Atomic Trapping and Recoil Ion Spectrometry for Precision β-decay Measurements

Atom trapping and Recoil Ion Spectrometry for -decay (and other BSM) studies H.W. Wilschut, KVI, Groningen Or why it is easier to measure things standing still

Initial perspective using -decay for new physics searches “To move correlation measurements into the 10-3 precision (and beyond) it is essential to obtain correlations differentiated in angle and momentum”

Or why it is easier to measure things standing still The role of trapping • The trap sample: • isotope (isomer) selective • spin manipulation • point source, no substrate • recoil ion momentum spectrometry • Ideal environment • for precision experiments • Also for APNC, edm…

Outline • Which isotopes can we use when atom trapping • Which are being pursued in -decay/status • Need to capture and detect • Differentiated measurements (and why are they difficult) • Some odd ends

Which particles are useful? • Have chosen to use isotopes in the searches for new physics (but need to keep an eye on other searches) • Measure “forbidden” decays (here: -decay where particles dare not go): “short-lived” • Measure “forbidden” moments (APNC, edm): “long-lived”

? ? There was not much to choose in Cs isotopes ….. There are only a few…..

e.g. Cs isotopes A=114 to 148 There are plenty…..

To study -decay need to collect and observe: # candidates decrease

KVI RIMS Trace analysis Next on menu Which atoms can be trapped Advantage clear for EDM and APNC but for -decay? Of course you can try ion trapping instead but we can discuss that…

-decay For -decay light isotopes relevant, atomic trapping covers a large part of the chart, still most are useless

Correlations in -decay • Correlation factors a…R connected by underlying theory • Andwith observations outside nuclear -decay • Which correlation most potential? (help!) • Identified D (TRV)as most potential (but willing to change) • In any case: • must learn the trade with “a”:ignore spin degrees of freedom

Expression for ½+ ½+ transitions No FSI D=0 if all formfactors are real finite D due to weak magnetism The possible size of D and the effect of the FSI(Theory group KVI - masters thesis Marc van Veenhuizen)

g=-0.99 + 0.0005i Comparison of FSI and TRV Different momentum dependence at < 10-4 level similar results for 3/2+ 3/2+ effect negligable on a, A and B

But first: Inclusive observables Recoil distribution Impact of - on recoil Fermi Gamow-Teller Recoil e  e Recoil  Vector Scalar

Best measurement for aFermi Adelberger et al. PRL83(99)1299 32Ar(0+)  32Cl(0+) + e+ +  ; 32Cl  31S + p aF=0.9989(52)(39) 107 cts S V exp line shape Higher order corrections folded in: not measured Improved mass measurements made: waiting for new folding

Learning from atom trap measurements on “a” • TRIUMF (Behr et al.): 38Km(0+ 0+) aF=0.992(8)(5) promised: ?(3)(3) making progress in polarization 36K(2+), 37K(3/2+) (A, towards D). • LANL (Vieira et al.): 82Rb TOP for A, halted? • LBL: 21Na (3/2+ 3/2+) a= 0.524±0.005syst (+ a problem we can solve) tried 19Ne (no success) will try FORT for 21Na • Ion trap methods: Paul-trap 6He (aGT) and WITCH project. • KVI: first start with 21Na

Structure of -decay is V - A “beyond” to be found from S, P or T But P not possible? Intermezzo S Scalar P Pseudo Scalar ??? V Vector (GV) A Axial Vector (GA) T Tensor Search and analysis in the early 60’s: 0- 0+ (first-forbidden decays) based on  polarization and shape factor using heavy nuclei. Lightest nuclei 0- 0+ are 50K(?) and 90Rb (37%) &92Rb(94%) How about recoil spectra/ correlations? Will it get us anywhere?

Production Target Magnetic Separator Ion Catcher RFQ Cooler MOT Particle Physics AGOR cyclotron MeV keV eV meV neV Nuclear Physics Atomic Physics TRIP - Trapped Radioactive Isotopes:-laboratories for fundamental Physics Beyond the Standard Model TeV Physics EDM/-decay TRIP

21Na production @ TRIP KVI 21Na 16O Observed production rate in the reaction p(21Ne,21Na)n 50 Hz/pnA/mg[H2]/cm2 Dispersive plane QD QD DD DD QD QD T1 Achromatic focus Detector AGOR beam B = p/q  vA/Z E  A2 TOF  A/Z  Traps TOF TRIP

Principle idea MOT + RIMS  detector Not SM MeV SM MCP start stop -V0 0 +V0 V0 (keV) TOF E// very efficient X,Y  E for charged recoils

ion beam n = 5 6 7 8 resolution 6 m/s ! MOTRIMS (KVI atomic physics, S. Knoop) O6+ + Na  O5+(n) + Na+ Na O5+ 8 7 6 n=5

Setup at TRIUMF (Behr et al.) for 38mK (t1/2=0.93 s; 0+  0+) 21Na production Cooling stage Trapping & detection Freedman/Vetter setup LBL 21 Na N. Scielzo thesis++ Two realizations

19% 3% 78% 0.3% + versus - + decay  recoil neutral (80%) 21Na (11p + 10n)  21Ne (10p + 11n) + + • Neutrals not efficient • MCP inefficient and tricky • +momentum  q-dist • 2 background (511 keV) systematic errors: • RIMS related 41% • Unwanted decays (off walls etc.) 26% •  detection 24% - decayrecoil 1+ : 80%  no good? (3 branch) 25Na (11p + 14n)  25Mg (12p + 13n) + -

A problem that can be solved Scielzo et al. measured for 21Na a=0.5243 ± 0.0066 ± 0.0049 ± 0.0041  (deviating 2.3 )stat. 6105 evt’ssystematic branching 3/2+21Na 22.47s remeasure + 5/2+ 9 ps 0.3505 5.1±0.2 % 3/2+ 21Ne

Conclusions • Atomic trapping a starting point for various studies • RIMS is essential for -decay studies • Trapping has its specific problems (-/+) • Polarization (D, A) being developed • TRIP starts working…. but long way to go

Atomic Trapping and Recoil Ion Spectrometry for Precision β-decay Measurements