MiniBooNE : Current Status

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5th International Workshop on Neutrino Beams and
Instrumentation

• LSND the significance.
• Calibration and detector response.
• Neutrino Physics
• CCQE
• CC p
• NCE
• The experiment is on track
• for an oscillation result.

Tank pmts hit gt 200 Veto pmts hit lt 6
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__________________
Booster n Beam
The Status of MiniBooNE Ray Stefanski
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_________ _________
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• Implications of LSND
• How many ?s?
• new flavors?
• ?/ ?/ ?R?

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LSND Dm2 1eV2 q 2

sterile

Atmospheric oscillations Dm2 10-3eV2 q 45
Solar oscillations Dm2 10-5 eV2 q 32
q the mixing angle
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Theory of Neutrinos R.N. Mohapatra http//www.phys
ics.umd.edu/ep/mohapatra/apsreportshort.pdf
The existing data on neutrinos have already
raised very important questions, such as the very
different mixing angles, that are blazing new
trails in physics beyond that Standard Model.
They are also helping to define sharp questions
to be addressed by near future experiments
Are neutrinos Dirac or Majorana? What is the
absolute mass scale of neutrinos? How small is
?13? How maximal is ?23? Is there CP
Violation in the neutrino sector? Is the mass
hierarchy inverted or normal? Is the LSND
evidence for oscillation true? Are there sterile
neutrino(s)?
(i) search for ßß0? decay, (ii) determination of
the sign of the Dm213, and (iii) measurement of
the value of ?13.
We believe that all support should be given to
MiniBooNE experiment until it provides a complete
resolution of the LSND result.
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• 8 GeV proton beam
• 1.6 ?s pulse, 5 Hz rate from Booster
• p Be ? mesons
• Mesons focused by magnetic horn
• focusing increases ? flux by factor of 6
• allow ?, anti-? running
• Mesons Decay in Flight (DIF)? ?
• E 700 MeV, L 541 m (L/E 0.77 m/MeV)

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• Neutrino candidate rate
• Neutrino candidates
• gt200 tank hits
• lt6 veto hits
• Constant rate over time
• c2/d.o.f. 49/53
• Tests performance of
• Tank DAQ
• Calibration stability
• 610,927 neutrino events
• recorded so far...
• 5.8?1020 POT
• 1.05 neutrino events
• per 1015 pot.

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Related Talks During the Workshop

• Booster Neutrino Beam (Tom Kobilarcik)
• Secondary Beam (Robert Nelson)
• Particle Production (Dave Schmitz HARP MB)
• Particle Production (Michel Sorel HARP K2K)
• Neutrino Beam Simulation (Eric Zimmerman T2K)
• Horn (Larry Bartoszek)
• Horn Exchange (Tom Kobilarcik)
• LMC (Terry Hart)

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Particle Identification

• Identify events using hit topology
• Use a boosted tree algorithm
• and ANN to separate e, mu, pi, delta
• Particle ID Variables
• Reconstructed physical observables
• Track length, particle production angle relative
  to beam direction
• Auxiliary quantities
• Timing, charge related early/prompt/late hit
  fractions, charge likelihood
• Geometric quantities
• Distance to wall

Nuc. Inst and Meth A, Vol 543/2-3
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Calibration System
Calibration data samples span oscillation
signal energy range
Electron data samples Michel electrons p0
photons
PMTs calibrated with laser system
Cosmic Muons Stopping, through-going Very
important most neutrino events have muons
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ne nm Flux Determination

Tungsten Scintillator
Scintillating Fiber Tracker

• LMC spectrometer
• K decays produce wider
• angle ? than ? decays
• a scintillating fiber tracker is used
• a permanent magnet
• gives momentum
• measurement
• Tungsten scintillator
• calorimeter seperates
• protons from muons

Permanent Magnet
LMC ? candidate event
Terry Hart
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Calibration

• Laser Flasks (4)
• Measure tube Q, timing response
• Change Intensity to study PMT response, and oil
  properties
• Muon tracker
• Track direction and entry point test track
  reconstruction in tank
• Cube System (7)
• optically isolated scintilation cubes
• tracker identifies cosmic ?, the subsequent
  Michel electron of known position is used for
  Energy calibration

m tracker
cosmic m
scintillation cube
Michel electron
Electron samples
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Expected ne sources to test and measure the
detectors response.
Michel electrons fix the detector Energy scale at
low energy 14.8 Energy reconstruction _at_ 50
MeV ?0 mass peak, sets the Energy scale and
resolution at medium Energy
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Low Energy Electron Samples
Currently used validating e PID!

• Michel Electrons
• Ee lt 52MeV
• Unlimited supply
• (2 KHz stopping m rate)
• Also fixes energy scale
• for calibration

• 2. nm e Elastic Scattering
• Ee lt 1000MeV
• Expect 100 events
• Purely leptonic
• small s uncertainty
• Event selection based on very
• forward kinematics
• Typically used to measure sin2qW and mB

Analysis in Progress!
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High Energy Sample Ee gt1.5 GeV

ne yield from Kaon decay BR( K ? ne)
5 BR( K0 ? ne) 30
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Relative Location Between NuMI and MB Beams.
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Neutrinos from NuMI (The E-898 ne calibration
beam)
Neutrino interactions have been observed in the
E-898 detector, generated by neutrinos from the
NuMI beam. MiniBooNE can now claim to be the
worlds first off-axis detector.

• MB is 111 mrad off the NuMI beam axis, and
• 750 m away from the NuMI target.
• MB triggers off the NuMI extraction kicker in
• the Main Injector.
• The beam spill contains 5 batches in 8 ms.
• A few 1000 events are expected in the range
• 0ltEvisiblelt2 GeV by the 2005
  shutdown.
• The expected ne ratio is 5 ?
• should provide thousands
• of events for calibration
• and particle ID!
• The rate of neutrino events is
• 0.5/pot.
• About 80 are nm , 15 are nm.
• 95 of the events come from
• near the NuMI target.

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nm Physics
Data Analysis

• 611,000 neutrino events recorded so far...
• 5.8?1020 POT
• 260K CCQE
• 165K CC ?
• 105K NC Elastic
• 45K NC ?0

(CCQE)
(NCE)
(CC ?)
(NC ?0)
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nm CCQE

• Were making preliminary comparisons between
  measured distributions and MC expectations
• Ex Q2 (Sensitive to nuclear effects such as
  Pauli blocking
• and the Axial Mass.)
• CCQE are a class of events that
• are the largest class of events
• can be used to validate flux,
• can constrain Intrinsic ?e background due to
• ? decay
• Can be used in a search for ?? disappearance
• for ?m2 0.1 - 10 eV2
• For event selection we use Fisher
• discriminant to isolate events with a
• ?-like Cerenkov ring in final state.

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CCQE

• Simple reconstruction with QE kinematics
• Measure muon energy and angle
• Reconstruct neutrino energy and Q2

Preliminary
Preliminary
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CC p

• Primary background to CCQE analysis
• All previous measurements at bubble
  chambers, 7000 total evts, all on
  light targets, few
  measurements at low E.
• Event Selection
• At least 2 Michels,
• parent neutrino event
• in beam spill
• Separate into close and
• far Michels based on
• distance to
• end of muon track.
• Close Michels from ?-
• ?- capture on C
• ? 2026?1.5 ns
• Far Michels come
• from p
• ? 2197?0.04 ns

221815 ns
205714 ns
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CC p

• Simple reconstruction (for now)
• Assume events are QE with Delta, instead of
  having recoil nucleon
• Dont use pion information in reconstruction

??
?
W
A
?
A
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NC p0 Jen Raaf, Cincinnati

• Background to ?e appearance (dominant mis-ID)
• ? crucial for distinguishing ??-gt??, ??-gt?s in
• atmospheric experiments.
• The angular distribution constrains models for
• NC ?0 production
• Event Selection
• No decay electron, 2 Cerenkov rings gt 40 MeV each
• signal yield extracted from fit with background
  MC
• fit assuming 2 rings
• Examine mass spectrum, kinematics
• Bin data in kinematic quantities ?0 momentum, E
  asymmetry, angle of ?0 relative to beam, extract
  binned yields
• Compare distributions to MC expectations

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NC p0
Errors are shape errors Dark grey flux
errors Light grey optical model

• ?0 mass is in good agreement with MC.
• Cos ??0 sensitive to production mechanism
  (coherent is forward,
• resonant is nearly flat.)
• Fall-off at high p is reflects the fall-off in
• neutrino flux.

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NuFact05 presented by J. Morfin
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MB oscillation sensitivity for 1021 pot (top)
and 5 X 1020 (bottom) using the energy fit
method. Blue (yellow) is LSNDs 90 (99) CL
allowed region.
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Conclusion

• The LSND effect provides a hint of what might be
  a complex and wonderful world of extra neutrinos.
• MiniBooNE has accumulated 58 of 1021 pot needed
  for 4-5 ? coverage of LSND
• Already have worlds largest ? dataset in 1 GeV
  range
• Reconstruction and analysis algorithms are
  working well
• CCQE compare with flux predictions,
  disappearance analysis
• CC ? measure cross section
• NC ?0 measure cross section, analyze coherent
  contribution
• ?e appearance analysis well under way plan on
  opening box later this year.
• E-944 is approved to run through 2006, perhaps
  with anti-neutrinos.

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