Experimental searches for antikaonic clusters

The existence of antikaonic nuclear clusters, quasi-bound systems composed of an antikaon and a nucleus, is an important issue both theoretically and experimentally. By using all available experimental data, which are rather old and poor in statistics, a qualitative theoretical consensus is that antikaon nucleus interaction is attractive and strongly absorptive. However, there remain large uncertainties in quantitative estimates on these strengths, which prevents from drawing a definite conclusion. In the experimental side, new data are recently accumulated. Here I summarize the present experimental status on the antikaonic clusters mainly obtained in stopped K− reactions.