(Niculescu, Berman)

Electromagnetic strangeness production is an important part of Jefferson Lab’s experimental program. Several experiments have been approved to run in all three experimental halls. These experiments include kaon electro- and photoproduction on hydrogen, deuterium, ³He, and ⁴He. We are analyzing the data for the latter three.

Kaon photoproduction on deuterium is governed by three main mechanisms:

· the elementary amplitudes of the six kaon production reactions possible on the nucleon

(gp ® K⁺L, gp ® K⁺S⁰, gp ® K⁰S⁺, gn ® K⁺S- , gn ® K⁰L, and gn ® K⁰S⁰);

· the Fermi motion of the proton and neutron inside the deuteron (the momentum distribution of

nucleon momenta is calculated using the deuteron wave function); and

· the interaction between the final-state hadrons.

Experimental information exists for the first three exclusive kaon photoproduction channels; however, there are no previous data for kaon photoproduction on the neutron. One of the goals of experiment E89-045 [Mec89] was to investigate open strangeness photoproduction on the neutron. These studies will provide additional information about isospin dependence, since the elementary operator for S- production could be quite different from the operator for S⁰ production [Le92].

We have investigated the gn ® K⁺S- channel as part of a broader study of kaon photoproduction on deuterium. The data were acquired using the CLAS and the Photon-Tagging Facility. The photon-energy range covered was from 0.50 to 2.95 GeV. In the present analysis, the reaction gn ® K⁺S- was selected by detecting the K⁺ and the decay products of the S- ® p^-n. The pion was detected using the time-of-flight counters and the drift chambers, while the neutron was detected in the EC. The neutron momentum was determined from the time-of-flight information given by the EC. Preliminary differential cross sections are shown in Fig. 8 as a function of the invariant energy W and the kaon polar angle in the center-of-mass system.

Figure 8. Preliminary differential cross sections for gn ® K⁺S- are shown as a function of the invariant energy W and the kaon polar angle in the center-of-mass system, compared with theory [Ben98].

The current analysis provides complementary information to that obtained in photoproduction on the proton, furthering our understanding of the reaction mechanism that governs open strangeness production. Future work, besides finalizing the present analysis, will focus on the extraction of the final-state YN interaction, and extend our analysis to ³He and ⁴He (see Section B7). These results have been presented at the 2001 International Nuclear Physics Conference [Nic01] and at the Workshop on New Aspects of Quark Nuclear Physics with Polarized Photons in Honolulu [Nic03]. Our analysis report is under review within the CLAS Collaboration in preparation for submitting a PRL.

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Last modified: 03/31/05