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Beam measurement with -Update -

Beam measurement with -Update -. Reminder of proposed technique Use of horn-off data Use of horn2-off data? Effect of correcting for KL3 branching fractions and matrix elements Summary & Ongoing work. David Jaffe & Pedro Ochoa. 1) Brief reminder.

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Beam measurement with -Update -

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  1. Beam measurement with -Update - • Reminder of proposed technique • Use of horn-off data • Use of horn2-off data? • Effect of correcting for KL3 branching fractions and matrix elements • Summary & Ongoing work David Jaffe & Pedro Ochoa

  2. 1) Brief reminder Concept: Measurement of low energy can be used to constrain the flux, since: So look for whose father is a : True energy of true at the ND Ecut This is what we are trying to measure LE010185 carrot MC No from m+ above this energy (Ecut)

  3. The technique is the following: ● ● ● ● ● ● The most critical aspect of this measurement lies in the uncertainty of the C factor. (doc-1663, doc-1605)

  4. 2) Use of Horn-off data We made a first pass at C by studying its energy dependence: C(E). How? Horn-off data gives us a direct handle: Horn Off no mu+ Assumption: C(E) is the same for horn-off and horn-on data. This may actually be true if the differences between data and MC lie only in things that affect both situations (horns on & off) the same, like cross-sections and/or efficiencies. So the procedure we followed was to: Step1) Calculate C(E) by comparing horn-off data and MC. Step2) Test C(E) on the horn-on data and MC for E > Ecut=10GeV.

  5. Horn-off MC Step 1: Obtaining C(E) from horn-off data First, two words on antineutrino selection: ●Selected events in fiducial volume: 1<vtxz<5 & vtxr < 1.0m At least 1 track Track passes fit UVasym < 6 / ndf < 20 ●Selected events that satisfy some “basic” cuts: ●Used “NuBar-PID” cut at 0.27 (ref. doc-1657): Background composition Evaluating the selection on the horn-off MC gives 94.6% purity and 61.2% overall efficiency.

  6. Horn-off data and MC comparison for antineutrinos: ●Used all available MC and data (2.77e18 POT, taken in February). MC was scaled to the data. ● Uncertainty is dominated by data statistics. Data MC data/MC Horn-off Horn-off The right plot is our estimate of C(E). Step 2 is to test it ! Please note that (ref. slide 3) and therefore that, with infinite MC statistics, we have

  7. Horn-on MC Step 2: Testing C(E) in horn-on data ● Used same cuts as for horn-off data. Evaluation in horn-on MC gives 86.6% purity and 61.2% efficiency (including all cuts). ●Checked efficiency and purity as a function of energy to make sure that we are not affected by background at high energies (E > Ecut) Background composition

  8. ● Used 1.9e19 POT of R1.18.2 data (January 2006). MC was scaled to the data. ● Observe similar deficit of MC with respect to data, like in the horn-off case. Data MC data/MC Horn-on Horn-on

  9. Tried 3 different approaches when scaling the MC: Horn-on Horn-off Data Scaled MC Before scaling 1) 5th degree pol. Data MC Data Scaled MC 2) 2 constants Horn-on Data Scaled MC 3) Bin by bin Ratios of data & scaled MC in next slide…

  10. 1) 5th degree pol. 2) 2 constants 3) Bin by bin In order to evaluate this for the 3 “fits” took the ratio of data/scaled MC: Horn-on WITHOUT SCALING

  11. = MC C H / H m n H We observe that: ● The 3 fits perform similarly at E < Ehigh ~ 16 GeV and the results are encouraging in that region. ● Our assumption that cannot be said to hold beyond Ehigh ~ 16 GeV. ●C(E) seems to be consistent with a constant from Ecut < E < Ehigh. This suggests the following methods for estimating C: • i) Estimate C = CH for the horn-on or horn-off data/MC: • where H denotes events with Ecut < E < Ehigh. • ii) Similarly, estimate CL with the horn-off data: • where L denotes events with 0 < E < Ecut. • iii) The degree of agreement between the 3 estimates (CH(on), CH (off) and CL(off)) provides an estimate of the systematic uncertainty in C with a statistical uncertainty of a few percent from the horn-off data statistics of 2.77e18 POT.

  12. 3) Horn-2 OFF Flux Generation ●Idea was brought up by Milind that the mu+ may be getting focused mainly by the second horn. ●If that is the case, horn2-off data can be an extra tool for constraining C(E). ●In order to answer this, generated 1e7 POT of horn2-off flux: What’s this? Horn-2 OFF Normal Vertical units are flux per m2 per 5e5 POT.

  13. component The mu+ and non-mu+ components: all other components (π,K) Normal Horn-2 off Normal Horn-2 off ●It seems that the second horn focuses about ~3/5 of the mu+, but the rest is done by the first horn. This is less than we expected. ●The spectrum’s disruption is too severe for the non-mu+ components to use this data.

  14. 4) Corrections for Kl3 matrix elements and branching fractions ●In doc-1652, Stan noted that Kl3 matrix elements were not implemented correctly in gnumi. He also notes that the Ke3 branching fractions should by increased by 1.051 (K0L) and 1.064(K+) to take into account the latest measurements: PRL93 (2004)181802 & PRL91(2003) 261802, respectively ● Implications of correcting for the Kl3 ME and Br were investigated for the measurement of the flux from decays as well as the flux.

  15. Example of correcting gnumi V15 for Kl3 matrix element ‘correct ME’ gnumi ‘correct ME’ is not exactly as in doc-1652 but very nearly Top: solid line=gnumi, dashed=‘correct ME’ Middle:fitted correction factor to ratio Bottom: gnumi after correction

  16. Negligible systematic effect of Kl3 corrections on C(E) and method to extract the nm flux from m O(5%) effect on total ne flux of corrections for Kl3 Br and ME _

  17. Summary & Ongoing Work • Preliminary check with horn-off data is encouraging: • The hypothesis that C(E) is the same for horn-on and horn-off seems verified, at least for the region Ecut < E < Ehigh • The proposed method for determining C assumes it to be a constant that can be extracted from horn-on or horn-off data/MC. Comparison of C from the different data sets will provide an estimate of the systematic uncertainty in C. • Need to take NC and neutrino bkgd into account in estimation of C. • It seems that the second horn is not the only one to focus the m+. This combined with the fact that the spectrum is severely distorted make horn2-off running unappealing for this analysis. • Kl3 corrections do not appear to have significant impact on extraction of m component of nm flux. There appears to be a modest effect on the beam ne flux. Need corrected gnumi (or equivalent) for definite conclusions. • Improving the purity of the low energy nm sample is difficult. NuBarPID is a good first step. Currently investigating if we can exploit available track and event information to improve purity . (see Justin Evan’s doc-1682) _ _

  18. Backup NuBar-PID pdfs are: nu nubar

  19. Side note: story is a bit different for neutrinos ●Used same data sample as previous slide. MC was scaled to 2.77e18 POT ● Used same selection criteria, but with NuBar-PID < 0.27 data/MC Data MC Horn-off Horn-off

  20. Backup Horn-on data and MC for neutrinos: ● Used 1.9e18 POT of R1.18.2 data (January 2006). MC was scaled to the data. data/MC Data MC

  21. Effect of corrections to Kl3 Br and ME to ND flux energy spectra up to 60 GeV

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