H-dibaryon search by KEK-E522

Yoon, C. J.; Akikawa, H.; Aoki, Kazuo; Fukao, Y.; Funahashi, H.; Hayata, M.; Miwa, K.; Okada, Hiroaki; Saito, N.; Sato, H.; Shoji, K.; Takahashi, Hajime; Taketani, Kaoru; Asai, J.; Kurosawa, M.; Ieiri, M.; Hayakawa, T.; Kishimoto, T.; Sato, Akira; Shimizu, Y.; Yamamoto, Kentaro; Yoshida, T.; Hibi, T.; Nakazawa, Kimitaka; Ahn, J. K.; Choi, Bong‐Hyuk; Kim, S. J.; Kim, S. H.; Park, B. D.; Park, I. G.; Song, J.; Yoon, C. S.; Tanida, K.; Ohnishi, Akira

doi:10.1007/978-3-540-76367-3_25

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“…3. Several representative values of the ΛΛ scattering length were used: a ΛΛ =−0.5, −0.8, −1.9 fm, spanning a broad range of values suggested by analyses of ΛΛ correlations observed recently in relativistic heavy-ion collisions [30][31][32] and by analyzing the KEK-PS E522 [38] invariant mass spectrum in the reaction 12 C(K − , K + )ΛΛX near the ΛΛ threshold [39]. Again, the choice of a ΛΛ determines the one ΛΛ LEC required at LO, while the ΛΛN LEC was fitted to the ∆B ΛΛ ( 6 ΛΛ He)=0.67±0.17 MeV datum.…”

Section: Pacs Numbersmentioning

confidence: 99%

The onset of ΛΛ hypernuclear binding

et al. 2019

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Binding energies of light, A ≤ 6, ΛΛ hypernuclei are calculated using the stochastic variational method in a pionless effective field theory (/ πEFT) approach at leading order with the purpose of assessing critically the onset of binding in the strangeness S = −2 hadronic sector. The / πEFT input in this sector consists of (i) a ΛΛ contact term constrained by the ΛΛ scattering length aΛΛ, using a range of values compatible with ΛΛ correlations observed in relativistic heavy ion collisions, and (ii) a ΛΛN contact term constrained by the only available A ≤ 6 ΛΛ hypernucler binding energy datum of 6 ΛΛ He. The recently debated neutral three-body and four-body systems 3 ΛΛ n and 4 ΛΛ n are found unbound by a wide margin. A relatively large value of |aΛΛ| 1.5 fm is needed to bind 4 ΛΛ H, thereby questioning its particle stability. In contrast, the particle stability of the A = 5 ΛΛ hypernuclear isodoublet 5 ΛΛ H-5 ΛΛ He is robust, with Λ separation energy of order 1 MeV. PACS numbers: Introduction. Single-Λ and double-Λ (ΛΛ) hypernuclei provide a unique extension of nuclear physics into strange hadronic matter [1]. Whereas the behavior of a single Λ hyperon in atomic nuclei has been deduced quantitatively by studying Λ hypernuclei ( A Λ Z) from A=3 to 208 [2], only three ΛΛ hypernuclei ( A ΛΛ Z) are firmly established: the lightest known 6 ΛΛ He Nagara event [3] and two heavier ones, 10 ΛΛ Be and 13 ΛΛ B [4]. Remarkably, their binding energies come out consistently in shell-model calculations [5]. Few ambiguous emulsion events from KEK [6] and J- PARC [7] have also been reported. However, and perhaps more significant is the absence of any good data on the onset of ΛΛ hypernuclear binding for A < 6. In distinction from the heavier species, these very light s-shell species, if bound, could be more affected by microscopic strangeness S = −2 dynamics. An obvious issue is the effect of a possible ΞN dominated H dibaryon resonance some 20-30 MeV above the ΛΛ threshold [8,9] on ΛΛ hypernuclear binding in general.Several calculations of light A < 6 s-shell ΛΛ hypernuclei using ΛΛ interactions fitted to 6 ΛΛ He suggest a fairly weak ΛΛ interaction, with the onset of ΛΛ hypernuclear binding defered to A = 4. Indeed, a slightly bound I = 0

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