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The b -delayed deuteron-decay of 6 He

The b -delayed deuteron-decay of 6 He. J. Ponsaers , R. Raabe, F. Aksouh, D. Smirnov, I. Mukha, A. Sanchez, M. Huyse, P. Van Duppen, C. Angulo, O. Ivanov, J.C. Thomas. Introduction Experiment Analysis Conclusion. E. E. Probability density of a halo neutron.

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The b -delayed deuteron-decay of 6 He

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  1. The b-delayed deuteron-decayof 6He J. Ponsaers, R. Raabe, F. Aksouh, D. Smirnov, I. Mukha, A. Sanchez, M. Huyse, P. Van Duppen, C. Angulo, O. Ivanov, J.C. Thomas • Introduction • Experiment • Analysis • Conclusion

  2. E E Probability density of a halo neutron Usual probability density of a neutron r r 6He 6He = 2n-halo-nucleus Discovered in 1985: high interaction cross section.[1] Extended matter distribution. 6He is a Borromean system of a + n + n [1] : Tanihata I. et al. ; Phys. Rev. Letters (1985)

  3. II I E E Probability density of a halo neutron Usual probability density of a neutron r r 6He 6He = 2n-halo-nucleus Discovered in 1985: high interaction cross section.[1] Extended matter distribution. 6He is a Borromean system of a + n + n [1] : Tanihata I. et al. ; Phys. Rev. Letters (1985)

  4. II I E E Probability density of a halo neutron Usual probability density of a neutron r r 6He 6He = 2n-halo-nucleus Discovered in 1985: high interaction cross section.[1] Extended matter distribution. 6He is a Borromean system of a + n + n • We want to measure: • Branching ratio of the decay channel II: • very small (~10-6)  very difficult • Energy spectrum of the decay • particlesEa+d [1] : Tanihata I. et al. ; Phys. Rev. Letters (1985)

  5. Information provided by the deuteron-branch of 6He • High branching ratio  dineutron correlation

  6. Information provided by the deuteron-branch of 6He • High branching ratio  dineutron correlation • Low branching ratio  cigar correlation

  7. Information provided by the deuteron-branch of 6He • High branching ratio  dineutron correlation • Low branching ratio  cigar correlation [1] K. Riisager et al., Phys. Lett. B 235(1990)30 [2] M. J. G. Borge et al., Nucl. Phys. A 560(1993)664 [3] D. Anthony et al. Phys., Rev. C 65(2002)034310 [ 4] P. Descouvement and C. Leclercq- Willain, J. Phys. G 18(1992)L99 [5] M. V. Zhukov et al., Phys. Rev. C 47(1993)2937 [6] A. Csoto and D. Baye, Phys. Rev. C 49(1994)818 [6] suggests that we need a detailed description of the wave functions to explain the decay.

  8. The method • Problems in previous experiments: • High threshold energies for deuterons • Large uncertainties (difficult to normalize)

  9. The method • Problems in previous experiments: • High threshold energies for deuterons • Large uncertainties (difficult to normalize) • New method: 6He implantation in DSSSD • (Double Sided Silicon Strip Detector) • This can count implantations AND a + d decays

  10. The method • Problems in previous experiments: • High threshold energies for deuterons • Large uncertainties (difficult to normalize) • New method: 6He implantation in DSSSD • (Double Sided Silicon Strip Detector) • This can count implantations AND a + d decays DSSSD divided into 48 strips x 48 strips = 2304 pixels Small pixel size (300mm) • Get the energy drop of b-particles below the spectrum of the br.ratio • No problem for a + d detection

  11. The experiment Experiment: performed at CRC, Louvain-la-Neuve, Belgium 6He nuclei at 8 MeV periodically implanted into DSSSD detector. Beam on (1s): implantation and detection of 6He nuclei number of implantations counted absolute normalization for br.rat. very accurate Beam off (2s): detection of decay of 6He nuclei caught inside the detector

  12. 2 1 (Number of events)/(10keV) Beam on + off E (keV) Analysis 1. b-peak 2. 6He implants 3. partial E-collection 3

  13. 2 1 (Number of events)/(10keV) Beam on + off E (keV) Analysis 1. b-peak 2. 6He implants 3. partial E-collection 4. a + d events 1 3 1 (Number of events)/(10keV) 4 Time spectrum exp. fit 1: T1/2 = 806.0ms Beam off E (keV)

  14. 2 1 (Number of events)/(10keV) Beam on + off E (keV) Suspicious: background much higher than expected! Analysis 1. b-peak 2. 6He implants 3. partial E-collection 4. a + d events 1 3 1 (Number of events)/(10keV) 4 Time spectrum exp. fit 1: T1/2 = 806.0ms Beam off E (keV)

  15. 2 1 (Number of events)/(10keV) Beam on + off E (keV) Suspicious: background much higher than expected! Analysis 1. b-peak 2. 6He implants 3. partial E-collection 4. a + d events 1 3 1 (Number of events)/(10keV) 4 Time spectrum exp. fit 1: T1/2 = 806.0ms 2: T1/2 = 1102ms Beam off E (keV) 4 1 (Number of events)/(10keV) 4 Beam off E (keV)

  16. 2 1 (Number of events)/(10keV) Beam on + off E (keV) 1 (Number of events)/(10keV) Beam off E (keV) Analysis 1. b-peak 2. 6He implants 3. partial E-collection 4. a + d events 1 3 Suspicious: background much higher than expected! 4 Time spectrum exp. fit 1: T1/2 = 806.0ms 2: T1/2 = 1102ms 4 1 2.New fit: (Number of events)/(10keV) 4 162 ± 69 background events 425 a + d events Beam off E (keV)

  17. Conclusion and outlook • Total branching ratio: W = (2.03 ± 0.35) x 10-6 • Corresponds with the value from microscopic description • Large uncertainty from background events. • No reliable energy spectrum of a + d because we don’t know the energy spectrum of the background. • New measurement on 6He in Louvain-la-Neuve • Same experiment on 11Li at TRIUMF

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