The D0 Interacting Propagator (draft).
The material model used by D0Propagator takes into account the SMT
silicon wafers (ladders and wedges), the SMT trough and the beampipe.
Other material, including bulkheads and cables is not included. To
account for missing material, the model includes a "fudge factor," which
is currently set to 2.5 (which is too low). SMT material parameters,
including fudge factors are stored in the SMT material geometry, the
parameters for which can be found in rcp file
According to the D0Propagator model, the total mass of the SMT ladders and F-disks (that is, everything inside the SMT trough except the beampipe), including fudge factors, is 3.1 kg. I talked to Ron Lipton, who gave me a 9 year old incomplete spreadsheet, where the mass of the equivalent components was given as 14 kg.
Besides having too low SMT mass, the implementation of D0Propagator did not include energy loss in the SMT, but only multiple scattering. I have modified the D0Propagator code to include energy loss in the SMT. This involves changes to packages trfzp, trfxyp, and gtrprop, which changes I intend to test-release next week in t03.45.00.
As a test, I reconstructed some b-physics J/psi's with a version of d0reco made with the updated D0Propagator, and I also increased the mass of the SMT by a factor of 5. I call this version is called p14.05.01b. Plots are shown below. Results with other more standard versions of d0reco are similar to what I showed two weeks ago, but have been updated with more statistics.