Tests of Symmetries with Neutrons and Nuclei at Very Low Energies Stephan Paul TU-München

Overview Discrete Symmetries and beta decay – Violating symmetries in beta decay Decay correlations Search for right handed currents – Violating quark/lepton symmetry The unitarity of the CKM matrix Discrete Symmetries and electric dipole moments Mirror particles

 -decay of neutrons/nuclei  -decay rate: a, b, c, A, B, D.. depend on 10 coupling constants C i, C’ i Dependence different according to transitions (M F, M GT, J, J’) – Sensitivity to S, V, A, T, P interaction – Study nuclei and neutrons Sensitivity to symmetries – P-violating: A, B, C, R – T-violating: D, R If T-invariance holds, C i are real In standard model: a and A are related to

Neutrons versus Nuclei Neutrons are pure system – Easy to interpret – Difficult to handle – small radiative corrections – No model assumptions about Schiff-moment necessary (EDM) Nuclei as high statistics sample – Select transition type (pure Fermi/Gamow Teller possible) – High statistics – Cold atom technique, well focusable – High precision mass measurements necessary (  M/M < ) – Sensitive to nuclear matrix elements (lifetime, decay rate) – Technologically challenging but only small volumes necessary (EDM)

 Correlations Measure recoil baryon – Nucleus – Proton Spectral shape depends on transition type (F, GT) Obtain limits on scalar/tensor coupling 2005

Beta-Detector He atom trap 6 Li +  MCP Detector Nuclear decays Produce radioactive nuclei via e.g. cyclotron, Isolde… – Laser cooling and MOT trapping of ions – Gas cooling and Paul trapping/Penning trapping p/A’-momentum measurement via TOF Tag decay time via electron signal Accuracy aim * :  a/a  Efforts: (examples) – CAEN: study GT transitions ( 6 He):  a/a  0.5% (in reach) – CERN: study pure Fermi transitions ( 35 Ar) ongoing – TRI  P: 21 Na : * Ongoing efforts with different traps: TRIUMF, Argonne, CAEN, CERN

Neutron Decay Cold neutron beam from reactor Proton spectrum in retardation spectrometer Details see report from Monday at PANIC ‘08 Accuracy for next beam time:  a/a ~ 0.3%

Measurement of nuclei (Leuven) (see presentation on Monday) – Pure GT transitions selectable – Polarized nuclei require solid target  systematic effects (e-scattering) – Present accuracies  A ~ 1.8% Measurements of neutrons – High precision PERKEO data (Heidelberg/München) – Mixture of Fermi and GT transition  extract – New PERKEO III Improvement of statistical accuracy to  A/A = (from for Perkeo II) Also improved measurement of proton asymmetry C Measurements of A

Time Reversal Tests Measure polarization of e in polarized n-decay – Analyzer: Mott scattering of e on lead – Measure e-track twice – Precision: 2  – For details : see this conference Bodek at al.)   decay/e-scattering planes preliminary

Long lasting puzzle with CKM elements V ud and V us V us – V us revisited by kaon experiment K l3 decays – V us revisited by theory (formfactors) – New value for |V us |=0.2255(19) V ud – Measurements by nuclei (Fermi transitions: 0 +  0 + ) – New precise mass measurements Unitarity of CKM-Matrix

The ISOLTRAP experiment

Long lasting puzzle with CKM elements V ud and V us V us – V us revisited by kaon experiment K l3 decays – V us revisited by theory (formfactors) – New value for |V us |=0.2255(19) V ud – Measurements by nuclei (Fermi transitions: 0 +  0 + ) – New precise mass measurements V ud – Neutron lifetime  n  (A. Serebrov:  n = ± 0.7 stat ± 0.3 syst s) – Measurement e - -asymmetry A in  -decay – New  n  experiments under way Radiative corrections Nuclear corrections Unitarity of CKM-Matrix

Unitarity - Status With new values of V ud and V us : no problem with unitarity at 2  ! V ud 0 + CKM unitarity PDG

EDM Measurements with I,B P-even E P-odd with I,B T-odd E T-even  T-violation of H by d n  CP-violation (CPT-conservation) H = - (d n EJ+ m n B J) / |J| Forces in neutron violate T and P If d n  0

15 Ramsey method (split oscillatory fields) Two-chamber system Present limit: d n < 3  e  cm How to measure an EDM h  = ±  B B      ∙ d n  ∙ E  ħ + dE E - dE

UCN 3 He E-field New Joint EDM Experiment – n2EDM 16 B = 1  T  Lamor = 30 Hz E-Field = 130 KV / 10cm Sensitivity now: 1 turn / half year Later 10 to 100 times better. Other activities: (combine source and measurement) SNS EDM (combine source and measurement) Crystal channeling – new ILL High E-field Unknown systematics General aim: d n < e  cm

Argonne setup EDM of Nuclei Nuclei offer – High statistics ( 229 Xe) – Enhancement factors (see e.g. 225 Rn) Laser techniques for Zeeman cooling and trapping (Argonne, KVI) Ultracold atoms stored in dipole trap – Long coherence times (300s) – No vxE effect – Small magnetic volume Density distribution of nuclear charge has mixed octupole and quadrupole deformation J. Engel et al. Phys. Rev. C, 68, (2003)  Deformed charge distribution in some isotopes ( 225 Ra) Nucleon EDM enhances ≈ s 2 1 S 0 F = 1/2 7p 3 P 1 F = 1/2 m F = -1/2 m F = +1/2 m F = -1/2  + Excitation -- Fluorescence 1.Polarize  / 2 pulse 3.Free precess  / 2 pulse 5.Measure population

Electrodes Hyperpolarized liquid 129 Xe droplet 129 Xe EDM Experiment Superconducting pick-up coils and LTC Squids - P rotates with  L in field B 0 - E rotates with constant phase to P  E   L orthogonal ! Micro-fabricated glass Good magnetic field control due to small size New tool to investigate systematics (motional effects) Statistical sensitivity < ecm per measurement Array of experiments: different phases  of P and E tested simultaneously pick-up coils P. Fierlinger / TU-München

n-n’ oscillations Mirror neutrons – Restore parity violation by adding particles with V+A weak interaction Properties of mirror particles: – Same masses – Same couplings between mirror particles Ordinary –mirror particles interactions: – Gravity – Possible mixings between neutral particles (expect:  nn’ >>  n ) Mixing causes oscillations (w.o  B=2 sector as for n  n )

How To Detect ? Compare n-storage w/w.o. magnetic field Transition probability: Test P n  n’ (t) for different values  Consider N 0 /N  (t storage )

Results Use existing EDM setups running w/w.o. B-field OILL collaboration :  nn’ > 103s (95% CL) Serebrov et al: :  nn’ > 448s (90% CL) Results improves over previous limit by factor 400 Implications also for UHE cosmic rays – mirror particles may have longer flight path in universe (less p  -reactions with  generation due to smaller reaction rate of intermediate state p’ than asumed)  more UHE protons

The Structure of Weak Interaction Use neutron decay observing – with HFS analysis – Small branching fraction (BR=4∙10 -6 ) (83% 1s, 10% 2s) Unpolarized n decay in magnetic field within a reactor tube  Select F, m F of emerging hydrogen atom using spin filter method Physics:  Relative rates of F=0,1, m F =0,1 give signature for g S and g T  Rate of F=1, m F = -1 shows (V+A)

Experimental setup Measure HFS population and extract g s, g T,  At first step measure BR (integral hydrogen-rate) – 2s Stark quenching and deexcitation (fluorescent light) – Cs vapour e-capture

Thanks to the Organizers

Backup Slides

● repumping off ● repumping on S. De, L. Willmann, 3 Oct 2007 Big Step: Efficient Trapping of Barium Atoms TRI  P ● MOT signal ● Doppler-free beam signal (*100) MOT MOT S. De, L. Willmann, 3 Oct 2007 > 10 6 trapped atoms > 10 6 trapped atoms  = nm 5d6p 3 D 1  = nm  = nm MOT ● repumping on ● repumping off - Scheme avoids dark resonances - 7 lasers at one time needed s trap lifetime sufficient before transfer to e.g. FORT atoms trapped - improvements possible higher trapping efficiency achieved than for Ra - at TRI  P Ra atoms expected in trap

Radium – Barium Optical Trapping Radium – Barium Optical Trapping very similar level schemes – very similar leak rates  Cooled and trapped on intercombination line with Zeeman slower (Argonne: Phys. Rev. Lett. 98, , 2007)  7∙10 -7 cooling & trapping efficiency from atomic beam  ~ Ra ( Ra) atoms trapped  Cooled and trapped on resonance line with many laser repumping (KVI: S. De, L. Willmann et al., arXiv: , 2007)  cooling & trapping efficiency from atomic beam  10 6 xx Ba atoms trapped  method transferrable to Radium TRI  P

The Structure of Weak Interaction – Right handed currents (left-right symmetric models) W R, R Measure lefthandedness of the – Tensor or scalar forces g T, g S Measure ratio of (V-A) coupling strength and total strength Use neutron decay observing – with HFS analysis – Small branching fraction (BR=4∙10 -6 ) (83% 1s, 10% 2s)

Measurement Technique Unpolarized n decay in magnetic field within reactor tube – – Select F, m F of emerging hydrogen atom using spin filter method – Identify hydrogen from n-decay via Doppler shifted laser-ionization process Magnetic spectrometry – Rate: 0.3 H-atom/s in 2s-state Physics: – Relative rates of F=0,1, m F =0,1 give signature for g S and g T – Rate of F=1, m F = -1 shows (V+A)

Experimental setup Measure HFS population and extract g s, g T,  At first step measure BR (integral hydrogen-rate) – 2s Stark quenching and deexcitation (fluorescent light) – Cs vapour e-capture