Particle Physics with Slow Neutrons ILNGS Summer Institute, September 2005Torsten Soldner Particle Physics with Slow Neutrons I: Neutrons in the Standard Model II: Neutrons beyond the Standard Model Right-handed currents CP violation Baryon number violation Valery Nesvizhevsky: Gravitationally bound quantum states of neutrons: applications and perspectives

Particle Physics with Slow Neutrons ILNGS Summer Institute, September 2005Torsten Soldner I: Neutrons in the SM Introduction The neutron and its interactions Cold and ultracold neutrons Neutron decay in the Standard Model Theoretical description and observables Neutron lifetime Neutron lifetime and astrophysics Beta asymmetry Unitarity of the CKM matrix

Particle Physics with Slow Neutrons ILNGS Summer Institute, September 2005Torsten Soldner Passport of the neutron Massm n = (58) m p = (81) MeV Chargeq =  0.4(1.1)· e Spin  = ½ ħ Magnetic moment  n =  (45)  N =  (14)·10 -8 eV/T Electric dipole momentd n  0.63 · e·cm Life time  = 885.7(8) s Decay modesn  p e e  100% n  p e e   (to be detected) n  H e  4·10 -6 (to be detected)

Particle Physics with Slow Neutrons ILNGS Summer Institute, September 2005Torsten Soldner Fermi Pseudopotential Fermi pseudopotential n d~1Å V eV  Potential of wall Index of refraction  Storage of ultra cold neutrons in material bottles  Neutron guide

Particle Physics with Slow Neutrons ILNGS Summer Institute, September 2005Torsten Soldner Neutrons and Interactions Strong/nuclear WeakGravitational Kinetic energy: eV for 4m/s Electromagnetic Magnetic moment  magnetic scattering  magnetic potential eV for 1.7T  absorption  scattering  Fermi potential O(10 -7 eV) Decay P asymmetry Mass  gravitational potential eV per m

Particle Physics with Slow Neutrons ILNGS Summer Institute, September 2005Torsten Soldner Ultra Cold Neutrons Magnetic potential eV for 1.7TO(10 -7 eV) Fermi potentialStorage Let them fall down! (10 -7 eV per m) Detection 100Å, 100neV, 1mK, 5m/s,  10cm -3 Neutrons with less than ~ eV

Particle Physics with Slow Neutrons ILNGS Summer Institute, September 2005Torsten Soldner Cold Neutrons Transport B   3-10Å, 10meV, 30K, 1000m/s,  10 4 cm -3 V eV V Polarisation (same for UCN)

Particle Physics with Slow Neutrons ILNGS Summer Institute, September 2005Torsten Soldner Neutrons at Reactors From fission to ultra cold neutrons: 235 U+n  2 FF + (2-3) n + 200MeV Fast n:> 1MeV Intermediate:1MeV … 1eV Slow:< 1eV epithermal:1eV … 25meV thermal:  25meV cold:25meV … 50  eV very cold:50  eV … 200neV ultra cold:<200neV 235 U n 2MeV ν β γ γ β ν 235 U n 0.1eV 235 U n n 30K 300K

Particle Physics with Slow Neutrons ILNGS Summer Institute, September 2005Torsten Soldner Inside the ILL Reactor 1 m ILL7 H9 H8 H6 IH4 H5 ILL22 H4 H2 IH3 H3 H1 H12 H13 IH1 H10 H11 H7 VCS HCS HS IH2 thermal cold hot D2OD2O H2OH2O IH inclined tube

Particle Physics with Slow Neutrons ILNGS Summer Institute, September 2005Torsten Soldner Institute Laue Langevin: A Neutron User Facility

Particle Physics with Slow Neutrons ILNGS Summer Institute, September 2005Torsten Soldner Semileptonic Processes in the SM Propagator for W boson SU(2) L (V-A) structure of weak interaction Quark mixing: weak and mass eigenstates

Particle Physics with Slow Neutrons ILNGS Summer Institute, September 2005Torsten Soldner Weak coupling constant, V ud

Particle Physics with Slow Neutrons ILNGS Summer Institute, September 2005Torsten Soldner Complication: Neutron ≠ Quarks

Particle Physics with Slow Neutrons ILNGS Summer Institute, September 2005Torsten Soldner Measurement of and V ud Neutron lifetime: J.D. Jackson et al.: Phys. Rev. Lett. 106 (1957) 517 Angular correlation in the decay:

Particle Physics with Slow Neutrons ILNGS Summer Institute, September 2005Torsten Soldner The Neutron Lifetime Beam Detecting decay products along beam section e Storage Detecting surviving neutrons after storage Problem: Combination of absolute measurements, solid angle… Problem: Losses Problem: Losses energy dependent, spectrum changes

Particle Physics with Slow Neutrons ILNGS Summer Institute, September 2005Torsten Soldner Neutron Lifetime  Beam Experiments Penning trap for decay protons Neutron monitor n U 0V 800V L U 0V 800V L

Particle Physics with Slow Neutrons ILNGS Summer Institute, September 2005Torsten Soldner Neutron Lifetime  Beam Experiments SourceCorErr Neutron density ( 6 LiF foil area density, 6 Li cross section, solid angle, halo, …) Trap nonlinearity Proton backscatterer calc.0.4 Proton counting statistics1.2 Neutron counting statistics0.1 Total M.S. Dewey et al.: Phys. Rev. Lett. 91 (2003) ms proton trapping 76  s proton counting Background suppression  = (886.8  1.2  3.2) s (0.4% precision)

Particle Physics with Slow Neutrons ILNGS Summer Institute, September 2005Torsten Soldner Storage in Material Bottles – Losses Wall collision V  (20nm) x Upscattering H atom Same mass Large scattering cross section Wall, T  100KUCN, T  1mK Other atoms Dust Coherent interaction with wall Lost Heated Losses per collision Effective collision rate Variation of v (spectrum) or L (bottle size)  Extrapolation to  = 0 – Absorption

Particle Physics with Slow Neutrons ILNGS Summer Institute, September 2005Torsten Soldner Example – MAMpe BOttle A. Pichlmaier, PhD Thesis, TU München (1999)

Particle Physics with Slow Neutrons ILNGS Summer Institute, September 2005Torsten Soldner Systematic Effects… Faster neutrons  more wall collisions  faster losses Small energy changes  Spectrum changes during storage  Storage time not constant Surface properties really stable? (especially for liquid surfaces) Vacuum equal/constant? Temperature of surfaces Neutron detection efficiency size-dependent? Gravity corrections?  Extrapolation linear?

Particle Physics with Slow Neutrons ILNGS Summer Institute, September 2005Torsten Soldner The Smallest-Stated-Error Neutron Lifetime Measurements EffectCorErr Volume dep. of UCN detect. efficiency Spectral change dep. of UCN detect. effi0.3 Time dep. of upscattering due to spectrum change 0.2 Volume dep. of thermal neutron detect. effi UCN scattering on residual gas0.2 Epi-Fomblin neutrons in UCN spectrum0.2 Temperature gradients in UCN bottle0.15 A. Serebrov et al.: Phys. Lett. B 605 (2005) 72  = (885.4  0.9  0.4) s (0.1% precision)  = (878.5  0.7  0.3) s (0.1% precision) EffectCorErr Statistics0.7 Calculation of collision rate0.24 Energy dependence of losses per collision0.14 UCN spectrum uncertainties0.10 Trap size uncertainties0.06 UCN scattering on residual gas Uncertainty in the LTF Fermi potential0.004 S. Arzumanov et al.: Phys. Lett. B 483 (2000) 

Particle Physics with Slow Neutrons ILNGS Summer Institute, September 2005Torsten Soldner History of Neutron Lifetime World average [PDG] Last (single) measurement

Particle Physics with Slow Neutrons ILNGS Summer Institute, September 2005Torsten Soldner Magnetic Storage No surface interactions Losses by spin flips, easier to detect than in material bottles Losses still energy dependent eV for 1.7T Best magnetic storage experiment  = (877  10 ) s W. Paul et al.: Z. Phys. C 45 (1989) 25      

Particle Physics with Slow Neutrons ILNGS Summer Institute, September 2005Torsten Soldner Magnetic Storage – Present Project First test run (2003):  = (882  16 ) s A.Z. Andreev et al.: ILL Annual Report (2003) 92

Particle Physics with Slow Neutrons ILNGS Summer Institute, September 2005Torsten Soldner Neutron and Astrophysics 1: Big Bang Nucleosynthesis kT [MeV] t [s] d destroyed by  (kT < 2.2MeV, but N  / N B  10 9 )   decay rate   reaction rate He formation Freeze-out if Hubble expansion rate greater than reaction rate   T f   important for primordial 4 He content in Universe Depends on baryon density N B /N  =  10  Historical: First estimate of number of light neutrino families (important for cooling down) N = 2.6 ± 0.3

Particle Physics with Slow Neutrons ILNGS Summer Institute, September 2005Torsten Soldner Neutron and Astrophysics 1: Big Bang Nucleosynthesis Other primordial elements (D, 3 He, 7 Li) depend stronger on nuclear reaction rates Baryon density N B /N  =  10  can be derived from BBN – consistent? Consistent with CMB data?

Particle Physics with Slow Neutrons ILNGS Summer Institute, September 2005Torsten Soldner Neutron and Astrophysics 1: Big Bang Nucleosynthesis Other primordial elements (D, 3 He, 7 Li) depend stronger on nuclear reaction rates Baryon density N B /N  =  10  can be derived from BBN – consistent? Consistent with CMB data? Influence of  : Shift  by 9  (1%)  = 885.7(8)s  Y p = (6)  = 878.5(8)s  Y p = (6) Observed: large systematic uncertainties, Y p = 0.238(2)(5), Y p = … 0.258, … 878.5(8)s 885.7(8)s G.J. Mathews et al.: Phys. Rev. D 71 (2005)

Particle Physics with Slow Neutrons ILNGS Summer Institute, September 2005Torsten Soldner Neutrons and Astrophysics 2: Solar Cycle, Neutrino Production Solar luminosity  fusion rate  T, g A 2  Can derive T g A, g V still important for neutrino detection 8 B production strongly T dependent, rate  g A 5 Wrong g A 5 responsible for to low 8 B- e rate? No, would require  = 800s

Particle Physics with Slow Neutrons ILNGS Summer Institute, September 2005Torsten Soldner Neutrons and Neutrinos: Reaction Cross Sections Charged current Charged current (SNO, electron detection) Charged current

Particle Physics with Slow Neutrons ILNGS Summer Institute, September 2005Torsten Soldner V ud and the Beta Asymmetry Need to measure beta asymmetry A

Particle Physics with Slow Neutrons ILNGS Summer Institute, September 2005Torsten Soldner Unitarity of Quark Mixing From 0 +  0 + decays: Uncertainties for neutron may be higher (new lifetime exp.!) New results from V us could restore agreement If really new physics: More quark generations additional Z boson right-handed W bosons coupling to exotic fermions Supersymmetry Experimental side not settled! H. Abele et al.: Eur. Phys. J. C 33 (2004) 1 Neutron decay (A Perkeo II,  n ):

Particle Physics with Slow Neutrons ILNGS Summer Institute, September 2005Torsten Soldner V ud H. Abele et al.: Eur. Phys. J. C 33 (2004) 1 ProcessDisadvantageV ud Neutron beta decayg A and g V needed (or A and  ) (13)Error from A dominates 0 +  0 + ( 10 C, 14 O, 26m Al, 34 Cl, 38m K, 42 Sc, 46 V, 50 Mn, 54 Co) Nuclear structure effect corrections (5)Error theory- dominated Pion beta decaySmall branching ratio (56) Global fit to angles and phaseAssumes CKM unitarity – Theory error: Radiative corrections Enter in neutron decay and 0 +  0 + For pion decay theory error factor 2 smaller

Particle Physics with Slow Neutrons ILNGS Summer Institute, September 2005Torsten Soldner Beta Asymmetry A – How to measure A = (13) Solid angle? Polarisation / Flipping? Energy calibration? Background?

Particle Physics with Slow Neutrons ILNGS Summer Institute, September 2005Torsten Soldner Beta Asymmetry A - Experimental Situation Solid anglePolarisation B   M. Kreuz et al.: NIM A 547 (2005) 583 Energy calibration 207 Bi 113 Sn 137 Cs 109 Cd Background Decay prob.: Scattering : ~10 -3 , fast n: ~10 -4 E e  E 

Particle Physics with Slow Neutrons ILNGS Summer Institute, September 2005Torsten Soldner Beta Asymmetry A – Perkeo II (prelim)

Particle Physics with Slow Neutrons ILNGS Summer Institute, September 2005Torsten Soldner Summary – Neutrons in the Standard Model Two parameters of the Standard Model from neutron decay: V ud and Observables: Lifetime and correlation coefficients Difficult measurements: Low energies, slow decay, …  clever ideas for experiments needed – extrapolation techniques – relative measurements – use of magnetic fields Input parameter for solar cycle, BBN Test of CKM unitarity