Hadronic Parity Violation at the SNS Christopher Crawford University of Kentucky symmetries and interactions properties of the neutron NPDGamma & n- 3 He exp. designing coils with ϕ m MadisonSpencer

Weak Interaction Strong Interaction Hadronic Interaction (residual nuclear force) Standard Model of Particles E&M Interaction SPACE TIME

Degenerate Fermi Gas Particle Decay Higgs? Annihilation Standard Model of Automobiles

Symmetries Continuous Symmetries –space-time translation –rotational invariance –Lorentz boosts –gauge invariance Noether’s Theorem continuous symmetries correspond to conserved quantities –energy-momentum –angular momentum –center-of-momentum –electric charge Discrete Symmetries –parity P : x  -x –time T : t  -t –charge C : q  -q –particle P 12 : x 1  x 2 exchange Discrete Theorems –CPT theorem –spin-statistics theorem position symmetry conserved momentum

CPT theorem : ALL laws are invariant under CPT Car Symmetries LR R CP (charge, parity) 100 km/h 100 km/h 99.7 km/h T (time) I’m coming home … Be careful, some idiot’s going the wrong way on the freeway. Only one? They’re all over the place!

Parity-violation in weak interaction October 1, 1956 issue of the Physical Review Parity-transformation (P) :

Madame C.S. Wu

Hadronic Weak Interaction Desplanques, Donahue, & Holstein (DDH) formalism: –6 meson-nucleon coupling constants: range + isospin structure –pion channel dominated by neutral current (Z 0 ) –PV effects: interference between strong and weak vertex other treatments: –partial waves, chiral perturbation theory, lattice QCD N N N N Meson exchange STRONG (PC) WEAK (PV)

Why Study Hadronic PV? probe of atomic, nuclear, and hadronic systems –map out coupling constants –resolve 18 F, 133 Cs discrepancy –probe nuclear structure effects –anapole and qq contributions to PV electron scattering probe of QCD in low energy non-perturbative regime –confinement, many-body problem –sensitive to qq correlations –measure QCD modification of qqZ coupling n + p  d +  A  = f   h ρ h  1 n-captureelastic scatteringspin rotation np A  nD A  n 3 He A p np  n n  pp A z p  A z f  hρ0hρ hρ1hρ h2h h0h h1h

p-p and nuclei Existing Measurements Anapole Nuclear anapole moment (from laser spectroscopy) Polarized proton scattering asymmetries Light nuclei gamma transitions (circular polarized gammas)

Properties of the Neutron m n = m p + m e keV  n = ± 0.8 s q n < 2 x e d n < 3 x e cm  n =  N r m = fm r e 2 = fm 2 –3 valence quarks + sea –exponential magnetization distribution –pion cloud: spin 1/2 isospin 1/2 p p n n uududdupdown data from BLAST

Neutron sources - Reactors ILL, Grenoble, France

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

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

Guides - neutron optical potential slide courtesy A. Young

1B - Disordered Mat’ls Commission Backscattering Spectrometer Commission High Pressure Diffractometer Commission A - Magnetism Reflectometer Commission B - Liquids Reflectometer Commission Cold Neutron Chopper Spectrometer Commission Wide Angle Chopper Spectrometer Commission High Resolution Chopper Spectrometer Commission Fundamental Physics Beamline Commission A - Powder Diffractometer Commission Single Crystal Diffractometer Commission Engineering Diffractometer IDT CFI Funded Commission SANS Commission B - Hybrid Spectrometer Commission – Spin Echo 9 – VISION Flight Paths at the SNS

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

p (or d) d (or t) n γ What can we do with neutrons? fundamental symmetry tests of the standard model –neutron decay lifetime and correlations –PV: NPDGamma, 4 He spin rotation –T reversal: electric dipole moment Electron Proton Neutrino Neutron Spin A B C nEDM

Neutron Traps ultra cold neutrons: slow enough to be completely reflected by 58 Ni optical potential kinetic: 8 m/s thermal: 4 mK wavelength: 50 nm nuclear: 335 neV ( 58 Ni) magnetic: 60 neV (1 T) gravity: 102 neV (1 m) 3m g

Car Traps

R. Alarcon, L. Barron, S. Balascuta Arizona State University S.J. Freedman, B. Lauss Univ. of California at Berkeley S. Santra Bhabbha Atomic Research Center Todd Smith Univ. of Dayton G.L. Jones Hamilton College W. Chen, R.C. Gillis, J. Mei, H. Nann, W.M. Snow, M. Leuschner, B. Losowki Indiana University R.D. Carlini Thomas Jefferson National Accel.Facility E. Sharapov Joint Institute of Nuclear Research T. Ino, Y. Masuda, S. Muto High Energy Accel. Research Org. (KEK) C. B. Crawford, E. Martin Univ. of Kentucky J.D. Bowman (spokesman), N. Fomin, G.S. Mitchell, S. Penttila, A. Salas-Bacci, W.S. Wilburn, V. Yuan Los Alamos National Laboratory M.T. Gericke, S. Page, D. Ramsay Univ. of Manitoba L. Barron University National Autonomica de Mexico T.E. Chupp, M. Sharma Univ. of Michigan T.R. Gentile National Institute of Standards and Tech. S. Covrig, M. Dabaghyan, F.W. Hersman Univ. of New Hampshire P.N. Seo North Carolina State University G.L. Greene, R. Mahurin, M. Musgraves Univ. of Tennessee S. Baessler, D. Pocanic Univ. of Virginia NPDGamma Collaboration

PV Gamma Asymmetry

3 He Polarizer Overview of NPDGamma Setup Gamma Detectors LH 2 Target RF Spin Rotator Beam Monitors

3 He neutron polarizer n + 3 He  3 H + p cross section is highly spin-dependent  J=0 = 5333 b / 0  J=1 ¼ 0 10 G holding field determines the polarization angle rG < 1 mG/cm to avoid Stern-Gerlach steering Steps to polarize neutrons: 1.Optically pump Rb vapor with circular polarized laser 2.Polarize 3 He atoms via spin-exchange collisions 3.Polarize 3 He nuclei via the hyperfine interaction 4.Polarize neutrons by spin- dependent transmission n n + n n p p p p n n p p n n + p p P 3 = 57 %

Neutron Beam Monitors 3 He ion chambers measure transmission through 3 He polarizer

RF Spin Rotator –essential to reduce instrumental systematics spin sequence:   cancels drift to 2 nd order danger: must isolate fields from detector false asymmetries: additive & multiplicave –works by the same principle as NMR RF field resonant with Larmor frequency rotates spin time dependent amplitude tuned to all energies compact, no static field gradients holding field snsn B RF NPDGamma windings n- 3 He windings

16L liquid para-hydrogen target 15 meV ortho para capture E n (meV)  (b) 30 cm long  1 interaction length 99.97% para  1% depolarization super-cooled to reduce bubbles SAFETY !! p p p p para-H 2 p p p p ortho-H 2  E = 15 meV

CsI(Tl) Detector Array 4 rings of 12 detectors each –15 x 15 x 15 cm 3 each VPD’s insensitive to B field detection efficiency: 95% current-mode operation –5 x 10 7 gammas/pulse –counting statistics limited

activation of materials, e.g. cryostat windows Stern-Gerlach steering in magnetic field gradients L-R asymmetries leaking into U-D angular distribution (np elastic, Mott-Schwinger...) scattering of circularly polarized gammas from magnetized iron (cave walls, floor...)  estimated and expected to be negligible (expt. design) Systematics, e.g: AA stat. err. systematics (proposal) Statistical and Systematic Errors Systematic Uncertainties slide courtesy Mike Snow

LANSCE Results

2 nd phase at the SNS: SM polarizer Fe/Si on boron float glass, no Gd m = 3.0 critical angle n = 45 channels r = 9.6 m radius of curvature l = 40 cm length d = 0.3mm vane thickness T=25.8%transmission P=96.2%polarization N=2.2 £ n/soutput flux (chopped) simulations using McStas / ROOT ntuple NPDG at the FnPB: 50x higher luminosity 4x higher FOM of polarization 6x longer run time Goal:  A = 1 x 10 -8

n- 3 He PV Asymmetry S(I):  4 He J  =0 + resonance  sensitive to EFT coupling or DDH couplings  ~10%  I=1 contribution (Gerry Hale, qualitative)  A ~ -1–3x10 -7 (M. Viviani, PISA) ~ k n very small for low-energy neutrons - must discriminate between back-to-back proton-triton PV observables: Tilley, Weller, Hale, Nucl. Phys. A541, 1 (1992) n n + n n p p p p n n p p n n + p p n n p p n n p p

10 Gauss solenoid RF spin rotator 3 He target / ion chamber supermirror bender polarizer (transverse) FnPB cold neutron guide 3 He Beam Monitor transition field (not shown) FNPBn- 3 He Experimental setup longitudinal holding field – suppressed PC asymmetry RF spin flipper – negligible spin-dependent neutron velocity 3 He ion chamber – both target and detector

Projected Sensitivity Statistical SensitivitySystematic Sensitivity

Magnetic Scalar Potential

Examples capacitorsolenoid

Boundary Conditions

Designing fields from the inside out Standard iterative method: Create coils and simulate field. New technique: start with boundary conditions of the desired B-field, and simulate the winding configuration 1.Use scalar magnetic potential (currents only on boundaries) 2.Simulate intermediate region using FEA with Neumann boundary conditions (H n ) 3.Windings are traced along evenly spaced equipotential lines along the boundary red - transverse field lines blue - end-cap windings Magnetostatic calculation with COMSOL

Prototype RFSF Developed for static nEDM guide field 1% uniformity DC field

Conclusion The hadronic parity violation is a unique probe of short distance nuclear interactions and QCD structure Cold neutrons valuable for tests of symmetry in particle interactions –neutron capture is an important key to mapping the structure of the hadronic weak interaction We expect results of NPDGamma from the SNS in 2012 New techniques have been developed for designing magnetic fields – our “handle” on neutrons