Zelimir Djurcic Physics Department

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MiniBooNE Neutrino Experiment
Zelimir Djurcic Physics Department Columbia
University
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(No Transcript)
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Neutrino physics hot subject for the last few
years. Why?
Minimal Standard Model constructed with m?0
extensions with finite m? naturally give m?
ml2/MPlanck where ml is lepton mass and M is
scale for new physics
Non-zero neutrino mass tests new physics in a
very cost effective way.
Universe contains 330 ?/cm3 (410 ?/cm3), from
Big Bang. m? important ingredient for Dark
Matter problem. ??/?Blt 0.3 (WMAP) ??/?B lt 3.0
(Tritium decay) ?B 0.0470.006, ?M 0.290.07
and ?Tot 1.020.02
Interesting astrophysical probes allowing us to
look inside our Sun and Supernovae.
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Why Neutrino Mass Matters?
Cosmological Implications
Window on Physics at High E Scales

• Massive neutrinos with osc. important for heavy
  element production in supernova
• Light neutrinos effect galactic structure
  formation

See-Saw Mechanism
Heavy RHneutrino
Typical Dirac Mass
Set of very lightneutrinos
Set of heavysterile neutrinos
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How many neutrinos are there?
Experiment shows that the neutrinos produced in
muon interactions are different from neutrinos
involved in interactions with electrons.
A third kind of particle, the tau, is heavier
version of muon which is itself a heavier
version of the electron. (It has its own
neutrino as well.)
We have (at least) 3 kind of neutrinos the
electron neutrino (?e), the muon neutrino
(??), and the tau neutrino (??). Sterile ??
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Neutrinos in the Standard Model

• Neutrinos are the only fundamental fermions with
  no electric charge
• Neutrinos only interact through the weak force
• Neutrino interaction thru W and Z bosons exchange
  is (V-A)
• Neutrinos are left-handed(Antineutrinos are
  right-handed)
• Neutrinos are massless
• Neutrinos have three types
• Electron ?e ? e
• Muon ?? ? ?
• Tau ?? ? ?

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Neutrino Cross Section Very Small!

• Weak interactions are weak because of the massive
  W and Z boson exchange ? ? weak ? GF2 ?
  (1/MW or Z)4
• For 100 MeV Neutrinos
• ?(?e) 10-42 and ?(?n) 10-39 cm2 compared
  to ?(pp) 10-24 cm2
• A neutrino has a good chance of traveling through
  3 million earths before interacting at all!
• -Mean free path length in Steel 1013 meters!
  (Need big detectors and lots of ?s )

MW 80 GeVMZ 91 GeV
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Neutrino masses are interesting. How to measure
them?
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Experimental Limits on Neutrino Mass
Direct decay studies have made steady progress
but limited

• Electron neutrino
• 3H?3He ne e-
• Muon neutrino
• p?mnm decays
• Tau neutrino
• t? (np) nt decays

lt 2 eV
lt 170 keV
lt 18 MeV
? Need to use Neutrino Oscillations to probe
for smaller neutrino masses
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What are Neutrino Oscillations?
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Parameters of Mixing Matrix
Standard parametrization 3 rotations through
angles ?12 (?sol), ?23 (?atm), ?13 (unknown).
cij cos ?ij sij sin ?ij
? Dirac phase giving rise to CP-violating
effects in oscillations. a1, a2 Majorana phases,
not observable in oscillations.
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Neutrino Propagation
Flight path
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Oscillation Probability
A transition probability P can be defined. It is
an oscillatory function of the flight path L.
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Two Generation Model
Assume Only Two Neutrinos Mix
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Wave Analogy
?e
?e
sometimes the waves are in-phase
wave 1
wave 2
wave 1 wave 2
sometimes they are out of phase
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Oscillation Plots

• If you see an oscillation signal with
• Posc P ? ?P then carve out an allowed
  region in (?m2,sin22?) plane.
• If you see no signal and limit oscillation with
• PoscltP _at_90CLthen carve out an excluded
  region in the (?m2,sin22?) plane.

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• But we have 3-generations ne , nm, and nt
  (and maybe even more .. the
  sterile neutrino nss )

• Naively might expect the neutrino and quark
  matrix to look similar

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Sources of neutrinos artificial and natural
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Signal Regions (Mid 1990s)
LargeMixingSolution
SmallMixingSolution
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Theoretical Prejudices Before 1995

• Natural scale for ?m2 10 100 eV2 since
  needed to explain dark matter
• Oscillation mixing angles must be small like
  the quark mixing angles
• Solar neutrino oscillations must be small
  mixing angle MSW solutionbecause it is cool
• Atmospheric neutrino anomaly must be other
  physics or experimental problembecause it needs
  such a large mixing angle
• LSND result doesnt fit in so must not be an
  oscillation signal

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Theoretical Prejudices Before 1995
What we know now

• Natural scale for ?m2 10 100 eV2 since
  needed to explain dark matter Wrong
• Oscillation mixing angles must be small like
  the quark mixing angles
  Wrong
• Solar neutrino oscillations must be small
  mixing angle MSW solutionbecause it is cool
  Wrong
• Atmospheric neutrino anomaly must be other
  physics or experimental problembecause it needs
  such a large mixing angle Wrong
• LSND result doesnt fit in so must not be an
  oscillation signal
  Wrong

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Neutrino Revolution 1995-2005
K2K Accelerator Neutrino Exp.

• Atmospheric neutrino oscillations definitively
  confirmed
• Smoking Gun ? Super-K flux change with zenith
  angle
• Accelerator neutrino confirmation with KEK to
  Super-K exp. (K2K)
• Value of ?m2 1.5 to 3.5 10-3 eV2

Super-K (SK)Atmospheric NeutrinoExperiment
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Neutrino Revolution 1995-2005

• Solar Neutrino Oscillations Confirmed and
  Constrained
• Many different exps see deficit
• SNO experiments sees that total neutrino flux
  correct from sun but just changing flavor
• Kamland experiment using reactor neutrinos
  confirms solar oscillations
• Combination of experiments ? Large Mixing Angle
  MSW Solution

SNO Solar ? Exp.
Combination All Solar KamLAND
KamLAND Reactor Exp.
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The LSND Experiment
LSND took data from 1993-98 - 49,000 Coulombs
of protons - L 30m and 20 lt Enlt 53 MeV
Saw an excess of??e 87.9 22.4 6.0
events. With an oscillation probability of
(0.264 0.067 0.045). 3.8 s evidence for
oscillation.
Oscillations?
Signal p ? e n n p ? d ?(2.2MeV)
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After LSND Experiment
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How can one get 3 distinct ?m2 ?

• One of the experimental measurements is wrong
• One of the experimental measurements is not
  neutrino oscillations
• Neutrino decay
• Neutrino production from flavor violating decays
• Additional sterile neutrinos involved in
  oscillations
• CPT violation (or CP viol. and sterile ?s )
  allows different mixing for ?s and ??s

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KARMEN vs LSND

• Similar beam and detector to LSND
• Closer distance and less target mass ? x10
  less sensitive than LSND
• Joint analysis with LSND gives restricted region
  (Church et al. hep-ex/0203023)

• KARMEN also limits m ? e?ne n ratio BR
  branching lt 0.9 x 10-3 (90 CL)
• LSND signal would require
• 1.9x10-3 lt BR lt 4.0 x 10-3 (90 CL)
• ? m ? e?ne n unlikely to explain LSND signal
• (also will be investigated by TWIST exp. at
  TRIUMF)

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Are There Sterile Neutrinos?

• Reconcile three separate ?m2 by adding additional
  sterile ?s

• Constraints from atmos. and solar data? Sterile
  mainly associated with the LSND ?m2
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• 32
• 33 Models

Then these are the mainmixing matrix elements
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Next Step is MiniBooNE

• MiniBooNE will be one of the first experiments to
  check these sterile neutrino models
• Investigate LSND Anomaly
• Is it oscillations?
• Measure the oscillation parameters
• Investigate oscillations to sterile neutrino
  using ?? disappearance

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MiniBooNE Experiment
Need definitive study of ????e at high ?m2
MiniBooNE
Use protons from the 8 GeV booster ? Neutrino
Beam ltE?gt 1 GeV
12m sphere filled withmineral oil and 1500
PMTslocated 500m from source
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MiniBooNE Collaboration
Y. Liu, I. Stancu Alabama S. Koutsoliotas
Bucknell E. Hawker, R.A. Johnson, J.L. Raaf
Cincinnati T. Hart, R.H. Nelson, E.D.
Zimmerman Colorado A. Aguilar-Arevalo,
L.Bugel, L. Coney, J.M. Conrad, Z. Djurcic, J.
Link, J. Monroe, K. McConnel, D. Schmitz,
M.H. Shaevitz, M. Sorel, G.P. Zeller
Columbia D. Smith Embry Riddle
L.Bartoszek, C. Bhat, S J. Brice, B.C. Brown,
D.A. Finley, 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
Fermilab D. C. Cox, A. Green, H.-O. Meyer, C.
Polly, R. Tayloe Indiana G.T. Garvey,
C. Green, W.C. Louis, G.McGregor, S.McKenney,
G.B. Mills, H. Ray, V. Sandberg, B. Sapp, R.
Schirato, R. Van de Water, D.H. White Los
Alamos R. Imlay, W. Metcalf, M. Sung, M.O.
Wascko Louisiana State J. Cao, Y. Liu,
B.P. Roe, H. Yang Michigan A.O. Bazarko,
P.D. Meyers, R.B. Patterson, F.C. Shoemaker,
H.A.Tanaka Princeton A. Currioni, B.T.
Fleming Yale
MiniBooNE consists of about 70 scientists from 13
institutions.
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designed a beamline detector optimized for this
direct search
MiniBooNE Beamline
FNAL 8 GeV Booster
50 m decay pipe
decay region p ? mnm , K?mnm
little muon counters
measure K flux in-situ
magnetic horn meson focusing
MiniBooNE detector
450 m earth berm n nm ?ne?
movable absorber stops muons, undecayed mesons
magnetic focusing horn
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Beam to MiniBooNE
5.5 x 1020 POT
577,000 nm events (10k ns/week)

• proton output of FNAL Booster has improved
  dramatically
• 577k nm events providing a valuable sample to
• study low energy ( 1 GeV) neutrino physics

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MiniBooNE Horn

• technically, one of the most
• impressive components of MBooNE
• pulsed at 5 Hz, 170kA
• capable of running with polarity
• reversed ?? running
• increases ? flux by factor 6

• -1st horn failed past Fall
• (could not be brought up to safe operation)
• set world record with gt92M pulses
• (previous record set at BNL with 13M pulses,
  0.5 Hz)
• horn replaced
• 2nd horn performing well

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All together
LMC
Beamline
Booster
Decay Region
500m dirt
Target and Horn
Detector
Primary Beam (protons)
Secondary Beam (mesons)
Tertiary Beam (neutrinos)

• Primary Beam
• 8 GeV protons from Booster
• Into MiniBooNE beamline
• Secondary Beam
• Mesons from protons striking Be target
• Focused by magnetic horn
• Tertiary Beam
• Neutrinos from meson decay in 50m pipe
• Pass through 500m dirt (and oscillate?) to reach
  detector

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? Flux at MiniBooNE Detector

• nm
• mainly from p ? m nm
• ltEngt 700 MeV

• p production at target
• determined from global fit
• (worlds p data new BNL E910)

• high purity beam

predicted energy spectrum
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HARP Precision ?/K Production Measurement

• flux knowledge important for osc and ?s
• working w/ the HARP exp at CERN to mea- sure
  hadron prod off MiniBooNEtarget
• 1st goal measure p prod ? on Be at
• pp8.9 GeV/c (MiniBooNE replica target)
• additional measurements include
• p - prod ? (important for ? running)
• K prod ? (important for intrinsic ne)
• 30 Tb data still analyzing

target tomography
Be target is 71cm long, 1cm in diameter
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MiniBooNE Detector

• 12m diameter tank
• 800 tons ultra-pure mineral oil
• n interactions in oil produce
• - prompt ring of Cerenkov light
• - delayed isotropic scintillation light
• 1280 8 phototubes in
• interior signal region

• 240 8 phototubes
• in outer veto region

(gt 99 veto efficiency)
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Particle Identification

• Separation of ?? from ?e events
• Exiting ?? events fire the veto
• Stopping ?? events have a Michel electron after a
  few ?sec
• Also, scintillation light with longer time
  constant ? enhanced for slow pions and protons
• Cerenkov rings from outgoing particles
• Shows up as a ring of hits in the phototubes
  mounted inside the MiniBooNE sphere
• Pattern of phototube hits tells the particle type

Stopping muon event
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Particle Identification II
Cerenkov rings provide primary means of
identifying products of n interactions in
the detector
beam m candidate
nm n ? m- p
Michel e- candidate
ne n ? e- p
beam p0 candidate
nm p ? nm p p0
n n
p0 ? gg
ring profile ? can distinguish particles which
shower from those which dont
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Examples of Real Data Events
Charged Currentnm n ? m- pwith outgoing
muon (1 ring)
Neutral Currentnm n ? nm p0 pwith
outgoing p0 ? gg (2 rings)
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Muon Identification Signature m ? e nm
ne after 2msec
Charge (Size)
Time (Color)
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Events vs PMT Hits
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Neutrino Events
beam comes in spills _at_ up to 5 Hz each spill
lasts 1.6 ?sec trigger on signal from
Booster read out for 19.2 ?sec beam at 4.6,
6.2 ?sec no high level analysis needed to
see neutrino events backgrounds cosmic muons
decay electrons simple cuts
reduce non-beam backgrounds to 10-3
Current Collected data 577k neutrino candidates
for 5.5 x 1020 protons on target
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Calibration Sources
We have calibration sources spanning wide range
of energies
Michel electrons prod from ? decay provide E
calibration at low energy (50 MeV), good monitor
of light transmission, electron PID
15 E res at 53 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?
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Neutrino Energy Reconstruction

• For quasi-elastic events ( nmn?m-p and
  nen?e-p) ? Can use kinematics to
  find En from Em(e) and qm(e)

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Oscillation Analysis Status and Plans

• Blind (or Closed Box) ?e appearance analysis
• you can see all of the info on some events
• or
• some of the info on all events
• but
• you cannot see all of the info on all of the
  events
• Other analysis topics give early interesting
  physics results and serve as a cross check and
  calibration before opening the ?e box
• ?? disappearance oscillation search
• Cross section measurements for low-energy ?
  processes
• Studies of ?? NC ?0 production ?
  coherent (nucleus) vs nucleon
• Studies of ?? NC elastic scattering
• ? Measurements of ?s (strange quark
  spin contribution)

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?? Analyses
Use to understand ?e CCQE cross-section
CC quasi-elastic NC ?0 production NC
elastic
background to ?e appearance
Use to understand lower vertex
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Charged Current QE

• Selection
• Cosmic ray cuts
• Single ?-like ring
• Topology
• MC Data relatively normalized.
• Red Band MC 1? uncertainty from...
• flux shape
• cross-section
• Yellow Region idea of variation from...
• optical properties (atten. length, scintillation,
  scattering, ...)

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CCQE Reconstruction
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NC ?0

• Ntank gt 200, Nveto lt 6, Fid.Vol.
• No Michel electron
• Clear 2-ring fit on all events
• Each ring Eg1, Eg2 gt 40 MeV.

Signal yield extracted from fit with background
MC.
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?0 Variables
No preferred CM g direction, but distorted by
Lab Eg and 2 ring cuts.

• High Momentum tail
• from ? flux
• distorted by 2 ring cut

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NC Elastic Scattering
Monte Carlo
Select NTANK lt 150 NVETOlt 6
clear beam excess use random triggers to
subtract non-beam background
beam after strobe subtraction
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Appearance Sensitivity

• Look for appearance of ?e events above background
  expectation
• Use data measurements both internal and external
  to constrain background rates

• Fit to E? distribution used to separate
  background from signal.

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Intrinsic ?e in the beam
Small intrinsic ne rate ? Event Ratio
ne/nm6x10-3

• ne from m-decay
• Directly tied to the observed half-million nm
  interactions

• Kaon rates measured in low energy proton
  production experiments
• HARP experiment (CERN)
• E910 (Brookhaven)

• Little Muon Counter measures
• rate of kaons in-situ

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Mis-identification background

• Background mainly from NC p0 production
• nm p ? nm p p0
• followed by
• p0? g g where one g is lost because it
  is too low energy
• Over 99.5 of these events are identified and the
  p0 kinematics are measured
• ? Can constrain this background directly from the
  observed data

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MiniBooNE Oscillation Sensitivity

• Oscillation sensitivity and measurement
  capability
• Data sample corresponding to 1x1021 pot
• Systematic errors on the backgrounds average 5

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Run Plan

• At the current time have collected 5.5x1020
  p.o.t.
• Data collection rate is steadily improving as the
  Booster accelerator losses are reduced
• Many improvement being implemented into the
  Booster and Linac (these not only help MiniBooNE
  but also the Tevatron and NuMI in the future)
• Plan is to open the box when analysis is ready
  ? Current estimate is end of 2005
• Which then leads to the question of the next step
• If MiniBooNE sees no indications of oscillations
  with nm ? Need to run with?nm since LSND signal
  was?nm??ne
• If MiniBooNE sees an oscillation signal ? Then
  

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But Its Not All About MiniBooNE

• there are many
• neutrino experiments
• several of which have
• unearthed some
• surprises along
• the way

CHARM II
its an exciting time to be a neutrino physicist!