Speaker
Ms
Natalia Sokołowska
(Faculty of Physics, University of Warsaw)
Description
11Be is the neutron - rich nucleus expected to be a β-delayed proton emitter. The very
small branching ratio (BR) for this exotic decay mode (∼ 10e−6 ) was determined through
indirect observations based on accelerator mass spectrometry (AMS) [1, 2] and resulted
to be about two orders of magnitude larger than predicted [3]. The direct measurement of
the delayed proton emission probability and energy spectrum is particulary challenging,
given the small energy window available (∼ 280 keV). The measurement of the βp energy
spectrum is important for estimating the Gamow-Teller strength at high excitation ener-
gies and for testing models that predict a direct relation between βp and halo structure.
Moreover, recently a new hypothesis which may explain results of the AMS experiment
appeared. According to it, the neutron may have another decay channel in which unknown
particles are produced in the final state [4, 5].
In order to solve this puzzle, we decided to perform a series of measurements with
the Warsaw Optical Time Projection Chamber (OTPC) [6]. First tests were made in
February 2018 at JINR in Dubna. Those measurements were focused on studying the
behaviour of light nuclei in the region of 11Be in the chosen experimental conditions.
Additionally we measured 9C beta decay in which low-energy beta-delayed protons (165
keV) are emitted. The main experiment was performed in August/September 2018 at
HIE-ISOLDE in CERN. During this run a large amout of 11Be beta decays was observed.
A complementary measurement at LNS in Catania is planned for spring 2019 - during
this experiment BR for beta delayd alpha emission from 11Be will be determined.
The whole project is extremely challenging and complex, both from physical and tech-
nical point of view (low BR for β-delayed protons: 10e−8 ∼ 10e−6 , long half-life: T_1/2 = 13.7 s, and low energy of the protons ∼ 180 keV). It required the development of new solutions for the acquisition system and analysis software. More details on the project and the status of the data analysis will be presented.
[1] K. Riisager, Nucl. Phys. A 925, 112 (2014).
[2] K. Riisager et al., Phys. Lett. B 732, 305 (2014).
[3] M. J. G. Borge, et al. J. Phys. G, 40, 035109 (2013).
[4] B. Fornal and B. Grinstein, Phys. Rev. Lett. 120, 191801 (2018).
[5] M. Pfützner, K. Riisager, Phys. Rev. C 97, 042501(R) (2018).
[6] M. Pomorski et al., Phys. Rev. C 90, 014311 (2014).
Primary author
Ms
Natalia Sokołowska
(Faculty of Physics, University of Warsaw)
Co-authors
Mr
Adam Kubiela
(University of Warsaw)
Dr
Agnieszka Korgul
(University of Warsaw)
Mrs
Aleksandra Ciemny
(Faculty of Physics, University of Warsaw)
Dr
Aleksandra Fijałkowska
(Universtiy of Warsaw)
Mrs
Amanda Giska
(University of Warsaw)
Mr
Andrey Bezbakh
(JINR)
Prof.
Andrey Fomichev
(JINR)
Dr
Chiara Mazzocchi
(University of Warsaw)
Dr
Grzegorz Kamiński
(Heavy Ion Laboratry)
Mr
J.D. Ovejas
(IEM/CSIC)
Dr
Krzysztof Miernik
(University of Warsaw)
Dr
Luis Fraile
(Universidad Complutense de Madrid)
Dr
Marcin Pomorski
(University of Warsaw)
Prof.
Marek Pfutzner
(University of Warsaw)
Prof.
Maria Borge
(IEM/CSIS)
Mrs
S. Vinals
(IEM/CSIS)
Prof.
Wojciech Dominik
(University of Warsaw)
Prof.
Zenon Janas
(University of Warsaw)
Dr
Łukasz Janiak
(University of Warsaw)
