March 30, 2006 1

Beam measurement with -Update -

David Jaffe & Pedro Ochoa

e

1) Reminder of proposed technique2) Use of horn-off data3) Use of horn2-off data?4) Effect of correcting for KL3

branching fractions and matrix elements

5) Summary & Ongoing work

March 30, 2006 2

1) Brief reminder

Concept: Measurement of low energy can be used to constrain the flux, since:e

ee

So look for whose father is a :

LE010185 carrot MC

This is what we are trying to measure

True energy of true at the ND

No from above this energy (Ecut)

Ecut

March 30, 2006 3

The most critical aspect of this measurement lies in the uncertainty of the C factor. (doc-1663, doc-1605)

The technique is the following:

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2) Use of Horn-off data

We made a first pass at C by studying its energy dependence: C(E).

So the procedure we followed was to:

Step 1) Calculate C(E) by comparing horn-off data and MC.

Step 2) Test C(E) on the horn-on data and MC for E > Ecut=10GeV.

Assumption: C(E) is the same for horn-off and horn-on data. This may actually be true if the differences between data and MC lie only in things that affect both situations (horns on & off) the same, like cross-sections and/or efficiencies.

How? Horn-off data gives us a direct handle:

Horn Off

no mu+

March 30, 2006 5

Step 1: Obtaining C(E) from horn-off data

First, two words on antineutrino selection:

● Selected events that satisfy some “basic” cuts:

At least 1 trackTrack passes fitUVasym < 6 / ndf < 20

2● Used “NuBar-PID” cut at 0.27 (ref. doc-1657):

Evaluating the selection on the horn-off MC gives 94.6% purity and 61.2% overall efficiency.

Horn-off MC

● Selected events in fiducial volume: 1<vtxz<5 & vtxr < 1.0m

Background composition

March 30, 2006 6

Horn-off data and MC comparison for antineutrinos:

● Used all available MC and data (2.77e18 POT, taken in February). MC was scaled to the data.

● Uncertainty is dominated by data statistics.

The right plot is our estimate of C(E). Step 2 is to test it !

DataMC

data/MC

Horn-off Horn-off

Please note that (ref. slide 3) and therefore that,

with infinite MC statistics, we have

MCEcut

L LLdEECC /)(0

027.0/1/ offhorn

LL LCC

March 30, 2006 7

Step 2: Testing C(E) in horn-on data

● Used same cuts as for horn-off data. Evaluation in horn-on MC gives 86.6% purity and 61.2% efficiency (including all cuts).

● Checked efficiency and purity as a function of energy to make sure that we are not affected by background at high energies (E > Ecut)

Horn-on MC

Background composition

March 30, 2006 8

● Used 1.9e19 POT of R1.18.2 data (January 2006). MC was scaled to the data.

● Observe similar deficit of MC with respect to data, like in the horn-off case.

DataMC

data/MC

Horn-on Horn-on

March 30, 2006 9

Tried 3 different approaches when scaling the MC:

Before scaling

DataMC

DataScaled MC

1) 5th degree pol.

2) 2 constants

DataScaled MC

3) Bin by bin

DataScaled MC

Ratios of data & scaled MC in next slide…

Horn-on

Horn-onHorn-off

March 30, 2006 10

In order to evaluate this for the 3 “fits” took the ratio of data/scaled MC:

1) 5th degree pol.

2) 2 constants 3) Bin by bin

WITHOUT SCALING

Horn-on

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We observe that:

● The 3 fits perform similarly at E < Ehigh ~ 16 GeV and the results are encouraging in that region.

● Our assumption that cannot be said to hold beyond Ehigh ~ 16 GeV.

● C(E) seems to be consistent with a constant from Ecut < E < Ehigh. This suggests the following methods for estimating C:

onhornoffhorn ECEC )()(

i) Estimate C = CH for the horn-on or horn-off data/MC:

where H denotes events with Ecut < E < Ehigh.

ii) Similarly, estimate CL with the horn-off data:

where L denotes events with 0 < E < Ecut.

iii) The degree of agreement between the 3 estimates (CH (on), CH (off) and CL (off)) provides an estimate of the systematic uncertainty in C with a statistical uncertainty of a few percent from the horn-off data statistics of 2.77e18 POT.

MCL LLC /

MCH HHC /

March 30, 2006 12

Normal Horn-2 OFF

3) Horn-2 OFF Flux Generation

Vertical units are flux per m2 per 5e5 POT.

● Idea was brought up by Milind that the mu+ may be getting focused mainly by the second horn.

● If that is the case, horn2-off data can be an extra tool for constraining C(E).

● In order to answer this, generated 1e7 POT of horn2-off flux:

What’s this?

March 30, 2006 13

NormalHorn-2 off

NormalHorn-2 off

component all other components (π,K)

The mu+ and non-mu+ components:

● It seems that the second horn focuses about ~3/5 of the mu+, but the rest is done by the first horn. This is less than we expected.

● The spectrum’s disruption is too severe for the non-mu+ components to use this data.

March 30, 2006 14

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4) Corrections for Kl3 matrix elements and branching fractions

● In doc-1652, Stan noted that Kl3 matrix elements were not implemented

correctly in gnumi. He also notes that the Ke3 branching fractions should byincreased by 1.051 (K0L) and 1.064(K+) to take into account the latestmeasurements: PRL93 (2004)181802 & PRL91(2003) 261802, respectively

● Implications of correcting for the Kl3 ME and Br were investigated for themeasurement of the flux from decays as well as the flux.

March 30, 2006 15

Example of correcting gnumi V15 for Kl3 matrix element

‘correct ME’ is not exactly as in doc-1652 but very nearly

gnumi‘correct ME’

Middle:fitted correction factor to ratio

Top: solid line=gnumi, dashed=‘correct ME’

Bottom: gnumi after correction

March 30, 2006 16

Negligible systematic effect of Kl3 corrections on C(E) and method to extract the flux from

O(5%) effect on totale flux of corrections for Kl3 Br

and ME_

March 30, 2006 17

Summary & Ongoing Work Preliminary check with horn-off data is encouraging:

The hypothesis that C(E) is the same for horn-on and horn-off seems verified, at least for the region Ecut < E < Ehigh

The proposed method for determining C assumes it to be a constant that can be extracted from horn-on or horn-off data/MC. Comparison of C from the different data sets will provide an estimate of the systematic uncertainty in C.

Need to take NC and neutrino bkgd into account in estimation of C. It seems that the second horn is not the only one to focus the +. This

combined with the fact that the spectrum is severely distorted make horn2-off running unappealing for this analysis.

Kl3 corrections do not appear to have significant impact on extraction of component of flux. There appears to be a modest effect on the beam e flux. Need corrected gnumi (or equivalent) for definite conclusions.

Improving the purity of the low energy sample is difficult. NuBarPID is a good first step. Currently investigating if we can exploit available track and event information to improve purity . (see Justin Evan’s doc-1682)

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March 30, 2006 18

BackupNuBar-PID pdfs are:

nunubar

March 30, 2006 19

Side note: story is a bit different for neutrinos

DataMC

● Used same data sample as previous slide. MC was scaled to 2.77e18 POT

● Used same selection criteria, but with NuBar-PID < 0.27

data/MC

Horn-off Horn-off

March 30, 2006 20

Backup

DataMC

data/MC

● Used 1.9e18 POT of R1.18.2 data (January 2006). MC was scaled to the data.

Horn-on data and MC for neutrinos:

March 30, 2006 21

Effect of corrections to Kl3 Br and ME to ND flux energy spectra up to

60 GeV