NPDGamma Experiment: from LANSCE to the SNS

Christopher CrawfordUniversity of Kentucky

Parity Violation International Workshop (PAVI) 2009

Bar Harbor, ME2009-06-22

Outline

Hadronic Weak Interaction• DDH couplings• EFT couplings• Danilov parameters• existing data

NPDGamma @ LANSCE• experimental setup• results

NPDGamma @ SNS• upgrades• new sensitivity

n-3He @ SNS• experimental setup• R&D at LANSCE

NDTGamma• experimental setup• R&D at LANSCE

Conclusion

Madison Spencer

N N

N N

Meson exchange

STRONG(PC)

WEAK(PV)

Motivation

The Hadronic WeakInteraction is weak, but can be isolated

due to parity violation

W,Z range = 0.002 fm –probe short-range quark correlations in QCD nonperturbative regime

nuclear PV – test of nuclear structure models

test of EFT in ΔS = 0 sector(ΔI=1/2 rule not understood)

physics input to PV electron scattering experiments

0νββ decay – matrix elements of 4-quark operators

DDH picture

DDH Potential

isos

pin

rang

e

Desplanques, Donoghue, Holstein, Annals of Physics 124, 449 (1980)

EFT approach

Zhu, Maekawa, Holstein, Ramsey-Musolf, van Kolck, NP A748, 435 (2005)C.-P. Liu, PRC 75, 065501 (2007)

Danilov parameters

elastic NN scattering

S=1/2+1/2 I=1/2+1/2

equivalent to EFTin very low energy limit(generally much more

complicated)

C.-P. Liu, PRC 75, 065501 (2007)

Pion-less EFT Couplings

Liu, PRC 75, 065501 (2007)

�Ramsey-Musolf, Page, Ann. Rev. Nucl. Part. Sci. 56:1-52,2006

Hyun, Ando, Desplanques, nucl-th/0611018

Nuclear PV experiments

Adelberger, Haxton, Ann. Rev. Nucl. Part. Sci. 35, 501 (1985)

p-p and nuclei Anapole

D

ed Spin rot/Aγ

Existing data

p-p scat. 15, 45 MeV Azpp

p-α scat. 46 MeV Azpp

p-p scat. 220 MeV Azpp

n+p→d+γ circ. pol. Pγd

n+p→d+γ asym. Aγd

n-α spin rot. dφnα/dz

18F asym. ΔI =119F, 41K, 175Lu, 181Ta asym.133Cs, 205Tl anapole moment21Ne (even-odd)

GOAL – resolve couplingconstants from few-bodyPV experiments only

NPDGamma Collaboration

R. Alarcon1, S. Balascuta1, L. Barron-Palos2, S. Baeßler3, D. Bowman4, J. Calarco ,R. Carlini5, W. Chen6,T. Chupp7, C. Crawford8, M. Dabaghyan9, A. Danagoulian10, M. Dawkins11, N. Fomin12, S. Freedman13,T. Gentile6, M. Gericke14 C. Gillis11, G. Greene4,12, F. Hersman9, T. Ino15, G. Jones16, B. Lauss17, W. Lee18,M. M. Leuschner11, W. Losowski11, R. Mahurin12, Y. Masuda15, J. Mei11, G. Mitchell19, S. Muto15, H. Nann11,S. Page14, D. Pocinic, S. Penttila4, D. Ramsay14,20, A. Salas Bacci10, S. Santra21, P.-N. Seo22, E. Sharapov23,M. Sharma7, T. Smith24, W. Snow11, W. Wilburn10, V. Yuan10

1Arizona State University2Universidad Nacional Autonoma de Mexico

3University of Virginia 4Oak Ridge National Laboratory

5Thomas Jefferson National Laboratory6National Institute of Standards and Technology

7Univeristy of Michigan, Ann Arbor8University of Kentucky

9University of New Hampshire10Los Alamos National Laboratory

11Indiana University12University of Tennessee

13University of California at Berkeley

14University of Manitoba, Canada15High Energy Accelerator Research

Organization (KEK), Japan16Hamilton College

17Paul Scherer Institute, Switzerland 18Spallation Neutron Source

19University of California at Davis20TRIUMF, Canada

21Bhabha Atomic Research Center, India22Duke University

23Joint Institute of Nuclear Research, Dubna, Russia

24University of Dayton

NPDGamma parity-violating observable Aγ

Spallation neutron source – cold moderator

spallation sources: LANL, SNS• pulsed -> TOF -> energy

LH2 moderator: cold neutrons• thermal equilibrium in ~30 interactions

Frame overlap chopper

• Pulsed beam: time-of-flight determines neutron velocity, energy

• PV asymmetry is independent of energy

• Very slow neutrons can overlap with faster neutrons from later pulse

• Chopper rotor coated with Gd2O3 absorbs slow neutrons, opens window for faster ones

3He neutron polarizer

n + 3He → 3H + p cross section is highly spin-dependent

σJ=0 = 5333 b λ/λ0

σJ=1 ¼ 0

10 G holding field determines the polarization anglerG < 1 mG/cm to avoid Stern-Gerlach steering

Steps to polarize neutrons:

1. Optically pump Rb vaporwith circular polarized laser

2. Polarize 3He atoms viaspin-exchange collisions

3. Polarize 3He nuclei viathe hyperfine interaction

4. Polarize neutrons by spin-dependent transmission

n + n p pn pn +p

P3 = 57 %

Neutron Beam Monitors

3He ion chambers

measure transmissionthrough 3He polarizer

Neutron Polarization

RF spin rotator

• essential to reduce instrumental systematics- spin sequence: ↑↓↓↑ ↓↑↑↓ cancels drift to 2nd 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 for all energies- compact, no static field gradients

holding field

sn

BRF

Beam stability

16L liquid para-hydrogen target

15 m

eV

ortho

para

capture

En (meV)

σ(b

)

30 cm long → 1 interaction length

99.97% para → 1% depolarization

super-cooled to reduce bubbles

SAFETY !!

p p

para-H2

p p

ortho-H2

ΔE = 15 meV

16L liquid para-hydrogen target

CsI(Tl) Detector Array

4 rings of 12 detectors each• 15 x 15 x 15 cm3 each

VPD’s insensitive to B fielddetection efficiency: 95%current-mode operation• 5 x 107 gammas/pulse• counting statistics limited

Asymmetry analysisyield (det,spin)

P.C. asym

background asym

geometry factor

P.V. asym

RFSF eff. neutron pol. target depol.

raw, beam, inst asym

Engineering Runs

Cl

calibration asymmetry

Aγ= (-21.0±1.6)x10-6

LH2 run – Fall 2006

Number of good runs 5401 / 750 h

Average delivered proton current 89 A at 80 kW

Average beam pol. (3He spin filter)55 +/- 7.5 %

Spin-flip efficiency 98 +/- 0.8%

Para-hydrogen fraction in LH2 target 99.98 %

Beam depolarization in target2 %

Data loss (cuts, bad events)~1 %

Preliminary results

Aγ ,UD = −1.1± 2.1( )×10−7 Aγ ,LR = −1.9 ± 2.0( )×10−7Total statistical error:

Total systematic error:        a (very) conservative 10% mostly due to polarization

Preliminary results

Gain in sensitivity 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

projected sensitivity: δA = 1x10-8 in 107s

Installation: currently underway

Commissioning: mid 2009

Data-taking: early 2010

Experimental setup at the FnPB

Supermirror polarizer

FNPB guide

CsI Detector Array

Liquid H2 Target

H2 Vent Line

Beam Stop

Magnetic Field Coils

Magnetic Shielding

H2 Manifold Enclosure

NPDGamma cave and shielding

n-3He collaboration

J.D. Bowman (PI), S.I. Penttilä Oak Ridge National Laboratory

M.T. Gericke (PI), S.A. Page, Mark McCrea University of Manitoba

C.B. Crawford (PI), Y. Shin, E. Martin University of Kentucky

C. Gillis, J. Mei Indiana University

J. Martin University of Winnipeg

V. Gudkov University of South Carolina

M. Viviani INFN, Sezione di Pisa

A. Klein, A. Salas-Bacci, A. Hayes, G. Hale Los Alamos National Lab

R. Mahurin University of Tennessee

P.-N. Seo Triangle Universities Nuclear Lab

L. Barron Universidad Nacional Autónoma de México

n-3He PV Asymmetry

~ kn very small for low-energy neutrons

- essentially the same asym.- must discriminate betweenback-to-back proton-triton

S(I):

4He Jπ =0+ resonance

sensitive to EFT couplingor DDH couplings

~10% ΔI=1 contribution(Gerry Hale, qualitative)

A ~ 3x10-7 (M. Viviani, PISA)

PV observables:

19.81520.578

Tilley, Weller, Hale, Nucl. Phys. A541, 1 (1992)

Extraction of DDH couplings

np Aγ nD Aγ n3He Ap np φ nα φ pp Az pα Az

fπ -0.11 0.92 -0.18 -3.12 -0.97 -0.34

hρ0 -0.50 -0.14 -0. 23 -0.32 0.08 0.14

hρ1 -0.001 0.10 0.027 0.11 0.08 0.05

hρ2 0.05 0.0012 -0.25 0.03

hω0 -0.16 -0.13 -0. 23 -0.22 0.07 0.06

hω1 -0.003 -0.002 0.05 0.22 0.07 0.06

n-3He:

M. Viviani

(PISA)

μ-metal shield

1010 steelflux return

10 Gausssolenoid

RF spinrotator

3He target /ion chamber

supermirrorbender polarizer

(transverse)

FnPB coldneutron guide

3He BeamMonitor transition field

(not shown)

FNPB n-3He

Experimental setup

longitudinal holding field – suppressed PC asymmetry

RF spin flipper – negligible spin-dependent neutron velocity3He ion chamber – both target and detector

Solenoid holding field

uniformity requirements• δB~ 0.3 G μ¢δB/2En=10-10 < δAz• θz ~ 0.1± + alignment of wires

preliminary design• solenoid with compensation coils

at end for uniformity• μ-metal shield for residual earth’s field• 1010 steel flux return to prevent

saturation of μ-metal

design parameters• 3 m length x 50 cm diameter• B =10 G for spin flipper• j = 9 A/cm winding density• I0 = 1560 A (or end-cap windings)

simulation using COMSOL

1010 steelflux return

10 Gausssolenoid

4 m £ 55 cm diam.3 m £ 50 cm diam.

I0=1500+60 A turns I0

j = 8+1 A/cm

red - transverse field linesblue - end-cap windings

Radio frequency spin rotator

extension of design for NPDGamma• P-N Seo et al., Phys. Rev. ST Accel. Beam, vol

11, 084701 (2008)

new resonator for n-3He experiment• transverse horizontal RF B-field• longitudinal / transverse flipping• no fringe field - 100% efficiency• compact geometry - efficient

- small diameter solenoid• matched to driver electronics

for NPDGamma spin flipper

prototype design• parasitic with similar design for

nEDM guide field near cryostat• fabrication and testing at UKy – 2009

NPDGammawindings

n-3Hewindings

Magnetostatic calculation with COMSOL

3He target / ion chamber

MC simulations of sensitivityto proton asymmetry

• including wire correlations• δ A ~ 6 /pN

tests at LANSCE FP12• fission chamber flux calibration• prototype drift chamber R&D• new beam monitors for SNS

design of new ion chamber for NPDGamma, test at LANL

M. Gericke, U. Manitoba

LANSCE FP12 3He chamber R&D

NDPGamma vs. NDTGamma

capture cross section• 1000x smaller in D2O• σH = .3326 b, σD = .000519 b

neutron polarization• para-hydrogen: no depolarization• D2O: spin-flip scattering

expected asymmetry• 20 times larger than NPDGamma

• previous measurement (ILL)

• goal: measure δAγ = 4£10-7 at the SNS

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Compton Polarimetry test run at LANSCE: 2008, 2009

DePauw U., Indiana U., U. Kentucky, U.N.A. Mexico, Michigan U., Hamilton C., NIST, ORNL, LANL

B-field

3He cell 3He cell

Comptonpolarimeter

Comptonpolarimeter

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Neutron Depolarization in D2O

NDTγ Target Design

need extremely low background

conflict with D2 safety requirement of thick vacuum chamber

must shield gammas from all windows

D2O ice needs cooled from outside shielding

target thickness optimization: 13 cm Indiana Univ.

Conclusion

there is a viable program to measure the HWI with PV reactions in few-body systems

p-p, p-α elastic scattering complete

n-α spin rotation has taken data

n + p → d + γ will run at the SNS in 2010

n+3He → t + p will run at the SNS in 2011

n + p → d + γ and others are in planning stage

we will soon have significant tests of EFT in the ΔS = 0 sector using few-body reactions only