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NuMI Beam Flux

Sacha E. Kopp

University of Texas at AustinUniversity of Texas at Austin – 41

University of Southern California – 38

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Neutrino Beams 101:

g4numig4numi

Ž. PavlovićŽ. Pavlović

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Neutrino Beams 102:

• ND and FD spectra similar, but not identical

f

Near Detector

to farDetector

Decay Pipe

(soft)

(stiff)

n

target

2

222 1

11

L

Flux

221

43.0

EE

LE Beam

ND

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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.

Focu

sing

pe

ak

Focu

sing

pe

ak

Focu

sing

pe

ak

Ž. PavlovićŽ. Pavlović

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Hadron Production Uncertainty (I)

M. MessierM. Messier

LE10/185kA BeamLE10/185kA Beam pHE BeampHE Beam

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Hadron Production Uncertainty (II)

Spread due to models: 8% (peak) 15% (tail)

Spread due to models: 8% (peak) 15% (tail)

Marino, Kang, Yang, Yumiceva, Marino, Kang, Yang, Yumiceva,

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Hadron Production Uncertainties (III)

• 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

Before Neutrino Weighting After Neutrino Weighting

Ž. PavlovićŽ. Pavlović

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Effect of Hadron Reweighting

• pT reweighting by an amount consistent with Fluka/MARS models’ spread gives similar 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. PavlovićŽ. Pavlović

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Energy Scan Data

a) Satisfactory Agreement is better than

20-30% originally feared. We are likely therefore

within the error budget from Trisha/Jenny.

b) 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 VahleTrish Vahle

Data

Beam MC + Error

HEME

LE

Question: the agreement in these plots is (choose one)...

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Alternate Horn Currents

• 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.

Trish VahleTrish Vahle

Ž. PavlovićŽ. Pavlović

PBEAM MCND Data(R1.16)

LE10/200kALE10/185kALE10/170kA

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For m2, 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. PavlovićŽ. Pavlović

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Can We Demonstrate Beam Extrapolation?

• K2K says m2<510-3 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 VahlePredicted

FD Spectrum

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Antineutrinos

• Focusing uncertainties (current, alignment) haven’t been studied!

• Strongly urge ’s be eliminated from the 1020POT data.

• ‘Bare target’ beam spectrum ( sneaking through horn necks).

• GNuMI-v.17 was incorrect on this flux!

• Significant model differences (noted in NuMI-B-768 but not understood).

Marino, Kang, Yang, Yumiceva, Marino, Kang, Yang, Yumiceva,

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Conclusions• GNuMI-v.18 is our best effort. No major known ‘outstanding issues’.

• 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 m2 not affected by uncertainties

• 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 m2, but affects confidence in its error)

• 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).

• Long-term: upgrades to this analysis will require 6-12 mo. to achieve: Study of /K production ratio using MiniBooNE (6 mo.) g4numi (has significant geometry changes) (6 mo.) Use Mon’s to constrain ME and HE fluxes (6-12 mo.) Survey of hadro-production data, inclusion of NA49 & MIPP (12 mo.)