Lifetime measurement of the260 g.s. At SAMURAI

S. Storck*, C. Caesar, J. Kahlbow, V. Panin, D. S. Ahn, L. Atar, T. Aumann, H. Baba, K. Boretzky, H. Chae, N. Chiga, S. Choi, M. L. Cortés, D. Cortina-Gil, Q. Deshayes, P. Doornenbal, Z. Elekes, N. Fukuda, I. Gaparic, K. I. HahnZ. Halász, A. Hirayama, N. Inabe, T. Isobe, T. Kobayashi, D. Körper, Y. Kondo, Y. Kubota, I. Kuti, C. Lehr, M. Marques, M. Matsumoto, T. Murakami, I. Murray, T. Nakamura, T. Nilsson, H. Otsu, S. Paschalis, M. Parlog, M. Petri, D. Rossi, A. Saito, M. Sasano, H. Scheit, P. Schrock, Y. Shimizu, H. Simon, D. Sohler, O. Sorlin, L. Stuhl, H. Suzuki, I. Syndikus, H. Takeda, H. Törnqvist, Y. Togano, T. Tomai, T. Uesaka, H. Yamada, Z. Yang, M. Yasuda, K. I. Yoneda

*Corresponding author for this work

Research output: Contribution to journalConference articlepeer-review


The ground state of the neutron unbound nucleus26O is speculated to have a lifetime in the pico-second regime. In order to determine the decay lifetime of the26O ground state with high sensitivity and precision, a new method has been applied. The experiment was performed in December 2016 at the Superconducting Analyzer for MUlti-particle from Radio Isotope Beams (SAMURAI) at the Radioactive Isotope Beam Factory (RIBF) at RIKEN. A27F beam was produced in the fragment separator BigRIPS and impinged on a W/Pt target stack where26O was produced. According to the lifetime, the decay of26O happens either in or outside the target. Thus, the velocity difference between the decay neutrons and the fragment24O delivers a characteristic spectrum from which the lifetime can be extracted.

Original languageEnglish
Article number012106
Number of pages6
JournalJournal of Physics: Conference Series
Issue number1
Publication statusPublished - 23 Dec 2020
Event27th International Nuclear Physics Conference, INPC 2019 - Glasgow, United Kingdom
Duration: 29 Jul 20192 Aug 2019

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The incoming beam is identified using the ionization chamber (ICB) and tracked with the drift chambers (BDC 1 & 2 ). The time-of-flight measurement is initiated by the plastic scintillators SBT 1 & 2. The target was surrounded by three 300 µm thick single-area silicon detectors. Those are necessary to identify the incoming beam particles directly in front of the target and the fragments after the proton removal reaction to select the isotope of interest. One silicon detector was installed in front of the target stack and two behind. The target in which the reaction happened can already be identified in the ∆ν-spectrum, which makes it unnecessary to measure the energy loss between the individual target sheets. The silicon detectors act as targets themselves and therefore contribute to the background as indicated by the gray peaks in Fig. 4. The background originating from the silicon detectors can not easily be determined by an empty target run since the energy loss from the target would be missing and the peaks of the individual silicon detectors would overlap in the ∆ν-spectrum. However, the background contributions can be determined from a reference measurement with the 26F secondary beam where 25O is produced from proton removal but no lifetime is expected (τ < 10−21s) and thus a flat spectrum. The secondary beam 24O, with 210 MeV/u and a rate of ∼ 1000 cps, is very sharp in energy and and high intensity 48Ca primary beam and the BigRIPS team for their efforts in preparing the secondary beams. This work has been supported by DFG grant no. SFB 1245, BMBF contract 05P15RDFN1 and GSI-TU Darmstadt cooperation agreement.

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