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Measurement of the off-axis NuMI beam with MiniBooNE. Zelimir Djurcic Columbia University. Outline of this Presentation Off-axis Neutrino Beam NuMI flux at MiniBooNE MiniBooNE Detector and Reconstruction CC n m Sample NC p 0 Sample CC n e Sample.

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Zelimir djurcic columbia university

Measurement of the off-axis NuMI beam with MiniBooNE

Zelimir Djurcic

Columbia University

  • Outline of this Presentation

  • Off-axis Neutrino Beam

  • NuMI flux at MiniBooNE

  • MiniBooNE Detector and Reconstruction

  • CC nm Sample

  • NC p0 Sample

  • CC ne Sample

Brookhaven National Lab Seminar, 1/17/08



MiniBooNE Motivated the LSND Experiment Result

LSND observed a (~3.8) excess of anti-e events in a pureanti- beam: 87.9 ± 22.4 ± 6.0 events

In SM there are

only 3 neutrinos

 Models developed with 2 sterile ’s


Result of the MiniBooNE Oscillation Search

reconstructed neutrino energy bin (MeV)

200-300 300-475 475-1250

data 375 369 380

total background284 ± 25 274 ± 21 358 ± 35

Excess 91 ± 30 95 ± 27 22 ± 40

No Oscillation Signal Found!

MiniBooNE Data Shows Low Energy Excess!


NuMI Beam

MINOS Experiment

L~700 km

E~2-5GeV

  • 120 GeV protons ~ 3xE13/pulse.

  • Primarily for the MINOS long baseline experiment.

However, the NuMI beam points in the direction of MiniBooNE as well.


Off-axis Beam

On-axis, neutrino energy more tightly related to hadron energy.

Off-axis, neutrino spectrum is narrow-band and ‘softened’.

Easier to estimate flux correctly: all mesons decay to same energy .

 Detector

First Proposed

by BNL-E889

Target

Decay Pipe

Horns


Future off-axis Neutrino Experiments

On-axis beam

Off-axis beam

Use off-axis trick for optimized ->e search.

NOvA:

  • NuMI off-axis beam

  • 810km baseline

  • 14.5mrad; E~2GeV

T2K:

  • J-PARC 50GeV proton beam

  • Use SK as Far detector 295km away

  • 35 mrad; E~0.6GeV


NuMI beam and MiniBooNE detector

NuMI events (for MINOS) detected in MiniBooNE detector!

MiniBooNE

q

p, K

p beam

Decay Pipe

MiniBooNE detector is 745 meters downstream of NuMI target.

MiniBooNE detector is 110 mrad off-axis from the target

along NuMI decay pipe.


Analysis Motivation

Observation and analysis of an off-axis beam. Measurement of /K components of the NuMI beam.The NuMI beam provides MiniBooNE with an independent set of neutrino interactions.Enables a comparison of the Booster Neutrino Beam (BNB) with the NuMI neutrino beam (off axis):-Similar energy spectrum.-Proton target is further away (~746 m vs. 550 m)-Very different background composition.-Rich in e flux →can study e reactions in greater detail.


Joint collaboration between MiniBooNE and NuMI

Beam Information and Neutrino Fluxes at MiniBooNE are provided by the MINOS collaboration (BNL, U Texas).

Analysis of MiniBooNE data performed by the MiniBooNE collaboration.


Opportunity to demonstrate off-axis technique.

Known spectral features from , K decays.

Expected energy spectra is within MiniBooNE energy acceptance.

NuMI off-axis beam at MiniBooNE detector

stoppedp+

stopped K+

p+

K+


NuMI off-axis beam produces strong fluxes in both µ and e flavors.

The e ’s are helpful to study the MiniBooNE detector.

Provide a new setting for oscillation studies.

Rates:

NuMI off-axis(at MB) e ~6%

NuMI on-axis e ~1%

BNB on-axis e ~0.5%

NuMI as a “e Source”

stopped K+

m+

K+


Extensive experience with MINOS data.

MINOS acquired data sets in variety of NuMI configurations.

Tuned kaon and pion production (xF,pT) to MINOS data.

NuMI Neutrino Spectrum is “Calibrated”

MINOS nm

MINOS nm

  • Same parent hadrons produce neutrinos seen by MiniBooNE

  • Flux at MiniBooNE should be well-described by NuMI beam MC?

D.G. Michael et al, Phys. Rev. Lett. 97:191801 (2006)

D.G. Michael et al, arXiv:0708.1495 (2007)


Decays of hadrons produce neutrinos that strike both MINOS and MiniBooNE.

Parent hadrons ‘sculpted’ by the two detectors’ acceptances.

Plotted are pT and p|| of hadrons which contribute neutrinos to MINOS (contours) or MiniBooNE (color scale).

Two Views of the Hadron Decays

MiniBooNE

MiniBooNE

MINOS

MINOS


Higher energy neutrinos mostly from particles created in target.

Interactions in shielding and beam absorber contributes in lowest energy bins.

Plots show where the parent was created.

Neutrino Origin Along NuMI Beam Line

ne

nm

MiniBooNE

diagram not to scale!


Neutrino sources along NuMI beamline in target.

Higher energy neutrinos mostly from particles created in target.

Interactions in shielding and beam absorber contributes in lowest energy bins.



Flux Uncertainties in target.

Focusing uncertainties are negligible.

Uncertainty is dominated by production of hadrons.

  • off the target (estimated from MINOS tuning).

  • in the shielding (estimated in gfluka/gcalor).

  • in beam absorber (estimated in gfluka, 50% error assigned).

MINOS

Tuning

stopped mesons excluded in this plot


MiniBooNE in target.

(Booster Neutrino Experiment)

becomes

An off axis neutrino experiment

using Main Injector


NuMI Beam and MiniBooNE Detector in target.

NuMI events (for MINOS) detected in MiniBooNE detector!

MiniBooNE

q

p, K

p beam

Decay Pipe

MiniBooNE Detector:

12m diameter sphere

950000 liters of oil(CH2)

1280 inner PMTs

240 veto PMTs

Main trigger is an accelerator signal indicating a beam spill.

Information is read out in 19.2 s interval covering arrival of beam.


Detector Operation and Event reconstruction in target.

No high level analysis needed to see neutrino events

Events in DAQ window:no cuts

Removed cosmic ray muons:

PMT veto hits < 6

Removed cosmic ray muons

and -decay electrons:

PMT veto hits < 6 and

PMT tank hits > 200

6-batch structure of MI

about 10 s duration

reproduced.

Backgrounds: cosmic muons and decay electrons

->Simple cuts reduce non-beam backgrounds to ~10-5


Detector Operation and Event reconstruction in target.

The rate of neutrino candidates was constant: 0.51 x 10-15 /P.O.T.

Neutrino candidates counted with:PMT veto hits < 6 and PMT tank hits > 200

The data set analyzed here: 1.42 x 1020 P.O.T.

We have a factor two more data to analyze!


Particle Identification in target.

Čerenkovrings provide primary means of identifying

products of  interactions in the detector

m

candidate

nmn m- p

electroncandidate

nen  e-p

p0

candidate

nmp nm pp0

n n

p0→ gg


Events from NuMI detected at MiniBooNE in target.

Flux

Event

rates

NuMI event composition at MB

-81%, e-5%,-13%,e-1%

Neutrino interactions at carbon simulated by

NUANCE event generator: neutrino flux

converted into event rates.

Event

rates

CCQE 39%

CC + 26%

NC 0 9%


Analysis Algorithm in target.


Event Reconstruction in target.

The tools used in the analysis here are developed and verified

in MiniBooNE oscillation analysis of events from Booster beam.

Details:

Phys. Rev. Lett. 98, 231801 (2007),

arXiv:0704.1500 [hep-ex]

arXiv:0706.0926 [hep-ex]

Accepted for publ. by Phys.Rev.Lett.

and

Event selection very similar to what was used in MiniBooNE analyses.

To reconstruct an event:

-Separate hits in beam window by time into sub-events of related hits.

-Reconstruction package

maximizes likelihood of

observed charge and time

distribution of PMT hits to

find track position, direction

and energy (from the

charge in the cone) for

each sub-event.


Analysis Method in target.

Uses detailed, direct reconstruction of particle tracks, and ratio of fit likelihoods to identify particles.

Apply likelihood fits to three hypotheses:

-single electron track

-single muon track

-two electron-like rings (0 event hypothesis )

Compare observed light distribution to fit prediction:

Does the track actually look like an electron?

Form likelihood differences using minimized –logL quantities: log(Le/L) and log(Le/L)

log(Le/L)<0-like events

log(Le/L)

log(Le/L)>0e-like events

Example from MiniBooNE

Oscillation Analysis.

e


in target. CCQE Analysis


Analysis of the in target. CCQE events from NuMI beam

e

 CCQE (+n +p) has a two “subevent” structure

(with the second subevent from stopped  ee)

Tank Hits

Cerenkov 1

e

12C

nm

Cerenkov 2

n

Scintillation

p

Event Selection:

Subevent 1:

Thits>200, Vhits<6

R<500 cm

Le/L < 0.02

Subevent 2:

Thits<200, Veto<6


Visible E of in target.: final state interactions in  CCQE sample

Log(Le/L)< 0.02

Total MC

nNnXp0

Beam ne

nmp m-D

nmn m-p

nmn m-np+

Other nm Events

Events

Events

Data

CCQE

Monte

Carlo

“other”

CC+

CCQE

CC+

PRELIMINARY

Visible energy in tank [GeV]

Data (stat errors only)

compared to MC prediction

for visible energy in the

tank.

This sample contains 18000 events

of which 70% are CCQE’s.


Compare in target. CCQE MC to Data:Parent Components

Beam MC tuned

with MINOS near

detector data.

Cross-section

Monte Carlo

tuned with MB

measurement of

CCQE pars MA

and .

p

K

PRELIMINARY

arXiv:0706.0926 [hep-ex]

Visible energy in tank [GeV]

MC is normalized to data POT number with no further corrections!


Compare in target. CCQE MC to Data:Parent Components

p

K

PRELIMINARY

Visible energy in tank [GeV]

Predicted Kaons are matching the data out of box!


Systematic Uncertainties in in target. CCQE analysis

To evaluate Monte Carlo agreement with the data need estimate

of systematics from three sources:

-Beam modeling: flux uncertainties.

-Cross-section model: neutrino cross-section uncertainties.

-Detector Model:describes how the light emits, propagates, and

absorbs in the detector (how detected particle looks like?).

Detector Model

Cross-section

Visible energy [GeV]

Visible energy [GeV]

Total

PRELIMINARY

Beam

PRELIMINARY

Visible energy [GeV]

Visible energy [GeV]


Add Systematic uncertainty to in target. CCQE Monte Carlo

p

Predicted Pions are

matching the data

within systematics!

K

 visible energy distribution

PRELIMINARY

Visible energy in tank [GeV]

K

p

Outgoing angular distribution

PRELIMINARY

Information about

incoming :wrt NuMI

target direction.

cos 


in target. CCQE sample: Reconstructed energy E of incoming 

Reconstructed EQE:fromElepton

(“visible energy”) and lepton angle

wrt neutrino direction

p

K

PRELIMINARY

Understanding of the beam demonstrated:

MC is normalized to data POT number !


Conclusion from in target. CCQE analysis section

This is the first demonstration of the off-axis principle.

There is very good agreement between data and Monte Carlo:the MC need not be tuned.

Because of the good data/MC agreement

in  flux and because the  and e

share same parents the beam MC can

now be used to predict:

e rate, and

mis-id backgrounds for a e analysis.


in target.e CCQE Analysis


Backgrounds to in target.e CCQE sample

e CCQE (+n e+p)

When we try to isolate a sample of ecandidates

we find background contribution to it:

-0 (0) and radiative  (N) events, and

-”dirt” events.

Therefore, before analyzing e CCQE we constrain the

backgrounds by measurement in our own data.


Among the e-like mis-ids, in target.0 decays which are boosted, producing 1 weak ring and 1 strong ring is largest source.

Analysis of 0 events from NuMI beam

g

+

p

p

p

g

p0

g

g

Strategy:Don’t try to predict the

0 mis-id rate, measure it!

Measured rates of reconstructed 0…

tie down the rate of mis-ids

g

+

0

p

p

 decays to a single photon:

with 0.56% probability:

What is applied to select 0s

Event pre-selection:

1 subevent

Thits>200, Vhits<600

R<500 cm

log(Le/L)>0.05(e-like) log(Le/L)<0(0-like)


Analysis of in target.0 events from NuMI beam: 0 mass

The peak is 135 MeV/c2

Data

Monte

Carlo

0

e



e appear to be well modelled.

This sample contains 4900 events of which 81% are 0 events: world second largest 0 sample!


Analysis of in target.0 events from NuMI beam: 0 mass

The peak is 135 MeV/c2

Data

Monte

Carlo

0

e



The 0 events are well modeled with

no corrections to the Monte Carlo!


Analysis of in target.0 events from NuMI beam: 0 momentum

Data

Monte

Carlo



0

e

PRELIMINARY

We declare good MC/Data agreement

for 0 sample going down to low mass

region where ecandidates are showing up!

Further

Cross

Check!


Analysis of in target.dirt events from NuMI beam

dirt

shower

- “Dirt” background is due to  interactions

outside detector. Final states

(mostly neutral current interactions)

enter the detector.

- Measured in “dirt-enhanced” samples:

- we tune MC to the data selecting a sample

dominated by these events.

-”Dirt” events coming from outside deposit only a fraction

of original energy closer to the inner tank walls.

  • -Shape of visible energy and event vertex distance-to-wall distributions are well-described by MC: good quantities to measure this background

  • component.


Selecting the in target.dirt events

log(Le/L)>0.05(e-like)

Ee <550 MeV

Distance-to-wall<250 cm

m<70 MeV/c2(not 0-like)

Event pre-selection:

1 subevent

Thits>200, Vhits<600

R<500 cm

Fits to dirt enhanced sample:

Uncertainty in the dirt rate is less than 20%.

Dirt sample

  • interactions

    in the tank

Events/bin

Events/bin

PRELIMINARY

We declare good MC/Data agreement for the dirtsample.

Dist-to-wall of tank along track [m]

Visible energy [GeV]


Analysis of the in target.e CCQE events from NuMI beam

e CCQE (+n e+p)

1 Subevent

Thits>200, Vhits<6

R<500 cm, Ee>200MeV

Likelihood cuts as the

as shown below

+

Ee>200MeV cut is appropriate to remove e contribution from the dump

that is hard to model.

Mass(0) cut

Likelihood e/ cut

Likelihood e/ cut

Signal region

Signal region

Cut region

Cut region

MC example plots here come from Booster beam MC

Cut region

Signal region

Visible energy [MeV]

Visible energy [MeV]

Visible energy [MeV]

Analysis of e events: do we see data/MC agreement?


Visible energy of in target.e CCQE events

Data

Monte Carlo

e

Other 

0

dirt

PRELIMINARY

Visible energy in tank [GeV]

Data = 783 events.

Monte Carlo prediction = 662 events.

Before we further characterize data/MC agreement we have to account for the systematic uncertainties.


Systematic Uncertainties in in target.e CCQE analysis

Detector Model

Cross-section

PRELIMINARY

Beam

Visible energy [GeV]

PRELIMINARY

Visible energy [GeV]

Total

Visible energy [GeV]

Visible energy [GeV]

“dirt” component of Xsec: 20% error; 0 component of Xsec: 25% error


in target.e CCQE events: e visible energy and angular distribution

K

e visible energy distribution

KL

PRELIMINARY

p

Visible energy in tank [GeV]

All 

All 

Outgoing e angular distribution

PRELIMINARY

cos e


in target.e CCQE sample:Reconstructed energy E of incoming 

Outgoing electron angular distribution

PRELIMINARY

All e

All 


Summary of estimated backgrounds vs data in target.e CCQE sample

Looking quantitative into low energy and high energy region:

EQE [MeV] 200-900 900-3000

total background 401±66 261±50

e intrinsic 311 231

 induced 90 30

NC 0 30 25

NC →N 14 1

Dirt 35 1

other 11 3

Data 498±22 285±17

Data-MC 9770 2453

Significance 1.40  0.45 

At this point systematic errors are large: we cannot saymuch about the difference between low and high-E regions.In the future we will reduce e CCQE sample systematics constraining it with our large statistics  CCQE sample.



We performed analyses of neutrinos from NuMI beam observed with MiniBooNE detector. The sample analyzed here corresponds to 1.42x 1020 protons on NuMI target.

We observed good description of the data by Monte Carlo

with both  CCQE and e CCQE sample: successful

demonstration of an off-axis beam at 110 mrad.

 CCQE sample demonstrated proper understanding of the

Pion and Kaon contribution to neutrino beam.

PRELIMINARY


In the future we will reduce with MiniBooNE detector. The sample analyzed here corresponds to 1.42x 10e CCQE sample systematics constraining it with our large statistics  CCQE sample.

The e CCQE sample will be compared to what we observed with Booster beam.

We are currently reprocessing and collecting more data

(expect about 3 x 1020 P.O.T. collected by now.)

These errors

will be reduced

PRELIMINARY


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