neutrons, particles, and the universe

ESS 17.05.2002 Neutron Particle Physics

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NEUTRONS, PARTICLES, AND THE UNIVERSE

Dirk Dubbers, U. Heidelberg


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Derive the basic laws of nature …

e.g. 'gauge invariance' implies

E = /0

E+Bt = 0 B = 0

c2BEt = j/0

Maxwell eqs.,Schrödinger eq. electroweak eqs., quantum-chromodyn.,... (works beautyf.)

gravitation, masses, charges,families, ...(doesn't work yet)

The ultimate aims of PARTICLE Physics:

Link all this to cosmology:

A. OVERVIEW

… from simple symmetry principle(s)


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A short history of the UNIVERSE

Temperature

kT=10+19 GeV Planck scale

Grand Unification Inflation

Electroweak transition Nucleon freeze out

Nuclear freeze out Atomic freeze out

Galactic freeze out10-11 GeV (T=2.725K)

BigBang 10-43s 10-35s 10-12s 1 s 105y 109y today

Time


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High-energy particle physics at Tera-eV 10+12 eV

Studies on 2nd and 3rd particle families

The role of the NEUTRON

Beam energy in experiments:

Low-energy particle physics at Nano-eV 10-9 eV

Precision studies on 1st particle family 1st: d, u, e, e

3rd: b, t, , 2nd: s, c, ,


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Neutron-particle physics:

free neutronprovides more than two dozen observables

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 Data Booklet 2002

addresses about two dozen BASIC QUESTIONS

from particle physics and cosmology:


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B. SOME PAST ACHIEVEMENTS

WAS THERE A BIG BANG?

pre-1990: 'soft' qualitative evidence for Big Bang 1990: 'hard' numeric evidence for Big Bang:

after 10 min: light-element abundances:

Big-Bangcalculation

Astronomicalobservation

4He (24.0 0.5) % (23.8 0.6) %

2H 610-5 (4 2)10-5

3He 1.510-5 10-5 (?)

7Li 1.510-10 (1.2+0.9-0.3)10-10

n

p

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

redshifts and microwave- background

relative to hydrogen


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.Light-element abundances depend on: neutron lifetime neutrino cross-sections 1/ number of particle families N density of (ordinary) matter in universe

This makes: number of particle families N and density of the universe

accessible to observation! But: Largest error is due to neutron lifetime

. · · . · · . . . · · . . .

· . · .

UCN

n p+e–+e*

n+e p+e–

Measurement of in ultracold-neutron bottle

Tn 1 mK

From 4He yield: N = 13 /ln/0 = 20 /

Neutron lifetime :1985: (925 11) s 1990: (889 3) s2002: (885.8 0.9) s

is universe open, closed, or critical (flat) ?

n = noexp(– t/)


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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 :


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DOES THE UNIVERSE REACH ITS CRITICAL MASS?

Content of universe Density / crit

Luminous matter (0.25 0.05)%Dark ordinary matter (4 1)%Dark exotic matter 30%"Dark energy" 70%Total density ofuniverse

(100 5)% :flat universe

Density of ordinary matter

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

Y

/crit

Critical density

Answer: Yes, but not with ordinary matter!


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CAN MATTER CHANGE INTO ANTIMATTER?

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

Neutrinos oscillate: e ,

Kaons oscillate: K K*

'Lepton-number

oscillations' mc2 0.05 eV

'Strangeness oscillations' mc2 10-18 eV

-detection efficiency 1/

's

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

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


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The antineutron

detector

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

Experimental limit: nn* > 2.9 years < nHn*> 10-23 eV

(90% c.l.)


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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')

ON TOPOLOGICAL PHASES

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 neutrons1995: 'hidden symmetries' detected with microwaves2000: theory of 'off-diagonal Berry Phases' developed2001: first measurements with neutron interferometry

n(C) = Cn(R)n(R)·dR

SuperNovae do explode, though not on the computer.


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NEUTRON QUANTUM OPTICS

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

interferometry and spin-echo systems

= |I + II |2

This, too, is a neutron:

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


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HOW STRONG ARE NATURE'S FUNDAMENTAL FORCES?

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.

1. THE 'WEAK' FORCE:

Neutrons are sensitive to all four forces of nature


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Beam-time will start soon

Experiment:

(= e-)

neutrons spin up

Detector

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

Example: beta-asymmetry in neutron decay


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2. THE ELECTROMAGNETIC FORCE:

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

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

is needed for precision tests of Standard Modelexample: magnetic moment of muon

= e2/c =(2Rh/mec)½

nvn = h/m, h = Planck's const.

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

… plus R plus mp/me


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IS FREE FALL A CONTINUOUS PROCESS?

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

•_

_

_

3. THE GRAVITATIONAL FORCE:

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

Neutron: gravitational force/inertial force: = 1.00011 0.00017


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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 lengths app = -23.82(1) fm

anp = -17.1(2) fm

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

Position sensitive detectors

Position sensitive detectors

Focusedcold and thermal

neutrons

From target station 1 From target station 2

InteractionVolume Expected n-n scattering rate:

several events per minute

N.B.: n-n rate

(n-flux)2 !

C. ESS-FLAGSHIP EXPERIMENTS

UCN ?


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WHY HAS SO MUCH MATTER SURVIVED THE BIG BANG?

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 = 10-271 e cm= value required to explain our existence

if 'CP' explanation is wrong: EDM = 10-321 e cm= value predicted by the Standard Model

present experimental limit: EDM < 6.310-26 e cm

. ..q q* .

+EDM -

(90% c.l.)

CPT=1

Ultracold

neutrons !


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ESS-FLAGSHIP: NEW TYPE OF ULTRACOLD NEUTRON (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.

Solid-deuterium UCN-source


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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

Limits from neutron decay experiments:

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

left-right mixing phase: -0.20 < < 0.07

Present: neutrons very competitive with high-energy work

mL=81 GeV/c2

WL=W1cos–W2sinWR=W1sin+

W2cos

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

(90 % c.l.)


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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

Optical detection of Lyman- in fast coincidence

Cold neutrons

Decay volume

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

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

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


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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')

0%

50%

100%

'down' 'strange' 'bottom'

down strange bottom

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 ?

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


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Be- and p+ detector time-gated

Beam chopper

Beam chopper

Free-neutron cloud N = 2·108 neutrons

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

ESS neutron long-pulse t = 2 ms

103m/s

107m/s

ESS-FLAGSHIP: THE ULTIMATE NEUTRON-DECAY CORRELATION EXPERIMENT

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

decay products locked to B-field

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


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D. SUMMARY

Phase Transitions of the Universeand observables from neutron experiments

A. B.New Physics: Standard Model:

Temperature

10+19 GeV Planck- - GUTs - -

Inflation Electroweak

Nucleon freeze out Nuclear freeze out

Atomic freeze out Galactic freeze out

10-11 GeV

10-43s 10-35s 10-12s 1 s 105y 109y today

Time

dn

qn

n nbar

nnnbar

mWR,

Vud

gA /gV

n

-1

g

N

aWM

A ,P

, , , , ,

pp


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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.

E. CONCLUSION

neutrons, particles, and the universe

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