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Schleching 2/2008 3.1Präzisionsphysik mit Neutronen/3. n- Experimente jenseits des SM
Präzisions-Physik mit Neutronen1.Neutronenquellen2.Physik mit Neutronen, allgemein3.Neutronen-Experimente: jenseits SM4.Theorie Standard Modell5.Neutronen-Experimente: diesseits SM6.Theorie n-Zerfall
D. DubbersU. Heidelberg
Schleching 2/2008 3.2Präzisionsphysik mit Neutronen/3. n- Experimente jenseits des SM
1. Neutronenquellen1.1 Reaktor Neutronenquellen1.2 Spallations-Neutronenquellen1.3 Ultrakalte Neutronen
Schleching 2/2008 3.3Präzisionsphysik mit Neutronen/3. n- Experimente jenseits des SM
2. Physik mit Neutronen allgemein 2.1 Neutronen-Streuung2.3 Angewandte Neutronenphysik
Schleching 2/2008 3.4Präzisionsphysik mit Neutronen/3. n- Experimente jenseits des SM
Besonderheiten des Neutrons
Neutronen:• sehen besonders gut die leichten Atome (z.B. Wasserstoff-Brücken)• sehen einzelne Isotope (Kontrastvariation)• sehen Magnetismus (Spintronik)• sehen Bewegungen der Moleküle, Spins, (auch sehr langsame)
separat für alle Längenskalen (En ~ Anregungsenergien des Festkörpers, λn ~ Gitterkonstante des Festkörpers)
• sehen getrennt kohärente und inkohärente Prozesse • (Paar- und Autokorrelations-Funktionen)• machen wenig Vielfachstreuung• sind meist sehr durchdringend
Schleching 2/2008 3.5Präzisionsphysik mit Neutronen/3. n- Experimente jenseits des SM
3.Neutronen-Experimente jenseits des SM3.1 Einführung3.2 Einige Experimente
Schleching 2/2008 3.6Präzisionsphysik mit Neutronen/3. n- Experimente jenseits des SM
3.1 Einführung Temperature kT = 10+19 GeV Planck scale
10+16 GeV Grand Unification Inflation ... ... wenn H = å/a ≈ const. Chiral phase transition Nucleon freeze out Electroweak transition Nuclear freeze out Atomic freeze out
Galactic freeze out 10-11 GeV (T = 2.726 K) Big Bang 10-43 s 10-35 s 10-12 s 1 s 105 y 109 y today Time
…
t
History of the universe: a succession of phase transitions
Schleching 2/2008 3.7Präzisionsphysik mit Neutronen/3. n- Experimente jenseits des SM
The Standard Model of particle physics …small input: SYMMETRIES Gauge principle: ψ'(x) = eiθ(x) ψ(x)
('principia') applied to U(1)×SU(2)×SU(3),(+ Lorentz x' = L·x, + CPT etc. invariances, …)
rich output: INTERACTIONS basis for:
→ equations of motion Maxwell, technology,Schrödinger, chemistry,Dirac, molec. biology, … solar/nuclear power,
→ existence of photons, gluons, W±, Z0 (= carriers of interaction)
→ conservation of charges (= sources of interaction)
→ generation of masses
…is very successful ...
ψ:
ψ':
Schleching 2/2008 3.8Präzisionsphysik mit Neutronen/3. n- Experimente jenseits des SM
… but is only part of the picture:Unsolved problems:
3 particle families 12 masses →4 quark-phases + 4 lepton-phases
gravitation and quantum mechanicsbaryon-asymmetry of universe →
mass-energy content of universe …
Test all laws of physics with the highest possible precision(including energy conservation, Lorentz-, CPT-invariance, …).
To be tested, laws must be well known: this is the case mostly in the electroweak and the gravitational sector.
Schleching 2/2008 3.9Präzisionsphysik mit Neutronen/3. n- Experimente jenseits des SM
Particle physics at the lowest energies
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Schleching 2/2008 3.10Präzisionsphysik mit Neutronen/3. n- Experimente jenseits des SM
Precision reached in low-energy work- in energy: δE < 10─23 eV = ± 0.000 000 000 000 000 000 000 01 eV
reached in high-precision ultracold neutron and atom work
- in momentum: δp/p < 10─11: 1Å/10m preached in state-of-the-art neutron optics δp
- in mass: δm/m = ±10─11
reached in atomic mass spectrometry
- in time: δt/t = ±10─16
reached with atomic clocks
- in spin-polariz.: δP < 10─7
reached in polarized neutron work
Schleching 2/2008 3.11Präzisionsphysik mit Neutronen/3. n- Experimente jenseits des SM
Low energy: mostly 1st family
quarks leptons3rd: b t τ ντ
2nd: s c μ νμ
1st : d u e νe
first family is:- abundant, - long-lived, - useful.
Schleching 2/2008 3.12Präzisionsphysik mit Neutronen/3. n- Experimente jenseits des SM
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3.2 Einige Experimente: 1. Why is charge quantized?
Schleching 2/2008 3.13Präzisionsphysik mit Neutronen/3. n- Experimente jenseits des SM
Theory of charge quantization
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Schleching 2/2008 3.14Präzisionsphysik mit Neutronen/3. n- Experimente jenseits des SM
Big Bang theory: baryon density ~ 10−18 photon densitybaryon density = antibaryon density
Observation: baryon density ~ 10−9 photon densitybaryon density >> antibaryon density
possible explanation: Violation of 'CP-symmetry'
Experimentum crucis:Electric Dipole Moment dn of the neutron:
if 'CP' explanation is right: dn = 10−27 1 e cm= value required to explain our existence
if 'CP' explanation is wrong: dn = 10−32 1 e cm= value predicted by the Standard Model
Meas.time t from uncertainty rel. N Δφ ~ 1 with Δφ = ωBohr t = dn·E/ħ t,
i.e. error ΔN Δφ = N ½ ΔωBohr t = (ρUCNV)½ ΔdnE t ~ 1
~ 1 Bohr-period/year ~ 10−23 eV
2. Why has so much matter survived the Big Bang?
60 years of instrument
development
M.v.d. Grinten, K. Jungmann, Sa vorm., S. Paul, Di abend
Schleching 2/2008 3.15Präzisionsphysik mit Neutronen/3. n- Experimente jenseits des SM
3. Are there extra spatial dimensions?
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Schleching 2/2008 3.16Präzisionsphysik mit Neutronen/3. n- Experimente jenseits des SM
Neutron quantization in the earth's gravitational fieldUltracold neutrons (UCNs) probe Newton's law in the μ-meter and the pico-eV range, set limits on such extra forces.
0 1.4 2.5 3.3 4.1 peV
40 μm30 μm20 μm10 μm 0
Schleching 2/2008 3.17Präzisionsphysik mit Neutronen/3. n- Experimente jenseits des SM
UCN gravitational levels
Neutron density above the mirror measured with a position-sensitive detector with spatial resolution of 1.5 μm
Measurement of neutron transmission as a function of the height of the absorber above the neutron mirror.
Schleching 2/2008 3.18Präzisionsphysik mit Neutronen/3. n- Experimente jenseits des SM
Experimental limits on non-Newtonian gravity
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current experimental limits:
neutronAFM Casimir
atomic Casimir
Difficulties of AFM:Electrostatics, geometry, roughness, lateral Casimir force, theory
Ph. Schmidt-Wellenburg, Sa Vorm.; Schleching 2006
Schleching 2/2008 3.19Präzisionsphysik mit Neutronen/3. n- Experimente jenseits des SM
Neutrinos oscillate: νe↔ νμ , etc. Δm:
Lepton number oscillations Le ↔ Lμ, etc. 0.05 eV
Kaons oscillate: K ↔ K'Strangeness oscillations S ↔ S 10−18 eV
Do neutrons oscillate? n ↔ nbarBaryon-number oscillations B ↔ B ?
Neutron oscillations allowed in various Grand-Unified Theories
4. Neutron oscillations
a) Is baryon number conserved?
Schleching 2/2008 3.20Präzisionsphysik mit Neutronen/3. n- Experimente jenseits des SM
The antineutron
detector
'Appearence experiment':Experimental limit τn nbar > 0.86·108 s (90% c.l.)
m·c2 = <n|H|nbar> < 10−23 eVprobes 105 GeV range (model dependent)Heidelberg-ILL-Padova-Pavia collaboration (M. Baldo-Ceolin et al., 1994)
The magnetically shielded beam < 5 nT
The ILL neutron oscillation experiment
Schleching 2/2008 3.21Präzisionsphysik mit Neutronen/3. n- Experimente jenseits des SM
b) Is Dark Matter from a mirror world?Is there a sterile mirror world?
Mohapatra, 2005: n ↔ nmirror
can neutrons spontaneously disappear into sterile,
i.e. unobservable mirror neutrons?
Search for neutron − mirror-neutron oscillations
Experiment: U. Schmidt, spring 2007:
using zero-field spin-echo apparatus at FRM2, and ultrafast 'CASCADE' n-detector
'disappearence experiment' - experimental limit:
NB>0/NB=0 = 1.00002(3) → τn-nmirror > 2.7 s (90% c.l.)
September 2007: New limit from ILL, Serebrov et al.: τn-nmirror > 400 s (90% c.l.)
K. Kirch, Mo Abend?
Schleching 2/2008 3.22Präzisionsphysik mit Neutronen/3. n- Experimente jenseits des SM
Summary: low-energy neutron physics beyond S.M.
• Why is charge quantized? (qn)
• Why is so much matter and so little antimatter in the universe? (EDM)• Are there hidden dimensions of space-time? (n-free fall)• Can matter oscillate into antimatter? (n-nbar)• Is there a sterile mirror world? (n-nmirror)… (Paul Di Abend)