Systematic uncertanties

[jtenavidal]

We considered several major sources of systematic uncertainties:

1. angular dependence of the pion-production cross-section (for the undetected-pion subtraction)
2. Effects of fiducial cuts on undetected particle subtraction
3. Photon identification cuts
4. The sector-to-sector variation of the data to e-GENIE ratio
5. The model dependence of the acceptance correction
6. Uncertainties in the normalization measurement.

[jtenavidal]

angular dependence of the pion-production cross-section (for the undetected-pion subtraction)

When we rotated events containing pions around the momentum transfer vector, we assumed that the cross-section did not depend on ϕ. We tested the ϕ independence of the pion-production cross-section by weighting the subtraction using the measured ϕ-dependent H(e, e′pπ) cross-sections of ref. 59. This changed the subtracted spectra by about 1% and was included as a systematic uncertainty.

[jtenavidal]

Effects of fiducial cuts on undetected particle subtraction

The subtraction of events with undetected pions depends on the CLAS acceptance for such particles. The final spectrum should be independent of the CLAS pion acceptance. We estimated the effect of varying the CLAS acceptance on the undetected particle subtraction by comparing the results using the nominal fiducial cuts and using fiducial cuts with the ϕ acceptance in each CLAS sector reduced by 6° or about 10–20%. This changed the resulting subtracted spectra by about 1% at 1.159 and 2.257 GeV and by 4% at 4.453 GeV. This difference was included as a point-to-point systematic uncertainty.

[jtenavidal]

Photon identification cuts

We also varied the photon identification cuts. We identified photons as neutral particle hits in the calorimeter with a velocity greater than two standard deviations (3σ at 1.159 GeV) below the mean of the photon velocity peak (at v = c). We varied this limit by ±0.25σ. This gave an uncertainty in the resulting subtracted spectra of 0.1%, 0.5% and 2% at 1.159, 2.257 and 4.453 GeV, respectively.

[jtenavidal]

The model dependence of the acceptance correction

We calculated the acceptance correction factors using both G2018 and SuSAv2. We shifted the G2018 results so that the energy reconstruction peaks lined up at the correct beam energy. We used the bin-by-bin average of the two correction factors as the acceptance correction factor and the bin-by-bin difference divided by 12 as the uncertainty. We averaged the uncertainty over the entire peak to avoid large uncertainties due to small misalignments. See Extended Data Fig. 8a–f.

[jtenavidal]

Uncertainties in the normalization measurement

The overall normalization was determined using inclusive 4.4-GeV H(e, e′) measurements. The measured and simulated H(e, e′) cross-sections agreed to within an uncertainty of 3%, which we use as a normalization uncertainty.

[jtenavidal]

https://docdb.lns.mit.edu/e4nudb/0000/000008/002/e4v%20Feb%2015%202021%20Collaboration%20Meeting%20%28Update%29.pdf if you go to the end of the backup there are several slides on the systematics

[jtenavidal]

https://github.com/adishka/e4nu/blob/987541f1e2b57a2ea618e2d9ca3bf4fa490f37ee/myFunctions.cpp#L905

[jtenavidal]

https://github.com/adishka/e4nu/blob/987541f1e2b57a2ea618e2d9ca3bf4fa490f37ee/myFunctions.cpp#L1167

[jtenavidal]

BKG uncertanties issue: https://github.com/e4nu/e4nuanalysiscode/issues/124