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Neutrino Beam Flux Analysis: Hadron Production Uncertainties and Advanced Fitting Techniques

This paper presents a comprehensive examination of neutrino beam flux as conducted at the University of Texas at Austin. It delves into hadron production uncertainties affecting peak and tail behaviors in neutrino spectra, highlighting a combination of analyses and instrumentation measurements that inform these uncertainties. The study emphasizes the importance of comparing near detector (ND) data with Monte Carlo (MC) simulations and introduces methodologies for energy scan data and beam extrapolation. It concludes with a discussion on the implications for neutrino oscillation studies and future analytical needs.

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Neutrino Beam Flux Analysis: Hadron Production Uncertainties and Advanced Fitting Techniques

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  1. University of Texas at Austin – 41 University of Southern California – 38 NuMI Beam Flux Sacha E. Kopp University of Texas at Austin

  2. Neutrino Beams 101: g4numi Ž. Pavlović

  3. Neutrino Beams 102: p+ to far Detector (stiff) target • ND and FD spectra similar, but not identical qf p+ qn (soft) Decay Pipe ND Near Detector LE Beam

  4. ND Flux Error • All effects not including hadron production uncertainties. • Some uninvestigated effects noted in position paper (minos-doc-1278) were since studied in supporting document (minos-doc-1283) • As discussed in minos-doc-1283, in many cases these errors backed up by actual beam instrumentation measurements. Focusing peak Focusing peak Focusing peak Ž. Pavlović

  5. Hadron Production Uncertainty (I) LE10/185kA Beam pHE Beam M. Messier

  6. Hadron Production Uncertainty (II) Spread due to models: • 8% (peak) • 15% (tail) Marino, Kang, Yang, Yumiceva,

  7. Hadron Production Uncertainties (III) After Neutrino Weighting Before Neutrino Weighting • Can in principle fit ND data to beam MC by weighting/deweighting as a function of pion xF and pT. • For now, attempted crude approach to parameterize the effect via several pion pT distributions. Fluka 2005 Ž. Pavlović

  8. Effect of Hadron Reweighting • pT reweighting by an amount consistent with Fluka/MARS models’ spread gives similar n flux spread (comforting). • Allows us also to explore the correlations between the LE/ME/HE beams – we can fit this? • In principle can expand to fits to work in both xF and pT. Ž. Pavlović

  9. Energy Scan Data Question: the agreement in these plots is (choose one)... • Satisfactory • Agreement is better than 20-30% originally feared. • We are likely therefore within the error budget from Trisha/Jenny. • Not satisfactory • Want to fit this to constrain hadron production in the MC • By eye, a tweak of pT alone cannot accommodate all 3 beams. • Proper fit requires evolution of pT vs.xF of pions (not yet attempted). Trish Vahle Data Beam MC + Error HE ME LE

  10. Alternate Horn Currents LE10/200kA LE10/185kA LE10/170kA • Alternate horn currents sample different pion pT’s –information which complements energy scan. • Beam MC not yet propagated through GMINOS. • At present, ceci n’est pas un analysis. PBEAM MC ND Data (R1.16) Trish Vahle Ž. Pavlović

  11. For Dm2, why do we really care? • Answer #1: If David tweaks hadron production to match ND data with MC, he will induce change in predicted FD flux • 5% in the tail • 1-2% in the peak • Answer #2: If Trish uses F/N method and takes ND as ‘truth’, the right plot is FD ‘uncertainty band’ Ž. Pavlović

  12. Can We Demonstrate Beam Extrapolation? • K2K says Dm2<510-3 eV2 HE beam does not have oscillations. • Compare FD data with extrapolated spectrum from ND. • Different issues in HE and LE beams, but can serve as a nice ‘check’. • Requires more data to make this meaningful (1 wk. = 5E18 POT) Jenny Thomas, Trisha Vahle Predicted FD Spectrum

  13. Antineutrinos • ‘Bare target’ beam spectrum (p- sneaking through horn necks). • GNuMI-v.17 was incorrect on this flux! • Significant model differences (noted in NuMI-B-768 but not understood). • Focusing uncertainties (current, alignment) haven’t been studied! • Strongly urge n’s be eliminated from the 1020POT data. Marino, Kang, Yang, Yumiceva,

  14. Conclusions • Systematic errors should cover us for now. • Several have been supplied as correlated error distortions • Hadron production currently supplied as an ‘error envelope’ (no correlations). • GNuMI-v.18 is our best effort. No major known ‘outstanding issues’. • Short-term: demonstration of understanding of the beam requires ~3 months • Fit our beam MC to the ND data as function of pion/kion xF and pT • Uses LE/ME/HE energy scan & 170/200 kA running in LE10 position (won’t change the central value of Dm2, but affects confidence in its error) • Long-term: upgrades to this analysis will require 6-12 mo. to achieve: • Study of p/K production ratio using MiniBooNE (6 mo.) • g4numi (has significant geometry changes) (6 mo.) • Use mMon’s to constrain ME and HE fluxes (6-12 mo.) • Survey of hadro-production data, inclusion of NA49 & MIPP (12 mo.) • It is a central discussion how we want to present the results • Have enough analysis done to demonstrate understanding of the beam • Have enough analysis done to claim Dm2 not affected by uncertainties

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