Zelimir Djurcic a and Zarko Pavlovic b

1
Analysis of ?? and ?e events from NuMI beamline
at MiniBooNE

• Zelimir Djurcic (a) and Zarko Pavlovic (b)
• Columbia University
• (b) University of Texas Austin

• 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

2
Analysis Motivation
Joint collaboration between MiniBooNE and
NuMI.Observation and analysis of an off-axis
beam. Measurement of ?/K components of the NuMI
beam.Check of nm CCQE and ne CCQE interactions
independent from Booster beam neutrinos.ne-rich
sample to study MiniBooNE reconstruction and
particle identification algorithms.Performing
physics analysis complementary to MinibooNE
analyses.
3
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.
4
The Woes of Knowing the n flux

• For wide-band() neutrino beams,
• Use MC simulation
• Particle production
• Focusing
• Measure in the detector
• Use some process with known cross section
• History has several examples of substantial
  corrections to these estimates
• ANL 12 B.C. in ZGS horn beam
• FNAL 15 B.C., 400GeV horn beam
• BNL E734, AGS horn beam
• Gargamelle, CERN PS beam

Borodovsky et al., Phys. Rev. Lett. 68, 274
(1992) (BNL E776 ) got flux correct, right out
of the box
() Narrow-band beams can more readily measure
fluxes directly
5
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 n.

n Detector
First Proposed by BNL-E889
q
Decay Pipe
Target
Horns
6
Future off axis experiments
On-axis beam
Off-axis beam

• Use off-axis trick for optimized nm?ne search

• NOvA
• NuMI off-axis beam
• 810km baseline
• 14.5mrad Enu2GeV

• T2K
• J-PARC 50GeV proton beam
• Use SK as Far detector 295km away
• 35 mrad Enu0.6GeV

7
NuMI Off-axis Beam at MiniBooNE

• Opportunity to demonstrate off-axis technique
• Known spectral features from p, K decays
• Expected energy spectra softened to within
  MiniBooNE acceptance

8
NuMI as a ne Source

• NuMI off-axis beam produces strong flux in both
  nm and ne flavors.
• The nes are helpful to study the MiniBooNE
  detector.
• Hopefully one can do some physics with a
  enhanced ne beam
• NuMI on-axis ne 1 NuMI off-axis ne 6BNB
  on-axis ne 0.5

stopped K
K
m
9
NuMI Spectrum is Calibrated

• Extensive experience with MINOS data
• MINOS acquired datasets in variety of NuMI
  configurations
• Tuned kaon and pion production (xF,pT) to MINOS
  data

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. 97191801
(2006) D.G. Michael et al, arXiv0708.1495 (2007)
10
Two views of the same decays

• 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)

MiniBooNE
MiniBooNE
MINOS
MINOS
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Neutrino Sources along NuMI beam
ne

• Higher energy neutrinos mostly from particles
  created in target

• Interactions in shielding and beam absorber
  contributes in lowest energy bins
• Colors indicate theorigin of ? parents

nm
MiniBooNE
diagram not to scale!
12
Flux Uncertainties

• 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
13
MiniBooNE
(Booster Neutrino Experiment)
becomes
An off axis neutrino experiment using Main
Injector
14
NuMI Beam and MiniBooNE Detector
NuMI events (for MINOS) detected in MiniBooNE
detector!
MiniBooNE
q
p beam
p, K
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.
15
Detector Operation and Event reconstruction
No high level analysis needed to see neutrino
events
Events in DAQ windowno cuts
Removed cosmic ray muons PMT veto hits lt 6
Removed cosmic ray muons and ?-decay
electrons PMT veto hits lt 6 and PMT tank hits gt
200
6-batch structure of MI about 10 ?s
duration reproduced.
Backgrounds cosmic muons and decay electrons
-gtSimple cuts reduce non-beam backgrounds to 10-5
16
Detector Operation and Event reconstruction
The rate of neutrino candidates was constant
0.51 x 10-15 /P.O.T. Neutrino candidates counted
withPMT veto hits lt 6 and PMT tank hits gt 200
The data set analyzed here 1.42 x 1020 P.O.T.
We have a factor two more data to analyze!
17
Particle Identification
Cerenkov rings provide primary means of
identifying products of ? interactions in
the detector
m candidate
nm n ? m- p
electron candidate
ne n ? e- p
p0 candidate
nm p ? nm p p0
n n
p0 ? gg
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Events from NuMI detected at MiniBooNE
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
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Analysis Algorithm
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Event Reconstruction
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),
arXiv0704.1500 hep-ex
arXiv0706.0926 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.
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Analysis Method
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?)lt0 ?-like events
log(Le/L?)
log(Le/L?)gt0 e-like events Example from
MiniBooNE Oscillation Analysis.
e
?
22
?? CCQE Analysis
23
Analysis of the ?? CCQE events from NuMI beam
?? CCQE (?n ? ?p) has a two subevent
structure (with the second subevent from stopped
?? ???e e)
Tank Hits
Cerenkov 1
e
?
12C
nm
Cerenkov 2
n
Scintillation
p
Event Selection
Subevent 1 Thitsgt200, Vhitslt6 Rlt500 cm
Le/L? lt 0.02
Subevent 2 Thitslt200, Vetolt6
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Visible E of ? final state interactions in ??
CCQE sample
Log(Le/L?)lt 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 CCQEs.
25
Compare ?? CCQE MC to DataParent 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
arXiv0706.0926 hep-ex
Visible energy in tank GeV
MC is normalized to data POT number with no
further corrections!
26
Compare ?? CCQE MC to DataParent Components
p
K
PRELIMINARY
Visible energy in tank GeV
Predicted Kaons are matching the data out of box!
27
Systematic Uncertainties in ?? 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 Modeldescribes 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
28
Add Systematic uncertainty to ?? 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 ??
29
?? CCQE sample Reconstructed energy E? of
incoming ?
Reconstructed E? QEfrom Elepton (visible
energy) and lepton angle wrt neutrino direction
p
K
PRELIMINARY
Understanding of the beam demonstrated MC is
normalized to data POT number !
30
Conclusion from ?? CCQE analysis section
This is the first demonstration of the off-axis
principle. There is very good agreement between
data and Monte Carlothe 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.
31
?e CCQE Analysis
32
Backgrounds to ?e CCQE sample
?e CCQE (?n ? ep)
When we try to isolate a sample of ?e
candidates 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.
33
Among the e-like mis-ids, ?0 decays which are
boosted, producing 1 weak ring and 1 strong
ring is largest source.
Analysis of ?0 events from NuMI beam
g
p0
g
?
g
?
StrategyDont 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 Thitsgt200,
Vhitslt600 Rlt500 cm
log(Le/L?)gt0.05 (e-like) log(Le/L?)lt0 (?0-like)
34
Analysis of ?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!
35
Analysis of ?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!
36
Analysis of ?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 ?e candidates
are showing up!
Further Cross Check!
37
Analysis of dirt events from NuMI beam

• - 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.

38
Selecting the dirt events
log(Le/L?)gt0.05 (e-like) Ee lt550 MeV
Distance-to-wall lt250 cm m?lt70 MeV/c2 (not
?0-like)
Event pre-selection 1 subevent Thitsgt200,
Vhitslt600 Rlt500 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 dirt
sample.
Dist-to-wall of tank along track m
Visible energy GeV
39
Analysis of the ?e CCQE events from NuMI beam
?e CCQE (?n ? ep)
1 Subevent Thitsgt200, Vhitslt6 Rlt500 cm, Eegt200MeV
Likelihood cuts as the as shown below

Eegt200MeV cut is appropriate to remove ?e
contribution from the dump that is hard to model.
Likelihood e/? cut
Likelihood e/? cut
Mass(?0) 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?
40
Visible energy of ?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.
41
Systematic Uncertainties in ?e CCQE analysis
Detector Model
Cross-section
PRELIMINARY
Beam
Visible energy GeV
Visible energy GeV
PRELIMINARY
Total
Visible energy GeV
Visible energy GeV
dirt component of Xsec 20 error ?0 component
of Xsec 25 error
42
?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
43
Outgoing electron angular distribution
?e CCQE sample Reconstructed energy E? of
incoming ?
All ?e
PRELIMINARY
All ??
44
Summary of estimated backgrounds vs data ??e CCQE
sample
Looking quantitative into low energy and high
energy region
E? QE MeV 200-900 900-3000
total background 40166
26150 ?e intrinsic
311 231 ?? induced
90 30
NC ?0
30 25
NC ??N? 14 1
Dirt 35
1 other
11 3
Data 49822
28517 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.
45
Summary and Future Steps
46
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
47
In the future we will reduce ?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
48
Backups
49
Neutrino Sources along NuMI beam

• Higher energy neutrinos mostly from particles
  created in target
• Interactions in shielding and beam absorber
  contributes in lowest energy bins

50
NuMI Off-axis Beam at MiniBooNE

• 1st opportunity to demonstrate off-axis technique
• Known spectral features from p, K decays
• Expected energy spectra softened to within
  MiniBooNE acceptance

stopped p
stopped K
stopped K-
51
NuMI as a ne Source

• NuMI off-axis beam produces strong flux in both
  nm and ne flavors.
• The nes are helpful to study the MiniBooNE
  detector.
• Hopefully one can do some physics with a pure
  ne beam (only a few past proposals on how to
  build such a beam).

52
Detector Modeling
Detector (optical) model defines how light of
generated event is propagated and detected in
MiniBooNE detector
Sources of light Cerenkov (prompt, directional
cone),and scintillationfluorescence of oil
(delayed, isotropic)
Propagation of light absorption, scattering
(Rayleigh and Raman) and reflection at walls, PMT
faces, etc. We have developed 39-parameter
Optical Model.
Strategy to verify model External Measurements
emission, absorption of oil, PMT
properties. Calibration samples Laser flasks,
Michel electrons, NC elastic events. Validation
samples Cosmic muons (tracker and cubes).
53
Low energy ? cross sections
Imperative is to precisely predict signal bkgd
rates for future oscillation experiments We
need data on nuclear targets! (most past data on
H2, D2)
MINOS, NuMI
K2K, NOvA
MiniBooNE, T2K
Super-K atmospheric ?
54
Cross-section uncertainties in the analysis
MAQE, elosf 6, 2 (stat bkg only) QE ?
norm 10 QE ? shape function of
E? ??e/?? QE ? function of E? coh/res
ratio NC ?0 norm 25 ? ? N??rate 7
BF EB, pF 9 MeV, 30 MeV ??s
10 MA1? 25 MAN?
40 DIS ? 25
Determined from MiniBooNE ?? QE data
MiniBooNE data Other Experiments
Determined from other experiments
55
Energy Calibration
We have calibration sources spanning wide range
of energies and all event types !
Michel electrons from ? decay provide E
calibration at low energy (52.8 MeV), good
monitor of light transmission, electron PID
12 E res at 52.8 MeV
?0 mass peak energy scale resolution at medium
energy (135 MeV), reconstruction
cosmic ray ? tracker cubes energy
scale resolution at high energy (100-800 MeV),
cross-checks track reconstruction
provides ? tracks of known length ? E?
56
Are the neutrinos coming from the target?
Geological Survey ?Y24.80,?XZ87.50.
57
Are the neutrinos coming from the target?
58
Are the neutrinos coming from the target?
Measurement of exiting muons from neutrino
interaction ?Y24.40,?XZ87.250.
59
?? CCQE events Q2 distribution
60
PID cuts efficiency for ?e CCQE events
Precuts
Log(Le/L?) Log(Le/L?) invariant mass
61
Rejecting ?-like events
log(Le/L?)gt0 favors electron-like hypothesis
Separation is clean at high energies where
muon-like events are long.
This does not separate e/?0 as photon conversions
are electron-like.
62
Rejecting ?0-like events
63
?0 mass in ?0 momentum bins
?0 momentum bins are 0ltP? lt0.2, 0.2ltP?
lt0.3, 0.3ltP? lt0.4, 0.4ltP? lt0.5, 0.5ltP? lt0.6,
0.6ltP? lt0.8, 0.8ltP? lt1.0, 1.0ltP? lt1.2, 1.2ltP?
lt1.6,and P? gt1.6GeV/c2
64
?0 momentum
In an analysis of neutral ?0 sample from
Booster beam we used this distribution to tune MC
to data no need to do it here.
65
Selecting the dirt events
Event pre-selection 1 subevent Thitsgt200,
Vhitslt600 Rlt500 cm
log(Le/L?)gt0.05 (e-like) Ee lt550 MeV
Distance-to-wall lt250 cm m?lt70 MeV/c2 (not
?0-like)
True ? energy
66
Does the dirt sample constrain events in ?e CCQE
sample?
Lets use ?e CCQE cuts dirt cuts this is the
overlap
cos ?e
67
Visible energy of ?e CCQE events systematic
uncertainty
Visible energy in tank GeV
Visible energy in tank GeV
68
Visible energy of ?e CCQE events with dirt cuts
Visible energy in tank GeV
Visible energy in tank GeV
69
cos?e and Ee of ?e CCQE events with dirt cuts
cos ?e
70
We have an indication of data over MC excess
below 0.9 GeV with 1.4? significance could it be
due to a signal?

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