Fitter Window

The Fitter window gives information about the currently selected fit, and allows some fit parameters to be set manually. At the bottom of the window are three buttons:

The Do Fit button runs the Online fitter on the current event. If the current event already has an Online fit, the new fit will overwrite the existing Online fit.

The Next Fit button cycles through the available fits if the event has more than one fit. Note that the water levels are displayed as special types of fits, so displaying a 'Water' or 'D2O' fit will give information about the corresponding water level.

The Manual Fit button adds a new fit at position (0,0,0) with direction (0,0,1) and time 0 to the event. This gives you a starting point for performing a Manual fit.

The fit parameters can be then changed by either typing them into the Fitter window, or by dragging/rotating the fit in the main image window. After changing a fit, the fit name is changed to Manual (if not already a Manual fit), and the Radius and Sigma (the mean time difference) for the new fit are calculated and displayed.

The quantities displayed in the fit window are explained in the following table:

Fitter Name identifying the fitter that was run. XSnoed generates three special fitter names: Manual, Online, Water, and D2O. The number in brackets after the fitter name is the index of the fit for the event (starting at zero for the first fit).

Position The x,y,z position of the fit vertex in detector coordinates, expressed in centimeters.

Radius The distance from the center of the detector to the fit vertex in centimeters.

Time The fitted event time in nanoseconds.

Direction The x,y,z cosines of the fitted event direction.

Cone Angle The half angle of the Cherenkov cone displayed for this fit, displayed in degrees. The default cone angle is 41.40 degrees. The intersection of the Cherenkov cone with the PSUP is shown in the image windows.

Chisq The chi-squared of the fit for the Online fitter. For a Manual fit, this displays the Sigma of the hits from the fit time. For other fit types, this displays the Quality of the fit. The meaning of this value is specific to the fitter type.

Fit Hits The number of hits that participated in the fit. This will be the number of hits in the event minus the discarded hits and the hits that were thrown out by the fitter. To avoid long calculation delays, XSNOED will only pass a maximum of 400 hits to the fitter for any given event. It does this by sending every Nth hit to the fitter, where NHIT/N <= 400.

NHITW The number of hits within a fixed-width window relative to the fitted event times. Only valid for the Online fitter. This window width is usually +-10 nanoseconds, and is specified in the fitter configuration file, fitter.dat.

Fitter	Name identifying the fitter that was run. XSnoed generates three special fitter names: Manual, Online, Water, and D2O. The number in brackets after the fitter name is the index of the fit for the event (starting at zero for the first fit).
Position	The x,y,z position of the fit vertex in detector coordinates, expressed in centimeters.
Radius	The distance from the center of the detector to the fit vertex in centimeters.
Time	The fitted event time in nanoseconds.
Direction	The x,y,z cosines of the fitted event direction.
Cone Angle	The half angle of the Cherenkov cone displayed for this fit, displayed in degrees. The default cone angle is 41.40 degrees. The intersection of the Cherenkov cone with the PSUP is shown in the image windows.
Chisq	The chi-squared of the fit for the Online fitter. For a Manual fit, this displays the Sigma of the hits from the fit time. For other fit types, this displays the Quality of the fit. The meaning of this value is specific to the fitter type.
Fit Hits	The number of hits that participated in the fit. This will be the number of hits in the event minus the discarded hits and the hits that were thrown out by the fitter. To avoid long calculation delays, XSNOED will only pass a maximum of 400 hits to the fitter for any given event. It does this by sending every Nth hit to the fitter, where NHIT/N <= 400.
NHITW	The number of hits within a fixed-width window relative to the fitted event times. Only valid for the Online fitter. This window width is usually +-10 nanoseconds, and is specified in the fitter configuration file, fitter.dat.