High-Resolution Spectroscopy of ${}_{\Lambda }{}^{16}\mathbf{N}$ by Electroproduction

An experimental study of the ${}^{16}\mathrm{O}(e,e^{\prime }{K}^{+}){}_{\Lambda }{}^{16}\mathrm{N}$ reaction has been performed at Jefferson Lab. A thin film of falling water was used as a target. This permitted a simultaneous measurement of the $p(e,e^{\prime }{K}^{+})\Lambda ,{\Sigma }^0$ exclusive reactions and a precise calibration of the energy scale. A ground-state binding energy of $13.76\pm 0.16\mathrm{MeV}$ was obtained for ${}_{\Lambda }{}^{16}\mathrm{N}$ with better precision than previous measurements on the mirror hypernucleus ${}_{\Lambda }{}^{16}\mathrm{O}$. Precise energies have been determined for peaks arising from a $\Lambda$ in $s$ and $p$ orbits coupled to the $p_{1/2}$ and $p_{3/2}$ hole states of the ${}^{15}\mathrm{N}$ core nucleus.

Figure 1

Excitation energy spectrum of the $p(e,e^{\prime }{K}^{+})\Lambda ,{\Sigma }^0$ on hydrogen, used for energy scale calibration. The fitted positions (not shown on the plot) for the peaks are $-0.04\pm 0.08\mathrm{MeV}$ and $76.33\pm 0.24\mathrm{MeV}$.

Figure 2

The ${}_{\Lambda }{}^{16}\mathrm{N}$ binding-energy spectrum obtained after kaon selection with aerogel detectors and RICH. The electron-kaon random-coincidence contribution evaluated in a large timing window is superimposed on the spectrum in the left panel. The right panel shows the spectrum after this background has been subtracted.

Figure 3

The ${}_{\Lambda }{}^{16}\mathrm{N}$ binding-energy spectrum. The best fit using Voigt functions (solid curve) and a theoretical prediction (dashed curve) are superimposed on the data. See text for details.