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NEUTRONS, PARTICLES, AND THE UNIVERSE. Dirk Dubbers, U. Heidelberg. A. OVERVIEW. The ultimate aims of PARTICLE Physics :. Maxwell eqs., Schrödinger eq. electroweak eqs., quantum-chromodyn., ...  (works beautyf. ) gravitation, masses, charges, families,

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Neutrons particles and the universe

NEUTRONS, PARTICLES,

AND THE UNIVERSE

Dirk Dubbers, U. Heidelberg

ESS 17.05.2002 Neutron Particle Physics


Neutrons particles and the universe

A. OVERVIEW

The ultimate aims of PARTICLE Physics:

Maxwell eqs.,

Schrödinger eq. electroweak eqs., quantum-chromodyn.,

...  (works beautyf.)

gravitation, masses, charges,

families,

...(doesn't work yet)

Derive the basic laws of nature …

e.g. 'gauge invariance' implies 

E = /0

E+Bt = 0 B = 0

c2BEt = j/0

… from simple symmetry principle(s)

Link all this to cosmology:

ESS 17.05.2002 Neutron Particle Physics


Neutrons particles and the universe

ESS 17.05.2002 Neutron Particle Physics


Neutrons particles and the universe

The role of the NEUTRON

Beam energy in experiments:

 High-energy particle physics at Tera-eV10+12 eV

Studies on 2nd and 3rd particle families

3rd: b, t, ,  2nd: s, c, ,

Low-energy particle physics at Nano-eV10-9 eV

Precision studies on 1st particle family1st: d, u, e,e

ESS 17.05.2002 Neutron Particle Physics


Neutrons particles and the universe

Sensitivity of neutron experiments:

Energy:E ~ 10-22 eV

Momentum:p/p = 10-11

Polarization:P ~ 10-7

Neutron exp’t:

EDM: E/ ~ 1/month

n-charge: 1Å on 10m

P-violation: 0.000010 spinrot.

Neutron-particle physics:

free neutron

provides more than two dozen observables

Neutron Data Booklet 2002

addresses about two dozen

  • BASIC QUESTIONS

from particle physics and cosmology:

ESS 17.05.2002 Neutron Particle Physics


Neutrons particles and the universe

B. SOME PAST ACHIEVEMENTS

  • WAS THERE A BIG BANG?

redshifts and microwave- background

pre-1990: 'soft' qualitative evidencefor Big Bang

 1990: 'hard' numeric evidence for Big Bang:

after 1 sec:freeze-out of neutron/proton ratio to 1/7:

after 10 min:light-element abundances:

relative to hydrogen

n

p

ESS 17.05.2002 Neutron Particle Physics


Neutrons particles and the universe

  • .Light-element abundances depend on:

    • neutron lifetime 

    • neutrino cross-sections  1/

    • number of particle families N

    • density  of (ordinary) matter in universe

n  p+e–+e*

n+e p+e–

is universeopen, closed, or critical (flat) ?

This makes: number of particle familiesN

and density of the universe

accessible to observation! But:

Largest error is due to neutron lifetime

From 4He yield:

N = 13 /

ln/0 = 20 /

. · · . · · . . . · · . . . · .· . UCN

Measurement of  in ultracold-neutron bottle Tn  1 mK

Neutron lifetime :1985: (925  11) s

1990: (889  3) s

2002: (885.8  0.9) s

n = noexp(– t/)

ESS 17.05.2002 Neutron Particle Physics


Neutrons particles and the universe

  • HOW MANY FAMILIES OF PARTICLES POPULATE THE UNIVERSE?

1989: Big Bang result, with new neutron lifetime:

N = 2.6  0.3 i.e. N is limited to 3 families.

Confirmed later by high-energy experiment:

N = 3.00  0.02 now used as input

in Big Bang calculations.

Z0 - width at CERN

This leaves the average densityof the universe as the only unknown parameter :

ESS 17.05.2002 Neutron Particle Physics


Neutrons particles and the universe

  • DOES THE UNIVERSE REACH ITS CRITICAL MASS?

Answer: Yes, but not with ordinary matter!

Density of ordinary matter 

Critical  density

Y

/crit

Present status: Neutron lifetime is still largest source of error in 4He-abundance calculation

ESS 17.05.2002 Neutron Particle Physics


Neutrons particles and the universe

  • CAN MATTER CHANGE INTO ANTIMATTER?

 Neutrinos oscillate: e  ,

'Lepton-number oscillations'mc2  0.05 eV

's

-detection efficiency  1/

'Strangeness oscillations' mc2  10-18 eV

 Kaons oscillate: K  K*

 Do neutrons oscillate n  n*(neutron  antineutron, 'n-nbar' )

'Baryon-number oscillations' B = +1  -1

Baryon-number oscillations are allowed in some Grand-Unified Theories.

ESS 17.05.2002 Neutron Particle Physics


Neutrons particles and the universe

The antineutron detector

Experimental limit: nn* > 2.9 years

< nHn*>  10-23 eV

(90% c.l.)

Present: limit on neutron oscillations probes 105 GeV range Future: neutron-oscillation search with UCN ?

ESS 17.05.2002 Neutron Particle Physics


Neutrons particles and the universe

  • HOW ARE THE HEAVIER ELEMENTS FORMED IN SUPERNOVA EXPLOSIONS?

Within seconds, solar-system masses are created in Super-Nova explosions. The field urgently needs neutron-nuclear data.(from neutron-fission products 'far-off stability')

SuperNovae do explode, though not on the computer.

  • ON TOPOLOGICAL PHASES

n(C)=  Cn(R)n(R)·dR

Mathematical 'theories of connections'

are right at the heart of avant-guard physics.

1984: Berry's theorems on 'topological phases'

1985: first measurements with polarized neutrons

1995: 'hidden symmetries' detected with microwaves

2000: theory of 'off-diagonal Berry Phases' developed

2001: first measurements with neutron interferometry

ESS 17.05.2002 Neutron Particle Physics


Neutrons particles and the universe

  • NEUTRON QUANTUM OPTICS

R(3600) = -1 Aharonov-Bohm Aharonov-Casher squeezed states beat optics dressed neutrons optical pumping ...

This, too, is a neutron:

 = |I + II |2

Status: Non-classical states of neutrons and UCN can be produced and used in neutron-interferometry and spin-echo systems

ESS 17.05.2002 Neutron Particle Physics


Neutrons particles and the universe

  • HOW STRONG ARE NATURE'S FUNDAMENTAL FORCES?

Neutrons are sensitive to all four forces of nature

1. THE 'WEAK' FORCE:

Neutron-decay measurements:

• neutron lifetime  = (885.8  0.9) s

• electron-neutrino correlation a = -0.102  0.005

• beta asymmetry A = -0.1189  0.0007

• neutrino asymmetry B = 0.983  0.004

• triple-correlation D = -(0.55  0.95)10-3 . . .

give nucleon-lepton weak-interaction coupling-constants:

Vector: gV = (1.1470  0.0016)10-5 (c)3 GeV-2

Axial-vector: gA = (-1.4602  0.0008)10-5 (c)3 GeV-2

Phase(V-A): = 180.070  0.120.

ESS 17.05.2002 Neutron Particle Physics


Neutrons particles and the universe

Example: beta-asymmetry in neutron decay

Experiment:

  (= e-)

neutrons  spin up

  Detector

Beam-time will start soon

Problem is over-determined: precision tests beyond the Standard Model (see below)

ESS 17.05.2002 Neutron Particle Physics


Neutrons particles and the universe



2. THE ELECTROMAGNETIC FORCE:

The strength of the electromagnetic force is given by the fine-structure constant

 = e2/c =(2Rh/mec)½

neutron measurements of:

h/mn = (3.956 033 3  0.000 000 3)10-7 m2s-1

mn/mp = 1.001 378 418 87  0.000 000 000 58

give a model-independent value:

-1 = 137.036 011  0.000 005

nvn = h/m, h = Planck's const.

… plus R plus mp/me

 is needed for precision tests of Standard Model

example: magnetic moment of muon

Theory (input ):

g=2.002 331 8320(14)

Experiment: 3 deviation?

g=2.002 331 8404(30)

Status: Neutron data give strengths of 2 of the 4 forces of nature

ESS 17.05.2002 Neutron Particle Physics


Neutrons particles and the universe

Neutron: gravitational force/inertial force:  = 1.00011  0.00017

3. THE GRAVITATIONAL FORCE:

  • IS FREE FALL A CONTINUOUS PROCESS?

Quantization of UCN in the earth's gravitational field: Do neutrons fall in 'steps'? Answer: yes, they do!

•_

_

_

4. THE 'STRONG' FORCE:(see below)

ESS 17.05.2002 Neutron Particle Physics


Neutrons particles and the universe

C. ESS-FLAGSHIP EXPERIMENTS

  • DO THE STRONG AND ELECTROMAGNETIC FORCES ACT INDEPENDENTLY?

Standard Model: strong interactions of proton-proton, proton-neutron, and neutron-neutron must all be equal.

But: scattering lengthsapp = -23.82(1) fm

anp = -17.1(2) fm 

ESS FLAGSHIP: DIRECT MEASUREMENT OF NEUTRON - NEUTRON SCATTERING LENGTH ann

UCN ?

N.B.: n-n rate  (n-flux)2 !

Expected n-n scattering rate: several events per minute

ESS 17.05.2002 Neutron Particle Physics


Neutrons particles and the universe

  • WHY HAS SO MUCH MATTER SURVIVED THE BIG BANG?

. ..qq*.

Big Bang theory: matter and antimatter should annihilate each other

vs. evidence:we exist

explanation: violation of 'CP-symmetry' ?

(Sacharow 1965)

experimentum crucis:

Electric Dipole Moment (EDM) of the neutron:

if 'CP' explanation is right: EDM = 10-271 ecm

= value required to explain our existence

if 'CP' explanation is wrong: EDM = 10-321 e cm

= value predicted by the Standard Model

present experimental limit: EDM < 6.310-26e cm

CPT=1

Ultracold neutrons !

-

EDM

+

(90% c.l.)

ESS 17.05.2002 Neutron Particle Physics


Neutrons particles and the universe

ESS-FLAGSHIP: NEW TYPE OF ULTRACOLD NEUTRON (UCN) SOURCE

 Solid-deuterium UCN-source

Future: Question of dominance of matter over antimatter will be solved in the next twenty years. ESS should be in the game and provide strongest UCN source in the world.

ESS 17.05.2002 Neutron Particle Physics


Neutrons particles and the universe

  • IS THE LEFT-HANDEDNESS OF NATURE AN "EMERGENT PROPERTY"?

Standard Model:

Electroweak Interaction is 100% left-handed

Did Universe start left-right symmetric, i.e. is left-handedness an 'emergent property' ?

If so, then 'right-handed' heavy brother of W-boson must exist

did parity violation arise as an order-parameter during a phase transition of the vacuum in the early universe

Limits from neutron decay experiments:

mass of right-handed W:mR > 280 GeV/c2

left-right mixing phase: -0.20 <  < 0.07

mL=81 GeV/c2

WL=W1cos–W2sinWR=W1sin+W2cos

(90 % c.l.)

Present: neutrons very competitive with high-energy work

ESS 17.05.2002 Neutron Particle Physics


Neutrons particles and the universe

ESS-FLAGSHIP: SPONTANEOUS TRANSFORMATION OF A FREE NEUTRON INTO A HYDROGEN ATOM

Experimentum crucis: would isolate effect of right-handed boson

Fast-hydrogen recoil detector

n  H(2S) + e*mS:+½  +1 +½ (left-hd.) mS:+½  +1 –½ (right-hd.)

Decay volume

Cold neutrons

Optical detection of Lyman- in fast coincidence

Interesting event signature. Expected n  H rate:10 events/minute

Future: sensitive yes/no experiment on origin of P-violation

ESS 17.05.2002 Neutron Particle Physics


Neutrons particles and the universe

  • IS QUARK-MIXING DONE PROPERLY?

When quarks are subject to electroweak force:

'down' = down + some strangeness + some bottomness

'strange' = strange+ some downness + some bottomness

'down' = down + some strangeness + some downness( with respect to 'mass eigenstates')

quark mixing matrix is 'unitary' (pure rotation in 'flavor' space)

Standard Model of Particle Physics requires:

this 'quark-mixing' should be a zero-sum game

From neutron decay experiments:

3.0 standard deviations from zero observed: = -0.0083  0.0028

Present: puzzling deviation from Standard Model ?

ESS 17.05.2002 Neutron Particle Physics


Neutrons particles and the universe

ESS-FLAGSHIP: THE ULTIMATE NEUTRON-DECAY CORRELATION EXPERIMENT

ESS neutron long-pulset = 2 ms

Beam chopper

 = 4.5 Å,  = 1.5 Å I = 1.2 ·1010/s (peak)

Free-neutron cloud N = 2·108 neutrons

103m/s

Future: neutron decay at rate N/ =2·105/s studied under optimum conditions

107m/s

time-average: 104/s present rate: 2 ·102/s

Beam chopper

B

decay products locked to B-field

e- and p+ detector time-gated

ESS 17.05.2002 Neutron Particle Physics


Neutrons particles and the universe

D. SUMMARY

ESS 17.05.2002 Neutron Particle Physics


Neutrons particles and the universe

E. CONCLUSION

Neutron-particle and neutron-nuclear physics is a successful and growing field of neutron science.

in recent years: + 4 university chairs + 4 associate profs. solely in D

ESS WILL PROVIDE AN OPTIMAL TOOL FOR THEIR WORK.

ESS 17.05.2002 Neutron Particle Physics


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