(Status of ) The search for nm to ne

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(Status of ) The search for nm to ne oscillations
at MiniBooNE Andrew Bazarko Princeton
University 9 October 2003 WIN03 Weak
Interactions and Neutrinos Lake Geneva, Wisconsin
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MiniBooNE status snapshot MiniBooNE has been
running for 1 year at Fermilab
acquired 15 of goal 1021 protons on target
At the moment (Sept mid Nov) accelerator is
shutdown important accelerator
improvements are underway
MiniBooNEs first event beam-induced muon
(Labor Day weekend 2002)
Outline Overview of the experiment
(preview of tomorrows tour) First neutrino
events and analysis Outlook
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nm beam from m decay at rest energy 20-53 MeV
baseline 30 m L/E 1 m/MeV
LSND
Evidence for
Dm20.2-10 eV2
87.922.46.0 events
(Bugey is ne disappearance)
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• 3 light neutrino flavors
• Solar (KamLAND) neutrinos
• mostly
• Atmospheric (K2K) neutrinos
• mostly

Where does LSNDs Dm20.2-10 eV2 fit in this
picture??
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n Oscillation Scenarios
With current results from solar, atmospheric, and
LSND n-oscillation searches (3 Dm2s), we have an
interesting situation
Only 3 active n
3 active1 sterile n
CPT violation
OR...
OR...
OR...
- not a good fit to data
- possible(?)
- possible(?)
Need to definitively check the LSND result.
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• Goal test LSND with
• 5-s sensitivity over
• whole allowed range
• higher statistics
• different signature
• different backgrounds
• different systematics

?
detector
8 Gev Booster
target
Tevatron
Main Injector
MiniBooNE!
Fermilab
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BooNE Fermilab Booster Neutrino Experiment
Y. Liu, I. Stancu Alabama S. Koutsoliotas
Bucknell E. Hawker, R.A. Johnson, J.L. Raaf
Cincinnati T. Hart, E.D. Zimmerman
Colorado Aguilar-Arevalo, L.Bugel, J.M. Conrad,
J. Formaggio, J. Link, J. Monroe, D. Schmitz,
M.H. Shaevitz, M. Sorel, G.P. Zeller
Columbia D. Smith Embry Riddle

• First phase MiniBooNE
• Single detector, nm ne
  appearance
• L/E500 m/500 MeV ..30 m/30 MeV (LSND)

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. J. Nienaber, E. Prebys, A.D.
Russell, P. Spentzouris, R. Stefanski, T.
Williams Fermilab D. C. Cox, A. Green, H.-O.
Meyer, R. Tayloe Indiana 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, D.H. White Los
Alamos R. Imlay, W. Metcalf, M. Sung, M.O.
Wascko Louisiana State J. Cao, Y. Liu,
B.P. Roe Michigan A.O. Bazarko, P.D. Meyers,
R.B. Patterson, F.C. Shoemaker, H.A.Tanaka
Princeton
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MiniBooNE
LMC
?
K

8GeV
Booster
magnetic horn
decay pipe
450 m dirt
detector
absorber
and target
25 or 50 m
8-GeV protons on Be target ? p, K,, focused by
horn decay in 50-m pipe, mostly to nm
all but n absorbed in steel and dirt
ns interact in 40-ft tank of mineral
oil charged particles
produce light
detected by phototube array
Look for electrons produced by mostly-nm beam
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The Booster
8 GeV proton accelerator supplies beam to all
Fermilab experiments
It must now run at record intensity
MiniBooNE runs simultaneously with the
collider program goals
MiniBooNE negligible impact on
collider improvements to Booster good for NuMI
5x1020 p.o.t per year (1x1021 total)
MiniBooNE
Booster
antiproton source TeVatron NuMI 120 GeV fixed
target
Main Injector
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Booster performance
July 2002 - Sept 2003
We are pushing the Booster hard Must limit
radiation damage and activation of Booster
components increase protons but decrease
beam loss steady improvements careful
tuning understanding optics need factor of
2-3 to reach goal 1021 p.o.t. by early
2005 further improvements coming collimator
project (now) large-aperture RF cavities

goal intensity
MiniBooNE startup
red Booster output (protons/minute)
blue energy loss per proton
(W-min/proton)
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Target and magnetic horn
Increases neutrino intensity by 7x
170 kA in 140 msec pulses _at_ 5 Hz
the horn
Prior to run, tested to 11M pulses has
performed flawlessly 40M pulses in situ
the target
the target
Worlds longest-lived horn
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Intrinsic ne in the beam
Monte Carlo
p?m nm enenm K?p0 ene KL?p-
ene
important bkgd to osc search Tackle this
background with half-million nm interactions
in detector HARP experiment (CERN) E910
(Brookhaven) Little Muon Counter 25 m /
50 m decay length option
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Little Muon Counter (LMC)

• off-axis (7o) muon spectrometer
• K decays produce higher-energy
• wide-angle muons than p decays
• clean separation of muon parentage
• scintillating fiber tracker

temporary LMC detector (scintillator paddles)
commission data acquisition 53 MHz beam
RF structure seen
Monte Carlo
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The MiniBooNE detector
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MiniBooNE detector
pure mineral oil (Cherenkovscint 31) total
volume 800 tons (6 m radius) fiducial
volume 445 tons (5m radius)
Phototube support structure provides opaque
barrier between veto and main volumes
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Pattern of hit tubes (with charge and time
information) allows reconstruction of track
location and direction and separation of
different event types.
e.g. candidate events
size charge red early, blue late
muon from nm interaction
Michel electron from stopped m decay after nm
interaction
p0 g two photons from nm interaction
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Understanding the detector
Laser flasks
four Ludox-filled flasks fed by optical fiber
from laser
397 nm laser (no scintillation!) modeling other
sources of late light
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Stopping muon calibration system
Scintillator tracker above the tank
Optically isolated scintillator cubes in
tank six 2-inch (5 cm) cubes one
3-inch cube
stopping muons with known path length
calibration sample of muons up to 700 MeV
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Michel electrons (electrons from the decay of
stopped muons)
m candidate lifetime (ns)
plentiful source from cosmics and
beam-induced muons
cosmic muon lifetime in oil measured t 2.15
0.02 ms expected t 2.13 ms
(8 m- capture)
PRELIMINARY
Michel electron energy (MeV)
Energy scale and resolution at Michel endpoint
(53 MeV)
15 E resolution at 53 MeV
Michel electrons throughout detector (rlt500 cm)
PRELIMINARY
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Neutrino events
beam comes in spills _at_ up to 5 Hz each spill
lasts 1.6 msec trigger on signal from
Booster read out for 19.2 msec beam at 4.6,
6.2 msec no high level analysis needed to
see neutrino events backgrounds cosmic muons
decay electrons simple cuts
reduce non-beam backgrounds to 10-3
160k neutrino candidates in 1.5 x 1020
protons on target
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The road to nm g ne appearance analysis
Blind ne 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
Early physics other analyses before nm g ne
appearance interesting in their own right
relevant to other experiments necessary
for nm g ne search vets data-MC
agreement (optical properties, etc.)
and reliability of reconstruction algorithms
progress in understanding backgrounds
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Early physics
NC elastic
CC quasi-elastic
abundance 15 usually sub-C dominated by
scintillation
abundance 40 simple topology one muon-like
ring proton rarely above C
low Ntank (pmt hits) high late light fraction
select sharp events 88 purity
understanding of scintillation sensitive to
nucleon strange spin component
kinematics Em, qm g En, Q2 relatively
well-known s nm disappearance
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CC nm quasi-elastic events
PRELIMINARY
selection topology ring
sharpness on- vs. off-ring
hits timing
single m-like ring prompt
vs. late light
Evis
c variables combined in a Fisher
discriminant
PRELIMINARY
cos qm
data and MC relatively normalized
yellow band Monte Carlo with current uncertaintie
s from

• flux prediction
• sCCQE
• optical properties

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sensitive to nm disappearance
Neutrino energy
kinematic reconstruction assume nm n g m-
p use Em, qm to get En
En
PRELIMINARY
Monte Carlo
PRELIMINARY
Q2
energy resolution
lt10 for Engt800 MeV
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Preliminary nm disappearance sensitivity
systematics dominated from uncertainty in
flux prediction
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NTANKgt200, NVETOlt6, no decay electron perform two
ring fit on all events require ring energies E1,
E2 gt 40 MeV
NC p0 production
fit mass peak to extract signal yield including
background shape from Monte Carlo
note bkgd also peaking
PRELIMINARY
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p0 production angle
sensitive to production mechanism
coherent is highly forward peaked
data and MC are relatively normalized MC shape
assumes Rein-Sehgal cross sections
PRELIMINARY
cos qp0
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p0 decay angle and p0 momentum
cos qCM
PRELIMINARY
CM frame
lab frame
small g g opening angle
qCM p/2
p0 momentum
a
cosqCM 0
qCM 0
photon energies asymmetric
PRELIMINARY
a
cosqCM 1
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NC elastic scattering
PRELIMINARY
Now select NTANK lt 150 NVETOlt 6
Background subtraction
PRELIMINARY normalized strobe data
PRELIMINARY beam with unrelated background
PRELIMINARY
clear beam excess use random triggers to
subtract non-beam background
beam after strobe subtraction
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nm NC elastics
Consider NTANK spectrum
MC and data shapes agree qualitatively for
NTANKgt50
Unknown component NTANKlt30
data and MC relatively normalized for NTANKgt50
Late light selection
fit event vertex for NTANKgt50 calculate fraction
of late hits select events with significant late
light
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ne appearance sensitivity
preliminary estimates, backgrounds and signal
1500 intrinsic ne
500 m mis-ID
cover LSND allowed region at 5 s
500 p0 mis-ID
updated estimates coming
currently expect results in 2005
1000 LSND-based nm?ne
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Conclusions
steadily taking data currently at 15 of
1021 p.o.t
beam is working well, but still need higher
intensity improvements underway (shutdown)
will be key
first sample of neutrino physics detector
and reconstruction algorithms are working well
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