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 • Introduction • Antineutrino selection • Feasibility study • Systematics March 13th 2007

2. Introduction • David and Pedro proposed making this measurement with pME data (minos-doc-2706). Getting that data seems complicated. • 2 main reasons: • Fear of moving target after previous experience. • Some people feel physics case not strong enough. • Could we use the already existing pHE data taken after the shutdown? • With pHE data expect: • Improvement since antineutrinos from m+ decay in pHE (n(m+)pHE) peak at higher energies (i.e. better separation with n(m+)LE). • Degradation since less POT (~2.0x1019) and higher systematics. • Beginning of talk considers only statistics of available pHE data. Without sufficient statistical precision would not proceed further.

3. nm CC nm CC NC Selection • Used daikon-cedar MC: 4.11x1018 POT of pHE and 1.07x1020 POT of LE. • Use (at least for now) nubar-PID selection (minos-doc-2377): LE-10 pHE • Use cut at nubar-PID > 0.9: • Some features of PID in cedar not completely understood. For now treat as black box.

4. Background • Selection in LE configuration: Selection vs. Ereco Selection vs. Etrue Parent: p K m+ Background composition Efficiency and Purity

5. Background • Selection in pHE configuration: Selection vs. Ereco Selection vs. Etrue Parent: p K m+ Efficiency and Purity Background composition

6. n(m+) LE n(m+) pHE n(p-,K-) pHE n(p-,K-) LE Feasibility study • Background is problem in pHE. For now ignore. • Make feasibility study with fitted spectra: very distinct Scaled to 1x1020 POT

7. Procedure: - fit pHE-LE with spectral shapes from MC. - scale n(m+)LE and n(m+)pHE by parameters parLE and parHE. n(p,K)pHE-n(p,K)LE Note: Assume infinite MC and LE statistics one fit n(m+)pHE n(m+)LE x parLE x parHE Fake experiment at 2e19 POT • Good agreement for n(p,K)pHE-n(p,K)LEin MC and in feasibility study: in feasibility study in MC Scaled to 2e19 POT Scaled to 2e19 POT

8. Assume we getn(p,K)pHE-n(p,K)LEexactly. • Fit done manually (described in minos-doc-2504) • Results of 5,000 fits at 2.0x1020 POT of pHE data: 13% stat. uncertainty ! • n(m+)pHE peaking at higher energy really helps us. • Less correlation between parameters than in pME case (c.f. minos-doc-2504) 90% C.L. 68.3% C.L. • However… (see next slide)

9. Systematics • Systematics are the key to this measurement. Mainly: • n(p,K)pHE-n(p,K)LE correction. • Background in pHE. • From experience with pME cross-section shape uncertainties should not be big problem. • Preliminary look at C = n(p,K)pHE-n(p,K)LE: Note: As pointed out by Stan, best way to look at C is not in percentage form. This is just to get an idea. • If want to know beam ne’s to ~30%, need to know C to ~20% or better if it is the dominant systematic uncertainty. • Maybe can absorb some of this uncertainty by adding another parameter that scales C. Will look into it.

10. Summary & Ongoing work • Measurement is possible to 13% from statistics point of view, using already existing pHE data. • Work in progress to understand the 2 main systematics: • n(p,K)pHE-n(p,K)LE correction • Background in pHE selection. • Goal is to incorporate this into ne analysis with MCNN selection.

11. Backup

12. n(m+) LE n(m+) pHE n(p-,K-) pHE n(p-,K-) LE • Smooth spectra scaled to 1e18 POT

13. If get wrong n(p,K)pHE – n(p,K)LE by -50%:

14. If get wrong n(p,K)pHE – n(p,K)LE by +50%:

15. If get wrong n(p,K)pHE – n(p,K)LE by -30%: • If get wrong n(p,K)pHE – n(p,K)LE by +30%:

16. If get wrong n(p,K)pHE – n(p,K)LE by -15%: • If get wrong n(p,K)pHE – n(p,K)LE by +15%: