Using the pHE data to measure the beam n e ’s from m + decay

1. Using the pHE data to measure the beam ne’s from m+ decay David Jaffe and Pedro Ochoa • Reminder • Updated Statistical error • Horn 1 systematics • Summary June 14th 2007

2. - Fit using MC shapes. Scale n(m+)LE and n(m+)pHE by parameters parLE and parHE. n(p,K)pHE-n(p,K)LE Reminder • Procedure: - Take pHE-LE difference. Correct for n(m+)pHE n(m+)LE x parHE x parLE • Main systematics associated with this measurement: • C=n(p,K)pHE-n(p,K)LE correction. • Background in nubar selection. • Previous study (doc-2909) showed that pHE background is not big concern. • But the previous assessment of C was too pessimistic and done with too few statistics, so it is redone here.

3. Update on statistical error • Previous study (doc-2783) assumed 2.0x1019 POT of pHE data and a statistical error of ~13% in the measurement was quoted. • But more precisely, the pHE data taken after the 2006 shutdown corresponds to 1.6x1020 POT. So repeated the fit with this number: 90% C.L. 68.3% C.L. • New statistical error in n(m+)LE is 15%.

4. Horn 1 systematics • How well can we determine C = n(p,K)pHE- n(p,K)LE? • Work by David suggests C mostly affected by horn1 & target geometry, as one would expect (minos-doc-2841) Ex: horn1 current increase by 2% in pHE neutrino beam • So obtained ratios of spectra with systematics over nominal spectra using gnumi: Good agreement with pbeam • Systematics considered are: • Obtained gnumi ratios are shown in the next 5 slides.

5. n(m+) n(m+) n(p-,K-) n(p-,K-) nominal with systematic Horn current -1% le010z185i le250z200i

6. n(m+) n(m+) n(p-,K-) n(p-,K-) nominal with systematic Horn current +1% le010z185i le250z200i

7. n(m+) n(m+) n(p-,K-) n(p-,K-) nominal with systematic Horn offset by 1mm le010z185i le250z200i

8. n(m+) n(p-,K-) nominal with systematic Target in LE position -1cm le010z185i

9. n(m+) n(p-,K-) nominal with systematic Target in LE position +1cm le010z185i

10. Converted these ratios to reconstructed energy using the ntuples: Ex: target position increased by 1cm in LE (no events in first bin) Convert to Ereco • Used these ratios(Ereco) to scale the spectra in our feasibility study and obtain systematic shifts. • Nominal spectra are used to do the fit which contains spectra including these systematics. • Infinite MC and LE data statistics are assumed.

11. Example: Horn offset by 1mm n(m+) pHE with systematics nominal n(m+) LE with systematics result of fit Systematics: Results of fit: pHE-LE corrected for background and nominal C fit  Bias of 3%  Bias of 3%

12. Summary of biases in measurement: • This assumed same horn conditions for pHE and LE running (except for target displacement). If that is not the case need to work with other combinations: • Also need to add the error associated with hadron production.

13. Measurement of n(m+)pHE is more affected by horn1 & target systematics than n(m+)LE. Fortunately we don’t care. Summary & Ongoing work • The statistical error of the measurement with 1.6x1019 POT of pHE data is ~15%. • Main sources of systematic errors seem to be under control. Next step: carry out the measurement

14. Backup

15. Horn current -1% n(m+) pHE with systematics nominal n(m+) LE with systematics result of fit Systematics: Results of fit: pHE-LE corrected for background and nominal C fit  Bias of -14%  Bias of -15%

16. Horn current +1% n(m+) pHE with systematics nominal n(m+) LE with systematics result of fit Systematics: Results of fit: pHE-LE corrected for background and nominal C fit  Bias of -9%  Bias of -14%

17. Target -1cm n(m+) pHE with systematics nominal n(m+) LE with systematics result of fit Systematics: Results of fit: pHE-LE corrected for background and nominal C fit  Bias of 1%  Bias of -6%

18. Target +1cm n(m+) pHE with systematics nominal n(m+) LE with systematics result of fit Systematics: Results of fit: pHE-LE corrected for background and nominal C fit  Bias of 7%  Bias of -6%