e+e- -> Z Higgs Large (L2) detector
Run 1, Evt 1: MCP #20 - 885 MeV electron with large impact parameter.
Track parameters: d0 = -11.2 cm, curvature (k) = -0.010/cm, z0 = -1.6 cm, phi0 = -0.677, tan(lambda) = -0.45;
also, pt = 885 MeV, radius of curvature is 98.3 cm
Found problem in HelicalSwimmer in which the track parameters were not being interpreted correctly. Both the curvature and xy distance of closest approach are signed quantities. Tracker versions 1.1.9 and higher have the problem fixed as shown above.
Track parameters: d0 = 48.2 cm, curvature (k) = 0.052/cm, z0 = -91.4 cm, phi0 = -0.329, tan(lambda) = -3.72;
also, pt = 175 MeV, radius of curvature is 19.4 cm
The xy distance of closest approach, d0, is calculated to be less than 30 cm, but it appears that the closest approach is nearly 50 cm. A calculation of the center of the circle (C) and the radius of curvature (19.4 cm) gives the xy distance of closest approach to be 48 cm. Will use the difference in radii (dR) and the sign from the deviation from orbit (d0) for now as shown above.
...
Check tracking finding and fitting for low energy spiral tracks.XY view
Missed spirals at 90, 80 and 45 deg.
YZ view - Displayed in Z along direction of energy flow from 2 jets.
One lower energy track moving to +Z is found on second spiral. A converted photon gives rise to an e+e- pair at TPC inner field cage (at y = +50 cm).