Experimental techniques and performance of $\Lambda$-hypernuclear spectroscopy with the $(e,e^{\prime}K^{+})$ reaction

TL;DR

This paper reviews the development and performance of $ ext{(e,e'}K^+)$ reaction spectroscopy for $ ext{Λ}$-hypernuclei, highlighting new spectrometer systems and improved energy resolution achieved in recent experiments at JLab.

Contribution

It introduces a new spectrometer system with enhanced resolution and accuracy for $ ext{Λ}$-hypernuclear spectroscopy using the $ ext{(e,e'}K^+)$ reaction, and details experimental techniques and results.

Findings

Achieved energy resolution of about 0.5 MeV FWHM.

Measured $ ext{B}_ ext{Λ}$ with an accuracy of ≤0.2 MeV.

Demonstrated improved performance in hypernuclear spectroscopy.

Abstract

The missing-mass spectroscopy of $\Lambda$ hypernuclei via the $(e,e^{\prime}K^{+})$ reaction has been developed through experiments at JLab Halls A and C in the last two decades. For the latest experiment, E05-115 in Hall C, we developed a new spectrometer system consisting of the HKS and HES; resulting in the best energy resolution ($E_{\Lambda} \simeq0.5$-MeV FWHM) and $B_{\Lambda}$ accuracy ($B_{\Lambda}\leq0.2$ MeV) in $\Lambda$-hypernuclear reaction spectroscopy. This paper describes the characteristics of the $(e,e^{\prime}K^{+})$ reaction compared to other reactions and experimental methods. In addition, the experimental apparatus, some of the important analyses such as the semi-automated calibration of absolute energy scale, and the performance achieved in E05-115 are presented.