Neutron-rich hypernuclei: evidence for 6ΛH and search for 9ΛHe
1 Dipartimento di Fisica, Politecnico di Torino, corso Duca degli Abruzzi 24, Torino, Italy
2 INFN Sezione di Torino, via P. Giuria 1, Torino, Italy
3 Laboratori Nazionali di Frascati dell’INFN, via E. Fermi 40, Frascati, Italy
4 Department of Physics, Seoul National University, 151-742 Seoul, South Korea
5 Dip. di Ingegneria Meccanica e Industriale, Università di Brescia, via Valotti 9, Brescia, Italy
6 INFN Sezione di Pavia, via Bassi 6, Pavia, Italy
7 Dipartimento di Fisica, Università di Torino, via P. Giuria 1, Torino, Italy
8 SUBATECH, École des Mines de Nantes, Université de Nantes, CNRS-IN2P3, Nantes, France
9 INFN Sezione di Trieste, via Valerio 2, Trieste, Italy
10 Dipartimento di Fisica, Università di Trieste, via Valerio 2, Trieste, Italy
11 CEA, Irfu/SACM, Gif-sur-Yvette, France
12 Dipartimento di Fisica Università di Bari, via Amendola 173, Bari, Italy
13 INFN Sezione di Bari, via Amendola 173, Bari, Italy
14 Department of Physics, Kyoto University, Sakyo-ku, Kyoto, Japan
15 Department of Physics, Shahid Behesty University, 19834 Teheran, Iran
16 INAF-IFSI, Sezione di Torino, corso Fiume 4, Torino, Italy
17 RIKEN, Wako, Saitama 351-0198, Japan
18 Racah Institute of Physics, The Hebrew University, Jerusalem 91904, Israel
a e-mail: firstname.lastname@example.org
The FINUDA experiment at DAΦNE, Frascati, has found evidence for the neutron-rich hypernucleus 6ΛH studying (π+, π−) pairs in coincidence from the K−stop+6Li → 6ΛH+π+ production reaction followed by 6ΛH → 6He + π− weak decay. The production rate of 6ΛH undergoing this two-body π− decay has been found to be (2.9 ± 2.0) · 10−6/K−stop.
Its binding energy has been evaluated to be BΛ(6ΛH) = (4.0 ± 1.1) MeV with respect to 5H + Λ, jointly from production and decay. A systematic difference of (0.98 ± 0.74) MeV between BΛ values derived separately from decay and from production has been tentatively assigned to the 6ΛH 0+g.s. → 1+ excitation.
A similar investigation has been carried out for the neutron-rich hypernucleus 9ΛHe studying the K−stop + 9Be → 9ΛHe + π+ reaction in coincidence with the 9ΛHe → 9Li + π− weak decay; an upper limit for the production rate of 9ΛHe undergoing the two-body π− decay has been found to be 4.2 · 10−6/K−stop (90% C.L.).
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