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Degenerate Fermi Gas Particle Decay Higgs? Annihilation Standard Model of Automobiles
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Hadronic Parity Violation at the SNS
Christopher CrawfordUniversity of Kentucky
2011-01-31
• symmetries and interactions
• properties of the neutron
• NPDGamma & n-3He exp.
• designing coils with ϕm
Madison Spencer
Weak Interaction
Strong Interaction
Hadronic Interaction(residual nuclear force)
Standard Model of Particles
E&M InteractionSPACE
TIM
E
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 P12: x1 x2
exchange
• Discrete Theorems– CPT theorem– spin-statistics theorem
position symmetry
conserved momentum
CPT theorem: ALL laws are invariant under CPT
Car Symmetries
L RR
CP (charge, parity)
100km/h
100km/h
99.7km/h
T (time)
I’m coming home …
Be careful, some idiot’sgoing 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 (Z0)– 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 18F, 133Cs 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 = -0.11 f
+ -0.001 hρ1
+ -0.003 h1
n-capture elastic scatteringspin rotation
np A nD A n3He Ap np n pp Az p Az
f -0.11 0.92 -0.19 -3.12 -0.97 -0.34
hρ0 -0.50 -0.036 -0. 23 -0.32 0.08 0.14
hρ1 -0.001 0.10 0.019 0.11 0.08 0.05
hρ2 0.05 0.0006 -0.25 0.03
h0 -0.16 -0.033 -0. 23 -0.22 -0.07 0.06
h1 -0.003 -0.002 0.041 0.22 0.07 0.06
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 Neutronmn = 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
rm = 0.889 fm
re2 = -0.116 fm2
– 3 valence quarks + sea– exponential magnetization
distribution– pion cloud:
spin 1/2 isospin 1/2
p n
uud uddup down
data from BLAST
Neutron sources - ReactorsILL, 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’lsCommission 2010
2 - Backscattering Spectrometer Commission 2006
3 - High Pressure Diffractometer Commission 2008
4A - Magnetism Reflectometer Commission 2006
4B - Liquids ReflectometerCommission 2006
5 - Cold Neutron Chopper Spectrometer Commission 2007
18 - Wide Angle Chopper Spectrometer Commission 2007
17 - High Resolution Chopper SpectrometerCommission 2008
13 - Fundamental Physics Beamline Commission 2007
11A - Powder Diffractometer Commission 2007
12 - Single Crystal Diffractometer Commission 2009
7 - Engineering Diffractometer IDT CFI Funded Commission 2008
6 - SANS Commission 2007
14B - Hybrid Spectrometer Commission 2011
15 – 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 ofquantum 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, 4He spin rotation– T reversal: electric dipole moment
Electron
Proton
Neutrino
Neutron SpinA
B
C
nEDM
Neutron Trapsultra cold neutrons:
slow enough to be completely reflected by 58Ni optical potential
kinetic: 8 m/sthermal: 4 mKwavelength: 50 nm
nuclear: 335 neV (58Ni)magnetic: 60 neV (1 T)gravity: 102 neV (1 m)
3mg
Car Traps
R. Alarcon, L. Barron, S. BalascutaArizona State University
S.J. Freedman, B. LaussUniv. of California at Berkeley
S. SantraBhabbha Atomic Research Center
Todd SmithUniv. of Dayton
G.L. JonesHamilton College
W. Chen, R.C. Gillis, J. Mei, H. Nann, W.M. Snow, M. Leuschner, B. Losowki
Indiana University
R.D. CarliniThomas Jefferson National Accel.Facility
E. SharapovJoint Institute of Nuclear Research
T. Ino, Y. Masuda, S. MutoHigh Energy Accel. Research Org. (KEK)
C. B. Crawford, E. MartinUniv. of Kentucky
J.D. Bowman (spokesman), N. Fomin, G.S. Mitchell, S. Penttila, A. Salas-Bacci,
W.S. Wilburn, V. YuanLos Alamos National Laboratory
M.T. Gericke, S. Page, D. RamsayUniv. of Manitoba
L. BarronUniversity National Autonomica de Mexico
T.E. Chupp, M. SharmaUniv. of Michigan
T.R. GentileNational Institute of Standards and Tech.
S. Covrig, M. Dabaghyan, F.W. HersmanUniv. of New Hampshire
P.N. SeoNorth Carolina State University
G.L. Greene, R. Mahurin, M. MusgravesUniv. of Tennessee
S. Baessler, D. PocanicUniv. of Virginia
NPDGamma Collaboration
PV Gamma Asymmetry
3He Polarizer
Overview of NPDGamma Setup
Gamma DetectorsLH2 TargetRF Spin RotatorBeam Monitors
3He neutron polarizer• n + 3He 3H + p cross section is highly spin-dependent
J=0 = 5333 b /0
J=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 transmission
through 3He polarizer
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 to all energies• compact, no static field gradients
holding field
sn
BRF
NPDGammawindings
n-3Hewindings
16L liquid para-hydrogen target
15 m
eV
ortho
para
capture
En (meV)
(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
E = 15 meV
CsI(Tl) Detector Array• 4 rings of 12 detectors each
– 15 x 15 x 15 cm3 each• VPD’s insensitive to B field• detection efficiency: 95%• current-mode operation
– 5 x 107 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
stat. err.
systematics
(proposal)
Statistical and Systematic Errors
Systematic Uncertainties
slide courtesy Mike Snow
LANSCE Results
2nd phase at the SNS: SM polarizer Fe/Si on boron float glass, no Gd
m = 3.0 critical anglen = 45 channelsr = 9.6 m radius of curvaturel = 40 cm lengthd = 0.3mm vane thickness
T=25.8% transmissionP=96.2% polarizationN=2.2£1010 n/s output flux (chopped)
simulations using McStas / ROOT ntuple
NPDG at the FnPB:50x higher luminosity 4x higher FOM of polarization 6x longer run timeGoal: A = 1 x 10-8
n-3He PV Asymmetry
S(I):
4He J =0+ resonance
sensitive to EFT couplingor DDH couplings
~10% I=1 contribution(Gerry Hale, qualitative)
A ~ -1–3x10-7 (M. Viviani, PISA)
~ kn very small for low-energy neutrons- must discriminate between back-to-back proton-triton
PV observables:
19.81520.578
Tilley, Weller, Hale, Nucl. Phys. A541, 1 (1992)
n + n p pn pn +p n p
np
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 velocity• 3He ion chamber – both target and detector
Projected SensitivityStatistical Sensitivity Systematic Sensitivity
Magnetic Scalar Potential
Examplescapacitor solenoid
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 (Hn)
3. Windings are traced along evenly spaced equipotential lines along the boundary
red - transverse field linesblue - 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