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Parity Violation and the Neutron – Physics at the SNS, Oak Ridge Nat. Lab. Christopher Crawford Cosmic Lunch 2010-02-19 • Interactions and Symmetries • Properties of the Neutron • Spallation Neutron Source (SNS) Madison Spencer TIME Standard Model of Particles SPACE E&M Interaction Weak Interaction Strong Interaction Hadronic Interaction (residual nuclear force) Standard Model of Automobiles Annihilation Higgs? Degenerate Fermi Gas Particle Decay Symmetries • – – – – • • Continuous Symmetries Discrete Symmetries – – – – space-time translation rotational invariance Lorentz boosts gauge invariance Noether’s Theorem parity P : x -x time T : t -t charge C : q -q particle exchange P12: x1 x2 continuous symmetries • correspond to conserved quantities – energy-momentum – angular momentum – center-of-momentum – electric charge Discrete Theorems – spin-statistics theorem – CPT theorem position symmetry conserved momentum Car Symmetries T (time) R 100 100 km/h km/h km/h 99.7 L R Be careful, some idiot’s CP (charge, parity) going the wrong way I’m coming home … on the freeway. Only one? They’re all over the place! CPT theorem: ALL laws are invariant under CPT Parity-violation in weak interaction (1956) Parity-transformation (P) : r r October 1, 1956 issue of the Physical Review Co Ni e e 60 Madame C.S. Wu 60 Properties of the Neutron 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 spin 1/2 up down isospin 1/2 p n uud udd rm = 0.889 fm re2 = -0.116 fm2 – 3 valence quarks + sea – exponential magnetization distribution – pion cloud: data from BLAST Neutron sources - Reactors ILL, Grenoble, France 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 Spallation Neutron Source (SNS) • spallation sources: LANL, SNS – pulsed -> TOF -> energy • LH2 moderator: cold neutrons – thermal equilibrium in ~30 interactions Neutron current at the end of a 24.3 m long guide with 150 A proton current 5 4 3 Neutron current (x10 5 neutrons/ms/cm 2 /pulse) 6 2 1 0 0 10 20 30 Time of Flight (ms) 40 50 60 Beamline 13 Allocated for Nuclear Physics (FnPB) 11A - Powder Diffractometer Commission 2007 9 – VISION 7 - Engineering Diffractometer IDT CFI Funded Commission 2008 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 17 - High Resolution Chopper Spectrometer Commission 2008 18 - Wide Angle Chopper Spectrometer Commission 2007 3 - High Pressure Diffractometer Commission 2008 1B - Disordered Mat’ls Commission 2010 2 - Backscattering Spectrometer Commission 2006 FnPB Cold & UCN Line FnPB – Fundamental Neutron Physics Beamline Choppers Shutter 14 m guide, 10x12 cm2, 1 m from moderator What can we do with neutrons? • scattering / diffraction – complementary to X-ray Bragg diffraction – large penetration – large H,D cross section • life sciences • fuel cell research • oil exploration • fundamental tests of quantum mechanics – neutron interferometry • • • • scattering lengths neutron charge radius spinor 4 periodicity gravitational phase shift – quantum states in a gravitational potential What can we do with neutrons? • fundamental symmetry tests of the standard model A Electron – neutron decay lifetime and correlations – PV: NPDGamma, 4He spin rotation C – T reversal: electric dipole moment Proton nEDM dd (or t) nn pp (or d) γ Neutron Spin B Neutrino Neutron Traps ultra cold neutrons: 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) Car Traps