Fundamentale Wechselwirkung Neutronenphysik W.Heil  Einleitung  Präzisionsexperimente mit ultrakalten Neutronen und Perspektiven  ß-Zerfall des Neutrons und Tests des Standard Modells  Zusammenfassung

NEUTRON  discovery 1932 ( J. Chadwick )  + 9 Be  n + 12 C ( via H(n,p)-reaction )  Q <  e , Baumann et al., ´88  Spin: I = ½ ;  n =  K  T =  0.8 s, PDG 2004 ( n  p + e + e ) Particle physics at low energies  EDM of the neutron ( CP-violation )  Beta-decay experiments: neutron lifetime measurements angular correlation experiments  Quantum states and gravitation  n-n oscillation, n-n‘ oscillation, … Neutrons as probe: = h / mv : O(Ǻ) scattering amplitude: ~, b c  b i  r e  3 fm structure and dynamic of condensed matter takes part on all four known fundamental interactions ( strong, weak, elmg., gravitative)

Spectrum of Neutrons UCN: v < 6 m/s storage experiments

Fluence rate (  10 9 cm -2 s -1 ) (20) Fluence rate (  10 8 cm -2 s -1 ) 8 (10) (5)

CP-violation and EDM  EDM is a test for flavour diagonal CP - test of structure of vacuum at small distance scales - background free probe for ‚new physics‘  CP in nucleons (neutron) needed for - Baryogenesis problem (matter vs. anti-matter in the universe) - test of CP violating part in QCD ( -term )  EDM can be studied in -Diamagnetic atoms -Paramagnetic atoms, molecules ( CP electron-EDM) -Neutron ( CP in quark sector )

EDM verletzt P und T Symmetrie Neutron EDM:

 d n < 3  e  cm (90% CL) [e  cm] The neutron EDM: Progress at  order of magnitude per decade Standard Model out of reach strong contrains on e.g. Super Symmetry exp. vs theory Proposed limits on d n  ( ) e·cm C.A.Baker et al.,

Ramsey’s Technique Free precession... Apply  /2 spin flip pulse... “Spin up” neutron... Second  /2 spin flip pulse. B B B E E - +

Apparatus Neutron storage chamber HV B-field coils E = 7 kV/cm B = 1  T Hg co-magnetometer Neutron EDM result  d n  < 3  e  cm

Sensitivity figure at present: visibility:   0.5 ( neutron polarisation ) electric field: E  7 kV/cm ( limited by Hg co–magnetometer ) storage time : T = 130 s ( limited by T 2 of Hg co-magnetometer ) N ucn /batch : N  (  ucn  1 cm -3 - UCN density !!! ) 1 day of data (  360 Ramsey-cycles ) : 1 year of data ( 250 days ) : statistically limited !!!

Density of neutrons with velocities between v and v+dv at thermal equilibrium Density of ultra-cold neutrons: 0 ≤ E ≤ V F ILL-Grenoble: T 0 =300 K  = 2.2x10 5 cm/s V F = 200 neV  0 = 6  n/cm 2 /s  UCN  40 cm -3 gain due to cooling UCN production ( conventional )

 1000 / cm 3 liquid D 2 : 25 l T = 25K  40 / cm 3

Superthermal UCN sources ( E n =  ) >> k B T >> E UCN R.Golub, J.M.Pendlebury, Phys.Lett. A53,133 (1975) T  0.5 K

at present : P  1 UCN/cm 3 /s Superfluid He ( T  0.5K) Cryogenic Neutron EDM Experiment at ILL

solid deuterium Cryostat with neutron detector research reactor TRIGA-Mainz UCN TOF-spectrum   / pulse Mainz, TUM collaboration EPJ A (’07) in press

UCN density / cm 3 Experiments: - nEDM - n-lifetime - n quantum states in the Earth‘s grav. field - angular correlation coefficents in n ß-decay -...

Test Newton with Neutrons Quantum states and gravitation Newton + Yukawa Potential arising from higher-dimensional gravity, gauge forces or massive scalar fields - strength factor - Yukawa-length

Neutron mirror: polished glass plate 10 cm long Nature (2002), Phys. Rev. D ( 2003). 1 peV 2 peV 3 peV 4 peV UCN v ↑  1 cm/s rate: mHz

Baeßler et al. PRD 2007 Westphal, Abele, Baeßler arXiv:hep-ph/ Limits

Obserables in neutron ß-decay p n e-e- Neutron lifetime Beta-Asymmetry Jackson et al., PR 106, 517 (1957): Neutrino-Electron-Correlation Standard Model

(re-)measured by: PENELOPE aSPECT PDG 2006: ! CKM-Unitarity of first row: Kaon decay

Neutron lifetime measurements  beam experiments (e -, p) … register the decay products from a well-defined volume traversed by a beam of well-determined fluence rate (absolute measurement)  storage experiments …measure the decay product of an ensemble of neutrons as a function of time and determine the slope (relative measurement), but … n MAMPE

Neutron Lifetime versus Year Serebrov et al., Phys. Lett. B 605, 72 (2005) (878.5 ± 0.7 ± 0.3) seconds Data points used by PDG 2004 for averaging BWF 2005

New approach… magnetic storage ( PNPI, ILL, TUM ) bottle made of super- conducting magnets measure storage and decay expected ( FRM II ): 10 8 V= 700 L goal: rel.statistical uncertainty

new V us value Perkeo II ( Abele et al.) (Wu-experiment) Perkeo (2002): Perkeo (2006): corrections to superallowed 0 + →0 + nuclear ß-decay Hardy,Towner, arXiv: v1, Oct‘07 lower average Ft-values higher V ud

… towards a strong source of n-decay products cold neutron guide ILL, FRM II : A = 100 cm 2  10 6 n-decays s -1 m -1

… PERC (Dubbers et al.)

Zusammenfassung: Neutronenphysik (heute) - d N < 3  e cm - Unitarität der CKM-Matrix (  = (14) - Quantenzustände im Gravitationsfeld (peV) - … Angenommen das Neutron hätte die Größe der Erde...  x  1  m Neutronenphysik (morgen)  ab 2010: leistungsstarke Quellen ultrakalter Neutronen ( PSI, FRMII, ILL,TRIGA, …) mit Dichten 10 2 < < 10 4 cm -3  leistungsstarke Quellen für e -, p aus dem Neutron ß-Zerfall ( PERC,…) sensitiv auf d N  ecm Gravitation: E  eV n-Lebensdauer: nn‘, nn –Oszillationen … …