Post on 17-Dec-2015
transcript
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