First tried to reproduce Jeff’s cuts described in his talk at Oxford (minos-doc 1409):

For this, used tracks in fiducial volume (1m<vtxz<5m & vtxr < 1.0m), and:

1) q/p > 02) Fit.pass + chi2<ndf <10 + UVasym < 63)|(q/p)/(σ q/p)|<0.34) Prob(chi2,ndf)>0.15) Dave’s PID > 0.4

1) Jeff’s cuts

Jeff’s cuts of Oxford

Results in next slide…

All neutrinosSelected as antineutrinosBackground

Background composition

Overall efficiency: 52.486%Overall purity: 98.21%

Jeff’s cuts work very good but for our analysis we cannot tolerate the background. Worked on improving the NuBarPID !The first improvement came out by noticing that separation is better for longer events:

2) Our selection

(q/p) / (σ q/p)0 < Planes < 30 30 <= Planes < 60 60 <= Planes < 90

90 <= Planes < 120 120 <= Planes < 153

So tried the following 2D PDFs for the NuBarPID (in addition to #planes, y, and dcosz)

neutrinos antineutrinos

Note: Every “row”, or slice of planes (for instance from 0 to 30) is normalized to unity, as seen in previous slide. This is to keep the effect of the #planes PDF separate (and not be E dependent)

An improvement is observed !

After

BeforeAfter

Pu

rity

Efficiency

nunubar

Some events are really well separated !

Here the efficiency does not include the basic cuts.

In addition, David J. found out that cutting on the difference between the momentum from curvature and the momentum from range can help us reduce the background. Tried this as an extra cut in the NuBarPID:

• Used NuBarPID with 4PDFs: 1) the 2D q/p/(σ q/p) vs. planes histogram2) planes 3) y4) cosz

• The pdfs were made with no cuts required, except the basic ones:

At least 1 trackTrk.fit.pass==1U-Vasym < 6 /ndf < 20

2

• Plots of Purity vs. Efficiency were made. The efficiency now includes all cuts (including the basic track quality ones, and the one).

In other words, efficiency is measured with respect to all CC nubar events.

xP

pp

range

rangecurvature

NuBarPID and

- No extra cut- x=1.0- x=0.5- x=0.3- x=0.15

An improvement is seen, but it’s not enough !

NuBarPID and:

- No extra cut- x=0.15 cut- Prob(chi2,ndf)>0.1 cut

Among other attempts, tried combining the NuBarPID with one of Jeff’s cuts, the Prob( ,ndf) > 0.1 one:

2

BINGO !

Interesting ! Separation looks different when calculating doing the PDFs with and without the fit significance cut:

nunubar

In both cases the fit significance cut is applied. The difference is whether or not the PDFs were calculated with it or not.

At the end, not much difference in separation even if shape above is so different

PDFs done with fit sig. cutPDFs done without fit sig. cut

NuBarPIDNuBarPID

PDFs done without fit sig. cut PDFs done with fit sig. cut

nunubar

Pu

rity

Efficiency

Tried combining NuBarPID + fit significance cut + cut: 4.0

range

rangecurvature

P

pp

Pu

rity

EfficiencyNuBarPID

nunubar

NuBarPID + fit sig. + prange cutNuBarPID + fit sig.

It actually works slightly worse ! Will stick to NuBarPID + fit significance.

Note: PDFs were calculated with all corresponding cuts included.

From now on always included fit significance cut (among all others) when calculating the PDFs.

Now, need to see what happens as a function of energy.

Make a NuBarPID cut at 0.7 and see what happens:

NuBarPID > 0.7 puts you here

Pu

rity

Efficiency

If make cut at NuBarPID>0.7 find:

Overall efficiency: 50.21%Overall purity: 99.48%

All neutrinosSelected as antineutrinosBackground

How does this cut at 0.7 compare to Jeff’s cuts?

Jeff’s cutsNuBarPID + fit sig. cut at 0.7

Purity Efficiency

What if we crank it up a little more? See next slides…

If make cut at NuBarPID=0.75 find:

Overall efficiency: 48.52%Overall purity: 99.63%

All neutrinosSelected as antineutrinosBackground

If make cut at NuBarPID=0.80 find:

Overall efficiency: 46.67%Overall purity: 99.73%

All neutrinosSelected as antineutrinosBackground