Electromagnetic Production of Kaons on the Nucleon

Abstract

Studies of the electromagnetic production of strange quarks began in the 1950s as something of a curiosity that puzzled experimentalists and theorists alike. As the datasets increased, concomitant advances in theoretical models were realized. A paradigm shift occurred in the 1990s with the development of second-generation facilities at ELSA, MAMI, SPring-8, and JLab, which brought nuclear physics experiments forward by orders of magnitude in counting statistics compared to the first-generation efforts. This was an utter boon to strangeness physics investigations, and to date, more than 50 dedicated experiments in kaon photo- and electroproduction have been completed at facilities around the world, leading to a host of experimental observables that have enabled significant advances in the exploration of strongly interacting systems that decay via $s\bar{s}$ quark pair creation. This review was designed to provide the first-ever in-depth overview of both the experimental and theoretical progress in the field of the electromagnetic production of strangeness. This work looks back over 70 years of past developments, discusses ongoing work and near-term plans, and details future possibilities being considered for third-generation facilities. Throughout this work, the primary impacts of these explorations are highlighted, along with connections to a wide range of related phenomenological applications. An important goal of this review is to provide a complete, self-contained guide into this field prepared at a level that is relevant for both new and seasoned scientists, whether experimentalists, phenomenologists, or theorists, to better understand what has been accomplished by so many dedicated folks-each building on what has come before-and to appreciate the exciting future potential for continued studies in this area. A more complete abstract is provided in the paper.

Figures (96)

• Figure 1.1: (a) Stacked histogram of the full experimental $\gamma N \to KY$ photoproduction database including $\gamma p$ and $\gamma n$ data as a function of year. (b) Stacked histogram of the full experimental $e p \to e'KY$ electroproduction database as function of year. The blue histograms represent the cross section measurements and the red histograms represent the polarization measurements. The total number of data points for each type of measurement is listed on each plot.
• Figure 2.1: Kinematic variables for (a) kaon electroproduction on the nucleon and (b) kaon photoproduction on the nucleon. In panel (b), the photon $\gamma$ may be either real or virtual. In the latter case, the process is referred to as virtual photoproduction, which corresponds to the electroproduction process shown in panel (a).
• Figure 2.2: Kinematics for kaon electroproduction on the nucleon in the kaon-hyperon c.m. frame.
• Figure 2.3: Target $(x,y,z)$ and recoil $(x',y',z')$ coordinate frames used to define the directions of the target and recoil polarizations Knochlein:1995qz.
• Figure 2.4: Feynman diagrams for the Born terms contributing to kaon photoproduction on the nucleon, $\gamma+p \to K^+ + \Lambda$: (a) $s$-channel with an intermediate proton, (b) $t$-channel with an intermediate kaon, and (c) $u$-channel with an intermediate $\Lambda$ hyperon.