We have studied the reaction p + 27 Al → 3 He + p + π − + X at recoil-free kinematics. An η meson possibly produced in this reaction would be thus almost at rest in the laboratory system and could therefore be bound with high probability, if nuclear η states exist. The decay of such a state through the N * (1535) resonance would lead to a proton-π − pair emitted in opposite directions.For these conditions we find some indication of such a bound state. An upper limit of ≈ 0.5 nb is found.

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Here, the operation of a field-effect transistor based on a single InAs nanowire gated by an ionic liquid is reported. Liquid gating yields very efficient carrier modulation with a transconductance value 30 times larger than standard back gating with the SiO 2 /Si ++ substrate. Thanks to this wide modulation, the controlled evolution from semiconductor to metallic-like behavior in the nanowire is shown. This work provides the first systematic study of ionic-liquid gating in electronic devices based on individual III-V semiconductor nanowires: this architecture opens the way to a wide range of fundamental and applied studies from the phase transitions to bioelectronics.