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

KVI PAC meeting, 25 november 2005

(spokesperson B.Blank)

CKM mixing matrix

b

s

d

VVV

VVV

VVV

b

s

d

tbtstd

cbcscd

ubusud

coupling quark states in the Standard Model

unitarity condition

Vud ~ 95 %Vus ~ 5 %Vub ~ 0… %

1VVV 2ub

2us

2ud

Vud nuclear 0+ 0+ decaysneutron 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)

deviation to

unitarity

Vud

nuclear

0+ 0+

n

pdg 04

n

Se 05

Vus

K decay: pdg04

+ LR 84~ 2 ~ 2 ok

K: all results

+ LR 84ok ok ~ 2

K: all results

+ Ci 05~ 2 ~ 2 ok

the situation today

Mass crises? W. Marciano @ NUPAC ISOLDESavard et al. PRL 95, 102501 (2005)

matrix element

coupling constant

Fermi decay and CVC

2F

2V MG

Kft

Correction terms

2

ifMF

for T = 1 states

udFV VGG

then ft = constant for given isospin

Fermi 0+ 0+ transitions and CVC hypothesis

radiative correctionsR nucleus independent (~ 2.4 %)R nucleus dependent (~ 1.5 %)

isospin symmetry breaking

C ~ 0.5 %

RR 11tt

2 21- NSF F CM M

21 1

2 1

constant

R C NSV R

KFt ftG

nuclear structure insight: C - NS

Experimental ft measurementsprecision measurements required

to test Ft value ~10-3

QEC mass measurements

f ~ QEC5

T1/2, BR -decay studies

t = T1/2 / BRStatus in 2005

9 best cases10C, 14O, 26mAl, 34Cl, 38mK, 42Sc, 46V, 50Mn, 54Co

many recent results

22Mg T1/2, BR Texas A&MQEC ANL, ISOLDE

34Ar T1/2, BR Texas A&MQEC ISOLDE

62Ga T1/2, BR GSI, Jyväskylä,Texas A&M

74Rb T1/2 ,BR TRIUMF, ISOLDEQEC ISOLDE

46V QEC CPT Argonne

T1/2

QEC

BR

0+

0+

Average Ft value

Ft = 3074.4 ± 1.2 s

10-3 ~ 10-2

~ 10-1

~ 10-0

Further experimental directions

best casessame theo. and exp. errorfew improvements(10C, 14O)

TZ = -1 nuclei, sd/f shellsbranching ratio exp. test of IM

TZ = 0 nuclei, Z > 30decay, masses C increases with Z

Theoretical corrections

Coulomb correctionC = IM + RO

IM isospin mixingcan be tested with non analoguebranching ratios

RO radial overlap

challenges for TZ = -1 nuclei

Hardy, Towner 2004

similar T1/2 of parent and daughterprecise determination is difficult

branching ratio < 100 %:BR determination requires very precise gamma efficiencycalibration (<10-3 !!!)

need for decay studies

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

Present letter of intent

Why KVI? Ti refractiveClean production (inverse kinematics)3He(40Ca,42Ti)1n or 12C(40Ca,42Ti)12BFavorable yields

Best 0+ 0+ decay cases

Experimental precision reaches theoretical calculations level

Theoretical corrections should be calculated in different formalisms(currently mainly shell model)

46V mass recentlyre-measured(JYFL, ANL)

10C branching ratio

14O branching ratio:only from G.S. feeding

Hardy, Towner 2004

Detection requirements

a Low Energy Facility is obviously the best suited for this kind of measurements.

which kind of equipment ?

QEC mass measurements (Z > 30)(Penning) trap

most sophisticated equipment, but appears in all physicscase conclusions

T1/2 , BR decay studies

short half-lives ( <100 ms )fast tape transport systemprecision: mainly statistics (production rates)

branching ratios ( for TZ=-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 absoluteefficiency calibration

Experimental test of corrections

CNSR 11Ftft

need for wider range of experimental data to test theoretical corrections

assuming a constant Ft value…

Hardy, Towner 2004

heavier TZ = 0 nuclei

further from stabilitylower production rates

lower proton binding energy higher radial overlap correction

high charge Zstronger isospin mixing effects

important Coulomb correction C

higher shells involved theoretical uncertainties

recent measurementsfor 62Ga and 74Rb

Conclusion

CKM matrix unitarity: still an open question

- neutron decay half-life

- form factor calculation in Vus 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 TZ=0 nuclei

- branching ratios for TZ = -1 nuclei