1. P. Ochoa, September 20061 Using Muon Removed files to assess the purity of the nubar-PID selection Pedro Ochoa MINOS Collaboration Meeting September 2006

2. P. Ochoa, September 20062 all NC L010185 MC For a cut at nubar-PID=1.0, MC shows: Overall purity: 99.75% Overall efficiency: 45.98% Do we believe this high purity? Introduction Nubar-PID selection allows to separate antineutrinos with very high purity and reasonable efficiency: fiducial volumetrack qualityfit probability 1m < Z vtx < 5m r vtx < 1m track fit pass / ndf < 20 UV asym < 6 ++ Prob(, ndf) > 0.1 Basic cuts: then apply nubar-PID:

3. P. Ochoa, September 20063 Background (124 events total) Can separate the background into two categories:  Category 1:  - is reconstructed as  + due to hard scattering and/or pattern recognition problems = misidentified  Category 2: tracker fooled by positive particle (decay in flight, proton, pion, kaon… ) = fake Use IdHEP of tracked particle: trkIdHEP=13  Category 1 trkIdHEP!=13  Category 2 ++ -- ++ ++ p About ~1/3 of the background pertains to category 2: 124 background events of nubarPID > 1.0 selection SelectionCategory 2 % nubarPID > 1.032.3 ± 4.2 nubarPID > 0.931.8 ± 3.3 nubarPID > 0.525.2 ± 1.4 *Note: Category 1 contains a small component of misidentified negative stuff from hadronic shower.

4. P. Ochoa, September 20064 Category 2 example – NC (  decay in flight) tracked particle

5. P. Ochoa, September 20065 Category 2 example – NC (proton)

6. P. Ochoa, September 20066 Category 2 example – CC (Λ c + )

7. P. Ochoa, September 20067 Category 2 example – CC (K+)

8. P. Ochoa, September 20068 True_y of CC, category 2 CC subcategory of Category 2 events seem to be high y “Good” MRCC selection: Means: Data: 0.952 MC: 0.958 data MC scaled to POT data MC scaled to POT Means: Data: 0.975 MC: 0.973 best_purity > 0.8 best_complete > 0.8 best_purity_phw > 0.8 best_complete_phw > 0.8  Can use MRCC files to answer whether category 2 events are reasonably well modeled. Event has to be best match to original Purity= Completeness= (see Anna H. talk, minos- doc 2164)

9. P. Ochoa, September 20069 data MC scaled to # events data MC scaled to POT Run MRCC Data and MC though selection data/MC

10. P. Ochoa, September 200610 data MC scaled to # events data MC scaled to POT MC: 38.8 ± 10.4 nubar-PID > 1.0 region: Data: 30 ± 5.5 MC: 34.2 ± 9.1 nubar-PID > 1.0 region: Data: 30 ± 5.5 nubar-PID > 0.5 region: MC: 88.8 ± 9.4 Data: 96 ± 9.8 nubar-PID > 0.5 region: MC: 78.1 ± 8.8 Data: 96 ± 9.8  Scaled to # events:  Scaled to POT: Looking at the signal region:

11. P. Ochoa, September 200611 data MC scaled to # events data MC scaled to # events data/MC nubar-PID > 1.0 selection nubar-PID > 0.5 selection What about energy dependence?

12. P. Ochoa, September 200612 Summary  Nothing crazy. Lack statistics…  Analysis shows so far that “category 2” background in our nubar-PID > 1.0 selection can be scaled overall by a factor of 0.77 ± 0.25  Ultimately also need to:  Account for MRCC efficiency and purity  Compare subcategories in MRCC and in MC  What to do if more statistics reveal a considerable energy dependence? One possibility: use ratios in previous slides to scale background binned in reco energy (removing primary CC  energy if applicable).

13. P. Ochoa, September 200613 BACKUP

14. P. Ochoa, September 200614 NC - Pion decay in flight

15. P. Ochoa, September 200615 CC - Pion

16. P. Ochoa, September 200616 nubar-PID > 0.0 signal: MC: 1895 ± 72 Data: 2123 ± 46 nubar-PID > 0.0 signal: MC: 1666 ± 64 Data: 2123 ± 46 data MC scaled to # events data MC scaled to POT

17. P. Ochoa, September 200617 nubarPID>1.0 nubarPID>0.5nubarPID>0.0