1. Evaluate the 3-variable acceptance matrix.
2. Examine the general availability of the matrix with Monte-Carlo data for various reactions.
3. Apply the matrix to the real data.
Here, we exhibit the steps 1,2 and the final results are shown in the next report. First of all, the conditions to evaluate the matrix are tabulatted below.
| software | GEANT3.21 (with tracking parameters optimized to lower energy) |
| generated particles | Λ + N (simulated independently) |
| dynamics (matrix evaluation, Λ/N momenta) | Uniform on (280.,720.)(N)/(280.,720.)(Λ) MeV/c |
| dynamics (matrix evaluation, cos(ΛN) ) | Uniform on (-1.,-0.6) |
| dynamics (matrix evaluation, orientation ) | Uniform on (-0.45,0.45),(0.,0.15π/0,85π,1.15π/1.85π,2&pi),(0,2π) for cosα,β,γ |
| dynamics(dummy data) Λn ; | K-+4He->2S0 +d,2S0 +p+n follwed by 2S0 -> Y0n, and 3S++n follwed by 3S+-> Y0d,Y0pn |
| dynamics(dummy data) Λp ; | K-+4He->2S+ +n + n follwed by 2S0 -> Y0p, and 3S0+p follwed by 3S0-> Y0nn |
| generated event number | 1.0*1010 |
| target center | (-0.3,0.,1.3):E549 |
| x/y generation point distribution | 4.0 cm sigma Gaussian centered at (x,y)=(-0.3,0.) |
| z generation point distribution | uniform |
| multiple scattering | on(Moliere) |
| energy loss straggling | on(Gauss/Landau/Vavilov are internally selected adequately) |
| nuclear reaction of n/p/π | n is treated by FLUKA+MICAP. Other ones are by GHEISHA. |
| coincidense time gate for PA-PB | 45 nsec |
| Birk's coefficient for plastic scintillator | 0.013/(MeV/cm) |
| energy resolution of scintillators | infinite |
| time resolution of PA/PB for p | 60(PA)/80(PB) psec |
| T0-NC convoluted time resolution for n | 220 psec |
| time resolution of TC_B for π | 250 psec |
| analysis inefficiency for p/n/&pi selection | p:properly simulated(1/βVS EPB+ENT) /n: neglected (software threshold , 3 MeVee, is taken into account) / &pi:neglected(VDC+TC_B hits are just required) |
| analysis inefficiency for p/&pi energy correction | simulated with exact reaction/&Lambda-decay vertices, direction cosines on PDC/VDC. |
| analysis inefficiency for &Lambda reconstruction | simulated with realistic Mp&pi gate, 1108.~1124. MeV/c2. |
| bin widths | 10 MeV/c for p&Lambda and pN, 0.025 for cos&theta&Lambda N,10 MeV/c2 for M&Lambda N and M3S |