NPD  and NDT  Experiments Christopher Crawford University of Kentucky NPD  run at LANSCE preparations for SNS run feasibility test of NDT  MadisonSpencer

HWI experimental program C.-P. Liu, LA-UR , Mar 2007

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

p-p and nuclei Existing measurements Spin rot/A  Anapole Circular components Medium with circular birefringence Linear Polarization ? Spin rotation Neutron spin rotation

The NPDGamma Collaboration Alracon 1, S. Balascuta 1, L. Barron-Palos 2, S. Baeßler 3, J.D. Bowman 4, R.D. Carlini 5, W.C. Chen 6, T.E. Chupp 7, C. Crawford 8, M. Dabaghyan 9, A. Danagoulian 10, M. Dawkins 11, N. Fomin 12, S.J. Freedman 13, T.R. Gentile 6, M.T. Gericke 14 R.C. Gillis 11, G.F. Greene 4,12, F. W. Hersman 9, T. Ino 15, G.L. Jones 16, B. Lauss 17, W. Lee 18, M. Leuschner 11, W. Losowski 11, R. Mahurin 12, Y. Masuda 15, J. Mei 11, G.S. Mitchell 19, S. Muto 15, H. Nann 11, S. Page 14, S.I. Penttila 4, D. Ramsay 14,20, A. Salas Bacci 10, S. Santra 21, P.-N. Seo 22, E. Sharapov 23, M. Sharma 7, T. Smith 24, W.M. Snow 11, W.S. Wilburn 10 V. Yuan 10 1 Arizona State University 2 Universidad Nacional Autonoma de Mexico 3 University of Virginia 4 Oak Ridge National Laboratory 5 Thomas Jefferson National Laboratory 6 National Institute of Standards and Technology 7 Univeristy of Michigan, Ann Arbor 8 University of Kentucky 9 University of New Hampshire 10 Los Alamos National Laboratory 11 Indiana University 12 University of Tennessee 13 University of California at Berkeley 14 University of Manitoba, Canada 15 High Energy Accelerator Research Organization (KEK), Japan 16 Hamilton College 17 Paul Scherrer Institute, Switzerland 18 Spallation Neutron Source 19 University of California at Davis 20 TRIUMF, Canada 21 Bhabha Atomic Research Center, India 22 Duke University 23 Joint Institute of Nuclear Research, Dubna, Russia 24 University of Dayton

Overview of NPD  experiment

Overview of NPDG experiment

Pulsed neutron beam ~6x10 8 cold neutrons per 20 Hz pulse at the end of the 20 m supermirror guide (largest pulsed neutron flux)

LANSCE Flight Path 12 Beam Line The peak moderator brightness at 3.3 meV is 1.25 x 10 8 n/s/sr/cm 2 /meV/mA. The pulsed neutron source allows us to know the neutron time of flight. The installed beam chopper allows us to select a range of neutron energies. The ability to select only part of the neutron spectrum is an important tool and determines the ability to effectively polarize, spin-flip and capture the neutrons as well as take beam-off data when it is closed. Seo P.N., et al., Nucl. Instr. and Meth. Accepted 2003

Beam stability

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

Neutron Polarization

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

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 pressurized to reduce bubbles SAFETY !! p p p p para-H 2 p p p p ortho-H 2  E = 15 meV

Ortho-Para Conversion Cycle

O/P Equilibrium Fraction

Neutron Intensity on Target

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 –optimized for asymmetry

Asymmetry Analysis yield (det,spin) P.C. asym background asym geometry factor P.V. asym RFSF eff.neutron pol.target depol. raw, beam, inst asym

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

Left-Right Asymmetries Parity conserving: Three processes lead to LR-asymmetry –P.C. asymmetry Csoto, Gibson, and Payne, PRC 56, 631 (1997) –elastic scattering beam steered by analyzing power of LH 2 eg. 12 C used in p,n polarimetry at higher energies P-wave contribution vanishes as k 3 at low energy –Mott-Schwinger scattering interaction of neutron spin with Coulomb field of nucleus electromagnetic spin-orbit interaction analyzing power: at 45 deg 0.23 x x ~ at 2 MeV

Detector position scans 5 mm resolution ~ 1 deg target detector UP-DOWNLEFT-RIGHT

Engineering Runs Cl calibration asymmetry A  = (-21.0  1.6)x10 -6

Production run of NPD  at LANSCE 2006 NPD  ran in 2006 at LANSCE for about 3 months collecting 4-5 Tb of data. The apparatus was well commissioned, except for the LH2 target which was approved just before the cycle. The target accommodated over 700 h of good  -asymmetry data. mean proton current 89  A or 3.4 £ 10 7  /pulse over 4 £ 10 6 pulses at 20 Hz

Preliminary Hydrogen Results:

Total statistical error: Total systematic error: a (very) conservative 10% mostly due to pol.

Preliminary Hydrogen Results:

Spallation Neutron Source (SNS) 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

Planned Power Ramp-up of SNS Operations LANSCE:  A MeV h/half-year => 80 MWh/half-year

Better experiment NPD  at the FnPB – major changes Curved beamline – less  background New polarizer - supermirror bender –figure of merit 3-4 times of FOM of the 3He spin filter. –Improved target illumination - beam spot on target up to 8” in diameter. Thinner aluminum windows in the cryostat –Reduction in material thickness in beam by a factor of 2 –Reduced backgrounds - improved absorption of scattered neutrons. –Experiment better modeled with MCNP. –Modified LH2 target will not affect target performance or safety. 60 Hz pulses – DAQ and spin flipper. (20 Hz at LANSCE) New spin flipper to accommodate larger beam diameter. New beam monitors - only one between polarizer and target. Better guide field - more homogeneous.

The NPDGamma Experiment at FnPB Supermirror polarizer FNPB guide CsI Detector Array Liquid H 2 Target H 2 Vent Line Beam Stop Magnetic Field Coils H 2 Manifold Enclosure Spin Flipper

Magnetic and radiological shielding integrated shielding: 9”-18” concrete walls 0.25”–0.75” 1010 steel open design for LH 2 safety, access to experiment external field B < 50 mG shield npd  from B-field of other experiments flux return for uniform magnetic field: Stern-Gerlach steering

Magnetic Field B-field gradients must be < 10 mG/cm –prevent Stern-Gerlach steering of neutrons –prevent depolarization of 3 He in spin filter B-field modeled in OPERA3D (S. Balascuta) Flux return / shielding on ceiling,floor,sides extra coil needed to compensate higher ceiling flux return

Neutron beam chopper design: opening angles

Beam Polarization

New supermirror polarizer two methods of neutron polarization –spin-dependent n- 3 He absorption cross section –magnetized SM coating selectively absorbs 1 spin state supermirror polarizer –spin-dependent reflection from magnetized supermirror coating –high polarization possible –requirements: at least 1 reflection preserve phase space

Design of supermirror polarizer McStas optimization of polarizer for NPDGamma as a function of (bender length, bend radius, #channels) 96% polarization, 30% transmission ) 2.6£10 10 n/s 4x improvement in P 2 N

Background in  -detector indicates that detector requires more in beam related  -shielding Beam Ring 1 Ring 2 Ring 3 Ring 4 40% 22% 17% 20%

Gain in the figure of merit at the SNS:Gain in the figure of merit at the SNS: –12.0 x brighter at the end of the SNS guide – 4.1 x gain by new SM polarizer – 6.5 x longer running time – + Higher duty factor at SNS  A ~ 1×10 -8 in 10 7 s at the SNS  A ~ 1×10 -8 in 10 7 s at the SNS Installation: currently underwayInstallation: currently underway Commissioning: early 2009Commissioning: early 2009 Sensitivity of NPDGamma to A  at SNS

NDT  vs NPD  capture cross section –  H =.3326 b,  D = b neutron polarization –para-hydrogen: no depolarization –D 2 O: spin-flip scattering expected asymmetry –20 times larger than NPDGamma –previous measurement (ILL) –goal: measure  A  = 4£10 -7 at the SNS

NDT  Target Design need extremely low background conflicting D 2 safety requirement: thick vacuum chamber must shield gammas from all windows D 2 O ice needs cooled from outside shielding target thickness optimization: 13 cm

NDT  Detectors will use the NPD  detectors –possibly run in counting mode to discriminate background –200 kHz * 10 7 s * 48 detectors = events or A  P n = ~1  s decay time in CsI crystals will test counting rates and energy resolution at LANSCE July 2008

Neutron Depolarization in D 2 O Compton Polarimetry test run at LANSCE, July 2008 DePauw U., Indiana U., U. Kentucky, U.N.A. Mexico, Michigan U., Hamilton C., NIST, ORNL, LANL B-field 3 He cell Compton polarimeter Compton polarimeter

Summary NPD  successful run at LANSCE –will achieve  A=1£10 -8 at the SNS –theory in good shape: will determine f  or  t NDT  a possible follow-up experiment at the SNS –test run at LANCE to demonstrate feasibility –need modern calculation of sensitivity to couplings both experiments are applicable to ChPT low-energy limit

Simple Level Diagram of n-p System; is primarily sensitive to the ∆I = 1 component of the weak interaction Low-energy continuum states Bound states Weak interaction mixes in P waves to the singlet and triplet S-waves in initial and final states. Parity conserving transition is M1. Parity violation arises from mixing in P states and interference of the E1 transitions. A  is coming from 3 S P 1 mixing and interference of E1-M1 transitions -  I = 1 channel Mixing amplitudes:

Meson exchange model DDH formalism: –6+1 meson-nucleon coupling constants –pion channel dominated by neutral current (Z 0 ) –PV effects: interference between strong and weak vertex N N N N Meson exchange STRONG (PC) WEAK (PV) Desplanques, Donoghue, Holstein, Ann. Phys (1980)

EFT approach Zhu, Maekawa, Holstein, Ramsey-Musolf, van Kolck, Nucl. Phys. A748, 435 (2005) Liu, nucl-th/

Existing Measurements

Relevance Systematic study of the NN weak interaction described in terms of a model independent theory appropriate at the low energy scale. NN weak interaction effects enter into nucleon structure (needed for standard model tests) and atomic parity violation measurements. 5 EFT parameters : Correspond to: NPDGamma asymmetry relation to EFT constant: C.-P. Liu, Nuclear Physics Phys. Rev. C 75, (2007)

Danilov Parameters Zero range limit: Ramsey-Musolf, Page, Ann. Rev. Nucl. Part. Sci. 56:1- 52,2006 PV NN-interaction

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 np A  nD A  np  n n  pp A z p  A z f  hr0hr hr1hr h2h h0h h1h 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 r h  1 n-captureelastic scatteringspin rotation Bowman

Why study hadronic PV? Liu, nucl-th/ Ramsey-Musolf, Page, Ann. Rev. Nucl. Part. Sci. 56:1- 52,2006