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Charged-particle spectroscopy of exotic nuclei with the Optical TPC

Charged-particle spectroscopy of exotic nuclei with the Optical TPC. Marek Pf ü tzner Faculty of Physics, University of Warsaw. b -delayed particle emission.  When the b decay energy is large, many exotic channels are available.

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Charged-particle spectroscopy of exotic nuclei with the Optical TPC

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  1. Charged-particle spectroscopy of exotic nuclei with the Optical TPC MarekPfütznerFaculty of Physics, University of Warsaw M. Pfützner, Isolde Workshop, CERN, November 25-27, 2013

  2. b-delayed particle emission When the b decay energy is large, many exotic channels are available Blank and Borge, Progress in Part. Nucl. Phys. 60 (2008) 403 M. Pfützner, Isolde Workshop, CERN, November 25-27, 2013

  3. counting gas at atmospheric pressure p HV electrodes incomingidentified ion p ionizationelectrons e gating electrode charge amplification Trigger light PMT CCD Recordingsystem TPC with optical readout b2a decay of 8Li b3adecay of 12N  Decay event 6He  a + d seen on the background of about 104 beta rays M. Pfützner, Isolde Workshop, CERN, November 25-27, 2013

  4. OTPC M. Pfützner, Isolde Workshop, CERN, November 25-27, 2013

  5. b3p 11% b3p 0.08% b2p b2p b3p b3p bp bp Decays of 45Fe and 43Cr 2p NSCL/MSU, 2007 QEC = 18.7 MeV T1/2 = 7 ms 45Fe 44Mn+p 2p b+ b+ 43 Cr+2p  70%  30% IAS IAS bpa b2p b4p 40Ca+3p bp 40Ti+pa 41Sc+4p 41Sc+2p b2p bp 43V+2p 42Ti+3p 43V 42Ti+p 45Mn Pomorski et al., Phys. Rev. 83 (2011) 014306 44Cr+p Miernik et al., Eur. Phys. J. A 42 (2009) 431 Miernik et al., PRL 99 (07) 192501 M. Pfützner, Isolde Workshop, CERN, November 25-27, 2013

  6. Decay channels of 43Cr Dossat et al., Nucl. Phys. A 792 (2007) 18 11660 81% 12 0.08% 1020 7% Dossat et al. no protons 12% Pomorski et al., Phys. Rev. C 83 (2011) 014306 M. Pfützner, Isolde Workshop, CERN, November 25-27, 2013

  7. 43Cr puzzle  12% for the b-no-proton branch of in 43Cr is surprizingly large! 3/2+ 43Cr T1/2 = 211 msQEC=16.100.23 MeV From mirror symmetry 0.57 % 2 % < 3 % 0.03 % 0.003 % Sp=190(230) keV 7/2 0.12 % 43V Pomorski et al., Phys. Rev. C 83 (2011) 014306 Warburton & Alburger, Phys. Rev. C 38 (1988) 2822 M. Pfützner, Isolde Workshop, CERN, November 25-27, 2013

  8. Study of 48Ni NSCL/MSU, 2011 58Ni @ 160 MeV/u + natNi  48Ni 46Fe 44Cr 46Fe 44Cr Pomorski et al., PRC 83 (11) 061303(R) M. Pfützner, Isolde Workshop, CERN, November 25-27, 2013

  9. Track reconstruction  Example reconstruction of b-delayed proton from 44Cr PMT CCD Pomorski et al., to be published Ep = 1280 (30) keVQ = 24(4)° M. Pfützner, Isolde Workshop, CERN, November 25-27, 2013

  10. b-delayed protons from 44Cr Dossat et al., Nucl. Phys. A 792 (2007) 18 5542 identified ions of 44Cr 4098 properly stopped 210 decays observed Dossat : A clear new line at 730(20) keV 97 reconstructed protons No beta background! This work Dossat et al. 2.6(4)% 1.3(3)% 0.3(1)% Pomorski et al., to be published M. Pfützner, Isolde Workshop, CERN, November 25-27, 2013

  11. b-delayed protons from 46Fe 471 identified ions of 46Fe 269 properly stopped 148 decays observed Dossat et al., Nucl. Phys. A 792 (2007) 18 Dossat : 19 reconstructed protons M. Pfützner, Isolde Workshop, CERN, November 25-27, 2013

  12. b2p channel in 46Fe  One good event! PMT CCD 46Fe 46Fe  M. Pfützner, Isolde Workshop, CERN, November 25-27, 2013

  13. b2p channel in 46Fe  Both protons escaped the detector. From the length of tracks we know only that: This cannot go through the IAS! 3090 Dossat et al., Nucl. Phys. A 792 (2007) 18 Pomorski et al., to be published M. Pfützner, Isolde Workshop, CERN, November 25-27, 2013

  14. Simultaneous vs. sequential  In all cases investigated, the b2p emission proceeds sequentially. In principle, however, both protons can go simultaneously.  A simple direct model of 2p emission describes both mechanisms. Both sequential and simultaneous modes visible.  According to this model, as long as the simultaneous emission dominates. M. Pfützner, Isolde Workshop, CERN, November 25-27, 2013

  15. b3p in 31Ar  Experiment at FRS, August 2012 expected b3p ? 31Ar

  16. Tillley et al., NP A 747 (2004) 155 b decay of 8He ?  The previous experiment on 8He b decay : ISOLDE (1992) M. Borge et al., NP A 560 (1993) 664 Observation of strong b-delayed triton channel The branching: BGT 5.2, log ft = 2.9 !  Essentially, this is the tetra-neutron decay to a triton and a neutron! (If the clustering approximation is the good one). 2a

  17. Decays to particle bound states of 8Li Dubna, Acculinna, 2009/2012 CCD a a 8He PMT 2a

  18. Final-state continuum in 8Li  2 decay Mianowski, PhD thesis Bhattacharya et al. PRC73(2006) 055802

  19. Reconstruction of a-t-n decay event CCD 4He 3H Q = 4.3 MeV 8He PMT Ea = 1150 keVEt = 2570 keVEn = 610 keV We see about 400 triton events.The branching for the bt is 0.9 %

  20. Feeding of a-t-n decaying states

  21. Feeding of a-t-n decaying states 0.9% BGT evaluation is in progress Mianowski, Janas, to be published Mianowski, PhD thesis M. Pfützner, Isolde Workshop, CERN, November 25-27, 2013

  22. Study of 29P(p,g) via 31Ar b2p  There is astrophysical interest in the reaction rate of 29P(p,g)30Si. The proton width of the relevant states above 29P+p threshold can be studied by b2p decay of 31Ar Koldste et al., PRC 87 (2013) 055808  Very hard to identify 300 keV line because of b-background and noise.  OTPC offers a straightforward and clean method to detect such a transition Proton ranges in pure helium: 300 keV  R = 20 mm 830 keV R = 100 mm M. Pfützner, Isolde Workshop, CERN, November 25-27, 2013

  23. Search for 19Ne(p,g) via 20Mg bp  The key reaction for the breakout from the hot CNO cycle into the rp-process is 19Ne(p,g)20Na. It is expected to be dominated by a single resonance at 457 keV. Wallace et al., Phys. Lett. B712 (2012) 59 Piechaczek et al., NPA 584 (1995) 509  Search for the 457 keV line in the 20Mg bp spectrum failed. The present limit for the feeding of the state is 0.02%  OTPC could be used to verify/improve this limit in the background free measurement M. Pfützner, Isolde Workshop, CERN, November 25-27, 2013

  24. Summary • The OTPC detector is an efficient tool to search for very rare multiparticle decays or to investigate particle decays obscured by beta background. • Can provide precise branching ratios for b-delayed particle channels. Although the energy resolution is worse than for Si detectors, yields complementary data for low-energy particles. • b2p emission discovered in 46Fe. Decay of one atom observed! • b3p emission finally observed in 31Ar. See the Gunvor’s talk later this session! • Strong b-delayed triton emission confirmed for 8He. By recording tracks of both a and t, the decay energies were reconstructed in the model independent way. Will shed light on the mechanism of the decay and provide the BGT strength for the t-emitting states. • Possible applications include search for low-energy b-delayed proton channels of astrophysical interest, like 31Ar b2p  29P or 20Mgbp  19Ne . M. Pfützner, Isolde Workshop, CERN, November 25-27, 2013

  25. Thank you! The main work was done by two PhD students:Sławek Mianowski and Marcin Pomorski M. Pfützner, Isolde Workshop, CERN, November 25-27, 2013

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