Precision measurement of the half-life and branching ratio of the T=1/2 mirror β decay of
37KT. Kurtukian-Nieto, P. Ascher, B. Blank, G. Canchel, M. Gerbaux, J. Giovinazzo, S. Grévy
Centre d'Etudes Nucléaires de Bordeaux-Gradignan, France
A. BacquiasIPHC Strasbourg, France
H. Bouzomita, G. F. Grinyer, J. C. Thomas
GANIL Caen, France
C. Couratin, X. Flechard, E. LienardLPC-Caen, France
I. MateaIPN-Orsay, France
J. LiendoUniversidad Simon Bolivar, Venezuela
Contact person CERN-Isolde: M. Kowalska
41st Meeting of the INTC. CERN, November 3rd, 2011
Teresa Kurtukian Nieto November 3rd, 2011 2CERN-INTC-P-311
Measurements needed :• Qvalue• Branching ratio of super-allowed transition• -decay half-life• - angular correlation coefficient
QEC
T1/2
BR
Superallowed Mixed Mirror β decay
ft = f(Qec) * T1/2 / BR
O. Naviliat-Cuncic and N. Severijns PRL 102, 142302 (2009)
consistent test of CVC from a set of nuclear transitions other than super-allowed pure Fermi
Teresa Kurtukian Nieto November 3rd, 2011 3CERN-INTC-P-311
Introduction: quark-mixing matrix CKM
b
s
d
VVV
VVV
VVV
b
s
d
tbtstd
cbcscd
ubusud unitarity condition: 1VVV 2
ub2
us2
ud
O. Naviliat-Cuncic, N. Severijns
Teresa Kurtukian Nieto November 3rd, 2011 4CERN-INTC-P-311
2011
Least known quantity: Fermi / Gamow-Teller ratio second least known quantity: half-lives
Existing measurements
2009
JYFL ISOLDE
xxxxxx
Teresa Kurtukian Nieto November 3rd, 2011 5CERN-INTC-P-311
Why to measure 37K ?
T=1/2, decay is predominantly 3/2+ to 3/2+ mixed Fermi/GT decay
Correlation measurements to be performed:
• our collaboration E. Lienard et al.
@ GANIL 19Ne,35Ar,29P,37K,39Ca
• D. Melconian et al. @ TRIUMF 2012
using laser-cooled 37K
(Melconian PhDThesis (2005), AIP C. Proc.1342 (2011) 53
Arxiv: 1108.2530v1 [nucl-ex] 11 Aug 2011)
Aim:• ΔT1/2 ~ 0.1 %
• ΔB.R. ~ 0.1 %
Teresa Kurtukian Nieto November 3rd, 2011 6CERN-INTC-P-311
Our recent efforts : 38-39Ca
ISOLDE 2007
Blank et al., EPJ A 44,363 (2010)
38Ca T1/2 = 443.8 ± 1.9 ms
Teresa Kurtukian Nieto November 3rd, 2011 7CERN-INTC-P-311
Our recent efforts : 38-39Ca
ISOLDE 2007
Blank et al., EPJ A 44,363 (2010)
39Ca T1/2 = 860.7 ± 1.0 ms
Teresa Kurtukian Nieto November 3rd, 2011 8CERN-INTC-P-311
Half-life and BR measurement of 37K
radioactiveions
detection- gas counter- germanium
GSI tapesystem
Experimental procedure:• production with Ti target• separation with HRS/GPS A=37
• only 37Ca T1/2=181.1(10) ms • accumulation on tape during 1 s• tape transport into setup• after 2.5 s, measurement for 20T1/2
• tape move and new cycle starts
Detection setup at LA1 beamline
Teresa Kurtukian Nieto November 3rd, 2011 9CERN-INTC-P-311
β detection setup
4π gas counter • two single-wire gas counter
• P5 (95% Ar, 5% CH4) or CF4
• moving tape passes through a slit between the two detectors
• thin aluminised Mylar entrance windows allows to detect low-energy β particles
• Active volume 2 x 37.4 cm3
Advantage of using a gas counter:
•Electronic thresholds:
• For the gas counter operated in the plateau region, the electronic detection threshold is too low for losses from that source to have any effect on the overall efficiency.
• Plastic scintillatior and photomultipliers tubes impose a non-negligible low-energy electronic thresholds.
Teresa Kurtukian Nieto November 3rd, 2011 10CERN-INTC-P-311
Measurements with• a fast DAQ system - two electronic chains: 4 μs and 8 μs fixed dead-time • a listmode DAQ system - half-life measurement with 100μs DT - γ-ray measurement for branching ratio
search for systematic errors:
- different CFD thresholds- different detector HV- different gas flow- different cycle times
Experimental details
beam
detection- gas counter- germanium
GSI tapesystem
Detection setup at LA1 beamline
Teresa Kurtukian Nieto November 3rd, 2011 11CERN-INTC-P-311
Beam request
• cycle length: 1s + 2.5s + 20T1/2 = 28 s• effective rate: 1000 37K decays detected/cycle
• i.e. count rate: few 103 37K per second• 3 days of effective counting: ~ 7.7 million 37K decays• 2 days search for systematic errors ~ 13 million 37K decays (total) ΔT1/2 < 0.1 %• within 5 days (15 shifts) ~ 40 000 β-γ for 2796 keV ε=0.3% ΔBR < 0.1 %• 1 shift to optimise production-----------------------------------------------------------------------------Total request: 16 shifts
Aim:• T1/2 ~ 0.1 %• BR ~ 0.1 %
Accumulation Decay of 37Ca
Measuring time
Thank Thank you you
Teresa Kurtukian Nieto November 3rd, 2011 13CERN-INTC-P-311
4π gas counter
anode wire
Thin windows
tape
Gas counter halves
• two single-wire gas counter
• P5 (95% Ar, 5% CH4) or CF4
• moving tape passes through a slit between the two detectors
• thin aluminised Mylar entrance windows allows to detect low-energy β particles
• Active volume 2 x 37.4 cm3
Teresa Kurtukian Nieto November 3rd, 2011 14CERN-INTC-P-311
Contaminants expected
Teresa Kurtukian Nieto November 3rd, 2011 15CERN-INTC-P-311
Experimental setup at JYFL
Teresa Kurtukian Nieto November 3rd, 2011 16CERN-INTC-P-311
preli
minary
JYFL 2009
T1/2 = 4123.4(51) msT1/2 = 2546.4(18) ms
T. Kurtukian Nieto, A. Bacquias et al.
Our recent efforts : 29P and 31S
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