Core (or COG) Fit

I3TopRecoCore calculates a Shower core, using the sqrts of the pulse amplitude as weights and calculating the COG of these. If no Pulses are available, it can also be run with Hits, but then no sqrt is used and the result is worse (no equal distribution between the tanks).

  • datareadout [string, DEFAULT=”ITSimData”] Name of the input Pulses from the data to be used

  • showercore [string, DEFAULT=”ShowerCOG”] Name of the output I3Particle

  • ntanks [DEFAULT=all of them] Number of highest-charge tanks to use

  • weighting_power [DEFAULT=0.5] power for the weighting - the weight will be PE^power

  • verbose [bool, DEFAULT=false]

Plane Wave Fit

I3TopRecoPlane calculates what plane wave fits the shower front best. Therefore it calculates the minimum of this:

\[\chi^2 = \sum_i w_i (t_i^{measured} - t_i^{fit})^2 = \sum_i \frac{(t_i - T_0 + \frac {u\,x_i + v\,y_i}{c})^2}{\sigma^2}\]

The fit parameters are the average time \(T_0\) and the shower direction, represented by u and v. Using the COG of the x and y in that weights (\(w_i=1/\sigma^2\)), \(T_0\) decouples from the other parameters and they all can be calculated easily from the matrix of their linear system. The \(\sigma\) is set to 5 ns for all pulses equally as a rough approximation.

The calculation goes through 2 iterations. In between, a correction for the different tank heights is applied.

  • datareadout [string, DEFAULT=”ITSimData”] Name of the input Pulses from the data to be used

  • showerplane [string, DEFAULT=”ShowerPlane”] Name of the output I3Particle

  • trigger [int, DEFAULT=3] Set a software trigger on how many stations required in the input Pulses.

  • EventHeaderName [DEFAULT=”IceTopEventHeader”] Event header name

  • verbose [bool, DEFAULT=false]