Speaker
Description
Besides a rich polarized-target program, the HERMES experiment at HERA took a wealth of deep-inelastic scattering (DIS) data on light and heavy nuclear gas targets. Together with an excellent hadron identification, this allowed the study of medium-induced flavor conversion in semi-inclusive DIS. A
predicted high sensitivity of the nuclear modification factor for $K^-$ in semi-inclusive DIS in respect to the medium-induced flavor conversion is observed for the first time experimentally at HERMES when comparing hadron production on heavy targets to that on a deuterium target. Instead of increased
suppression, like for other hadrons (pions and $K^+$), due to parton-energy loss of the leading quarks, the nuclear modification factor for $K^-$ exhibits a rise at large values of $x_B$ and $z$ due to the proliferation of the $K^-$ constituent quarks $s$ and $\bar u$ and gluons from the induced flavor conversion, which counters the effect of parton-energy loss. The results of the measured $x_B$ spectra on three nuclear targets (Ne, Kr and Xe), as well the
measured $z$ spectra at different $x_B$ slices will be presented and discussed.
