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

2. CKM mixing matrix coupling quark states in the Standard Model unitarity condition V ud ~ 95 % V us ~ 5 % V ub ~ 0… % V ud nuclear 0 +  0 + decays neutron decay  Part. Data Group (2004)  Serebrov et al. (2005) pion beta decay (larger uncertainty) V us K X decays + form factor  Leutwyler-Roos (1984)  Cirigliano et al. (2005) deviation to unitarity V ud nuclear 0 +  0 +  n pdg 04  n Se 05 V us K decay: pdg04 + LR 84 ~ 2  ok K: all results + LR 84 ok ~ 2  K: all results + Ci 05 ~ 2  ok the situation today Mass crises? W. Marciano @ NUPAC ISOLDE Savard et al. PRL 95, 102501 (2005)

3. matrix element coupling constant Fermi decay and CVC Correction terms for T = 1 states then ft = constant for given isospin Fermi 0 +  0 + transitions and CVC hypothesis  radiative corrections  R nucleus independent (~ 2.4 %)  R nucleus dependent (~ 1.5 %)  isospin symmetry breaking  C ~ 0.5 % nuclear structure insight:  C -  NS

4. Experimental ft measurements precision measurements required to test Ft value  ~10 -3 Q EC mass measurements f ~ Q EC 5 T 1/2, BR  -decay studies t = T 1/2 / BR Status in 2005  9 best cases 10 C, 14 O, 26m Al, 34 Cl, 38m K, 42 Sc, 46 V, 50 Mn, 54 Co  many recent results 22 Mg T 1/2, BRTexas A&M Q EC ANL, ISOLDE 34 Ar T 1/2, BRTexas A&M Q EC ISOLDE 62 Ga T 1/2, BR GSI, Jyväskylä, Texas A&M 74 Rb T 1/2,BRTRIUMF, ISOLDE Q EC ISOLDE 46 VQ EC CPT Argonne T 1/2 Q EC BR 0+0+ 0+0+

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

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

7. Theoretical corrections Coulomb correction  C =  IM +  RO  IM isospin mixing can be tested with non analogue branching ratios  RO radial overlap

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

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

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

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

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

14. Hardy, Towner 2004 heavier T Z = 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  C higher shells involved  theoretical uncertainties recent measurements for 62 Ga and 74 Rb

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