Using the pHE data to measure the beam n e ’s from m + decay

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Using the pHE data to measure the beam e’s from + decay

David Jaffe and Pedro Ochoa

March 13th 2007

Introduction Antineutrino selection Feasibility study Systematics

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Introduction David and Pedro proposed making this measurement with pME

data (minos-doc-2706). Getting that data seems complicated. 2 main reasons: Fear of moving target after previous experience. Some people feel physics case not strong enough.

Could we use the already existing pHE data taken after the shutdown? With pHE data expect:

Improvement since antineutrinos from + decay in pHE ((+)pHE) peak at higher energies (i.e. better separation with (+)LE).

Degradation since less POT (~2.0x1019) and higher systematics. Beginning of talk considers only statistics of available pHE data.

Without sufficient statistical precision would not proceed further.

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Selection

Some features of PID in cedar not completely understood. For now treat as black box.

Use (at least for now) nubar-PID selection (minos-doc-2377):

Used daikon-cedar MC: 4.11x1018 POT of pHE and 1.07x1020 POT of LE.

CC CCNC

Use cut at nubar-PID > 0.9:Efficiency Purity

LE 56.2% 99.1%

pHE 51.3% 97.1%

LE-10 pHE

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ParentK

+

Selection in LE configuration:

Background composition

Background

Selection vs. ErecoSelection vs. Etrue

Efficiency and Purity

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ParentK

+

Selection in pHE configuration:

Background composition

Background

Selection vs. ErecoSelection vs. Etrue

Efficiency and Purity

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(+) pHE

(+) LE

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

Background is problem in pHE. For now ignore. Make feasibility study with fitted spectra:

Scaled to 1x1020 POT

Feasibility study

very distinct

7Scaled to 2e19 POT Scaled to 2e19 POT

Fake experiment at 2e19 POT

in MCin feasibility

study

one fit

x parLE(+)pHE

(,K)pHE-(,K)LE

x parHE(+)LE

Good agreement for (,K)pHE-(,K)LE in MC and in feasibility study:

Note: Assume infinite MC and

LE statistics

Procedure: - fit pHE-LE with spectral shapes from MC. - scale (+)LE and (+)pHE by parameters parLE and parHE.

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13% stat. uncertainty !

Assume we get (,K)pHE-(,K)LE exactly.

Results of 5,000 fits at 2.0x1020 POT of pHE data:

90% C.L. 68.3% C.L.

Less correlation between parameters than in pME case (c.f. minos-doc-2504)

(+)pHE peaking at higher energy really helps us.

However… (see next slide)

Fit done manually (described in minos-doc-2504)

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Systematics Systematics are the key to this measurement. Mainly:

(,K)pHE-(,K)LE correction. Background in pHE.

Preliminary look at C = (,K)pHE-(,K)LE:

| Bias in parLE | | Bias in parHE |

C wrong by ± 50% ~64.5% 53.5%

C wrong by ± 30% ~38.1% ~32.1%

C wrong by ± 15% ~19.2% ~16.1%

Note: As pointed out by Stan, best way to look at C is not in percentage form. This is just to get an idea.

If want to know beam e’s to ~30%, need to know C to ~20% or better if it is the dominant systematic uncertainty.

From experience with pME cross-section shape uncertainties should not be big problem.

Maybe can absorb some of this uncertainty by adding another parameter that scales C. Will look into it.

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Summary & Ongoing work

Measurement is possible to 13% from statistics point of view, using already existing pHE data.

Work in progress to understand the 2 main systematics:

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

Background in pHE selection.

Goal is to incorporate this into e analysis with MCNN selection.

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Backup

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• Smooth spectra scaled to 1e18 POT

(+) pHE (+) LE

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

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If get wrong(,K)pHE – (,K)LE by -50%:

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If get wrong(,K)pHE – (,K)LE by +50%:

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Using the pHE data to measure the beam n e ’s from m + decay

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