Neutron-rich Λ-Hypernuclei study with the FINUDA experiment

¹ INFN Sezione di Torino, via P. Giuria 1, Torino, Italy
² Dipartimento di Fisica, Università di Torino, via P. Giuria 1, Torino, Italy

^a e-mail: botta@to.infn.it

Published online: 20 March 2014

Abstract

The FINUDA experiment at DAΦNE, Frascati, has found evidence for the neutron-rich hypernucleus $\text{H}\Lambda 6$ studying (π⁺, π⁻) pairs in coincidence from the $K_{\text{stop}}^{-}+{}^{\text{6}}\text{L}\text{i}\to {}_{\Lambda }{}^6\text{H}+{\pi }^{+}$ production reaction followed by ${}_{\Lambda }{}^6\text{H}\to {}^6\text{H}\text{e +}{\pi }^{-}$ weak decay. The production rate of ${}_{\Lambda }{}^6\text{H}$ undergoing this two-body π⁻ decay has been found to be $(2.9\pm 2.0)\cdot {10}^{-6}/K_{\text{stop}}^{-}$. Its binding energy has been evaluated to be $B_{\Lambda }({}_{\Lambda }{}^{6}H)=(4.0\pm 1.1)$ MeV with respect to $({}^5\text{H}+\Lambda )$, jointly from production and decay. A systematic difference of (0.98 ± 0.74) MeV between B_Λ values derived separately from decay and from production has been tentatively assigned to the ${}_{\Lambda }{}^6\text{H}{\text{ 0}}_{\text{g}\text{.s}\text{.}}^{+}\to 1^{+}$ excitation. A similar investigation has been carried out for the neutron-rich hypernucleus ${}_{\Lambda }{}^9\text{H}\text{e}$ studying the $K_{\text{stop}}^{-}+{}_{}{}^{\text{9}}\text{B}\text{e}\to {}_{\Lambda }{}^9\text{H}\text{e}+{\pi }^{+}$ reaction in coincidence with the ${}_{\Lambda }{}^9\text{H}\text{e}\to {}_{}{}^{\text{9}}\text{L}\text{i + }{\pi }^{-}$ weak decay; an upper limit for the production rate of ${}_{\Lambda }{}^9\text{H}\text{e}$ undergoing the two-body π⁻ decay has been found to be $4.2\cdot {10}^{-6}/{\text{K}}_{stop}^{-}$ (90% C.L.).