1 Using the pHE data to measure the beam e ’s from  + decay David Jaffe and Pedro Ochoa March 13 th 2007  Introduction  Antineutrino selection  Feasibility study  Systematics

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  + decay in pHE ( (  + ) pHE ) peak at higher energies (i.e. better separation with (  + ) LE ).  Degradation since less POT (~2.0x10 19 ) and higher systematics.  Beginning of talk considers only statistics of available pHE data. Without sufficient statistical precision would not proceed further.

3 Selection  Some features of PID in cedar not completely understood. For now treat as black box.  Use (at least for now) nubar-PID selection (minos-doc-2377):  Used daikon-cedar MC: 4.11x10 18 POT of pHE and 1.07x10 20 POT of LE.  CC NC  Use cut at nubar-PID > 0.9: EfficiencyPurity LE56.2%99.1% pHE51.3%97.1% LE-10pHE

4 Parent  K  +  Selection in LE configuration: Background composition Background Selection vs. E reco Selection vs. E true Efficiency and Purity

5 Parent  K  +  Selection in pHE configuration: Background composition Background Selection vs. E reco Selection vs. E true Efficiency and Purity

6 (  + ) pHE (  + ) LE (  ,K - ) pHE (  ,K - ) LE  Background is problem in pHE. For now ignore.  Make feasibility study with fitted spectra: Scaled to 1x10 20 POT Feasibility study very distinct

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

8 13% stat. uncertainty !  Assume we get ( ,K) pHE - ( ,K) LE exactly.  Results of 5,000 fits at 2.0x10 20 POT of pHE data: 90% C.L.68.3% C.L.  Less correlation between parameters than in pME case (c.f. minos-doc-2504)  (  + ) pHE peaking at higher energy really helps us.  However… (see next slide)  Fit done manually (described in minos-doc-2504)

9 Systematics  Systematics are the key to this measurement. Mainly:  ( ,K) pHE - ( ,K) LE correction.  Background in pHE.  Preliminary look at C = ( ,K) pHE - ( ,K) LE : | Bias in parLE || Bias in parHE | C wrong by ± 50%~64.5%53.5% C wrong by ± 30%~38.1%~32.1% C wrong by ± 15%~19.2%~16.1% 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 e ’s to ~30%, need to know C to ~20% or better if it is the dominant systematic uncertainty.  From experience with pME cross-section shape uncertainties should not be big problem.  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:  ( ,K) pHE - ( ,K) LE correction  Background in pHE selection.  Goal is to incorporate this into e analysis with MCNN selection.

11 Backup

12 Smooth spectra scaled to 1e18 POT (  + ) pHE (  + ) LE (  ,K - ) pHE (  ,K - ) LE

13  If get wrong  ( ,K) pHE – ( ,K) LE by -50%:

14  If get wrong  ( ,K) pHE – ( ,K) LE by +50%:

15  If get wrong  ( ,K) pHE – ( ,K) LE by -30%:  If get wrong  ( ,K) pHE – ( ,K) LE by +30%:

16  If get wrong  ( ,K) pHE – ( ,K) LE by +15%:  If get wrong  ( ,K) pHE – ( ,K) LE by -15%: