NuMI Neutrino Flux Prediction Leo Aliaga The 10th International - PowerPoint PPT Presentation

NuMI Neutrino Flux Prediction Leo Aliaga The 10th International Workshop on Neutrino Beams and Instrumentation ( NBI2017 ) September 18-22, 2017, Tomai-mura

14.6 mrad off-axis NuMI NOvA on-axis Two Challenges: 1. Beam focusing uncertainties (every mm matters): alignment, materials, etc. G4NuMI GEANT4 9_2_p03 FTFP_BERT 2. Hadron production uncertainties: big discrepancies between hadronic models. 2 09-19-2017 Leonidas Aliaga | NuMI Neutrino Flux Prediction

MINERvA Strategy for Predicting the Flux Accounting for every optical modeling uncertainty. 1. Calculate an a-priori flux Correcting the hadron production in the beam line to constrain to external hadron production data. Checking our results with the low recoil event rates (low-nu method): flux shape measurement. 2. Use in-situ measurements Applying an additional constraint from the neutrino - electron scattering events. Develop every tool in such a way they can be used 3. Package to Predict the FluX by any experiment at NuMI (PPFX). 3 09-19-2017 Leonidas Aliaga | NuMI Neutrino Flux Prediction

Some geometrical improvements Effect of 1mm water layer around the Horn 1 water layer addition / nominal inner conductor LE at MINERvA Flux ratio 4% effect around the LE flux peak. More accurate description of the inner conductor (IC) of Horn 1 designed for LBNF - Improved segmentation of the IC surface - Check the neck shape (cylinder). 5% (14%) effect in the LE (ME) falling edge of the flux peak at MINERvA. 4 09-19-2017 Leonidas Aliaga | NuMI Neutrino Flux Prediction (Implemented by Paul Le Brun)

total: ~1.4 <interactions> / ν μ Interaction Map LE Mode at MINERvA LE Mode at MINERvA 5 09-19-2017 Leonidas Aliaga | NuMI Neutrino Flux Prediction

total: ~1.4 <interactions> / ν μ Understanding the Flux LE Mode at MINERvA LE Mode at MINERvA <interaction>/ ν μ π + produced by protons Proton Projectile < 0.001 not shown E ν in 0-20 GeV Particle produced 6 09-19-2017 Leonidas Aliaga | NuMI Neutrino Flux Prediction

External Data? What Sort of Data is Available? • Hadron production data at the relevant energies for NuMI (references in the backup slides): Inelastic/absorption Thin Target Data π p p Kp π π Thick Target Data π p Kp p π π Checking the consistency with the MINERvA low-nu measurement, we decided to use a prediction based only on thin target correction 7 09-19-2017 Leonidas Aliaga | NuMI Neutrino Flux Prediction

How do We Use the Data to Correct the Models? We apply a weight to the neutrino yield based on the its hadronic interaction history. The cascades that lead to a neutrino are tabulated at generation: kinematics of the interactions and the amount of material traversed by every particle. The correction is applied event by event at analysis time. Two corrections are applied (data/MC): 1. Beam attenuation. 2. Hadron production. The systematics is evaluated by using the “multi-universe” technique where each datapoint is a parameter (see backup). 8 09-19-2017 Leonidas Aliaga | NuMI Neutrino Flux Prediction

1. Beam Attenuation m a e b e l c i t r a p When the particle interacts in a volume r material m a e b e l c i t r a When the particle passes through the p r volume without interacting material The amount of material: rN A ρ /A . Two variables are important here: The σ Data and σ MC disagreement . 9 09-19-2017 Leonidas Aliaga | NuMI Neutrino Flux Prediction

Amount of Material Traversed Muon neutrino parent: LE Mode at MINERvA LE Mode at MINERvA References: - C: 6 mol/cm 2 ≈ 40 cm - Al: 1 mol/cm 2 ≈ 10 cm - He: 1 mol/cm 2 ≈ 500 m 10 09-19-2017 Leonidas Aliaga | NuMI Neutrino Flux Prediction

Data - MC Comparison Inelastic cross section Absorption cross section Pion on Aluminum Proton on Carbon Reference (Geant4): Reference (Geant4): σ absorption = 243.2 mbar σ absorption = 344 mbar 11 09-19-2017 Leonidas Aliaga | NuMI Neutrino Flux Prediction

2. Hadron Production For thin target data (NA49 for instance): ( f=Ed 3 σ /dp 3 : invariant production cross section) The scale allows us to use NA49 for proton on carbon in 12-120 GeV (calculated with FLUKA). It was checked by comparing with NA61 at 31 GeV (negligible difference). For thick target data (MIPP): 12 09-19-2017 Leonidas Aliaga | NuMI Neutrino Flux Prediction

Example: NA49 Data/MC comparison (closed circles = statistical error < 2.5%, Open circles = statistical error 2.5-5.0%, Crosses > 5%). pC -> π + X LE Mode at MINERvA Contours: 2.5, 10, 25, 50 correction (Data/MC)) and 75 % of the pion yields. - Systematics are highly correlated bin-to-bin. - Systematics and statistical errors are considered uncorrelated each other. Systematic uncertainties = 3.8% (added in quadrature). 13 09-19-2017 Leonidas Aliaga | NuMI Neutrino Flux Prediction

If There is not Direct Data Extending the data coverage Constrain pA interactions with pC adding an additional uncertainty found by comparing A dependence of Barton, Skubic and Eichten. Use theoretical guidance (isospin arguments, quark counting arguments, etc.) What if data is not available? Guided by the agreement with other datasets: processes categorized by projectile and produced particle. 40% error assigned in 4 x F bins. 14 09-19-2017 Leonidas Aliaga | NuMI Neutrino Flux Prediction

Average Number of Interactions π , K and nucleons LE Mode at MINERvA LE Mode at MINERvA productions from pC based on data (mainly NA49). We assume large uncertainties for meson incident. ~2.2 for very low E ν and ~1.4 for the rest • nucleon-A (quasi-elastics, extension from carbon to other materials, production outside data coverage, etc). 15 09-19-2017 Leonidas Aliaga | NuMI Neutrino Flux Prediction

Average Number of Interactions At NOvA ME Mode at NOvA ~3.0 for low E ν and ~1.5-1.6 for the rest 16 09-19-2017 Leonidas Aliaga | NuMI Neutrino Flux Prediction

A Priori Flux Results for LE MINERvA • MINERvA published the flux prediction for LE NuMI beam based on thin target data correction Phys. Rev. D 94, 092005 (2016) 17 09-19-2017 Leonidas Aliaga | NuMI Neutrino Flux Prediction

A Priori Flux Results for NOvA Near Detector The same procedure has been fully implemented by NOvA for its a priori flux prediction in NOvA 18 09-19-2017 Leonidas Aliaga | NuMI Neutrino Flux Prediction

Conclusions For NOvA, MINERvA (and MINOS+) and other experiments it is crucial to have a precise measurement of the flux with small uncertainties. The hadron production is the main source of uncertainties. Applied all relevant existing data to constrain the flux reduce the uncertainties. We develop an open and free computational tool called PPFX to share our result with other NuMI experiments. - Currently use by MINERvA and NOvA . - It has been adapted for DUNE and it is being used by the ND systematics 19 09-19-2017 Leonidas Aliaga | NuMI Neutrino Flux Prediction

Conclusions 20 09-19-2017 Leonidas Aliaga | NuMI Neutrino Flux Prediction