Core-Excited States of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mmultiscripts><mml:mrow><mml:mi mathvariant="normal">C</mml:mi></mml:mrow><mml:mprescripts/><mml:mrow><mml:mi>Λ</mml:mi></mml:mrow><mml:mrow><mml:mn>12</mml:mn></mml:mrow><mml:mrow/><mml:mrow/></mml:mmultiscripts></mml:mrow></mml:math>Hypernuclei Formed in the (<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msup><mml:mrow><mml:mi>π</mml:mi></mml:mrow><mml:mrow><mml:mo>+</mml:mo></mml:mrow></mml:msup></mml:mrow><mml:mo>,</mml:mo><mml:mi> </mml:mi><mml:mrow><mml:msup><mml:mrow><mml:mi>K</mml:mi></mml:mrow><mml:mrow><mml:mo>+</mml:mo></mml:mrow></mml:msup></mml:mrow></mml:math>) reaction

A spectroscopic study of the $_{\ensuremath{\Lambda}}^{12}\mathrm{C}$ hypernucleus by the (${\ensuremath{\pi}}^{+}, {K}^{+}$) reaction has been performed using a new superconducting kaon spectrometer (INS-SKS) at the KEK 12 GeV Proton Synchrotron with an energy resolution of 2 MeV (FWHM). In addition to two prominent peaks which correspond to the $s$ and $p$ orbitals of a $\ensuremath{\Lambda}$ hyperon, for the first time two smaller peaks were clearly observed at excitation energies of 2.6 and 6.9 MeV. These two peaks are interpreted as states where the $^{11}\mathrm{C}$ excited core and a $\ensuremath{\Lambda}$ hyperon in the $s$ orbit are weakly coupled. The excitation energies and the cross sections of these peaks provide information on the $\ensuremath{\Lambda}N$ interaction.