1. 25 April 20061 Antineutrino selection for constraining the e beam Goal: extract component of  rate from  + decays Requirement: High purity at low neutrino energy Pedro Ochoa(CalTech) & David Jaffe(BNL) This is what we are trying to measure Result: Development of preliminary ‘standard’ cuts

2. 25 April 20062 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) Petyt PID > 0.4 Starting point: Jeff Hartnell’s cuts Jeff’s cuts of Oxford Using powerpoint, a miracle of modern technology, the current results are compared to Jeff’s Oxford results on next slide…

3. 25 April 20063 Jeff Background Comparable results achieved All neutrinos Selected as antineutrinos Background Pedro Overall efficiency: 52.5% Overall purity: 98.2% Pedro Background composition

4. 25 April 20064 Overall efficiency: 52.5% Overall purity: 98.2% Reconstructed neutrino energy (GeV) This is what we are trying to measure All antineutrinos Selected as antineutrinos Background

5. 25 April 20065 Jeff’s cuts work well but for our analysis we want lower background at low energy.  Worked on improving the NuBarPID ! The first improvement came out by noticing that separation is better for longer events (all distributions normalized to unit area) : Our selection (q/p) / (σ q/p) 0 < Planes < 3030 <= Planes < 6060 <= Planes < 90 90 <= Planes < 120120 <= Planes < 153  

6. 25 April 20066  So tried the following 2D PDFs for the NuBarPID (in addition to number of planes, y, and dcosz) neutrinosantineutrinos Note: Every “row”, or slice of planes (for instance from 0 to 30) is normalized to unity, as seen in previous slide. This reduces the energy dependence of these 2D PDFs and keeps them independent of the PDF of the number of planes. (q/p) / (σ q/p) Event length (planes)

7. 25 April 20067  An improvement is observed ! After Before After Purity Efficiency Some (probably very long) events are really well separated ! Here the efficiency does not include the basic cuts.   Before

8. 25 April 20068 Now for something slightly different: Scan 30 events with looser Petyt PID cut to try to increase low E acceptance Cuts: 1m<vtxz<5m vtxr<1.0m q/p > 0 UVasym < 6 Prob(chi2,ndf)>0.1 Petyt PID > 0.0 0.5<Rnear<2m Rnear (m) Rnear = smallest radius on track. Small radius: near coil hole, higher Bfield. Large radius: lower Bfield Accept

9. 25 April 20069 Scan results for non-CC    that passed cuts on previous page identity

10. 25 April 200610 Conclusion from scan: Comparison of momentum from range and curvature can reject some 1)protons because conversion of range to momentum assumes muon mass and 2)  - because range of kinked tracks is unchanged. Effect of cut on (p(curve)-p(range))/p(range) for   investigated on following pages. Would it be useful for CC  analysis? Alternative might be to compare expected and measured dE/dx for strips on track.

11. 25 April 200611 Based on scan result, Pedro tried adding an extra cut on (p(curvature)-p(range))/p(range), only for tracks that stopped in the detector, to the NuBarPID: Used NuBarPID with 4PDFs: 1) 2D q/p/(σ q/p) vs. planes 2) planes 3) y 4) cosz The pdfs were made with with following basic cuts applied: 1 < Zvtx < 5m Rvtx < 1m At least 1 track Trk.fit.pass==1 U-V asym < 6 /ndf < 20 Plots of Purity vs. Efficiency were made. The efficiency now includes all cuts (including a cut on ). In other words, efficiency is measured with respect to all CC nubar events.

12. 25 April 200612 NuBarPID and - No extra cut - x=1.0 - x=0.5 - x=0.3 - x=0.15 A small improvement, but it’s not enough !

13. 25 April 200613 NuBarPID and: - No extra cut - x=0.15 cut - Prob(chi2,ndf)>0.1 cut Combination of NuBarPID with one of Jeff’s cuts, Prob(,ndf) > 0.1 = “fit significance cut” gave the best performance :  BINGO !

14. 25 April 200614 Interesting ! Separation looks different when calculating doing the PDFs with and without the fit significance cut: 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. cut PDFs done without fit sig. cut NuBarPID PDFs done without fit sig. cutPDFs done with fit sig. cut Purity Efficiency  

15. 25 April 200615 Tried combining NuBarPID + fit significance cut + cut: Purity Efficiency NuBarPID NuBarPID + fit sig. + prange cut NuBarPID + fit sig. No improvement. Will stick to NuBarPID + fit significance. Note: PDFs were calculated with all corresponding cuts included.  

16. 25 April 200616 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  

17. 25 April 200617 Compare NuBarPID> 0.7 to purity & eff’y with Jeff’s cuts: PurityEfficiency Jeff’s cuts NuBarPID>0.7 and Prob(chi2,ndf)> NuBarPID>0.7 and Prob(chi2,ndf)>0.1 This is what we trying to measure Overall efficiency: 50.2% Overall purity: 99.5% Low energy purity improved but with some loss of efficiency Some increase in higher energy efficiency

18. 25 April 200618 NuBarPID>0.7 Eff’y 50.2% Purity 99.5% NuBarPID>0.75 Eff’y 48.5% Purity 99.6% NuBarPID>0.80 Eff’y 46.7% Purity 99.7% Further tightening of NuBarPID cut Characteristics of remaining events? Current study probably suffers from lack of stats

19. 25 April 200619 Conclusions Jeff Hartnell did a good job. NuBarPID >0.7 improves purity at low energy with some loss of efficiency. We now have preliminary selection criteria for a  sample to constrain the e flux. May still investigate possible further improvements in low energy  selection Any of this applicable to other analyses?

20. 25 April 200620

21. 25 April 200621 If make cut at NuBarPID>0.7 find: Overall efficiency: 50.21% Overall purity: 99.48% All neutrinos Selected as antineutrinos Background

22. 25 April 200622 If make cut at NuBarPID=0.75 find: Overall efficiency: 48.52% Overall purity: 99.63% All neutrinos Selected as antineutrinos Background

23. 25 April 200623 If make cut at NuBarPID=0.80 find: Overall efficiency: 46.67% Overall purity: 99.73% All neutrinos Selected as antineutrinos Background