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MiniBooNE
Hirohisa A. TanakaPrinceton University
Weak Interactions and Neutrinos Workshop 2003 (Lake Geneva, WI)
H. A. Tanaka – WIN 2003 1
Overview:
BooNE: Booster Neutrino Experiment
• The Beam
• The Detector and Calibration Devices
• Beam Data
• Conclusions
See Andrew Bazarko’s talk for oscillation discussion
H. A. Tanaka – WIN 2003 2
BooNE is for Booster:
The Fermilab Booster:
• 8 GeV protron synchrotron
Provides protons for:
• MiniBooNE
• Main InjectorAntiprotons, Tevatron
120 GeV Fixed Target, NuMI
MiniBooNE beamline
• 1.6 µsec p batch on Be
• Electromagnetic Horn (+)Focus 2ndary particles
• 50 m decay region π+ → µ+νµ
Design Performance
• 5× 1012 p/batch at 5 Hz
• 5× 1020 POT/year
H. A. Tanaka – WIN 2003 3
BooNE is for Neutrino:
10-5
10-4
10-3
10-2
10-1
0 0.5 1 1.5 2 2.5 3E n (GeV)
Frac
tion
of n
m F
lux
/ 0.1
GeV
nm Fluxne Flux
PRELIMINARY Predicted Neutrino Flux:
• Sanford-Wang parameterization:Global fit to p− Be π+ data
• Kaons from MARS
• Dominant Processes at ∼ 1 GeV:
• CC Quasi-elastic
• NC Elastic
• Resonance
Comparable energies to Off-Axis proposals
H. A. Tanaka – WIN 2003 4
BooNE is for Experiment:
MiniBooNE:
• 540 m from target
• 6.1 m radius sphereMineral oil target
• Optical barrier at 575 cm
• Inner “Tank” region
• Outer Veto region
• 1280 8” PMTs in Tank (10%)
• 240 8” PMTs in Veto
Detect neutrino interactions via C and Scintillation light
H. A. Tanaka – WIN 2003 5
Calibration Devices:
Muon Tracker + Cubes:
• Muon Hodoscope above detector
Four layers of scintillator bars
Independent track reconstruction
• Scintillator Cube
Seven cubes throughout detector
Independent vertex reconstruction
Stopping muons with precisely known pathlength
Laser Flask:
• Prompt monochromatic light
Pulsed via 397 and 438 nm laser
• Varying intensity
sub-1 p.e. → multi p.e.
• Varying location
Four flasks + bare fiber in detector.
Study PMT hit reconstruction
Study oil optical properties.
H. A. Tanaka – WIN 2003 6
The CollaborationUniversity of Alabama Y.Liu, I.Stancu
Bucknell University S.Koutsoliotas
University of Cincinnati E.Hawker, R.A.Johnson, J.L.Raaf
University of Colorado T.Hart, R.H. Nelson, E.D.Zimmerman
Columbia University A. Aguilar-Arevalo, L.Bugel, J.M.Conrad, J.Formaggio,
J.Link, J.Monroe, D. Schmitz, M.H.Shaevitz,
M.Sorel, G.P. “Sam” Zeller
Embry Riddle Aeronautical University D.Smith
Fermi National Accelerator Laboratory L.Bartoszek, C.Bhat, S.J.Brice, B.C.Brown, D.A.Finley,
B.T.Fleming, R.Ford, F.G.Garcia, P.Kasper, T.Kobilarcik,
I.Kourbanis, A.Malensek, W.Marsh, P.Martin, F.Mills,
C.Moore, P.Nienaber, E.Prebys, A.D.Russell,
P.Spentzouris, R.Stefanski, T.Williams
Indiana University D.C. Cox, J.A. Green, H.Meyer, R.Tayloe
Los Alamos National Laboratory G.T.Garvey, C. Green, W.C.Louis, G.McGregor,
S. McKenney, G.B.Mills, V.Sandberg, B.Sapp, R.Schirato,
R.Van de Water, N. Walbridge, D.H.White
Louisiana State University R.Imlay, W.Metcalf, M.Sung, M.Wascko
University of Michigan J.Cao, Y.Liu, B.P.Roe
Princeton University A.O.Bazarko, P.D.Meyers, R.B.Patterson,
F.C.Shoemaker, H.A.Tanaka
H. A. Tanaka – WIN 2003 7
Neutrino Data:
• Inclusive distributions
• Charged Current quasi-elastic scattering
• Neutral Current elastic scattering
• Neutral Current π0 production
∼ 1× 1020 protons-on-target analyzed
Comparisons to Monte Carlo are relatively normalized.
See Andrew Bazarko’s talk for discussion on Oscillation Analysis
H. A. Tanaka – WIN 2003 8
Neutrino Events!
sec)mAverage Tank Time (4 6 8 10 12 14 16 18
sec
mE
vent
s/0.
2
0
5000
10000
15000
20000
25000
All Events
Event time is calculated from “subevent”:First cluster of > 10 hits contiguous in time.
Beam Events:
• Arrive in 1.6 µsec window[4.6, 6.2] µsec
• Event time:From average of tank hits
• Excess is clearly seen
Backgrounds:
• Cosmic Muons
• Decay electrons
Backgrounds can be eliminated with multiplicity cuts (Tank/Veto PMT Hits).
H. A. Tanaka – WIN 2003 9
Neutrino Events!
Veto cut eliminates cosmic µ:
• Single MIP ∼ 18 hitsMost are throughgoing.
• Eliminate with NV ETO < 6
Remaining Background:
• Decay electrons (< 200 Hits)Muon enters before window.
• Env./Noise (< 20 Hits) sec)mAverage Tank Time (4 6 8 10 12 14 16 18
sec
mE
vent
s/0.
2
0
1000
2000
3000
4000
5000
6000<6VETON
Remaining background eliminated with Tank Multiplicity cut.
H. A. Tanaka – WIN 2003 10
Neutrino Events!
sec)mAverage Tank Time (4 6 8 10 12 14 16 18
sec
mE
vent
s/0.
2
0
500
1000
1500
2000
2500
3000>200TANK<6, NVETON
Remaining background eliminated with NTANK > 200. S/B > 1000
∼ 150K “clean” candidates in ∼ 1.5× 1020 protons-on-targetApproximately 50%/50% CC Quasi-elastic/Single Pion
H. A. Tanaka – WIN 2003 11
νµ Quasi-Elastic Events:
Size of Ball = Charge
Red = early, Blue = late
nm m-
n p
W
CX
νµ + n → µ− + p
• Abundant (40%)
• Simple topology:one muon-like ringproton rarely above C threshold
• Obtain Eµ, θµ from fit
H. A. Tanaka – WIN 2003 12
Selecting Quasi-Elastic Events:
Selection
• Single µ-like ring, decay electron
• Ring profile/sharpness
• Time of hits
• Minimize energy bias
→ Fisher discriminant
• MC indicates ∼ 88% puritySome background is irreducible
• Relatively well-known cross section
→ cross-check of flux prediction∼ 28K CC QE candidates
0
0.1
0.2
-1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1cos qm
Frac
tion
of E
vent
s / (1
/15)
Data
Monte Carlo
0
0.1
0.2
-1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1cos qm
Frac
tion
of E
vent
s / (1
/15)
Data
Monte Carlo
H. A. Tanaka – WIN 2003 13
Neutrino Energy:0
(GeV)GenmnE
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6
Gen mn
/Emn
ED
0
0.1
0.2
0.3
0.4
0.5
0
2
GennEb + 2 = a
2 Gen
nEn ED
a = 3.788008e-02b = 8.364264e-02
PRELIMINARYMonte Carlo-simulatednm CC quasi-elastic events
Kinematic Reconstruction:
Assume:νµ + n → µ− + p
→ obtain Eν via Eµ, θµ
Account for:
• Binding energy
• Muon mass
• C threshold
∼ 10% resolution for Eν > 500 MeV
H. A. Tanaka – WIN 2003 14
Q2 and Eν :
0
0.1
0.2
0.3
0 0.5 1 1.5 2 2.5 3
Q2 (GeV2)
Fra
ctio
n of
Eve
nts
/ 0.1
GeV
2
Data
Monte Carlo
Q2 = −(pν − pµ)2
• Form factors (f1,2, g1) depend on Q2
• Nuclear effects at low Q2
Eν (Incident Neutrino Energy):
• Measures incident flux
0
0.1
0.2
-1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1cos qm
Frac
tion
of E
vent
s / (1
/15)
Data
Monte Carlo
H. A. Tanaka – WIN 2003 15
Neutral Current Elastic Scattering:
0 200 400 600 800 1000 120002000400060008000
10000120001400016000180002000022000
Eve
nts
Tank Hits
PRELIMINARY
Neutral Current Elastic
All Events
νµ + (p/n) → νµ + (p/n)• Typically sub-C:
Dominated by scintillation
• low NTANK, large late light fraction
• Large cross section (∼ 15%)
• Sensitive to strange spin component
Background subtraction:• Beam excess clearly visible
Non-beam background
• Decay electrons
• Environmental
• Subtract with random triggers
s)mAvg. PMT Time (0 2 4 6 8 10 12 14 16 18 20
0
5000
10000
15000
20000
25000
30000
35000
40000
All Beam DataEve
nts
0 2 4 6 8 10 12 14 16 18 200
5000
10000
15000
20000
25000
30000
35000
40000
Normalized Strobe DataEve
nts
0 2 4 6 8 10 12 14 16 18 20
0
2000
4000
6000
8000
10000
Beam after
Strobe Subtraction
Eve
nts
PRELIMINARY PRELIMINARY PRELIMINARY
s)mAvg. PMT Time ( s)mAvg. PMT Time (
H. A. Tanaka – WIN 2003 16
Neutral Current Hit Spectrum:Low multiplicity events:
• Strobe background subtraction
• Unknown component NTANK < 30
• 50 hit threshold for vertex fitNormalize MC to NTANK > 50 yield
Tank Hits0 20 40 60 80 100 120 140 160 1800
2000
4000
6000
8000
10000
Eve
nts
Beam DataMonte Carlo
THits (Hits)0 20 40 60 80 100 120 140 160 1800
200
400
600
800
1000
Eve
nts/
10 H
its
Beam DataMonte CarloMC, NC Elastic
PRELIMINARY Late light Selection:
• Fit event vertex for NTANK > 50 events
• Calculate fraction of late hits
• Select events with significant late light
Agreement for NTANK > 50 with/without late light cut.
H. A. Tanaka – WIN 2003 17
Neutral Current π0 Production:
Physics Interest:
• Background for νe
• Limits on Sterile ν
Primary Mechanisms:
• Resonance:
ν + (p/n) → ν + ∆∆ → (p/n) + π
• Coherent:
ν + C → ν + C + π0Size of Ball = Charge
Red = early, Blue = late
H. A. Tanaka – WIN 2003 18
Reconstructing Two Ring Events:
Blue: Cherenkov Light
Red: Scintillation
• Fourteen parameter fit:
• Vertex of decay (4)
• Direction of photons (4)
• Mean emission points (2)
• C/Sci Intensity(4)
• Kinematics from C Intensity
• mc2 =√
2E1E2(1− cos θ12)• ~p = E1u1 + E2u2
E1, E2 derived from C rings.
• No (e/µ) Ring Identification
H. A. Tanaka – WIN 2003 19
Inclusive Mass Distribution:
)2 Mass (GeV/c0.1 0.2 0.3 0.4 0.5
)2Ev
ents
/ ( 0
.02
GeV
/c
0
200
400
600
800
1000
0.1 0.2 0.3 0.4 0.50
200
400
600
800
1000
Mass = 0.1356 ± 0.0009 2GeV/c
Width = 0.0209 ± 0.0009 2GeV/c
= 0pNum. 2425 ± 107 Events
PRELIMINARY
Signal + BackgroundBackground
Bin data in kinematic quantities:
• Momentum (pπ0)
• Angle relative to beam (cos θπ0)
• CM Decay angle (cos θCM)
Event Selection:
• No decay electrons
• NTANK > 200, NV ETO < 6
• E1, E2 > 40 MeV
Signal shape from Res.+Coh. π0s
Background shape from Monte Carlo(Contains π0s from FSI, etc.)
EML Fit to extract signal yield
Extract binned yields
→ Get distribution
H. A. Tanaka – WIN 2003 20
π0 Angular Distributions:
CMqcos 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
Fra
ctio
n of
Eve
nts/
0.1
0
0.02
0.04
0.06
0.08
0.1
0.12
0.14
0.16
0.18
0.2
Data w/ statistical errors
yield extraction systematic errors
PRELIMINARY
MC w/ statistical +
π0 Lab Production AngleSensitive to production mechanism
• Coherent is highly forward peaked
• Resonance is less forward-peaked
MC assumes Rein-Sehgal cross-sections
π0 CM Decay Angle
• Should be flat (pseudoscalar)
• Distorted by Eγ cut, inefficiency
• Probes inefficiencies from:asymmetry, ring merging
0pqcos -1 -0.5 0 0.5 1
Fra
ctio
n of
Eve
nts/
0.2
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
Data w/ statistical errors
MC w/ statistical +yield extraction systematic errors
PRELIMINARY
H. A. Tanaka – WIN 2003 21
π0 Momentum Distribution :
Momentum (GeV/c)0p0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8
Fra
ctio
n of
Eve
nts/
0.1
GeV
/c
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
Data w/ statistical errors
MC w/ statistical +yield extraction systematic errors
PRELIMINARY
Higher Momentum means:
• Energy asymmetry
• Smaller opening angle
Harder to Reconstruct
H. A. Tanaka – WIN 2003 22
Physics Outlook:
• CC Quasi-Elastic:Compare with flux predictions →νµ disappearance analysis.Probe low Q2 region
• Neutral Current Elastic:Measure σNC/σCC vs. Q2
Probe ∆s.
• NC π0 Production:Cross-section measurementBackground extrapolationAnalyze coherent contribution
10-1
1
10
10 2
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
sin2 2qmm
Dm
2 (eV
2 )
CDHS 90% CL exclusion limit
CCFR 90% CL exclusion limit
MiniBooNE 90% CL sensitivityPRELIMINARY
0pqGenerated cos -1 -0.5 0 0.5 1
Fra
c. E
v/0.
04
0
0.05
0.1
0.15
0.2
0.25
0.3
Coherent
Resonant
H. A. Tanaka – WIN 2003 23
Conclusions:
• MiniBooNE has been taking beam for ∼ 1 year.
• 1.5× 1020 protons-on-target
• 150K contained neutrino candidates
• Detector is working as expected.
• Reconstruction algorithms working well
• First sample of neutrino physics
More to come!
H. A. Tanaka – WIN 2003 24
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