It has been shown that a QE-like sample can be selected with a flat efficiency (as a function of reconstructed neutrino energy) from a MC sample with INTRANUKE turned off and with the old version of Neugen. The question is can this flat efficiency be retained using the same selection criteria but with a MC sample that has INTRANUKE turned on (in the old Neugen) and what effects does the new version of Neugen have on the QE-like sample selection?
For this study I have generated my PDFs with an old Neugen INUKE off MC sample and applied the same QE PID parameter value cuts to separate samples of old and new Neugen with INUKE turned on and off. All these MC samples correspond to the flat energy spectrum MC sets that Mike talked about last week.
The following plot shows the QE selection efficiency as a function of reconstructed neutrino energy for the old Neugen INUKE off (black) and INUKE on (red) samples and the new Neugen INUKE off (blue) and INUKE on (pink) samples (the same colour scheme as used my Mike last week):
It is hard to draw any conclusions from this mess of points. One slight problem is that the error bars for some of the samples look smaller than the scatter in the points - I have tried several methods to calculate the errors but their size is equivalent with all methods. (I believe that the scatter is due to the fact that I have fixed the ID parameter cut value in each bin to get a similar efficiency but this process was not too rigorous - the cuts were trained with the old Neugen INUKE off sample (black).)
The next plots break down the above one. Firstly I have looked at just old Neugen for the INUKE on/off samples:
INUKE does seem to affect the flatness in QE efficiency of the sample selection but only by a samll amount - the gradients of the 2 fitted lines fall within each others errors (and neither si a good fit anyway). INUKE on does lead to a reduced purity. The following plots show the QE efficiencies (black) and purities (red) for the INUKE off (left hand plot) and on (right hand plot) samples:
The purity plots have a similar structure but for the INUKE on sample there are many more RES and DIS events selected where pions have been re-absorbed by the nucleus. This is shown in the following plots for the old Neugen INUKE off (left hand plots) and old Neugen INUKE on (right hand plots) samples where the 4 plots correspond to the true QE, RES, DIS and NC events before (black) and after (red) the sample selection:
It can be seen that the INUKE on QE-like sample has about twice as many resonance events and three times as many DIS events selected as the INUKE off sample. Now, the efficiency and purity are correlated so in order to demonstrate the robustness of the QE-like sample selection to INUKE on or off I have tried fitting some functions to (efficiency*purity):
These plots show that the INUKE on sample has a lessened (efficiency*purity) for the reasons described above (more background selected) but that the shape of this quantity is changed only very slightly.
So how does the old Neugen INUKE off sample compare to a new Neugen INUKE off sample?
There seems to be some effect on the QE efficiency particularly at lower energies. In terms of sample composition the 2 samples have fairly equivalent fractions of events of any given type selected as QE-like (left hand 4 plots are old Neugen INUKE off, right hand 4 plots are new Neugen INUKE off):
Another question is how do the new Neugen INUKE on and off samples compare? The following plot shows the straight line fitted efficiences for these 2 samples:
The fitted lines lie on top of each other but the points are not so well matched (although still pretty simliar). As before I wanted to use the (efficiency*purity) plots as a measure of the robustness of the sample selection to the effects of INUKE:
All the fits show that there is a reduction in purity of the sample as expected from the increased background (see next plot - sorry about the colours being black and red again) but that the (efficiency*purity) has exactly the same shape between the 2 samples (left hand plots are new Neugen INUKE off and right hand 4 plots are new Neugen INUKE on).
As expected there is now a lesser additional background than with the old INUKE on/off comparison with about 1.5 times as many RES events selected as QE-like and about twice as many DIS events.
Finally I shall show the effect on the selected reconstructed energy spectrum for the 4 samples and also reweight these spectra for the standard beams (all distributions have been normalised to the number of events in the black sample (old Neugen INUKE off)). The left 4 plots is for old Neugen INUKE off (black) and on (red) and the right 4 plots for new Neugen with INUKE off (blue) and on (pink):
In all cases there is little effect on the position of the peak between INUKE on/off samples in the 2 versions of Neugen. As for the differences between the mean between the 2 versions of Neugen the new Neugen seems to have systematically lower energies than the old version but these differences are small and within the errors on the means. However, I would expect that the new version would lead to a systematic increase in energies as the energy from reabsorbed pions does not now disappear.