretical description and observables Neutron lifetime Neutron lifetime and astrophysics Beta asymmetry Unitarity of the CKM matrix I: Neutrons in the SM Particle Physics with Slow Neutrons I LNGS Summer Institute, September 2005 Torsten Soldner

  3. Mass mn= 1.001 378 418 70(58) mp = 939.565360(81) MeV Charge q = 0.4(1.1)·10-21e Spin  = ½ ħ Magnetic moment n = 1.913 042 73(45) N= 6.030 774 0(14)·10-8eV/T Electric dipole moment dn  0.63 ·10-25e·cm Life time  = 885.7(8) s Decay modes np e e  100% np e e   10-3 (to be detected)nH e 4·10-6 (to be detected) Passport of the neutron Particle Physics with Slow Neutrons I LNGS Summer Institute, September 2005 Torsten Soldner

  4. Fermi pseudopotential d~1Å n Potential of wall V 10-7eV • Index of refraction Neutron guide • Storage of ultra cold neutrons in material bottles Fermi Pseudopotential Particle Physics with Slow Neutrons I LNGS Summer Institute, September 2005 Torsten Soldner

  5. Strong/nuclear Magnetic moment magnetic scattering magnetic potential10-7eV for 1.7T Decay P asymmetry Mass gravitational potential10-7eV per m Neutrons and Interactions Electromagnetic absorption scattering Fermi potentialO(10-7eV) Weak Gravitational Kinetic energy: 10-7eV for 4m/s Particle Physics with Slow Neutrons I LNGS Summer Institute, September 2005 Torsten Soldner

  6. Magnetic potential • Detection Let them fall down! (10-7eV per m) Ultra Cold Neutrons 100Å, 100neV, 1mK, 5m/s, 10cm-3 Neutrons with less than ~ 10-7 eV • Storage Fermi potential O(10-7eV) 10-7eV for 1.7T Particle Physics with Slow Neutrons I LNGS Summer Institute, September 2005 Torsten Soldner

  7. Transport V • Polarisation(same for UCN) V 10-7eV 10-7eV 10-7eV 10-7eV   B Cold Neutrons 3-10Å, 10meV, 30K, 1000m/s, 104cm-3 Particle Physics with Slow Neutrons I LNGS Summer Institute, September 2005 Torsten Soldner

  8. n ν β n 2MeV 235U 235U n 0.1eV γ ν 30K γ n β 235U Neutrons at Reactors From fission to ultra cold neutrons: 235U+n2 FF + (2-3) n + 200MeV Fast n: > 1MeV Intermediate: 1MeV … 1eV Slow: < 1eV epithermal: 1eV … 25meV thermal:  25meV cold: 25meV … 50eV very cold: 50eV … 200neV ultra cold: <200neV 300K Particle Physics with Slow Neutrons I LNGS Summer Institute, September 2005 Torsten Soldner

  9. ILL22 H5 IH2 IH3 thermal H11 H8 H4 H12 H3 H7 H2 H6 cold H9 H1 H13 HS hot IH inclined tube ILL7 HCS VCS D2O H2O IH4 H10 IH1 1 m Inside the ILL Reactor Particle Physics with Slow Neutrons I LNGS Summer Institute, September 2005 Torsten Soldner

  10. Institute Laue Langevin: A Neutron User Facility Particle Physics with Slow Neutrons I LNGS Summer Institute, September 2005 Torsten Soldner

  11. SU(2)L (V-A) structure of weak interaction • Quark mixing: weak and mass eigenstates • Propagator for W boson Semileptonic Processes in the SM Particle Physics with Slow Neutrons I LNGS Summer Institute, September 2005 Torsten Soldner

  12. Weak coupling constant, Vud Particle Physics with Slow Neutrons I LNGS Summer Institute, September 2005 Torsten Soldner

  13. Complication: Neutron ≠ Quarks Particle Physics with Slow Neutrons I LNGS Summer Institute, September 2005 Torsten Soldner

  14. Angular correlation in the decay: J.D. Jackson et al.: Phys. Rev. Lett. 106 (1957) 517 Neutron lifetime: Measurement of  andVud Particle Physics with Slow Neutrons I LNGS Summer Institute, September 2005 Torsten Soldner

  15. Beam Detecting decay products along beam section Storage • Detecting surviving neutrons after storage • Problem: Combination of absolute measurements, solid angle… • Problem: Losses • Problem: Losses energy dependent, spectrum changes e The Neutron Lifetime Particle Physics with Slow Neutrons I LNGS Summer Institute, September 2005 Torsten Soldner

  16. Neutron monitor Penning trap for decay protons n U 800V 0V L 800V 800V U 800V 0V L 800V 800V Neutron Lifetime  Beam Experiments Particle Physics with Slow Neutrons I LNGS Summer Institute, September 2005 Torsten Soldner

  17. 10ms proton trapping76s proton counting Background suppression Neutron Lifetime  Beam Experiments • = (886.8  1.2  3.2) s(0.4% precision) M.S. Dewey et al.: Phys. Rev. Lett. 91 (2003) 152302 Particle Physics with Slow Neutrons I LNGS Summer Institute, September 2005 Torsten Soldner

  18. Upscattering – Absorption UCN, T 1mK Wall, T 100K • H atom • Same mass • Large scattering cross section Lost V Heated Other atoms Dust Coherent interaction with wall x   (20nm) Heated Losses per collision Effective collision rate Storage in Material Bottles – Losses Wall collision Variation of v (spectrum) or L (bottle size) Extrapolation to  = 0 Particle Physics with Slow Neutrons I LNGS Summer Institute, September 2005 Torsten Soldner

  19. 1.8 1.7 1.6 1.5 Stor-1 * 1000 [ s-1] 1.4 1.3 1.2 1.1 0 10 20 30 40  [s-1] Example – MAMpe BOttle A. Pichlmaier, PhD Thesis, TU München (1999) Particle Physics with Slow Neutrons I LNGS Summer Institute, September 2005 Torsten Soldner

  20. Faster neutronsmore wall collisionsfaster losses Small energy changes Spectrum changes during storage Storage time not constant Systematic Effects… • Surface properties really stable? (especially for liquid surfaces) • Vacuum equal/constant? • Temperature of surfaces • Neutron detection efficiency size-dependent? • Gravity corrections? Extrapolation linear? Particle Physics with Slow Neutrons I LNGS Summer Institute, September 2005 Torsten Soldner

  21. The Smallest-Stated-Error Neutron Lifetime Measurements • = (885.4  0.9  0.4) s(0.1% precision) • = (878.5  0.7  0.3) s(0.1% precision) 5.6 S. Arzumanov et al.: Phys. Lett. B 483 (2000) 15 A. Serebrov et al.: Phys. Lett. B 605 (2005) 72 Particle Physics with Slow Neutrons I LNGS Summer Institute, September 2005 Torsten Soldner

  22. History of Neutron Lifetime World average [PDG] Last (single) measurement Particle Physics with Slow Neutrons I LNGS Summer Institute, September 2005 Torsten Soldner

  23. No surface interactions Losses by spin flips, easier to detect than in material bottles Losses still energy dependent       Best magnetic storage experiment  = (877  10 ) s W. Paul et al.: Z. Phys. C 45 (1989) 25 Magnetic Storage 10-7eV for 1.7T Particle Physics with Slow Neutrons I LNGS Summer Institute, September 2005 Torsten Soldner

  24. Magnetic Storage – Present Project First test run (2003): • = (882  16 ) s A.Z. Andreev et al.: ILL Annual Report (2003) 92 Particle Physics with Slow Neutrons I LNGS Summer Institute, September 2005 Torsten Soldner

  25.   reaction rate Freeze-out if Hubble expansion rate greater than reaction rate   decay rate  Tf d destroyed by  (kT < 2.2MeV, but N / NB  109) 4He formation Neutron and Astrophysics 1: Big Bang Nucleosynthesis Depends on baryon density NB/N = 101010 kT [MeV] 1 Historical: First estimate of number of light neutrino families (important for cooling down) N= 2.6 ± 0.3 0.1   important for primordial 4He content in Universe 1 200 t [s] Particle Physics with Slow Neutrons I LNGS Summer Institute, September 2005 Torsten Soldner

  26. Other primordial elements (D, 3He, 7Li) depend stronger on nuclear reaction rates Baryon density NB/N = 101010 can be derived from BBN – consistent? Consistent with CMB data? Neutron and Astrophysics 1: Big Bang Nucleosynthesis Particle Physics with Slow Neutrons I LNGS Summer Institute, September 2005 Torsten Soldner

  27. Other primordial elements (D, 3He, 7Li) depend stronger on nuclear reaction rates Baryon density NB/N = 101010 can be derived from BBN – consistent? Consistent with CMB data? 885.7(8)s 878.5(8)s Influence of : Shift  by 9 (1%) = 885.7(8)s Yp = 0.2479(6)  = 878.5(8)s  Yp = 0.2463(6) Observed: large systematic uncertainties, Yp = 0.238(2)(5), Yp = 0.232 … 0.258, … G.J. Mathews et al.: Phys. Rev. D 71 (2005) 021302 Neutron and Astrophysics 1: Big Bang Nucleosynthesis Particle Physics with Slow Neutrons I LNGS Summer Institute, September 2005 Torsten Soldner

  28. Neutrons and Astrophysics 2: Solar Cycle, Neutrino Production Solar luminosity  fusion rate  T, gA2  Can derive T 8B production strongly T dependent, rate  gA5 Wrong gA5 responsible for to low 8B-e rate? No, would require  = 800s gA, gV still important for neutrino detection Particle Physics with Slow Neutrons I LNGS Summer Institute, September 2005 Torsten Soldner

  29. Neutrons and Neutrinos: Reaction Cross Sections Charged current Charged current Charged current(SNO, electron detection) Particle Physics with Slow Neutrons I LNGS Summer Institute, September 2005 Torsten Soldner

  30. Vud and the Beta Asymmetry Need to measure beta asymmetry A Particle Physics with Slow Neutrons I LNGS Summer Institute, September 2005 Torsten Soldner

  31. If really new physics: • More quark generations • additional Z boson • right-handed W bosons • coupling to exotic fermions • Supersymmetry Experimental side not settled! Unitarity of Quark Mixing H. Abele et al.: Eur. Phys. J. C 33 (2004) 1 Neutron decay (APerkeo II, n): From 0+0+ decays: Uncertainties for neutron may be higher (new lifetime exp.!) New results from Vus could restore agreement Particle Physics with Slow Neutrons I LNGS Summer Institute, September 2005 Torsten Soldner

  32. Vud Theory error: Radiative corrections Enter in neutron decay and 0+0+ For pion decay theory error factor 2 smaller H. Abele et al.: Eur. Phys. J. C 33 (2004) 1 Particle Physics with Slow Neutrons I LNGS Summer Institute, September 2005 Torsten Soldner

  33. Solid angle? • Polarisation / Flipping? • Energy calibration? • Background? Beta Asymmetry A – How to measure A = -0.1173(13) Particle Physics with Slow Neutrons I LNGS Summer Institute, September 2005 Torsten Soldner

  34. Polarisation   B M. Kreuz et al.: NIM A 547 (2005) 583 Energy calibration Background • Decay prob.: 10-7 • Scattering : ~10-3 • , fast n: ~10-4 • Ee  E 109Cd 113Sn 207Bi 137Cs Beta Asymmetry A - Experimental Situation Solid angle Particle Physics with Slow Neutrons I LNGS Summer Institute, September 2005 Torsten Soldner

  35. Beta Asymmetry A – Perkeo II 1997 2004 (prelim) Particle Physics with Slow Neutrons I LNGS Summer Institute, September 2005 Torsten Soldner

  36. Two parameters of the Standard Model from neutron decay: Vud and  Observables: Lifetime and correlation coefficients Difficult measurements: Low energies, slow decay, …  clever ideas for experiments needed – extrapolation techniques – relative measurements – use of magnetic fields Input parameter for solar cycle, BBN Test of CKM unitarity Summary – Neutrons in the Standard Model Particle Physics with Slow Neutrons I LNGS Summer Institute, September 2005 Torsten Soldner

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