Neutron Physics - Brookhaven National Laboratory · W. M. Snow Physics Department Indiana University NPSS, Bar Harbor Neutron Physics 5 lectures: 1. Physics/Technology of Cold and

W. M. SnowPhysics DepartmentIndiana UniversityNPSS, Bar Harbor

Neutron Physics

5 lectures:

1. Physics/Technology of Cold and Ultracold Neutrons2. Electroweak Standard Model Tests [neutron beta decay]3. Nuclear physics/QCD [weak interaction between nucleons]4. Physics Beyond the Standard Model [EDM/T violation, B]5. Other interesting stuff that neutrons can do [NNN interaction, searches for extra dimensions,…]

Other Interesting Physics

1. Neutron Gravitational Bound States2. Precision Few-Nucleon Physics: n-A scattering lengths3. T violation in Polarized Neutron/Polarized Target Transmission4. Bell’s Inequalities and Entangled QM States

Thanks for slides to: Hartmut Abele (Heidelberg), Valery Nezvishevsky (ILL), Muhammad Arif (NIST), Tim Black (UNC/Wilmington), Yuji Hasegawa (Atominstitut, Wein)

Classical and QM Point of ViewClassical and QM Point of View

Neutron Neutron Probability Distributions Above the Probability Distributions Above the MirrorMirror

Experimental ApparatusExperimental Apparatus

Observation of neutron gravitational Observation of neutron gravitational quantum statesquantum states

Comparison to TheoryComparison to Theory

Large extra dimensions?Large extra dimensions?

Neutron, Newtonian

Non-Newtonian Interaction

Neutron, Non-Newtonian

Ratio

TeV scale Quantum Gravity:

2)4(

2)4(

++= n

nPln

nPl MrM 2)4(

2)4(

++= n

nPln

nPl MrM 2)4(

2)4(

)4(2

24 ~1~

M

M

Mrg n

nnn

+

+2

)4(

2)4(

)4(2

24 ~1~

M

M

Mrg n

nnn

+

+

g = 9.85 ± 0.7 m/s2

Previous Previous LimitsLimits

Limits for alpha and lambdaLimits for alpha and lambda

H. A. et al., Lecture Notes in Physics, Springer, 2003

01.11.04 V.V.Nesvizhevsky

- Search for extra fundamental forces at short distances of 1 nm - 10 µm

-Verification of electrical neutrality of neutrons

Perturbation frequency, Hz

Transition probability

induced by

vibrating mass

eVE 18min 10−≈δ

6

12

min 10−≈− EE

Eδ

ijji wEE ⋅=− h

Hz26021 ≈ν

Quantum trap

Resonance transitions

Potential Applications in fundamental physics

Neutron Interferometer and Optics Facility (NIOF) at NIST

How a neutron interferometer works

Neutron

beam

Interferometer

O-beam

H-beam

Phaseshifter

Sample

∆ε

δ

Phase Shifter Angle (deg)

1000

500

0-2 -1 0 21

Visibility

∆φ

Outgoing

wave front

Incident

wave front

optV

∆φ

Sample

λ λλ/ n

λ λλ

D

Only neutron optics devicewhich can directly measurethe phase shift.

Visibility > 90%

Sample

Top View

Neutron wave functioncoherently split byBragg diffraction.

∆φ = − λΝbD

Coherent Neutron scattering lengths 1 cm n - beam

phase shifterSi (111)

vacuum cell

cell out

Temp B

3He detectors

Temp A

cell in

gas cell

quartzalignment

flag

Two n-A scattering lengths b± for I±1/2

Coherent scattering amplitude bcoh=sum over those amplitudes which do not change the QM state of the target

Phase shift proportional to bcoh

1950 1960 1970 1980 1990 20006.4

6.5

6.6

6.7

6.8

Year

Many MethodsBragg DiffractionChristiansen filterGravity reflectometryTotal reflectionInterferometryTransmission

D2 scattering length measurement

bnd = (6.6727 ± 0.0045) fm

Theoretical calculations of the coherent scattering length compared with the experimental value. The central dark band is the 1σ confidence band and the lighter band is the 2σ confidence band. Only 2 of the theories fall within 2σ.

Precision measurements in 3-body systems can see effectsof nuclear 3-body forces. No one knows what the nuclear 3-body force should look like.

Measurement of the n-3He coherent scattering length

3.5 × 10-48.250 × 1019 cm-3N1.0 × 10-43.380 × 105 PaP2.3 × 10-423.237 °CT1.0 × 10-41.0016 cmDcell

2.0 × 10-50.271207 nmλ

1.45 × 10-3-1.379 rad∆φcell

6.6 × 10-42.69 rad∆φnD

Relative σV / VValue VParameter

fm )007.0857.5(3 ±=Henbnew measurement

previous world average fm )041.0733.5(3 ±=Hen

b

fm )007.0854.5(3 ±=Hen

bnew world average

•P. R. Huffman, D. L. Jacobson, K. Schoen, M. Arif, T. C. Black, W. M. Snow, and S. A. Werner, A precision neutron interferometric measurement of the n-3He coherent neutron scattering length submitted to Phys. Rev. C.

5 .8

5 .8 5

5 .9

5 .9 5

6

6 .0 5

6 .1

-2 .5 -2 .4 5 - 2 .4 - 2 .3 5

C o m p a r is o n o f t h e o r y a n d e x p e r im e n t fo r c o h e r e n t a n d

in c o h e r e n t b o u n d n + 3 H e s c a t t e r in g le n g th s

b coh [

fm]

bi [ fm ]

A V 1 8

A V 1 8 + U I X E x p e r im e n t

A V 1 8 + U I X + V3

*

Comparisons with RGM calculations using modern NN potentials with 3N Forces*

*H. M. Hoffman and G. M. Hale, Phys. Rev. C 68, 021002(R) (2003).

TT--violation experiments in violation experiments in Polarized Neutron TransmissionPolarized Neutron Transmission

through Polarized Targets through Polarized Targets

H0nuclearspin, I

sn

π/2 flip

orMeissner

sheet

nkn

T-odd correlation in total cross section: (kn×I) · sn

nanalyzer

npolarizer

first step for Tfirst step for T--violation experiment violation experiment measurement of measurement of Xe Xe pseudomagnetismpseudomagnetism

TwoTwo--particle vs. twoparticle vs. two--space entanglemenspace entanglemen

2-Particle Bell-State Ψ = 1

2↑ I⊗ ↓ II + ↓ I⊗ ↑ II

I, II represent 2-Particles

Measurement on each particle A

Ia = +1 ⋅P a;+1

I+ –1 ⋅P a;–1

I

BII

b = +1 ⋅P b;+1

II+ –1 ⋅P b;–1

II

where P ξ;±1 = 1

2↑ ± eiξ ↓ ↑ ± e–iξ ↓

Then, AI, B

II= 0

2-Space Bell-State Ψ = 1

2↑ s⊗ I p + ↓ s⊗ II p

s, p represent 2-Spaces, e.g., spin &

Measurement on each property A

sα = +1 ⋅P α

s+ –1 ⋅P α+π

s

Bp

χ = +1 ⋅P χp

+ –1 ⋅P χ+πp

where P φ = 1

2ϕ + eiφ ϕ ϕ + e–iφ ϕ

Then, As, B

p= 0

==>> (Non-)Contextuality(In)Dependent Results for commuting Observables

Non-Locality: rI≠ rII for

PI(rI) & P

II(rII)

Schematic view of the experimentSchematic view of the experiment

Top ViewTop View

Manipulation of twoManipulation of two--subspacessubspaces(a) Path(a) Path (b) Spin(b) Spin

Oscillations with various spinOscillations with various spin--analysesanalyses

E' α=0, χ = 0.79π= N' 0,0.79π + N' π,1.79π

– N' 0,1.79π – N' π,0.79π÷ N' 0,0.79π + N' π,1.79π

+ N' 0,1.79π + N' π,0.79π= 0.542

In thesamemanner,

E' α=0, χ = 1.29πE' α=0.5π, χ = 0.79πE' α=0.5π, χ = 1.29π

weredetermined.

Violation of the BellViolation of the Bell--like inequalitylike inequality

E' α,χ =

N'+ + α,χ + N'+ + α+π,χ+π – N'+ + α,χ+π – N'+ + α+π,χN'+ + α,χ + N'+ + α+π,χ+π + N'+ + α,χ+π + N'+ + α+π,χ

where N'+ + α,χ = Ψ P α

s⋅P χ

pΨ

E' α1,χ1 = 0.542 ± 0.007E' α1,χ2 = 0.488 ± 0.012E' α2,χ1 = – 0.538 ± 0.006E' α2,χ2 = 0.483 ± 0.012

where

α1 = 0α2 = 0.50πχ1 = 0.79πχ2 = 1.29π

===>>> S' ≡ E' α1,χ1 + E' α1,χ2 – E' α2,χ1 + E' α2,χ2

= 2.051 ± 0.019 > 2

Cf. Max. violaion: SCf. Max. violaion: S’’=2.81>2=2.81>2confidence: 99.6%confidence: 99.6%