H igh precision study of the  decay of 42 Ti  V ud matrix element and nuclear physics

1. High precision study of the  decay of 42Ti  Vud matrix element and nuclear physics  Experimental and theoretical precisions  New cases: goals and challenges  Experimental requirements (spokesperson B.Blank) KVI PAC meeting, 25 november 2005

2. CKM mixing matrix Mass crises? W. Marciano @ NUPAC ISOLDE Savard et al. PRL 95, 102501 (2005) coupling quark states in the Standard Model unitarity condition Vud ~ 95 % Vus ~ 5 % Vub ~ 0… % the situation today Vud nuclear 0+g 0+ decays neutron decay  Part. Data Group (2004)  Serebrov et al. (2005) pion beta decay (larger uncertainty) Vus KX decays + form factor  Leutwyler-Roos (1984)  Cirigliano et al. (2005)

3. Fermi 0+g 0+ transitions and CVC hypothesis Fermi decay and CVC matrix element coupling constant for T = 1 states thenft = constant for given isospin Correction terms g radiative corrections DR nucleus independent (~ 2.4 %) dR nucleus dependent (~ 1.5 %) g isospin symmetry breaking dC ~ 0.5 % nuclear structure insight: dC - dNS

4. 0+ T1/2 QEC BR 0+ Experimental ft measurements precision measurements required to test Ft value ~10-3 QEC mass measurements f ~ QEC5 T1/2, BR b-decay studies t = T1/2 / BR Status in 2005  9 best cases 10C, 14O, 26mAl, 34Cl, 38mK, 42Sc, 46V, 50Mn, 54Co  many recent results 22Mg T1/2, BR Texas A&M QEC ANL, ISOLDE 34Ar T1/2, BR Texas A&M QEC ISOLDE 62Ga T1/2, BR GSI, Jyväskylä, Texas A&M 74Rb T1/2 ,BR TRIUMF, ISOLDE QEC ISOLDE 46V QEC CPT Argonne

5. Average Ft value ~ 10-0 ~ 10-1 10-3 ~ 10-2 Ft = 3074.4 ± 1.2 s

6. Further experimental directions best cases same theo. and exp. error few improvements (10C, 14O) TZ = -1 nuclei, sd/f shells branching ratio  exp. test of dIM TZ = 0 nuclei, Z > 30 decay, masses  dCincreases with Z

7. Theoretical corrections Coulomb correction dC = dIM + dRO dIM isospin mixing can be tested with non analogue branching ratios dRO radial overlap

8. challenges for TZ = -1 nuclei Hardy, Towner 2004  need for decay studies similar T1/2 of parent and daughter precise determination is difficult branching ratio < 100 %: BR determination requires very precise gamma efficiency calibration (<10-3 !!!)

9. Present letter of intent • Study of 42Ti • production rates required: • ~103 ions/sec • Proposed measurements: • T1/2 study with a gas detector, a tape transport system • and NaI detectors to tag with the 611 keV  of the 42Ti decay • branching ratio measurement with one Germanium detector • calibrated with a precision of 0.1% • Beam time requirements: • 6 shifts of a 40Ca beam on target at 10 MeV • 6 shifts of a 40Ca beam on target at 45 MeV Why KVI? Ti refractive Clean production (inverse kinematics) 3He(40Ca,42Ti)1n or 12C(40Ca,42Ti)12B Favorable yields

11. Best 0+g 0+ decay cases 10C branching ratio Hardy, Towner 2004 46V mass recently re-measured (JYFL, ANL) 14O branching ratio: only from b G.S. feeding Experimental precision reaches theoretical calculations level Theoretical corrections should be calculated in different formalisms (currently mainly shell model)

12. Detection requirements a Low Energy Facility is obviously the best suited for this kind of measurements. which kind of equipment ? QECgmass measurements (Z > 30) (Penning) trap most sophisticated equipment, but appears in all physics case conclusions T1/2 , BR gdecay studies short half-lives ( <100 ms ) fast tape transport system precision: mainly statistics (production rates) branching ratios ( for TZ=-1, non analogue decay branches ) need for very precise g intensities: efficient and very precise gamma detection g no need for segmentation: simple but efficient detectors to reach 10-3 precision level in absolute efficiency calibration

13. Experimental test of corrections assuming a constant Ft value… need for wider range of experimental data to test theoretical corrections

14. heavier TZ = 0 nuclei further from stability lower production rates lower proton binding energy  higher radial overlap correction high charge Z stronger isospin mixing effects  important Coulomb correction dC higher shells involved g theoretical uncertainties Hardy, Towner 2004 recent measurements for 62Ga and 74Rb

15. Conclusion CKM matrix unitarity: still an open question - neutron decay half-life - form factor calculation in Vus determination - weak interaction Nuclear Physics: Fermi 0+g 0+ transitions - CVC hypothesis confirmed at the level of 3x10-4 - many joint theoretical and experimental efforts Experimental challenges - masses of heavier TZ=0 nuclei - branching ratios for TZ = -1 nuclei