Simple in-medium meson-nucleon kinematics has been applied recently in calculations of strong interaction effects in kaonic atoms [1-4], pionic atoms and elastic scattering of low energy pions by nuclei [4]. More sensitive tests of this approach are possible with $K^+$-nucleus interactions below 800 MeV/c because of the superior penetration of kaons into nuclei. Using this approach, calculated reaction and total cross sections for the very low density nucleus $^6$Li agree with experiment to $\pm$3% throughout the energy range. Calculations are 3$\pm$4% too low for C, Si and Ca, thus quantifying phenomenologically the enhancement in the nuclear medium observed before [6-8]. A brief discussion of this open problem is included [9].

[1] A. Cieply et al., Phys. Lett. B 702 (2011) 402

[2] A. Cieply et al., Phys. Rev. C 84 (2011)

[3] E. Friedman, A. Gal, Nucl. Phys. A 899 (2013) 60 and references therein

[4] A. Gal et al., EPJ Web of Conferences 81 (2014) 01018 and references therein

[5] E. Friedman, A. Gal, Nucl. Phys. A 928 (2014) 128

[6] D.V. Bugg et al., Phys. Rev. 168 (1968) 1466

[7] P.B. Siegel, W.B. Kaufmann, W.R. Gibbs, Phys. Rev. C 31 (1985) 2184

[8] R.J. Peterson, Phys. Rev. C 60 (1999) 022201 and references therein

[9] E. Friedman, Nucl. Phys. A (2016), in press