1

Beam e’s from antineutrinos using the pME and LE beams

David Jaffe, Pedro Ochoa

December 8th 2006

Part 1: Reminder and update Part 2: Change in technique Part 3: Systematics

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Reminder

Goal is to measure from +

Idea is that spectrum is almost identical in the LE and pME configurations except for the + component:

from -,K-

LEpME

Selected events at 1.9x1019 POT

from -,K-

pME - LE

from +

LEMEpHE

diff

3

So take the pME-LE difference

from +

pME

parME

from +

LE

parLE

from -,K-)ME

( from -,K-)LE

(pME-LE)”TRUE” at 1e18 POT

And fit with two parameters:

To make feasibility study, get “true” distributions by fitting raw MC:

4

i D

ii

i

parMEparLEEDparMEparLE

2

22 )),((

),(

Now the fit is done “manually”:

Change in technique

2) Generate fake data by fluctuating pME “data” Di antineutrinos with a

Poisson (assume ∞ MC and LE data)

1) Generate typically 40,000 “expected histograms” Ei for

different combinations of parLE and parME

3) Compare the fake data with each expected histogram by means of a chi-squared:

(pME-LE)FAKE at 1e19 POT

4) Steps 2 and 3 are repeated 5000 times.

parLE=1parME=1

parLE=0parME=1

parLE=0.5parME=2

parLE=2parME=0.5

parLE=1parME=0

… etc

5) Get average and subtract the minimum

(Note: not using first bin)

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For example, at 2.5x1019 POT of pME data:

2 68.27%

90 %

At each fake experiment get best fit parameters:

24% measurement !

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Statistical sensitivity of the method vs. pME-POT:

Promising. Maybe can improve considerably by relaxing cuts.

Details available in

backup plots

2 types: 1) Not getting the right (pME-LE),K

from MC

2) Not getting the right shape(s) from MC.

from +, LE

from +, pMEpreliminary

What about systematics?

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Systematics

from -,K-)ME

( from -,K-)LE

Small correction of differences in ,K contributions to spectrum needs to be obtained from MC.

Vary contribution of difference by ±50%:

More generally: Observed no strong

dependence in POT

If correction is 50% too low

2.5x1019 POT

If correction is 50% too high

2.5x1019 POT

Note: true correction may be different than the one used here. Need more MC

LE

pME

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What if we don’t have the right shape? cross-section energy dependence has big uncertainty at low E

(plot by Donna Naples)

Estimating an error on the cross-section shape is hard. See talk in physics simulations parallel session.

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For now just try to be on safe side:

Varied cross-section parameters ma_qe, ma_res and kno_r (all) by 50%, 50% and 20% respectively

qe dis ma_qe x 1.5

ma_qe x 0.5

ratio ratio

res ratio

ma_res x 1.5

ma_res x 0.5

effect in total cross-section(modif cs / nominal cs)

ma_qe*1.5ma_res*1.5kno_r*1.2

ma_qe*0.5ma_res*0.5kno_r*0.8

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Effect of simultaneously increasing ma_qe, ma_res and kno_r (all) in the “true” data ( normal, with systematic):

from -,K- from -,K-

from + from +

pME

pME LE

LE

11

Performed the fit and introduced “success” parameters:

sucLE =#antineutrinos from + predicted by fit, LE

#antineutrinos from + in fake data, LE

sucME =#antineutrinos from + predicted by fit, pME

#antineutrinos from + in fake data, pME

2.5x1019 POT

With these (huge) variations in the cross-section, introduced a bias of only -2.3% and +10% (independent of POT).

ma_qe*1.5ma_res*1.5kno_r*1.2

2.5x1019 POT

ma_qe*0.5ma_res*0.5kno_r*0.8

With a more conservative scenario of varying ma_qe, ma_res and kno_r by 15%, 15% and 10% respectively, introduce a bias of ±2%

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Summary & Ongoing work

Being fairly conservative, and assuming we know (pME-LE),K to 30% and a 10% systematic (8% in pME) due to cross-section shape uncertainty we get:

Need more pHE MC statistics to see if we can do something similar with the pHE data.

Need to look into cross-sections a bit more to understand better and get a realistic estimate of shape uncertainty.

o Empty markers are for statistical uncertainty only

o Horizontal lines are systematic limits.

from +, LE

from +, pMEpreliminary

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Backup

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1x1019 POT, no systematics

68.27% 90 %

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2.5x1019 POT, no systematics

68.27% 90 %

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5x1019 POT, no systematics

68.27% 90 %

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7.5x1019 POT, no systematics

68.27% 90 %

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1.0x1020 POT, no systematics

68.27% 90 %

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from -,K- from -,K-

from + from +

pME

pME LE

LE

Effect of simultaneously decreasing ma_qe, ma_res and kno_r (all) in the “true” data ( normal, with systematic):

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When simultaneously increasing parameters:

Introduce the “success” parameters:

sucLE =#antineutrinos from + predicted by fit, LE

#antineutrinos from + in fake data, LE

sucME =#antineutrinos from + predicted by fit, pME

#antineutrinos from + in fake data, pME

Found the right result to 2.3% !

“real” data

fit

from + from +

pME LEObserved no dependence with POT

2.5x1019 POT

2.5x1019 POT

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Now simultaneously scale down ma_qe, ma_res and kno_r (all) by 50%, 50% and 20% respectively:

effect in total cross-section

Fit gives, at 2.5x1019 POT:

Got it right to ~10%:

“real” data

fit

Observed almost no

dependence in POT

(see backup)

2.5x1019 POT

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CS systematics (ma_qe + ma_res down by 50%, kno_r down by 20%)

1x1019 POT

5x1019 POT

7.5x1019 POT

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1x1020 POT

CS systematics (ma_qe + ma_res up by 50%, kno_r up by 20%)

1x1019 POT

5x1019 POT

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7.5x1019 POT

1x1020 POT

CS systematics (ma_qe + ma_res up/down by 15%, kno_r by 10%)

2.5x1019 POT

ma_qe*0.85ma_res*0.85kno_r*0.9

ma_qe*1.15ma_res*1.15kno_r*1.1