Review

Strange hadrons – strangeness in strongly interacting particles

P. Achenbach^1a, C. Ayerbe Gayoso¹, J.C. Bernauer^1,2, R. Böhm¹, D. Bosnar³, M. Bösz¹, L. Debenjak⁴, M.O. Distler¹, A. Esser¹, I. Friščić³, M. Gómez Rodríguez¹, K. Grießinger¹, P. Jennewein¹, M. Makek³, H. Merkel¹, U. Müller¹, L. Nungesser¹, J. Pochodzalla¹, M. Potokar⁴, T. R. Saito^1,5, S. Sánchez Majos¹, B.S. Schlimme¹, S. Širca^4,6, Th. Walcher¹, M. Weinriefer¹ and C.J. Yoon^1,7

¹ Institut für Kernphysik, Johannes Gutenberg-Universität, Mainz, Germany
² now at MIT-LNS, Cambridge, MA, USA
³ Department of Physics, University of Zagreb, Croatia
⁴ Jožef Stefan Institute, Ljubljana, Slovenia
⁵ GSI Helmholtz Center for Heavy Ion Research, Darmstadt
⁶ University of Ljubljana, Slovenia
⁷ now at Department of Physics and Astronomy, Seoul National University, Korea

^a patrick@kph.uni-mainz.de

Received: 8 July 2011
Revised: 21 July 2011
Published online: 23 September 2011

Abstract

In 2007 the Mainz Microtron MAMI has been upgraded to 1.5 GeV electron beam energy, crossing the energy threshold for open strangeness production. The strangeness quantum number, as carried by the strange quark, provides valuable information on the contribution of individual quark flavours to hadronic processes. Theoretically, the strange quark with its rest energy of order 150 MeV is particularly interesting because it can neither be treated as a massless nor as a heavy quark. Experimentally, an instrument of central importance for the charged kaon electro-production off the proton or light nuclei at MAMI is the magnetic spectrometer Kaos that was installed recently and is now routinely operated by the A1 collaboration.