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Beam n e ’s from antineutrinos

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Beam n e ’s from antineutrinos

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Beam ne’s from antineutrinos

− Preliminary Results −

David Jaffe and Pedro Ochoa

- Preliminaries
- Data & MC
- Expected sensitivities
- Preliminary results
- Outlook

September 27th 2007

C=n(p,K)pHE-n(p,K)LE

n(m+)LE

n(m+)pHE

n(p,K)pHE-n(p,K)LE

Preliminaries

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

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

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

npHE-nLE+C (simulated)

2) Apply a correction C for n from p- and K- parents

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

x parLE

x parHE

Preliminaries

- More details on the method in minos-doc 2783

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

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

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

- Systematic error from background uncertainty is practically negligible on n(m+)LE
- Errors in n(m+)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.

Data & MC

- Data & MC used:

- DATA le010z185i runI: 2.46x1019 POT

- DATA le010z185i runII: 2.21x1019 POT

cedar_phy

- DATA le250z200i runII: 1.41x1019 POT

- MC le010z185i: 4.44x1019 POT

daikon-cedar

all available !

- MC le250z200i: 1.19x1019 POT

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

- 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 !

All MC

p- parent

K- parent

KL parent

m+ parent

Background

All MC

p- parent

K- parent

KL parent

m+ parent

Background

- Data & reweighted MC antineutrino spectra:

data/MC (no SKZP)

data/MC

le010z185i

le010z185i

data/MC (no SKZP)

data/MC

le250z200i

le250z200i

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

n(p-,K-)LE

n(p-,K-)pHE

n(m+)LE

n(m+)pHE

Expected sensitivities

- Before fitting the data tested the routine with fake data.

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

- Fake data is produced by statistically fluctuating the histograms.
- The fit is done “manually” (no Minuit)

Background pHE

Background LE

- Scenario 1: “best possible”

- Distribution of 1000 fake experiments:

Χ2best fit = 28.6

Best possible stat. error

Accuracy of contour confirmed by distribution of fake experiments

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

Best fit

Wassup with the bias

68% C.L.

90% C.L.

One fake experiment

- Scenario 2: “now”

- Distribution of 1000 fake experiments:

Χ2best fit = 28.5

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

Best fit

68% C.L.

90% C.L.

One fake experiment

Preliminary results

- Our results, with statistical uncertainties only:

Best fit:

parLE=1.525 ± 0.37

parHE=0.522 ± 0.19

DΧ2

68% C.L.

90% C.L.

pHE(data) – LE(data) + C(MC)

Nominal case

(parLE=parHE=1)

Dχ2=16.9

Best fit

Prob(42.3,28) = 4.1%

Χ2best fit = 25.4

Prob(25.4,28) = 60.6%

pHE(data) – LE(data) + C(MC)

Preliminary results

- Fit results in other conditions:

Consistent with expectation as described in minos-doc 2909

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

ratio

SKZP

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

Outlook

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

- 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

For an infinite amount of pHE MC, LE data and LE MC

→max. goal

LE data =2x1020 POT

LE MC =2.5x1020 POT

pHE MC = 7x1019 POT

- 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

Summary

- Our preliminary results confirm the SKZP prediction of n(m+) to 1.4s (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.

Backup

All MC

p- parent

K- parent

KL parent

m+ parent

Background

All MC

p- parent

K- parent

KL parent

m+ parent

Background

- Data & raw MC antineutrino spectra:

data/MC

le010z185i

le010z185i

data/MC

le250z200i

le250z200i

raw MC

SKZP MC

- Applied SKZP to the MC:

le010z185i

ratio

ratio

p- parent

All MC

ratio

ratio

KL parent

K- parent

ratio

ratio

m+ parent

Background

→ What about the two running periods?

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

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

le250z200i bkgd

(Reweighted for runI)

le250z200i bkgd

(Reweighted for runII)

- Difference between the plots above is tiny !

difference

- Reweighted everything for runI.

All MC

p- parent

K- parent

KL parent

m+ parent

Background

All MC

p- parent

K- parent

KL parent

m+ parent

Background

Preliminary results

- Scale m+component by best fit values and compare with data:

le010z185i

data/MC (before)

data/MC (after scaling)

le010z185i

le250z200i

data/MC (before)

data/MC (after scaling)

le250z200i

Best fit:

parLE = 1.85

parHE = 0.44

- Preliminary results (no SKZP)

Nominal case

(parLE=parHE=1)

Real data

Dχ2=35.2

Best fit

Real data

DΧ2 = 1.0 contour

parLE = 1.495 ± 0.37

parHE = 0.502 ± 0.19

Outlook

With 1.41x1019 POT of le250z200i data, stat error in only le250z200i data-MC

Max goal

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

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 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