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1) Jeff’s cuts. 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 > 0 2) Fit.pass + chi2<ndf <10 + UVasym < 6 3)|(q/p)/( σ q/p )|<0.3 4) Prob(chi2,ndf)>0.1

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slide1

1) Jeff’s cuts

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 > 0

2) Fit.pass + chi2<ndf <10 + UVasym < 6

3)|(q/p)/(σ q/p)|<0.3

4) Prob(chi2,ndf)>0.1

5) Dave’s PID > 0.4

Jeff’s cuts of Oxford

Results in next slide…

slide2

All neutrinos

Selected as antineutrinos

Background

Overall efficiency: 52.486%

Overall purity: 98.21%

Background composition

slide3

2) Our selection

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:

(q/p) / (σ q/p)

0 < Planes < 30

30 <= Planes < 60

60 <= Planes < 90

90 <= Planes < 120

120 <= Planes < 153

slide4

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)

slide5

nu

nubar

  • An improvement is observed !

After

Some events are really well separated !

Purity

Here the efficiency does not include the basic cuts.

Before

After

Efficiency

slide6

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 histogram

2) planes

3) y

4) cosz

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

At least 1 track

Trk.fit.pass==1

U-Vasym < 6

/ndf < 20

• 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.

slide7

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 !

slide8

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

NuBarPID and:

- No extra cut

- x=0.15 cut

- Prob(chi2,ndf)>0.1 cut

 BINGO !

slide9

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

PDFs done without fit sig. cut

PDFs done with fit sig. cut

nu

nubar

nu

nubar

NuBarPID

NuBarPID

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

Purity

PDFs done with fit sig. cut

PDFs done without fit sig. cut

Efficiency

slide10

Tried combining NuBarPID + fit significance cut + cut:

Purity

nu

nubar

NuBarPID + fit sig. + prange cut

NuBarPID + fit sig.

NuBarPID

Efficiency

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

Note: PDFs were calculated with all corresponding cuts included.

slide11

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

Purity

Efficiency

slide12

All neutrinos

Selected as antineutrinos

Background

If make cut at NuBarPID>0.7 find:

Overall efficiency: 50.21%

Overall purity: 99.48%

slide13

Jeff’s cuts

NuBarPID + fit sig. cut at 0.7

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

Purity

Efficiency

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

slide14

All neutrinos

Selected as antineutrinos

Background

If make cut at NuBarPID=0.75 find:

Overall efficiency: 48.52%

Overall purity: 99.63%

slide15

All neutrinos

Selected as antineutrinos

Background

If make cut at NuBarPID=0.80 find:

Overall efficiency: 46.67%

Overall purity: 99.73%

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