MiniBooNE at First Physics
E. D. Zimmerman
University of Colorado
NBI 2003
KEK, Tsukuba
November 7, 2003

MiniBooNE at First Physics
Physics motivation: LSNDMiniBooNE overview
BeamDetector
Reconstruction and particle ID

First physics results
Status and near future

LSND decay-at-rest neutrino sourceνµ -> νe appearance search

Decay-at-rest Eν<53 MeV
Baseline 30 meters
Energy E<53 MeV

L/E ~ 1-1.5 km/GeV.

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LSND oscillation signature
From µ+ decay at rest:

Reconstruct e+ and γ withappropriate delayed coincidenceEvent selection criteria at LSND

R>10 = “golden mode”

LSND
20 MeV ≤ Evisible ≤ 60 MeV data
From R>10 sample (lowest background):

From fit to R distribution:

LSND
R>10 data
Energy distribution
consistent withoscillations∆m2 ~ 0.2-10 eV2

KARMEN2: similar expt in England, no evidence for oscillations.

Joint KARMEN-LSND analysis:
No disagreement
betweenexperiments
Narrows allowed
parameter range

Too many ∆m2's:
Only 3 light, weakly interacting neutrinos (LEP,SLD)
Solar/KAMLAND ∆m2: 7×10-5 eV2 (mostly νe -> νµ,τ)Atmospheric ∆m2: 2×10-3 eV2 (mostly νµ -> ντ)
LSND ∆m2: 0.2-10 eV2 (mostly νµ -> νe)∆m23 = ∆m21 + ∆m22
What's going on?
One set of experiments is not seeing oscillations
The neutrino sector contains nonstandard physics
beyond oscillations

New Physics I: Sterile Neutrinos

New Physics II: Maximal CPT violation(Barenboim, Borissov, and Lykken, hep ph/0212116)- Independent mass hierarchies for ν and ν.

neutrinos

antineutrinos- Proposed in 2001, but accomodates KamLAND- Side benefit: heavier antineutrinos allow early universe leptogenesis inthermal equilibrium- Compatibility with SuperK data may be a stretch.

BooNE
Target and HornLMC
451 meters
undisturbed earth

Booster
Decay pipe

MiniBooNE detector

BooNE will test the LSND result with:x10 statistics
Different beamDifferent energy
Different oscillation signature
Different systematics

Primary beam: 8 GeV protons from Fermilab Booster
Horn-focused secondary π, K decay in flight to neutrinos
500 meter oscillation baseline
800 ton mineral oil/Čerenkov detector

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BooNE Collaboration(with summer students)

Summer 2002

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BooNE Location on the Fermilab Site

BooNE's Neutrino Beam
The Booster
Horn and Target
Decay Pipe
Beam Absorbers
Kaon Monitoring (LMC)

The Booster
8 GeV proton acceleratorExtraction







Built to inject protons into Main Ring
Now injects Main Injector
Has excess capacity
Magnets cycle at 15 Hz

All beam extracted in a single turnPulse is 1.6 µs long; consists of ~82 bunches (“RFbuckets”) spaced 19 ns apart
10-5 duty factor -> eliminates non-beam backgrounds
New 8 GeV fixed target facility built for BooNE; canaccomodate other users too in futureDemands on the Booster
MiniBooNE
Booster beam
Main Injector
Tevatron

120 GeV Fixed TargetNuMI

Antiproton Source

Need record Booster performance for MiniBooNE tooperate at satisfactory rate simultaneously with the restof the FNAL program.
Beam losses are currently limiting the rate.

 

Must limit radiation levels andactivation of Booster components 

Booster Performance 

Decrease beam lossSteady improvements so farthroughIncrease proton rate

Careful tuning
Understanding optics
Rate about a factor of 2 or 3 below
what's needed for us to see 1021
p.o.t. before early 2005
Further improvements:
Collimator project (completedin Autumn 2003 shutdown)
Lattice improvements(later) larger aperture RF
cavities

red: Booster output (protons/minute)blue: energy loss per proton(W-min/proton)

Achieved 1.5×1020 protons on target before shutdown
began September 2.
Only 15% of goal. We are eagerly awaiting accelerator
improvements!

Secondary beam overview

We considered “borrowing” a second horn from BNL to increase
our flux, but...

...its condition was somewhat imperfect.

Target Pile

Time structure of the beam

Each 2-secondcycle:
10 Booster pulses
at 15 Hz rep. rate
(many variations
on this pattern depending onother experiments running,
Booster losses, etc.)

Horn and Target Region
Primary beam position monitor: air
multiwire
Target: 71 cm beryllium metal (1.7 λ0),resides inside horn
Horn:
Inner conductor thickness: 3 mm
Outer conductor thickness: 25 mm
Peak current: 170 kA
Pulse width: 140 µs
Voltage: ~4 kVBeryllium Target
Assembly

End View

Side View

Horn welding
and assembly.

Expected flux at MiniBooNE detector from GEANT4 Monte Carloπ+ production: “JAM” fit toexternal data using SanfordWang parametrization.
π− production: SanfordWang parameters from Choet al., PRD 4, 1967 (1971).
K+/K- production: crosssection table derived fromMARS production model
K0 production: MARS K+
cross-section weighted by
K0/K+ ratio from GFLUKAK-decay νe background
MiniBooNE will see ~200-400 νe from K+ and K0L
decays each year -- comparable to the yield fromoscillation physics if LSND is correct.
Goal is a systematic error of <10% on K-decay νe.
Information on these decays will come from:Monte Carlo (GEANT4, MARS, GFLUKA)

50%
disagreements!

Production measurements (BNL E910, HARP, plus other,older data)
In-situ measurement: LMC

Little Muon Counter
K decays produce higher transversemomentum muons than π decays
LMC: off-axis (7°) muon spectrometerclean separation of muon parentage

temporary LMC detector (scintillator paddles):

scintillating fiber tracker

shows that data acquisition is working
53 MHz beam RF structure seen

LMC: off-axis (7°) muon spectrometer

Monte Carlo

Data from temporary LMC detector
19 nsµ from πµ from Kmuon momentum at 7° (GeV)[PMT5 hit time] - [beam-on-target time]

(ns)

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Detector site, August 10, 1999

Tank assembly in place, May 4, 2000

Cables/Inner Structure Installation, February 2001

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Selecting Neutrino Events

Beam window 1.6 µs
3 simple cuts give
great rejection ofnon-ν events
No non-beam backgrounds
unlike LSNDParticle ID

Michel ecandidate (e fromµ decay)

Beam µcandidate

Event display key:
Size: PMT charge
Color: hit time (Red isearly, Blue is late.)

Beam π0candidate

Understanding the Detector
Laser Flasks
397 nm laser light
Four Ludox-filled flasks fed
by optical fiber from laser

To calibrate PMT's, wemeasurePMT charge
Timing response
Oil attenuation lengthStopping Muon Calibration System
Cosmic ray hodoscopes above the tank

Optically isolated scintillator cubes in tank:six 2-inch (5 cm) cubes
one 3-inch cube

Calibration sample consists ofmuons up to 700 MeV

µ

Michel electrons (fromdecays of stopped cosmicray muons) 

Michel Electron Measurements.(/+-*+, 
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#Energy scale and resolution
at Michel endpoint (53MeV)(8% of µ- capture) 

τ = 2.13 µs
expected:'()measured: τ = 2.15 ± 0.02 µs

 Muon lifetime in oil:

Data/MC Agreement in Vertex Reconstruction

Neutrino events:- NHIT > 200- NVETO < 6- r < 450cm- Timing

Initial Physics Measurements
νµ Quasielastic Scattering
Neutral Current π0 Production
Neutral Current Elastic ScatteringSignatures of neutrino interactions in BooNE
Čerenkov ring(µ-like or e-like)plus small scintillation
signal1 or 2 Čerenkov ringsplus larger scintillation
signalMostly higher energies.
A very ugly multi-ring
event!

Two e-like rings plus
larger scintillation
signal from recoil
nucleonSame as above, butmore forward-peaked

Recoil nucleon rarelyabove Čerenkovthreshold; signal isalmost entirely fromscintillation. Very few
PMT hits and low totalcharge.

CC νµ Quasielastic Events
Event selection  Topology
Ring sharpness
on- vs. off-ring hits
TimingSingle µ-like ring
Prompt vs. late light

Variables combined in a Fisher
discriminant

Flux predicton
σCCQE
Optical properties

θµ

Yellow Band: MC with current
uncertainties fromData and MC normalized to unit areaCC νµ Quasielastic Events



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νν

Eµ reconstruction:Assume νµn → µ−p
Use Eµ, θµ, to get EνFirst look at neutrino flux:

Preliminary νµ Disappearance Sensitivity

Systematics dominated due to uncertainty in flux prediction.

NC π Production
0NTANK > 200, NVETO < 6, no decay electron
Perform two-ring fit on ALL events.
Ring energies > 40 MeV 








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

Fit mass peak to extract signal yield including background shape from MC.

NC π Production Angle0

Production angle is sensitive toproduction mechanism:
coherent is highly forwardpeaked.

θπ



MC usesRein-Sehgal
cross-sections.





Data and MC are normalized tounit area.

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







NC π0 momentum and Eγ asymmetry













|E1 - E2| / (E1 + E2)









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NC Elastic Scattering
Select NTANK < 150, NVETO< 6
Use random triggers(Normalized Strobe Data)
to subtract non-beam background.

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A cut on the fraction of late light in these
events may help select NC elastic events.

νe Appearance Status
Blind analysis underway.
Potential νe candidates are notavailable for full analysis(particle ID, etc).
All events are available foranalyses which do not involve
particle ID, for detector checks
and Monte Carlo development
Sensitive to LSND region at 5 σ.
Updated estimates coming.
Currently expect results in 2005

Conclusions
Beam and detector running well
Still need more beam rate
First physics plots are here≤2 years to νe oscillation results:

Either we'll see oscillations and life
will be very interesting, or we won't -and phenomenology gets a lot easier.