Measurement of Parity-Violation in Cold Neutron Capture M. Dabaghyan for the NPDGamma Collaboration The n + p → d + γ Experiment at LANL

Outline 1. Hadronic Weak Interaction What… Why… How… 2. Experiment Hardware and measurements 3. Analysis and Results Asymmetry, Errors 4. Summary and Outlook Present and Future M. Dabaghyan for the NPDGamma Collaboration The n + p → d + γ Experiment at LANL

Why… Z 0 = 91.2 GeV W ± = 80.4 GeV range - ≤ 2×10 3 fm. π, ρ, ω ≤ 300 MeV. range - ≤ 1 fm. Bosons are too heavy M. Dabaghyan for the NPDGamma Collaboration The n + p → d + γ Experiment at LANL Explore weak interaction at low energies. The ΔI = ½ rule: Γ(K s 0 → π 0 π 0 ) » Γ(K + → π + π 0 ). Probe strong interaction at low energies. Study the weak interaction between hadrons

Weak Interaction μ → e - + υ μ + υ e n → p + e - + υ e n + p → n + p Weak processes M. Dabaghyan for the NPDGamma Collaboration The n + p → d + γ Experiment at LANL

Weak Interaction ΔS = 0 : strong Use Parity! Weak vs. Strong M. Dabaghyan for the NPDGamma Collaboration The n + p → d + γ Experiment at LANL

Parity Violation Two nucleon system: n + p → d + γ ΔS = 0, ΔI = 1 channel Study the weak interaction between hadrons P(x) = - x P(y) = - y P(z) = - z Parity P(s n ) = s n P(k γ ) = - k γ M. Dabaghyan for the NPDGamma Collaboration The n + p → d + γ Experiment at LANL

Why PV in n+p → d+γ ? Parity Violation M. Dabaghyan for the NPDGamma Collaboration The n + p → d + γ Experiment at LANL 3 S 1, I=0 3 P 1, I=1 1 P 1, I=0 3 S 1, I=0 3 P 1, I=1 1 P 1, I=0 1 S 0, I=1 3 P 0, I=1 Hindered transition n + p excited and ground states

How…ϑ M. Dabaghyan for the NPDGamma Collaboration The n + p → d + γ Experiment at LANL

Goal: DDH: DDH: Desplanques, Donoghue, Holstein, Annals of Physics 124, 1980, 449. M. Dabaghyan for the NPDGamma Collaboration The n + p → d + γ Experiment at LANL DDH Theoretical Estimate n+p→d+γ Cavaignac et al. Phys.Lett.B., , F Evans et al.; Bini et al. Phys.Rev.Lett Cs Wood et al. Science 275, 1753, 1997 Flambaum and Murray Phys. Rev. C 56, 1641, 1997 Compound Nuclei Bowman et al. LANL H π 1 so far… H π 1 (×10 -6 )

Experiment - Overview M. Dabaghyan for the NPDGamma Collaboration The n + p → d + γ Experiment at LANL Flight Path Neutron Guide Shielding Holding Field Beam Monitors Detector Array RF Spin Flipper Polarizer Analyzer Hydrogen Target Compound Targets

M. Dabaghyan for the NPDGamma Collaboration The n + p → d + γ Experiment at LANL 800 MeV Protons from ½ mile linac (~100μA) Protons hit the W spallation target to produce neutrons Neutrons are moderated by LH2 to ~ 100meV 20Hz pulses – 50ms frames – time of flight information Neutrons are delivered by an ~ 20m “supermirror” guide Flight – Path Experiment – Flight Path

Apparatus M. Dabaghyan for the NPDGamma Collaboration The n + p → d + γ Experiment at LANL

Apparatus – Flight Path Length M. Dabaghyan for the NPDGamma Collaboration The n + p → d + γ Experiment at LANL Bragg Transmission Flight Path Length L1L1L1L1 L2L2L2L2 L3L3L3L3 TnTn

3π acceptance 4 rings of 15×15×15 cm 3 CsI crystals VPD: insensitive to magnetic field High event rate: use current mode Low-noise preamps: < 0.1 mV RMS Operate at counting statistics 95% γ’s stopped in crystals Aligned with B 0 better than 1 o Measure Neutron Flux Experiment – γ-ray Detectors M. Dabaghyan for the NPDGamma Collaboration The n + p → d + γ Experiment at LANL

Experiment – Polarizer 3 He cell UnpolarizedNeutronsPolarizedNeutrons Helmholtz Coils Polarized Laser Light 12 cm in diameter, 5 cm thick 12 cm in diameter, 5 cm thick 4.9 atm·cm 4.9 atm·cm Relaxation time of 500 hrs Relaxation time of 500 hrs Typical polarization ~ 55% Boo-Boo M. Dabaghyan for the NPDGamma Collaboration The n + p → d + γ Experiment at LANL

- 3 barns - 3 barns barns! barns! Transmission Transmission 3 He as a Neutron Spin Filter n 3 He n Experiment – Polarizer M. Dabaghyan for the NPDGamma Collaboration The n + p → d + γ Experiment at LANL T n /T o TOF [ms]

Experiment – Polarizer Performance M. Dabaghyan for the NPDGamma Collaboration The n + p → d + γ Experiment at LANL

Experiment – Analyzer Measure Neutron Beam polarization Measure Neutron Beam polarization Measure RFSF efficiency Measure RFSF efficiency Optimize RFSF parameters Optimize RFSF parameters Function M. Dabaghyan for the NPDGamma Collaboration The n + p → d + γ Experiment at LANL

Experiment – Analyzer PEEK/glass components PEEK/glass components Uniform Temperature (165 o C) Uniform Temperature (165 o C) Non-metallic parts Non-metallic parts Polarized light from 2 sides Polarized light from 2 sides 30 W Laser 30 W Laser Oven Laser Optics M. Dabaghyan for the NPDGamma Collaboration The n + p → d + γ Experiment at LANL

Transport Suitcase 2.5 cm in diameter 2.5 cm in diameter 6.2 atm·cm 6.2 atm·cm Relaxation time of 130 hrs Relaxation time of 130 hrs Typical polarization ~ 47% Experiment – Analyzer Helmholtz coils create 12 Gauss field Running on batteries Loss of polarization: ~10%/hr TS - 12 M. Dabaghyan for the NPDGamma Collaboration The n + p → d + γ Experiment at LANL

Experiment – RF Neutron Spin Flipper Limit systematic effects Limit systematic effects 2 mm Al housing enough to isolate RF field 2 mm Al housing enough to isolate RF field 20 Hz pulse pattern: ↑↓↓↑↓↑↑↓ 20 Hz pulse pattern: ↑↓↓↑↓↑↑↓ Resonant Radio Frequency Spin Rotator M. Dabaghyan for the NPDGamma Collaboration The n + p → d + γ Experiment at LANL

Apply resonant ┴ RF field Apply resonant ┴ RF field B 1 =B 1 cos ω t Rotate neutron spins by π Rotate neutron spins by π α = γB 1 Δt α = γB 1 Δt B 1 = π L /d γt TOF B 1 = π L /d γt TOF Elements of NMR RFSF - NMR M. Dabaghyan for the NPDGamma Collaboration The n + p → d + γ Experiment at LANL

Optimization is performed using the Analyzer Optimization is performed using the Analyzer Normalized population difference between ↑↓ Normalized population difference between ↑↓ RFSF Efficiency Optimization RFSF – Parameter Optimization M. Dabaghyan for the NPDGamma Collaboration The n + p → d + γ Experiment at LANL

RFSF RFSF RFSF RFSF NMR Flip – 100% NMR Flip – 100% Compare NMR and RFSF flips Compare NMR and RFSF flips Scan off-axis by moving collimator+analyzer+M3 Scan off-axis by moving collimator+analyzer+M3 ε on axis = ± 0.12 ε on axis = ± 0.12 ε 1.3” beam left = ± 0.11 ε 1.3” beam left = ± 0.11 ε 1.3” beam right = ± 0.11 ε 1.3” beam right = ± 0.11 RFSF Efficiency Measurement RFSF – Efficiency M. Dabaghyan for the NPDGamma Collaboration The n + p → d + γ Experiment at LANL

PV in Compound Nuclei – Not so simple, so why bother? Some materials are in the beamline – Al, Cu, In … Reason 1. Study PV in nuclear targets – has not been done for this A-range Reason 2. M. Dabaghyan for the NPDGamma Collaboration The n + p → d + γ Experiment at LANL

Compound Nuclei – What can be done? Compound nuclei – complex – impossible to solve analytically. Treat matrix elements as independent random variables Obtain RMS for directional asymmetry, which is Estimate A γ RMS using Using spectroscopic information Γ w could be estimated independently: M. Dabaghyan for the NPDGamma Collaboration The n + p → d + γ Experiment at LANL

Large capture cross-section Small scattering cross-section Small incoherent cross-section Close level spacing Selection Criteria Compound Solid Targets Al Mn Co Cu Ti Cl In V Sc List of Solid Targets M. Dabaghyan for the NPDGamma Collaboration The n + p → d + γ Experiment at LANL

Compound Solid Targets M. Dabaghyan for the NPDGamma Collaboration The n + p → d + γ Experiment at LANL

Targets – LH 2 LH 2 Target Aluminum cylinder Aluminum cylinder Diameter of cm Diameter of cm 16L of LH 2 16L of LH 2 kept at ~ 17 K kept at ~ 17 K σ cap « σ scatt σ cap « σ scatt Para-H 2 : capture and coherent scatter Para-H 2 : capture and coherent scatter Ortho-H 2 : coherent and incoherent scatter Ortho-H 2 : coherent and incoherent scatter Cross sections M. Dabaghyan for the NPDGamma Collaboration The n + p → d + γ Experiment at LANL Cross Section meV σ s ortho σ s para σaσa

Ortho-Para conversion hrs Ortho-Para conversion hrs Two FeO 2 OPCs – 112 hrs Two FeO 2 OPCs – 112 hrs OPC #1 OPC #2 LH 2 target Neutron Beam Targets – LH 2 Ortho-to-Para Conversion M. Dabaghyan for the NPDGamma Collaboration The n + p → d + γ Experiment at LANL

Targets – LH 2 M2 M3 LH 2 Full measurement: Full measurement: Empty measurement: Empty measurement: Resulting in Resulting in Transmission Through LH 2 M. Dabaghyan for the NPDGamma Collaboration The n + p → d + γ Experiment at LANL

Data Analysis ϑ M. Dabaghyan for the NPDGamma Collaboration The n + p → d + γ Experiment at LANL

Raw Asymmetry Physics Asymmetry θ Data Analysis Sequence Asymmetry M. Dabaghyan for the NPDGamma Collaboration The n + p → d + γ Experiment at LANL

Table Motion Measurements Reconstructed Angles Detector Geometry M. Dabaghyan for the NPDGamma Collaboration The n + p → d + γ Experiment at LANL

Error from Left-Right Mixing into Up-Down Ideally cos ϑ and sin ϑ Neutron absorption probability Energy left by a γ in the crystal Geometry Factors Detector Geometry M. Dabaghyan for the NPDGamma Collaboration The n + p → d + γ Experiment at LANL

Depolarization in the targets Neutron Beam Depolarization M. Dabaghyan for the NPDGamma Collaboration The n + p → d + γ Experiment at LANL

Backgrounds and false asymmetries Electronic pick-up Activation Scattered neutrons Frame overlap γ ’s from spallation Few percent for solids More for LH 2 A Bkg = 0 Sources of Backgrounds M. Dabaghyan for the NPDGamma Collaboration The n + p → d + γ Experiment at LANL

Cuts Neutron beam current Detector sums/diff’s Beam fluctuations Detector saturation Valid spin sequences Cuts on the Data M. Dabaghyan for the NPDGamma Collaboration The n + p → d + γ Experiment at LANL

Systematics Multiplicative noise Additive noise Non-hydrogen target A γ Mott – Schwinger LR Stern – Gerlach steering Sources M. Dabaghyan for the NPDGamma Collaboration The n + p → d + γ Experiment at LANL

Huge known UD asymmetry Calibrate the experiment Chlorine Fit to Asymmetry Results - Chlorine A γ UD = (19.62) ×10 -6 A γ LR = (0.087) ×10 -6 M. Dabaghyan for the NPDGamma Collaboration The n + p → d + γ Experiment at LANL A γ = (19.47 ± 2.02 ) ×10 -6

Asymmetry Results - Chlorine A γ UD = (19.62) ×10 -6 A γ LR = (0.087) ×10 -6 M. Dabaghyan for the NPDGamma Collaboration The n + p → d + γ Experiment at LANL A γ = (19.47 ± 2.02 ) ×10 -6

Para-Hydrogen, A γ Para-Hydrogen, A γ More statistics Better knowledge of background Hydrogen Asymmetry Results - Hydrogen A γ = (0.95 ± 2.01 ) ×10 -7 M. Dabaghyan for the NPDGamma Collaboration The n + p → d + γ Experiment at LANL A γ UD = (1.7) ×10 -7 A γ LR = (1.1) ×10 -7

Results – The other targets Co Cu In Mn Sc Ti V Targets A γ (×10 -7 ) σ Aγ,stat (×10 -7 ) σ Aγ,syst (×10 -7 ) M. Dabaghyan for the NPDGamma Collaboration The n + p → d + γ Experiment at LANL σ Aγ,TOT (×10 -7 )

Summary M. Dabaghyan for the NPDGamma Collaboration The n + p → d + γ Experiment at LANL A γ = (0.95 ± 2.01 ) ×10 -7 H π 1 = (-2.1 ± 4.5 ) ×10 -6 LANL 2006, Production Phase 1 Preliminary Cavaignac et al. Phys.Lett.B., , 1977 A γ = (0.6 ± 1.8 ) ×10 -7 H π 1 = (-1.4 ± 4.0 ) ×10 -6 DDH Theoretical Estimate n+p→d+γ Cavaignac et al. Phys.Lett.B., , F Evans et al.; Bini et al. Phys.Rev.Lett Cs Wood et al., Science 275, 1753, 1997 Flambaum and Murray, Phys. Rev. C 56, 1641, 1997 Compound Nuclei Bowman et al. LANL H π 1 (×10 -6 ) n + p → d + γ LANL 2006, Preliminary

ORNL LANL JLAB University of Michigan Indiana University Indiana Univ. Cyclotron NIST University of New Hampshire University of Tennessee Univ. of California, Berkeley Univ. of California, Davis University of Manitoba University of Arizona Hamilton College North Carolina State Univ. JINR, Dubna, Russia Univ. of Dayton KEK, Japan J.D. Bowman, S. Penttila S.Wilburn.T.Ito,A. Klein,V.Yuan,A.Salas-Bacci, S.Santra R.D. Carlini T.E. Chupp, M. Sharma M. Leuschner, J. Mei, H. Nann, W.M. Snow, R.C. Gillis B. Losowki T.R. Gentile F.W. Hersman, M. Dabaghyan,H. Zhu,S. Covrig, M.Mason G.L. Greene, R. Mahurin S.J. Freedman, B. Lauss G.S. Mitchell M.T. Gericke, S. Page, D. Ramsay L. Barron-Palos, S. Balascuta G.L. Jones P-N. Seo E. Sharapov T. Smith T. Ino, Y. Masuda, S. Muto The NPDγ Collaboration M. Dabaghyan for the NPDGamma Collaboration The n + p → d + γ Experiment at LANL

Summary 1. Completed the third commissioning run of NPDGamma at LANL 2. Measured Angular Directional Asymmetry A γ in a number of medium-A range nuclei 3. Completed the first production phase of NPDγ at LANL 4. Measured the pion coupling constant H 5. M. Dabaghyan for the NPDGamma Collaboration The n + p → d + γ Experiment at LANL

Experiment – Neutron Guide m=3 super-mirror neutron guide ~ 20 m long, 58 Ni and 47 Ti V ≤ 7 m/s Specifications M. Dabaghyan for the NPDGamma Collaboration The n + p → d + γ Experiment at LANL

Three parallel plate ion chambers 3 kV bias Measure Neutron Flux Experiment – Beam Monitors M. Dabaghyan for the NPDGamma Collaboration The n + p → d + γ Experiment at LANL

Flight Path Length Bragg Transmission L1L1L1L1 L2L2L2L2 L3L3L3L3 Flight Path Length Measurement M. Dabaghyan for the NPDGamma Collaboration The n + p → d + γ Experiment at LANL

Two independent Gd 2 O 3 plated blades rotating at 1200 rpm Radius = 1024 m, aperture = 1.9 rad Fully open to fully close in 4 ms Specifications Experiment – Frame Overlap Chopper M. Dabaghyan for the NPDGamma Collaboration The n + p → d + γ Experiment at LANL

10 G vertical magnetic field Uniform and stable to 1 mG/cm Shim coils to minimize stray fields less than 0.5 mG/cm gradient ||B Largest gradient measured: dB z /dx = 6mG/cm (0.06%) Field Parameters Experiment – B-field M. Dabaghyan for the NPDGamma Collaboration The n + p → d + γ Experiment at LANL

Polarizing the Polarizer Collisional Mixing M. Dabaghyan for the NPDGamma Collaboration The n + p → d + γ Experiment at LANL