The E12-09007 experiment in CLAS12 of Hall B at Jefferson lab proposed to measure multiplicities and longitudinal double spin asymmetries for pions (π+,π−, π0) and kaons (K+, K−, K0s) in Semi-Inclusive Deep Inelastic Scattering (SIDIS) from both hydrogen and deuterium. The data will be used to measure the x-dependence of the strange parton distribution function (PDF) and will help constrain the global fits used to obtain the fragmentation functions (FF). In addition this data will allow the extraction of the individual contributions of quarks and anti-quarks to the nucleon spin. The experiment is scheduled in two parts: The first involves unpolarized beam and targets for multiplicity and strange PDF measurements. The second uses both polarized beam and targets for the flavor decomposition. The measurements will cover the x-range from 0.05 to 0.7. Part of the unpolarized measurements was achieved this last winter and data taking will proceed at the end of this year. The polarized part of the experiment will run in a few years.
The experiment requires the use of a Ring Imaging Cherenkov (RICH) for a successful charged kaon identification in the 3 to 8 GeV/c momentum range. One full RICH detector was recently built and is functional; a second one is under construction.