Download Hadronic Parity Violation and the Neutron

Parity Violation and the Neutron –
Physics at the SNS, Oak Ridge Nat. Lab.
Christopher Crawford
Cosmic Lunch
2010-02-19
• Interactions and Symmetries
• Properties of the Neutron
• Spallation Neutron Source (SNS)
Madison
Spencer
TIME
Standard Model of Particles
SPACE
E&M Interaction
Weak Interaction
Strong Interaction
Hadronic Interaction
(residual nuclear force)
Standard Model of Automobiles
Annihilation
Higgs?
Degenerate Fermi Gas
Particle Decay
Symmetries
•
–
–
–
–
•
•
Continuous Symmetries
Discrete Symmetries
–
–
–
–
space-time translation
rotational invariance
Lorentz boosts
gauge invariance
Noether’s Theorem
parity
P : x  -x
time
T : t  -t
charge C : q  -q
particle exchange
P12: x1  x2
continuous symmetries
•
correspond to
conserved quantities
– energy-momentum
– angular momentum
– center-of-momentum
– electric charge
Discrete Theorems
– spin-statistics theorem
– CPT theorem
position
symmetry
conserved
momentum
Car Symmetries
T (time)
R
100
100
km/h
km/h
km/h
99.7
L
R
Be careful, some idiot’s
CP (charge,
parity)
going the wrong way
I’m coming
home …
on the freeway.
Only one? They’re
all over the place!
CPT theorem: ALL laws are invariant under CPT
Parity-violation in weak interaction
(1956)
Parity-transformation (P) :
r r

October 1, 1956 issue of the Physical Review
Co Ni  e  e
60

Madame C.S. Wu
60

Properties of the Neutron
mn = 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
spin 1/2
up
down
isospin 1/2
p
n
uud
udd
rm = 0.889 fm
re2 = -0.116 fm2
– 3 valence quarks + sea
– exponential magnetization
distribution
– pion cloud:
data from BLAST
Neutron sources - Reactors
ILL, Grenoble, France
Spallation Neutron Source (SNS)
Oak Ridge National Laboratory, Tennessee
• spallation sources: LANL, SNS
– pulsed -> TOF -> energy
• LH2 moderator: cold neutrons
– thermal equilibrium in ~30 interactions
Spallation Neutron Source (SNS)
• spallation sources: LANL, SNS
– pulsed -> TOF -> energy
• LH2 moderator: cold neutrons
– thermal equilibrium in ~30 interactions
Neutron current at the end of a 24.3 m long
guide with 150 A proton current
5
4
3
Neutron current (x10
5
neutrons/ms/cm
2
/pulse)
6
2
1
0
0
10
20
30
Time of Flight (ms)
40
50
60
Beamline 13 Allocated for Nuclear Physics (FnPB)
11A - Powder
Diffractometer
Commission 2007
9 – VISION
7 - Engineering
Diffractometer
IDT CFI Funded
Commission 2008
6 - SANS
Commission 2007
12 - Single Crystal
Diffractometer
Commission 2009
5 - Cold Neutron
Chopper
Spectrometer
Commission 2007
13 - Fundamental
Physics Beamline
Commission 2007
4B - Liquids
Reflectometer
Commission 2006
14B - Hybrid
Spectrometer
Commission 2011
4A - Magnetism
Reflectometer
Commission 2006
15 – Spin Echo
17 - High Resolution
Chopper Spectrometer
Commission 2008
18 - Wide Angle
Chopper Spectrometer
Commission 2007
3 - High Pressure
Diffractometer
Commission 2008
1B - Disordered Mat’ls
Commission 2010
2 - Backscattering
Spectrometer
Commission 2006
FnPB Cold & UCN Line
FnPB – Fundamental Neutron Physics Beamline
Choppers
Shutter
14 m guide,
10x12 cm2,
1 m from
moderator
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
What can we do with neutrons?
• fundamental symmetry tests
of the standard model
A
Electron
– neutron decay lifetime and correlations
– PV: NPDGamma, 4He spin rotation
C
– T reversal: electric dipole moment
Proton
nEDM
dd (or t)
nn
pp (or d)
γ
Neutron Spin
B
Neutrino
Neutron Traps
ultra cold neutrons:
slow enough to be completely
reflected by 58Ni optical potential
kinetic:
8 m/s
thermal:
4 mK
wavelength: 50 nm
nuclear:
335 neV (58Ni)
magnetic: 60 neV (1 T)
gravity:
102 neV (1 m)
Car Traps