＜＜＜「@」を「__AT__」に置き換えています＞＞＞

To: "ml-np__AT__rcnp.osaka-u.ac.jp" , "sg-l__AT__yukawa.kyoto-u.ac.jp" 
Date: Thu, 7 May 2026 07:45:58 +0000
Subject: [Sg-l:10328] RIKEN FBSP Seminar by Ryoko Kino on May 15th 14:00
From: Tomona Kinugawa (Sg-l 経由) 

皆様

理研仁科センターの衣川です。少数多体系物理研究室のセミナー情報を転送します。

講演者：木野 量子氏（理研）

日時：5/15 14時〜

場所：研究本館 213号室 ・オンライン

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Meeting ID   943 7598 6147
Passcode    Y3APysU2

https://riken-jp.zoom.us/meeting/register/NMRXSZgSS8-aeVHtcvU6UQ

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Title:
Precise measurement of the Λ-binding energy difference between 3ΛH and 4ΛH via decay-pion spectroscopy at MAMI

Abstract:
Hypernuclei are ideal objects for extending our understanding of nuclear forces into the strangeness sector and for investigating the baryon–baryon interaction. The lightest and simplest hypernuclear bound system is the hypertriton (3ΛH), a three-body system consisting of a proton, a neutron, and a Λ hyperon. As the benchmark system of hypernuclear physics, the hypertriton has attracted renewed attention in recent years. Its Λ separation energy, measured in the 1960s, is remarkably small — on the order of 100 keV — implying that the Λ is only loosely bound to the deuteron. This picture predicted a lifetime close to that of the free Λ. However, multiple experiments in the 2010s reported significantly shorter lifetimes, creating a tension with the expected weak-binding behavior that became known as the "hypertriton puzzle." A coherent understanding has yet to be established, and precise measurements of both the binding energy and the lifetime are essential.
In this seminar, I will present the results of an experiment performed at MAMI (Mainz, Germany) in 2022–2024 by the A1 Collaboration, a Japan–Germany joint effort. We employed decay-pion spectroscopy, a technique that determines the binding energy by precisely measuring the monochromatic momentum of pions emitted in the two-body weak decay of hypernuclei at rest. This direct spectroscopic method allows an absolute determination of the binding energy, free from the model dependence inherent in other approaches.
After describing the experimental technique and discussing the reliability and validity of our method, I will introduce several theoretical works relevant to possible physical interpretations of our results. I hope this can serve as a starting point for discussion, and I very much look forward to hearing the perspectives of the theorists in the group.
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衣川友那 (Tomona Kinugawa)
Special Postdoctoral Researcher
Few-body Systems in Physics Laboratory, Nishina Center, RIKEN
tomona.kinugawa__AT__riken.jp
https://ribf.riken.jp/~Kinugawa/index_en.html
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To: "ml-np__AT__rcnp.osaka-u.ac.jp" , "sg-l__AT__yukawa.kyoto-u.ac.jp" 
Date: Thu, 7 May 2026 07:49:54 +0000
Subject: [Sg-l:10329] RIKEN FBSP Seminar by Mahboubeh SHAHRBAF MOTLAGH on May 12th 14:00
From: Tomona Kinugawa (Sg-l 経由) 

皆様

理研仁科センターの衣川です。少数多体系物理研究室のセミナー情報を転送します。

講演者：Mahboubeh SHAHRBAF MOTLAGH 氏 (University of Wrocław, Poland)

日時：5/12 (火) 14時〜

場所：研究本館 213号室 & オンライン

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zoom リンク

https://riken-jp.zoom.us/meeting/register/QaBZCPZcS9CkW0hpZMVV8g

 ======================
Title: Strangeness in Neutron Stars: From Realistic Interactions to Astrophysical Signatures

Abstract:

Hyperons, baryons containing strange quarks, are abundantly produced and studied in high-energy heavy-ion experiments such as HADES (GSI), ALICE (CERN), STAR (RHIC), and NA61/SHINE (CERN). These experiments provide important constraints on hyperon–nucleon and hyperon–hyperon interactions, establishing a crucial link between nuclear physics and astrophysics. Under the extreme densities present in neutron star (NS) interiors, hyperons are also expected to emerge; however, their actual presence remains one of the most fundamental open questions in the study of dense matter. Understanding their role is essential for constraining the equation of state (EOS) of strongly interacting matter and for connecting terrestrial measurements with astrophysical observations.

In the first part of this talk, I will present a microscopic study of hyperonic matter within the lowest-order constrained variational (LOCV) framework, extended to include interacting Λ hyperons. Using realistic spin- and parity-dependent Λ–N and Λ–Λ interactions constrained by hypernuclear data, I will discuss the resulting EOS, particle composition, sound speed, and macroscopic properties of neutron stars. The inclusion of Λ hyperons leads to a moderate softening of the EOS, reducing the maximum NS mass while remaining consistent with current observational constraints from NICER and gravitational-wave measurements. Our results indicate that Λ hyperons can be present in NS cores across the observed mass range without conflicting with these constraints.

In the second part, I will consider a relativistic mean-field (RMF) framework, specifically the DD2Y-T model, to illustrate how hyperonic degrees of freedom are incorporated in such approaches. I will further explore how the inclusion of bosonic dark matter candidates, such as sexaquarks (uuddss), can modify the hyperonic EOS. This combined treatment of hyperons and dark matter within hybrid models highlights how these two strangeness-bearing components may jointly influence the internal composition and observable properties of neutron stars. Furthermore, our results suggest that a smooth crossover from hadronic matter to quark matter provides a viable resolution to the strangeness dilemma in neutron stars.

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衣川友那 (Tomona Kinugawa)
Special Postdoctoral Researcher
Few-body Systems in Physics Laboratory, Nishina Center, RIKEN
tomona.kinugawa__AT__riken.jp
https://ribf.riken.jp/~Kinugawa/index_en.html