Spectrometer tune

Prior to the data taking, we will have precision field maps of the HKS spectrometer as described in section 4.6. They are obtained by the field mapping of HKS Q1, Q2 magnets and the dipole magnets under way at Mitsubishi, Kobe. Interference of the field distributions between the three magnets, and reproducibility of the field setting and the field distribution will be examined by simultaneous excitation of the three magnets. These field maps are also compared with those calculated using the TOSCA code. The field maps thus obtained are the basis of the precision tuning of the HKS spectrometer with the Splitter magnets and the first order matrices will be derived through the generated events based on the field maps.

For the Enge spectrometer, a good field map is known in the form of RAYTRACE input parameters. Combining the field distribution of the splitter magnet, events are generated and used to extract the transfer matrices of the Enge spectrometer. Because of the effect to the optics by tilting the Enge spectrometer, higher order terms are necessary to achieve the required momentum resolution.

Those matrices for HKS and Enge spectrometers are then fine tuned, using the real data as described in the following.

1. First order matrices for HKS spectrometer and Enge spectrometer are obtained based on the field maps measured prior to the data taking.
2. Sieve slit runs will be carried out and the data are used to further tune the transfer matrices of the two spectrometers.
3. Missing mass spectra in the CH$_2$(e,e'K$^+$)X reaction are taken and the mass scale of the spectra will be calibrated self-consistently utilizing the $\Lambda$ and $\Sigma$ peaks. In view of the large detection efficiency of the present spectrometer system, we expect to accumulate enough statistics within a few hours.
4. Finally, the missing mass spectrum of the $^{12}$C(e,e'K$^+$)X reaction is used to fine tune the matrices of HKS and Enge spectrometer. Correlations between the scattering angles, kaon momenta and scattered electron momenta with the ground state mass of $^{12}_\Lambda$B will be carefully studied to achieve the best mass resolution as was successfully done in the E89-009 experiment.