Bulletin of the American Physical Society
5th Joint Meeting of the APS Division of Nuclear Physics and the Physical Society of Japan
Volume 63, Number 12
Tuesday–Saturday, October 23–27, 2018; Waikoloa, Hawaii
Session CE: Mini-symposium on Strangeness Nuclear Physics Today and Tomorrow I |
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Chair: Akira Ohnishi, Yukawa Institute for Theoretical Physics Room: Hilton King's 1 |
Wednesday, October 24, 2018 7:00PM - 7:30PM |
CE.00001: Recent progress of hypernuclear physics Invited Speaker: Emiko Hiyama One of main goal in hypernuclear physics is to extract information on hyperon ($Y$)-Nucleon($N$) and Hyperon($Y$)-Hyperon($Y$) interaction. For a decade, we have been succeeded in obtaining information on $YN$ interaction. Now, next step, it is necessary to extract information on $YY$ interaction. For this purpose, experimentally, we performed search experiment of double \Lambda hypernuclei using emulsion and $\Xi hypernuclei$ by $(K^-,K^+)$ reaction. Along this situation, it is requested to predict what kind of double strangeness nuclei are bound and what kinds of $YY$ interaction can be extracted. In this session, I will overview theoretical effort so far and discuss future prospect. |
Wednesday, October 24, 2018 7:30PM - 7:45PM |
CE.00002: Spectroscopic study of $¥Xi$ hypernucleus by using the $^{12}{¥rm C}(K^{-},K^{+})$ reaction at J-PARC Shunsuke Kanatsuki We have measured an excitation energy spectrum of the $^{12}{¥rm C}(K^{-},K^{+})$ reaction at J-PARC K1.8 beam line. |
Wednesday, October 24, 2018 7:45PM - 8:00PM |
CE.00003: Investigation Status of S=-2 Hypernuclei in Nuclear Emulsion for the E07 Experiment at J-PARC May Sweet, Kazuma Nakazawa, Junya Yoshida, Masahiro Yoshimoto With the use of nuclear emulsion, S=-2 hypernuclei has been studied for aiming to understand \Lambda-\Lambda and \Xi-N interactions. So far we have succeeded to analyze 9 events of double-hypernuclei which introduced interaction energies. \DeltaB\Lambda\Lambda, between \Lambda hyperons on several nuclei in the world. However its knowledge is very limited. Therefore, to understand the \ Lambda-\Lambda and \Xi-N interactions without ambiguities, it is important to find at least several nuclear species with S=-2 and determine their \DeltaB\Lambda\Lambda. We carried out beam exposure to nuclear emulsions for the E07 experiment at J-PARC. The expected statistics of that shall be ten times more than that of the previous E373 experiment. With the aid of fully automated \Xi- tracking system, a typical twin single-hypernuclear event and several candidates of double lambda hypernuclei will be detected. Currently, one of the important task of strangeness nuclear physics is determination of the \Lambda-\Lambda interactions through \Xi- detection and mass measurement of new types of S=-2 hypernuclei. In this presentation, the investigation status of S=-2 hypernuclei in nuclear emulsion will be distributed. |
Wednesday, October 24, 2018 8:00PM - 8:15PM |
CE.00004: Experimental study of Xi hypernuclei Kazuma Nakazawa Double hypernuclei (S=-2 nuclei) as double-Lam and Xi hypernuclei were studied with nuclear emulsion. Regarding double-Lam hypernucleus, the NAGARA event has been set as a ruler for the discussion of the Lam-Lam interaction. The KISO event showed the presence of deeply bound state of Xi- inside nucleus. In the E373 experiment at KEK-PS, we have located ~430 Xi- stop events with evaporation track(s) with the recent analysis. Among them, several events were detected as two single-Lam hypernuclei emission at Xi- capture point in the emulsion. With the recent development of particle-charge-detection method, one event was uniquely identified for its nuclide and shows a deeper state than the KISO event case. Its bound seems the several MeV level, preliminary. This event was reported to has large errors for the binding energy due to ambiguity for the Xi- capture point at the JPS Autumn Meeting in 2017. We have developed a method to fix that by the swelling and slicing of a small piece of the emulsion sheet to watch the event from the side. In our talk, we present newly developed methods, and the preliminary result about the above event. |
Wednesday, October 24, 2018 8:15PM - 8:30PM |
CE.00005: Precise density measurement with mu+ for E07 nuclear emulsion at J-PARC Ryota Kuzuya, Masahiro Yoshimoto, Kazuma Nakazawa One of the main purposes of the E07 experiment at J-PARC is to understand Lambda-Lambda and Xi-N interactions via double hypernuclei with several nuclides in use of nuclear emulsion. For well understand, we need to precisely measure the masses of hypernuclei by decay daughters of them. To do so, the key point is to know kinetic energies daughters through accurate decision of the emulsion density. At present, the density is obtained by track length alpha rays with monochromatic energy from natural isotopes of Thorium and Uranium series in the emulsion. In addition to alpha rays, we will count mu+ particles from decay of stopped pi+ mesons in the density measurement to check the results by alphas. The range of mu+ is ~600 micron via also monochromatic energy. To detect mu+ from pi+ decay, we are developing an automated search method with the Vertex Picker, which scans whole area of the emulsion. The key point of the method is to distinguish mu+ from background of stopping proton. At present, well detection of mu+ was expected by simulation with Geant4. We will introduce the automatic search method for mu+ particles, and effectivity via density measurement with mu+. |
Wednesday, October 24, 2018 8:30PM - 8:45PM |
CE.00006: High-accuracy BΛ measurement of light hypernuclei in nuclear emulsion (1) Masahiro Yoshimoto, Naohiro Muramoto, Ryota Kuzuya, Junya Yoshida, Kazuma Nakazawa Measurement of charge symmetry breaking effect in hypernuclei is an important probe for the strangeness physics. Nuclear emulsion has an essential role to determine Λ binding energy (BΛ) of light hypernuclei, because we can measure the BΛ which have various mass numbers, atomic numbers and decay modes in the same emulsion plate. In recent years, measurements by counters have been advanced. The energy-level spacing and the ground state binding energy were obtained, but the differences from the past emulsion studies are left. A large error of BΛ of hypernuclei with A≥9 is due to less event number. We are performing the latest emulsion experiment, J-PARC E07. A huge number of light single hypernuclei, which is mainly produced by kaon-nucleus direct process, will be extracted from the “overall” analysis. A current analysis of small parts predicts that the ~106 of hypernuclei mesonic-like events are recorded, which is one order of higher than the past experiments. The high-accuracy BΛ measurement will be achieved with the new events. We will report the results of single hypernuclei candidates found in E07 emulsion plates and discuss the systematic error of the measurement with the advanced energy calibration method. |
Wednesday, October 24, 2018 8:45PM - 9:00PM |
CE.00007: Study of lifetime for light hypernuclei in J-PARC E07 experiment Naohiro Muramoto, Kazuma Nakazawa, Masahiro Yoshimoto, May Sweet The lifetime of free Λ is 263 +/- 2 ps. The Λ lifetime has been studied via the decay of |
Wednesday, October 24, 2018 9:00PM - 9:15PM |
CE.00008: Decay Pion Spectroscopy of 5ΛΛH at J-PARC Hiroyuki Fujioka, Tomokazu Fukuda, Emiko Hiyama, Toshio Motoba, Tomofumi Nagae, Sho Nagao, Toshiyuki Takahashi Investigation of hypernuclei with strangeness -2, i.e. Ξ-hypernuclei and double-Λ hypernuclei, is one of the most important subjects in strangeness nuclear physics. For example, observation of new double-Λ hypernuclear events in nuclear emulsion are expected at the J-PARC E07 experiment, which is in the analysis stage. Reaction spectroscopy for the 12C(K-,K+)12ΞBe reaction is planned as the J-PARC E70 experiment. We have conceived a novel counter experiment to investigate a double-Λ hypernucleus, 5ΛΛH, by means of decay pion spectroscopy. It can be produced by decay of 7Ξ-H, which can be tagged by reaction spectroscopy of the 7Li(K-,K+) reaction. We submitted a Letter of Intent to the J-PARC PAC in June 2018. We will introduce the proposed experiment and report the current status of feasibility studies. |
Wednesday, October 24, 2018 9:15PM - 9:30PM |
CE.00009: Design of a weak decay π- detector for 4H γ-ray spectroscopy Yuji Ishikawa, Mifuyu Ukai, Honoka Kanauchi, Takeshi Koike, Tatyana Rogers, Hirokazu Tamura, Manami Fujita, Ryotaro Honda, Koji Miwa, Takeshi Yamamoto The charge symmetry breaking (CSB) effect in the A=4 hypernuclei is a hot topic in strangeness nuclear physics. Recently, we observed a γ transition for 4ΛHe(1+→0+) at 1.406 ± 0.004 MeV in γ-ray spectroscopy experiment (J-PARC E13) with Ge detectors. Conversely, the energy splitting of 4ΛH(1+→0+) measured by NaI detectors is 1.09 ± 0.02 MeV. These results indicated existence of CSB in the ΛN interaction. We are planning to measure the energy of 4ΛH(1+→0+) more precisely with Ge detectors in the next experiment (J-PARC E63) to understand the origin of CSB. The 4ΛH(1+) state is produced via 7Li(K-,π-) reaction as a hyperfragment from highly excited unbound 7ΛLi states and the γ rays from 4ΛH(1+) is detected by Ge detectors. Moreover, we will install range counters around the target to detect the π- mesons from two-body weak decay of the 4ΛH(0+). Using the 7ΛLi missing mass and the π- energy, we can accurately identify the γ rays from 4ΛH(1+) among various hyperfragments such as 3ΛH, 4ΛHe and so on. Furthermore, we are considering lifetime measurement of light hypernuclei by installing the timing and the tracking detectors additionally. We are simulating decay π- detection to design the counters. In this talk, we will report the simulation result. |
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