1 / 25

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.

abarbee
Télécharger la présentation

Charged-particle spectroscopy of exotic nuclei with the Optical TPC

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  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

More Related