Tagmon
Pass0 Analysis for G2a
A pass0 analysis of the tagmon is described below. We analised the charged particle masses from ToF for the runs 20020-20056.
In figure 1 the masses of protons (black), positive (red) and negative (blue) pions are plotted as a function of the run number. It shows that there is one or more parameters varying in the mass reconstruction in the runs 045, 054 and 056. There is a shift toward higher masses for all three particles and an increase in the uncertainties for the runs 20045, 20054 and 20056. These values were obtained by a gaussian fit to the mass spectra, and the uncertainty is the gaussian width.
Fig. 1 Charged particles mass vs. run number.
Some differences are also evident from the comparison of the plots in figure 2 for the runs 020 and 056 that show the mass versus momentum spectra. For the run 020 the masses are independent of the momentum, while for the run 056 it is varying significantly with the momentum, the worst valves being at high moments.
Fig.2 Masses vs. momentum for proton and pion+
In figure 3 we show the
b versus momentum plots for runs 020 and 056. The also show differences in the spectra for those two runs. While the pions b are around 1 for high moment in run 020, it is around 0,9 in run 056.
Fig.3 Beta vs. momentum for proton and pion+
One could think that it would be due to a shift in the ToF time in run 056, but the figure 4 shows the spectra of st timex versus ToF time for those runs. They appear to be quite similar, so we may conclude that the time from ToF is correct.
Fig. 4 ST-time vs. ToF-time for runs 020 and 056
The results for runs 045 and 054 are similar to those for run 056.
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