New Results from MINOS
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Transcript of New Results from MINOS
NEW RESULTS FROM MINOS
Patricia Vahle, for the MINOS collaborationCollege of William and Mary
2The MINOS Experiment
P. Vahle, Neutrino 2010
Long base-line neutrino oscillation experiment
Neutrinos from NuMI beam lineL/E ~ 500
km/GeVatmospheric Δm2
Two detectors mitigate systematic effects
beam flux mis- modeling
neutrino interaction uncertainties
Far Detector735 km from Source
Near Detector1 km from
Source
3MINOS Physics Goals
P. Vahle, Neutrino 2010
Measure νμ disappearance as a function of energy Δm2
32 and sin2(2θ23)
test oscillations vs. decay/decoherence
Δm232
Δm221
νμ → νX
4MINOS Physics Goals
P. Vahle, Neutrino 2010
Measure νμ disappearance as a function of energy Δm2
32 and sin2(2θ23)
test oscillations vs. decay/decoherence
Mixing to sterile neutrinos?
Δm232
Δm221
νμ → νS
Δm214
5MINOS Physics Goals
P. Vahle, Neutrino 2010
Δm232
Δm221
Measure νμ disappearance as a function of energy Δm2
32 and sin2(2θ23)
test oscillations vs. decay/decoherence
Mixing to sterile neutrinos?
Study νμ→νe mixing measure θ13
νμ → νe
6MINOS Physics Goals
P. Vahle, Neutrino 2010
Measure νμ disappearance as a function of energy Δm2
32 and sin2(2θ23)
look for differences between neutrino and anti-neutrinos
Δm232
Δm221
νμ → νX
7MINOS Physics Goals
P. Vahle, Neutrino 2010
Measure νμ disappearance as a function of energy Δm2
32 and sin2(2θ23)
look for differences between neutrino and anti-neutrinos
More MINOS analyses: atmospheric neutrinos
(See A. Blake poster) cross section
measurements Lorentz invariance tests cosmic rays
Δm232
Δm221
νμ → νX
8The Detectors
P. Vahle, Neutrino 2010
1 kt Near Detector—measure beambefore oscillations
5.4 kt Far Detector—look for changes in the beam relative to the Near Detector
Magnetized, tracking calorimeters
735 km from source
1 km from source
9Detector Technology
P. Vahle, Neutrino 2010
Multi-anode PMT
ExtrudedPS scint.4.1 x 1 cm2
WLS fiber
ClearFiber cables
2.54 cm Fe
U V planes+/- 450
Tracking sampling calorimeters steel absorber 2.54 cm thick (1.4
X0) scintillator strips 4.1 cm wide (1.1 Moliere radii) 1 GeV muons penetrate 28 layers
Magnetized muon energy from range/curvature distinguish μ+ from μ-
Functionally equivalent same segmentation same materials same mean B field (1.3 T)
10Making a neutrino beam
P. Vahle, Neutrino 2010
11Making a neutrino beam
P. Vahle, Neutrino 2010
Production bombard graphite target with 120 GeV p+ from Main
Injector 2 interaction lengths 310 kW typical power
produce hadrons, mostly π and K
12Making a neutrino beam
P. Vahle, Neutrino 2010
Focusing hadrons focused by 2 magnetic focusing horns sign selected hadrons
forward current, (+) for standard neutrino beam runs
reverse current, (–) for anti-neutrino beam
13Making a neutrino beam
P. Vahle, Neutrino 2010
Decay 2 m diameter decay pipe result: wide band beam, peak determined by
target/horn separation secondary beam monitored (see L. Loiacono
poster)
14Beam Performance
P. Vahle, Neutrino 2010
Prot
ons
per
wee
k (x
1018
) Total Protons (x1020)
Date
15Beam Performance
P. Vahle, Neutrino 2010
1021 POT!
Prot
ons
per
wee
k (x
1018
) Total Protons (x1020)
Date
16Beam Performance
P. Vahle, Neutrino 2010
Previously published analyses
Prot
ons
per
wee
k (x
1018
) Total Protons (x1020)
Date
17Beam Performance
P. Vahle, Neutrino 2010
Data set for today’s report
Anti-neutrino running
High energy running
Prot
ons
per
wee
k (x
1018
) Total Protons (x1020)
Date
18
e-
CC νe Event
Events in MINOSNC Event
ν
P. Vahle, Neutrino 2010
νμ Charged Current events: long μ track, with hadronic activity at vertex neutrino energy from sum of muon energy
(range or curvature) and shower energy
CC νμ Event
μ-
Depth (m)
Tran
sver
se
posi
tion
(m
)
νμ + N → μ + X
Simulated Events
19
e-
CC νe Event
Events in MINOSNC Event
ν
P. Vahle, Neutrino 2010
CC νμ Event
μ-
Depth (m)ν
α+ N → ν α + X
Tran
sver
se
posi
tion
(m
)
Neutral Current events: short, diffuse shower event shower energy from calorimetric response
Simulated Events
20
e-
CC νe Event
Events in MINOSNC Event
ν
P. Vahle, Neutrino 2010
CC νμ Event
μ-
Depth (m)νe + N → e− + X
Tran
sver
se
posi
tion
(m
)
νe Charged Current events: compact shower event with an EM core neutrino energy from calorimetric response
Simulated Events
21Near to Far
P. Vahle, Neutrino 2010
Neutrino energy depends on angle wrt original pion direction and parent energy higher energy pions decay further along decay pipe angular distributions different between Near and Far
FDDecay Pipe
π+Target
ND
p
Far spectrum without oscillations is similar, but not identical to the Near spectrum!
Eν ≈0.43Eπ
1+γ2θν2
22Extrapolation
P. Vahle, Neutrino 2010
Muon-neutrino and anti-neutrino analyses: beam matrix for FD prediction of track events
NC and electron-neutrino analyses: Far to Near spectrum ratio for FD prediction of shower events
23
Unoscillated
Oscillated
νμ spectrum
νμ Disappearance
P. Vahle, Neutrino 2010
P(νμ → νμ )=1−siν2 2θ( )siν2(1.27Δμ 2L/ E)
spectrum ratio
Monte Carlo(Input parameters: sin22θ = 1.0, Δm2 = 3.35x10-3 eV2 )
Characteristic Shape
Monte Carlo
24
Unoscillated
Oscillated
νμ spectrum
νμ Disappearance
P. Vahle, Neutrino 2010
P(νμ → νμ )=1−siν2 2θ( )siν2(1.27Δμ 2L/ E)
spectrum ratio
Monte Carlo(Input parameters: sin22θ = 1.0, Δm2 = 3.35x10-3 eV2 )
Monte Carlo
sin2(2θ)
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Unoscillated
Oscillated
νμ spectrum
νμ Disappearance
P. Vahle, Neutrino 2010
P(νμ → νμ )=1−siν2 2θ( )siν2(1.27Δμ 2L/ E)
spectrum ratio
Monte Carlo(Input parameters: sin22θ = 1.0, Δm2 = 3.35x10-3 eV2 )
Monte Carlo
Δm2
26
CC events in the Near Detector
P. Vahle, Neutrino 2010
Show ND energy spectrum Majority of data
from low energy beam
High energy beam improves statistics in energy range above oscillation dip
Additional exposure in other configurations for commissioning and systematics studies
27Analysis Improvements
P. Vahle, Neutrino 2010
Since PRL 101:131802, 2008 Additional data
3.4x1020 → 7.2x1020 POT Analysis improvements
updated reconstruction and simulation
new selection with increased efficiency
no charge sign cut improved shower energy
resolution separate fits in bins of energy
resolution smaller systematic
uncertainties
See C. Backhouse, J. Mitchell, and J. Ratchford, M. Strait posters
28
Far Detector Energy Spectrum
P. Vahle, Neutrino 2010
No Oscillations:
2451
Observation: 1986
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Far Detector Energy Spectrum
P. Vahle, Neutrino 2010
Oscillations fit the data well, 66% of experiments have worse χ2
Pure decoherence† disfavored: > 8σPure decay‡ disfavored: > 6σ
(7.8σ if NC events included)†G.L. Fogli et al., PRD 67:093006 (2003) ‡V. Barger et al.,PRL 82:2640 (1999)
30Contours
P. Vahle, Neutrino 2010
Contour includes effects of dominant systematic uncertainties normalization NC background shower energy track energy
Δm2 = 2.35−0.08+0.11 ×10−3eV2
sin2 (2θ ) > 0.91 (90% C.L.)
31Contours
P. Vahle, Neutrino 2010
Contour includes effects of dominant systematic uncertainties normalization NC background shower energy track energy
Δm2 = 2.35−0.08+0.11 ×10−3eV2
sin2 (2θ ) > 0.91 (90% C.L.)
†Super-Kamiokande Collaboration (preliminary)
†
32
Neutral Current Near Event Rates
P. Vahle, Neutrino 2010
Neutral Current event rate should not change in standard 3 flavor oscillations
A deficit in the Far event rate could indicate mixing to sterile neutrinos
νe CC events would be included in NC sample, results depend on the possibility of νe appearanceSee P. Rodrigues
and A. Sousa poster
33
Neutral Currents in the Far Detector
P. Vahle, Neutrino 2010
Expect: 757 events Observe: 802 events No deficit of NC events
fs ≡Pνμ → νs
1−Pνμ → νμ
< 0.22 (0.40)αt90% C.L.no (with) νe appearance
R=Ndata −BG
SNC
1.09 ±0.06 (stαt.)±0.05 (syst.)(νo νe αππeαrανce)
1.01 ±0.06 (stαt.)±0.05 (syst.) (with νe αππeαrανce)
34νe Appearance
P. Vahle, Neutrino 2010
P(νμ → νe)≈siν2(2θ13)siν2(θ23)siν
2 1.27Δμ 312 LE
⎛⎝⎜
⎞⎠⎟ +
siν2(2θ12 )cos2(θ23)siν
2 1.27Δμ 212 LE
⎛⎝⎜
⎞⎠⎟ +
siν(2θ13)siν(2θ23)siν(2θ12 )siν 1.27Δμ 312 LE
⎛⎝⎜
⎞⎠⎟siν 1.27Δμ 21
2 LE
⎛⎝⎜
⎞⎠⎟cos 1.27Δμ 32
2 LE±δCP
⎛⎝⎜
⎞⎠⎟
A few percent of the missing νμ could change into νe depending on value of θ13
Appearance probability additionally depends on δCP and mass hierarchy
Δm322
Δm212
Normal Hierarchy Δm322
Δm212
Inverted Hierarchy?⇔
35
Looking for electron-neutrinos
P. Vahle, Neutrino 2010
11 shape variables in a Neural Net (ANN) characterize longitudinal and transverse energy
deposition Apply selection to ND data to predict background
level in FD NC, CC, beam νe each extrapolates differently take advantage of NuMI flexibility to separate
background components νe
selected region
• Data⎯ MC
BG RegionSee R. Toner, L. Whitehead, G. Pawloski poster
36νe Appearance Results
P. Vahle, Neutrino 2010
Based on ND data, expect: 49.1±7.0(stat.)±2.7(syst.)
37νe Appearance Results
P. Vahle, Neutrino 2010
Based on ND data, expect: 49.1±7.0(stat.)±2.7(syst.)
Observe: 54 events in the FD, a 0.7σ excess
38νe Appearance Results
P. Vahle, Neutrino 2010
for δCP =0, siν2 2θ23( )=1,
Δμ 322 =2.43×10−3 eV 2
siν2(2θ13) < 0.12 νorμ αl hierαrchy
siν2(2θ13) < 0.20 iνverteδ hierαrchyαt90%C.L.
arXiv:1006.0996v1 [hep-ex]
MINOS
7.01×1020 POT
39
Making an anti-neutrino beam
P. Vahle, Neutrino 2010
π-
π+
Target Focusing Horns 2 m
675 m
νμ
νμ
15 m 30 m
120 GeV p’s from
MI
Neutrino modeHorns focus π+, K+
νμ: 91.7% νμ: 7.0%νe+νe :1.3%
Even
ts
40
Making an anti-neutrino beam
P. Vahle, Neutrino 2010
π-
π+Target Focusing
Horns 2 m
675 m
νμ
νμ
15 m 30 m
120 GeV p’s from
MI
Anti-neutrino ModeHorns focus π-, K- enhancing the νμ flux
Neutrino modeHorns focus π+, K+
νμ:39.9% νμ:58.1%νe+νe :
2.0%
Even
ts
Even
ts
νμ: 91.7% νμ: 7.0%νe+νe :1.3%
41ND Anti-neutrino Data
P. Vahle, Neutrino 2010
Focus and select positive muons purity 94.3% after charge
sign cut purity 98% < 6GeV
Analysis proceeds as (2008) neutrino analysis
Data/MC agreement comparable to neutrino running different average kinematic
distributions more forward muons
See J. Evans, N. Devenish posterAlso A. Blake poster on atmospheric neutrinos
42ND Data
P. Vahle, Neutrino 2010
Data/MC agreement comparable to neutrino running
43FD Data
P. Vahle, Neutrino 2010
No oscillation Prediction: 155
Observe: 97 No oscillations
disfavored at 6.3σ
44FD Data
P. Vahle, Neutrino 2010
Δm2 = 3.36−0.40+0.45 ×10−3eV2
sin2 (2θ ) = 0.86 ± 0.11
No oscillation Prediction: 155
Observe: 97 No oscillations
disfavored at 6.3σ
45FD Data
P. Vahle, Neutrino 2010
46Comparisons to Neutrinos
P. Vahle, Neutrino 2010
47Comparisons to Neutrinos
P. Vahle, Neutrino 2010
48Summary
P. Vahle, Neutrino 2010
With 7x1020 POT of neutrino beam, MINOS finds muon-neutrinos
disappear
NC event rate is not diminished
electron-neutrino appearance is limited
With 1.71x1020 POT of anti-neutrino beam muon anti-neutrinos also
disappear with
we look forward to more anti-neutrino beam!
Δm2 = 2.35−0.08+0.11 × 10−3eV2 ,
sin2 (2θ ) > 0.91 (90% C.L.)
fs < 0.22(0.40)αt90% C.L.
sin2 (2θ13) < 0.12 (0.20)αt 90%C.L.
Δm2 = 3.36−0.40+0.45 ×10−3eV2 ,
sin2 (2θ ) = 0.86 ± 0.11
49 Backup Slides
P. Vahle, Neutrino 2010
50
LE 10 ME HE
Neutrino Spectrum
P. Vahle, Neutrino 2010
Use flexibility of beam line to constrain hadron production, reduce uncertainties due to neutrino flux
51Near to Far
P. Vahle, Neutrino 2010
Far spectrum without oscillations is similar, but not identical to the Near spectrum!
Eν ≈0.43Eπ
1+γ2θν2
52Far/Near differences
P. Vahle, Neutrino 2010
νμ CC events oscillate awayEvent topology
Light level differences (differences in fiber lengths) Multiplexing in Far (8 fibers per PMT pixel) Single ended readout in Near
PMTs (M64 in Near Detector, M16 in Far): Different gains/front end electronics Different crosstalk patterns
Neutrino intensityRelative energy calibration/energy resolution
Account for these lower order effects using detailed detector simulation
53
New Muon-neutrino CC Selection
P. Vahle, Neutrino 2010
54Shower Energy Resolution
P. Vahle, Neutrino 2010
55Energy Resolution Binning
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56
CC Systematic Uncertainties
P. Vahle, Neutrino 2010
Dominant systematic uncertainties: hadronic energy
calibration track energy calibration NC background relative Near to Far
normalization
57Resolution Binning
P. Vahle, Neutrino 2010
58Contours by Run Period
P. Vahle, Neutrino 2010
59
Rock and Anti-fiducial Events
P. Vahle, Neutrino 2010
Neutrinos interact in rock around detector and outside of Fiducial Region
These events double sample size, events have poorer energy resolution
Combined fit coming soon
60Fits to NC
P. Vahle, Neutrino 2010
Fit CC/NC spectra simultaneously with a 4th (sterile) neutrino
2 choices for 4th mass eigenvalue m4>>m3 m4=m1
61
Electron-neutrino Background Decomposition
P. Vahle, Neutrino 2010
62
Electron-neutrino Systematics
P. Vahle, Neutrino 2010
Stats. Err.
63
MRCC Background Rejection Check
P. Vahle, Neutrino 2010
R
Neutrino Energy: 5.3 GeV
Muon Energy: 3.2 GeVRemnant Energy: 2.1 GeVANN PID: 0.86
Mis-id rate: pred (6.42±0.05)% data (7.2±0.9)%
(stats error only)Compatible at 0.86σ
Remove muons, test BG rejection on shower remnants
64Checking Signal Efficiency
P. Vahle, Neutrino 2010
Test beam measurements demonstrate electrons are well simulated
65Checking Signal Efficiency
P. Vahle, Neutrino 2010
Check electron neutrino selection efficiency by removing muons, add a simulated electron
66
P. Vahle, Neutrino 2010
Hadron production and cross sections conspire to change the shape and normalization of energy spectrum~3x fewer antineutrinos for the same exposure
Making an antineutrino beam
67Anti-neutrino Selection
P. Vahle, Neutrino 2010
μ- Not Focused
Coil Hole
μ+ Focused
Coil Hole
68Anti-neutrino Systematics
P. Vahle, Neutrino 2010
69FD Anti-neutrino Data
P. Vahle, Neutrino 2010
Vertices uniformly distributed Track ends clustered around coil hole
70
Previous Anti-neutrino Results
P. Vahle, Neutrino 2010
Results consistent with (less sensitive) analysis of anti-neutrinos in the neutrino beamanti-neutrinos from unfocused beam component
mostly high energy antineutrinos
Analysis of larger exposure on going
71
Future Anti-neutrino Sensitivity
P. Vahle, Neutrino 2010
72Atmospheric Neutrinos
P. Vahle, Neutrino 2010
Rν /νδαtα / Rν /ν
MC =1.04−0.10+0.11 ±0.10
Δμ 2 −Δμ 2 =0.4−1.2+2.5 ×10−3eV 2