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Beam e’s from antineutrinos

David Jaffe and Pedro Ochoa

September 27th 2007

Preliminaries Data & MC Expected sensitivities Preliminary results Outlook

− Preliminary Results −

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3) Fit resulting distribution (top right) using shapes from the MC scaled by parameters parHE and parLE:

Preliminaries

x parLEx parHE

pHE-LE+C (simulated)

2) Apply a correction C for

from and parents

C=pHE-)LE

(+)pHE (+)LE

Goal is to measure the antineutrinos from + decay (brothers of beam e’s)

Antineutrinos from + are the most affected when changing the beam configuration. The technique for the measurement is:

1) Scale pHE and LE DATA to same POT and subtract

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Measurement can also be done with pME data (minos-doc 2706)

Systematic error from background uncertainty is practically negligible on LE

Errors in +)LE determination from horn & target systematics are in the order of ~5-10%

Systematic errors associated with hadron production uncertainties are yet to be determined. Some on this at the end.

Systematics were addressed in minos-docs 2909 & 3230. In particular:

Preliminaries

More details on the method in minos-doc 2783

Statistical error with 1.6x1019 POT of pHE data was expected to be ~15% (minos-doc 3230)

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Data & MC used:

DATA le010z185i runI: 2.46x1019 POT

DATA le010z185i runII: 2.21x1019 POT

DATA le250z200i runII: 1.41x1019 POT

MC le010z185i: 4.44x1019 POT

MC le250z200i: 1.19x1019 POT

Data & MC

cedar_phy

daikon-cedar

The le010z185i data used corresponds to the same data used in the latest CC analysis and is evenly distributed along that period (runI + beginning of runII) Thanks to Tricia for these pans !

POT values for DATA are after “good beam” cuts.

all available !

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Data & reweighted MC antineutrino spectra:

le010z185i

le250z200i

All MC parent parentL parent+ parentBackground

All MC parent parentL parent+ parentBackground

le010z185i

le250z200i

data/MC (no SKZP)data/MC

data/MC (no SKZP)data/MC

Note: SKZP “PiMinus_CedarDaikon”, run I configuration (more details in slides 16-17)

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Expected sensitivities

Before fitting the data tested the routine with fake data.

Used smoothed MC histograms (shown in grey) to construct scenario.

(+)pHE(+)LE

(-,K-)LE (-,K-)pHE

Background LE Background pHE

Fake data is produced by statistically fluctuating the histograms.

The fit is done “manually” (no Minuit)

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Wassup with the bias

Χ2best fit = 28.6

Scenario 1: “best possible”

LE DATA POT pHE DATA POT LE MC POT pHE MC POT

∞ 1.41x1019 ∞ ∞

One fake experiment

Best fit

Distribution of 1000 fake experiments:

Best possible stat. error

Accuracy of contour confirmed by distribution

of fake experiments

90% C.L.

68% C.L.

This is the best measurement we can do with the current amount of pHE data:

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Scenario 2: “now”

LE DATA POT pHE DATA POT LE MC POT pHE MC POT

4.67x1019 1.41x1019 4.4x1019 1.19x1019

Χ2best fit = 28.5

One fake experiment

Best fit

90% C.L.

68% C.L.

Distribution of 1000 fake experiments:

This is the kind of measurement we expect to do now:

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Prob(25.4,28) = 60.6%

χ2=16.9

Preliminary results

Χ2

Our results, with statistical uncertainties only:

pHE(data) – LE(data) + C(MC)

Best fit

Nominal case(parLE=parHE=1)

Best fit: parLE=1.525 ± 0.37parHE=0.522 ± 0.19

90% C.L.68% C.L.

Χ2best fit = 25.4

pHE(data) – LE(data) + C(MC)

Prob(42.3,28) = 4.1%

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par LE par HE χ2best fit

Normal 1.52 0.52 25.4

No SKZP 1.85 0.42 22.8

No Bkgd substraction

1.52 0.77 27.5

SKZP

Consistent with expectation as described in minos-doc 2909

Preliminary results

Fit results in other conditions:

Difference with “No SKZP” case stems mainly from ~15% difference in low energy (< 10 GeV) region of C:

How much of this change is attributed to hadron production only by SKZP, and how much to other effects?

ratio

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Outlook

How much more can the result be improved? (without taking more data)

For an infinite amount of pHE MC, LE data

and LE MC

→max. goal

Contours calculated assuming same best fit value and 1.41x1019 POT of pHE data:

For an infinite amount of LE data and LE MC, with current

amount of pHE MC (1.3x1019 POT)

LE data =2x1020 POT LE MC =2.5x1020 POT

with current amount of pHE MC

LE data & MC POT of ~2x1020 POT is already “infinite” for our purposes.

With ~5 times more pHE MC can get close to the max. goal

LE data =2x1020 POT LE MC =2.5x1020 POT pHE MC = 7x1019 POT

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Summary

Our preliminary results confirm the SKZP prediction of to 1.4(statistics only)

A couple of things left to do:

Run with more data & MC. Need ~5 times more pHE MC. Assign a systematic error to our measurement

A much smaller systematic error could be obtained by doing the measurement with pME data, as shown in minos-doc 2706.

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Backup

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le010z185i

le250z200i

Data & raw MC antineutrino spectra:

All MC parent parentL parent+ parentBackground

All MC parent parentL parent+ parentBackground

le010z185i

le250z200i

data/MC

data/MC

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Applied SKZP to the MC:

All MC parent

L parent

parent

+ parent Background

raw MCSKZP MC le010z185i

ratio

ratio

ratio

ratio

ratio

ratio

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le250z200i bkgd (Reweighted for runI)

le250z200i bkgd(Reweighted for runII)

difference

Reweighting in runI or in runII modality does not change the antineutrinos at all.

What about the background (made mostly of CC ’s)?

Difference between the plots above is tiny !

Reweighted everything for runI.

→ What about the two running periods?

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Preliminary results

le010z185i

le250z200i

All MC parent parentL parent+ parentBackground

All MC parent parentL parent+ parentBackground

le010z185i

le250z200i

data/MC (before)data/MC (after scaling)

data/MC (before)data/MC (after scaling)

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χ2=35.2

Preliminary results (no SKZP)

Real data

Best fit

Real data

Nominal case(parLE=parHE=1)

Best fit: parLE = 1.85 parHE = 0.44

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parLE = 1.495 ± 0.37

parHE = 0.502 ± 0.19

Χ2 = 1.0 contour

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Max goalWith 1.41x1019 POT of le250z200i data,

stat error in only le250z200i data-MC

With 1.41x1019 POT of le250z200i data, 2x1020 POT of le010z185i MC and 2.5x1020 POT of le010z185i Data

With 1.41x1019 POT of le250z200i data, 2x1020 POT of le010z185i MC and

2.5x1020 POT of le010z185i Data, and 4x1019 POT of le250z200i MC

Outlook

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With 1.41x1019 POT of le250z200i data, 2x1020 POT of le010z185i MC and

2.5x1020 POT of le010z185i Data, and 7x1019 POT of le250z200i MC

With 1.41x1019 POT of le250z200i data, 2x1020 POT of le010z185i MC and

2.5x1020 POT of le010z185i Data, and 1x1020 POT of le250z200i MC

With 1.41x1019 POT of le250z200i data, 2x1020 POT of le010z185i MC and

2.5x1020 POT of le010z185i Data, and 1.5x1020 POT of le250z200i MC