- New method to get cross section. This use the transport function, which is the lastest version, to make the cut at focal plane.
- Detail how to make this cut:
- The cut is combine of 2D (phi-y)+ 2D(theta-y) + 2D(x-y)
at focal plane, where these 2D are defined by the sieve positions from
the transport functions.
- Use transport function: x, y, theta, phi (at focal plane)
= function( y, dp, theta,phi --- at target). By fix 3 variables, we can
get, i.e. xfoc = f(phi_target) with phi_target run from phi_min to
- For a fix ytarget, dp, we can know limits of theta_target
and phi_target. Keep one of the angle (either phi_target or
theta_target) constant and make a "continous" point on the other
variables, i.e. phi(i) = phi_min + i*delta_phi, phi run from phi_min to
- Do the same, then we can get the boundary of 4 lines.
- There are 2 ways to make this cut:
- From phi_min to phi_max, there are npoints, we can do
fitting in this range and then just use a linear line ( y = a*x+b) to
cut. Combine all 4 lines together to define 4D cut at focal plane.
- Or we can use TCutG from ROOT to apply a polygon cut (which is a closed area defined by the points).
- Detail how to get cross section:
- Get solid angle by: run phase space + no radiation
effect, apply cut at focal plane, look at target angle and get solid
angle. In addition, this also give the boundary at target.
- Run elastic carbon, count how many events inside the boundary at target (which is mentioned above) called "tacc".
- Count how many events survived after focal plane cut, called "cacc". Sum cross section inside this cut called xsc.
- Cross section = xsc/tacc.
- Apply PID + dp cut, and 4D cut.
- Subtract background. Result between simulation and data can be found here.
- To do:
- Why 25%, 32% different between data and simulation?
- Check dp plot for simulation and data.
- Why 4D cut at focal plane with the right boundary still can not reproduce an exact boundary at target?