1

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

David Jaffe and Pedro Ochoa

June 14th 2007

Reminder Updated Statistical error Horn 1 systematics Summary

2

Reminder

x parLE(+)pHE

(,K)pHE-(,K)LE

x parHE(+)LE

Procedure: - Take pHE-LE difference. Correct for

- Fit using MC shapes. Scale (+)LE and (+)pHE by parameters parLE and parHE.

Previous study (doc-2909) showed that pHE background is not big concern.

Main systematics associated with this measurement: C=(,K)pHE-(,K)LE correction. Background in nubar selection.

But the previous assessment of C was too pessimistic and done with too few statistics, so it is redone here.

3

Update on statistical error

Previous study (doc-2783) assumed 2.0x1019 POT of pHE data and a statistical error of ~13% in the measurement was quoted.

But more precisely, the pHE data taken after the 2006 shutdown corresponds to 1.6x1020 POT. So repeated the fit with this number:

New statistical error in (+)LE is 15%.

90% C.L.

68.3% C.L.

4

Horn 1 systematics

How well can we determine C = (,K)pHE- (,K)LE?

So obtained ratios of spectra with systematics over nominal spectra using gnumi:

Ex: horn1 current increase by 2% in pHE

neutrino beam

Good agreement with pbeam

Systematics considered are:

horn 1 offset 1.0 mm

horn current offset 1%

Target displacement 1cm

Work by David suggests C mostly affected by horn1 & target geometry, as one would expect (minos-doc-2841)

Obtained gnumi ratios are shown in the next 5 slides.

5

Horn current -1%

le010z185i le250z200i

nominalwith systematic

(,K-) (,K-)

(+)(+)

6

Horn current +1%

le010z185i le250z200i

nominalwith systematic

(,K-)(,K-)

(+)(+)

7

Horn offset by 1mm

le010z185i le250z200i

nominalwith systematic

(,K-)

(+)

(,K-)

(+)

8

Target in LE position -1cm

le010z185i

(,K-)

nominalwith systematic

(+)

9

Target in LE position +1cm

le010z185i

(,K-)

nominalwith systematic

(+)

10

Converted these ratios to reconstructed energy using the ntuples:

Ex: target position increased by 1cm in LE

Convert to Ereco

)(),(

),(

185010

185011reco

izle

izle EKv

Kv

Used these ratios(Ereco) to scale the spectra in our feasibility study and obtain systematic shifts.

Nominal spectra are used to do the fit which contains spectra including these systematics.

Infinite MC and LE data statistics are assumed.

(no events in first bin)

)(),(

),(

185010

185011true

izle

izle EKv

Kv

11

Example: Horn offset by 1mm

LEpHE KvKv ),(),(

Systematics:

Results of fit:

with systematicsnominal

with systematicsresult of fit

pHE-LE corrected for background and nominal C

Bias of 3%

(+) pHE

Bias of 3%

(+) LE fit

12

Summary of biases in measurement:

Also need to add the error associated with hadron production.

Horn I -1% Horn I +1% Horn offset 1mm LE Target -1cm LE Target +1cm

Bias in parLE -15% -9% 3% 1% 1%

Bias in parHE -14% -14% 3% -6% -6%

This assumed same horn conditions for pHE and LE running (except for target displacement). If that is not the case need to work with other combinations:

Horn I -1% Horn I +1% Horn offset 1mm

Applying systematics to LE beam only

Bias in parLE -4% -5% 6%

Bias in parHE -6% -9% 6%

Applying systematics to pHE beam only

Bias in parLE -10% -3% -3%

Bias in parHE -9% -5% -2%

13

The statistical error of the measurement with 1.6x1019 POT of pHE data is ~15%.

Summary & Ongoing work

Measurement of (+)pHE is more affected by horn1 & target systematics than (+)LE. Fortunately we don’t care.

Main sources of systematic errors seem to be under control.

Next step: carry out the measurement

14

Backup

15

Horn current -1%

LEpHE KvKv ),(),(

Systematics:

Results of fit:

with systematicsnominal

with systematicsresult of fit

pHE-LE corrected for background and nominal C

Bias of -14%

(+) pHE

Bias of -15%

(+) LE fit

16

Horn current +1%

LEpHE KvKv ),(),(

Systematics:

Results of fit:

with systematicsnominal

with systematicsresult of fit

pHE-LE corrected for background and nominal C

Bias of -14%

(+) pHE

Bias of -9%

(+) LE fit

17

Target -1cm

LEpHE KvKv ),(),(

Systematics:

Results of fit:

with systematicsnominal

with systematicsresult of fit

pHE-LE corrected for background and nominal C

Bias of -6%

(+) pHE

Bias of 1%

(+) LE fit

18

Target +1cm

LEpHE KvKv ),(),(

Systematics:

Results of fit:

with systematicsnominal

with systematicsresult of fit

pHE-LE corrected for background and nominal C

Bias of -6%

(+) pHE

Bias of 7%

(+) LE fit