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735 km
The MINOS Long Baseline Neutrino Oscillation
Experiment
Jeff Nelson
William & Mary
Fermilab Users’ Meeting
June 6, 2007
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MINOS
• Overview
> Detector & beam
> Oscillation analysis
> Neutrino time of flight
• What’s New?
> 2nd year of running
> Advances
• Prospects Argonne • Athens • Benedictine • Brookhaven • Caltech • Cambridge Campinas • Fermilab • College de France • Harvard • IIT • Indiana
Minnesota-Twin Cities • Minnesota-Duluth • Oxford • Pittsburgh Rutherford • Sao Paulo • South Carolina • Stanford • Sussex • Texas
A&M • Texas-Austin • Tufts • UCL • William & Mary • Wisconsin
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MINOS Physics Goals
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321
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UUU
UUU
UUU eeee• Test the νμ → ντ oscillation hypothesis
> Measure precisely |Δm232| & sin22θ23
• PRL 97, 191801 (2006)
> Search for / constrain exotic phenomena
• Search for νμ → νe oscillations
• Compare ν, ν oscillations> CPT test
• Neutrino interaction physics
• Atmospheric neutrinos > PRD 75, 092003 (2007)
> PRD 73, 072002 (2006)
• Cosmic rays> hep-ex/0705.3815
> 10 papers to ICRC 2007
See poster by Jeff de Jong
Useful Approximations
νμ disappearance (2 flavors):
P(νμ→νx) = 1 - sin22θ23 sin2(1.27Δm232 L/E)
νe appearance:
P(νμ→νe) ≈ sin2θ23sin22θ13sin2(1.27Δm231 L/E)
where L, E are experimental parameters & θ23, θ13, Δm2
32 are to be determined
Δm232 = m3
2 – m22
ν1
ν2
ν3ν1
ν2
ν3
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Example of a disappearance measurement
Look for a deficit of νμ events at a distance…
Unoscillated
Oscillated
νμ spectrum
Monte Carlo
NC background
Monte Carlo
Spectral ratio
NC subtracted0.0033 eV2
)E/Lm267.1(sinθ2sin-1=)νν(P 222μμ Δ→
Unoscillated
Oscillated
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Example of a disappearance measurement
Look for a deficit of νμ events at a distance…
Unoscillated
Oscillated
νμ spectrum
Monte Carlo
NC background
Monte Carlo
Spectral ratio
NC subtracted0.0033 eV2
)E/Lm267.1(sinθ2sin-1=)νν(P 222μμ Δ→
Unoscillated
Oscillated
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Example of a disappearance measurement
Look for a deficit of νμ events at a distance…
Unoscillated
Oscillated
νμ spectrum
Monte Carlo
NC background
Monte Carlo
Spectral ratio
NC subtracted0.0033 eV2
)E/Lm267.1(sinθ2sin-1=)νν(P 222μμ Δ→
Unoscillated
Oscillated
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Producing the neutrino beam (NuMI)
• 120 GeV protons strike target>10 s pulse every ~2.4s>Typically running at 2.5e13 protons per pulse
• 2 magnetic horns focus secondary π/K• π/K decays produce neutrinos
>Moveable target & horn provides variable beam energy
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MINOS Detectors
Iron and Scintillator tracking calorimetersmagnetized steel planes <B> = 1.2T
1×4.1 cm2 scintillator strips
Multi-anode PMT readout
GPS time-stamping to synchronize FD data to ND/Beam
Main Injector spill times sent to the FD for a beam trigger
Far Detector5.4 kton
8 8 30 m3
484 planes
Near Detector1 kton
3.8 4.8 15 m3
282 steel planes
153 scintillator planes
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1pe PMT cross-talk
A 2 GeV νμ event in the far detector
Track Energy 2.04 GeV
Shower energy 0.20 GeV
q/p = -0.52 ± 0.03
< 2 PE
2 < PE < 20 PE
> 20 PE
Track hit
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Energy spectra in ND
LE10 pME pHE
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Energy spectra in ND
LE10 pME pHE
Data & Nominal MC discrepancy changes energy with beam tuneSuggests production of hadrons off the target is to blame
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Energy spectra in ND
LE10 pME pHE
• Took data in 6 different beam tunes (only 3 shown)• Varied the dependence on pT and x
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MINOS best-fit spectrum for 1.27×1020 POT
Measurement errors are 1 sigma, 1 DOF
See poster by Niki Saoulidousyst)+(stat1.00=2θsin
eV10×syst)+(stat2.74=Δm
0.13232
2-3+0.440.26 -
232
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PRL 97, 191801 (2006)
Systematics Δm2 (10-3 eV2)
sin22θ
Near/Far normalization 0.05 0.01
Absolute hadronic scale 0.06 0.05
NC contamination 0.09 0.05
All other systematics 0.04 0.01
Total systematic error 0.13 0.07
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MINOS allowed region for 1.27×1020 POT
Measurement errors are 1 sigma, 1 DOF
See poster by Niki Saoulidou
PRL 97, 191801 (2006)
syst)+(stat1.00=2θsin
eV10×syst)+(stat2.74=Δm
0.13232
2-3+0.440.26 -
232
-
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MCMC
Projected MINOS sensitivity
Statistical errors
90% C.L.
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Prospects
• Neutrino time of flight• New data
>2nd year running experience>Post-shutdown intensity
• Prospects for future >Advancing the oscillation analysis >Electron neutrino appearance>Neutral current>Antineutrinos>Non oscillation physics
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Neutrino Time of Flight(TOF)
• PDG limit is> |v−c|/c < 4 × 10-5 (95% C.L.)
> Exotic models predict values all the way up to this limit
• Separation between the detectors> L = 734,298.6 ± 0.7 m
• The TOF for a massless particle
> τ = 0.002449356 s
δ = -126 ± 32 (stat) ± 64 (syst.) ns
(v−c)/c = [5.1 ± 2.9 (syst. + stat.)] × 10-5 (68% CL)
hepex/0706.0437
δ (μs)
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Neutrino Time of Flight (TOF)
• PDG limit is> |v−c|/c < 4 × 10-5 (95% C.L.)
> Exotic models predict values all the way up to this limit
• Separation between the detectors> L = 734,298.6 ± 0.7 m
• The TOF for a massless particle
> τ = 0.002449356 s
δ = -126 ± 32 (stat) ± 64 (syst.) ns
(v−c)/c = [5.1 ± 2.9 (syst. + stat.)] × 10-5 (68% CL)
δ (μs)
hepex/0706.0437
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Relativistic mass measurement
• Use time and energy to compute a relativistic mass limit> If the neutrino have mass mv
its time of flight would be
where τ is the TOF for a massless particle
• We find> The limit is driven by the few points near edge
> With full data MINOS dataset ~10 MeV at 99% C.L.
Line = 68% C.L.Shaded = 99% C.L.
C.L. 68% MeV/c syst)+(stat17=m 2+33 56- ν
( )( )
νν
νmcm
τν
/E1=ET
2
hepex/0706.0437
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The 2nd year of MINOS running
1st year of running (published dataset)
Double datasetCollected with 99.4% live time
More !
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MI intensity improvements: slip stacking
• MI currently running in “2+5” slip stacking> 2 MI bunches for pbar
> 5 MI bunches for NuMI
• AD demonstrated “2+9” slip stacking> 2 MI bunches for pbar
> 9 MI bunches for NuMI
• New record for beam in the MI set in April
> 4.608×1020 POT with good transport efficiency
> Beam delivery limited to 4.0x1020 POT until we have a spare target in-hand (this summer)
• AD plans “2+9” as default after the shutdown
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How to we plan to exploit this new data?
• Modeling & reconstruction>Additional data at higher energies
>Updated flux model
>New hadronization & intranuclear scattering models
> Improved reconstruction & PID algorithms • Reduce NC systematic errors
>Ongoing improvements in calibration
• Working to extend the oscillation analysis to antineutrinos & higher energies
MC
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Since initial analysis, implemented beam fitting to antineutrinos
• Antineutrinos come from π - off the target> Rates shown are for normal running conditions
• Simultaneous neutrino and antineutrino fit > Compared to new p+C data from CERN NA49
Eur.Phys.J.C49:897-917,2007
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High energy neutrinos and kaon production
• Kaons decays tend to produce higher energy neutrinos> MIPP took p+C thin
target data at 120-GeV/c
• MIPP took thick-target data with our NuMI target> Forthcoming
K
ra
tio
pT<0.2 GeV/c
0.2<pT<0.4 GeV/c
Andre Lebedev, Harvard Ph.D., MIPP-doc-218
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→ e oscillation search
See poster by Tingjun Yang4×1020 POT
16×1020 POT
P(νμ→νe) ≈ sin2θ23 sin22θ13 sin2(1.27Δm231L/E)
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Tuned MC incl. systematic error
Neutral current (NC) events
• NC unaffected by νμ ντ oscillations
> Can test for sterile neutrino contributions
• Near detector NC energy spectrum> Far Detector data for this
analysis is still blinded
> Currently working on • Near/Far extrapolation
• FD systematic error evaluation
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Neutrino scattering in the near detector
• Intense NuMI beam > Recorded 3 ×1020 POT> 5 × 106 events in the fiducial volume
• Can explore new kinematic regions> Connect to precision higher energy
experiments
• Some non-oscillation analyses underway
> Total CC differential cross-section> Flux extraction> DIS differential cross-section> Structure functions> Quasi elastic scattering> Coherent production cross-section …
MC
See poster by Minsuk Kim MC
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Conclusions
Results from the first year of accelerator neutrino exposure
> It is consistent with νμ disappearance with the following parameters
> Data also used to measure the TOF and relativistic mass of neutrinos
(v−c)/c = (5.1 ± 2.9) × 10-5 (68% CL, syst. + stat.)
More than doubled the dataset since shutdown> Slip stacking offers the prospect of significant intensity
improvements after the shutdown
New analyses are underway on a number of samples
syst)+ (stat1.00=2θsin
eV10×syst)+(stat2.74=Δm
0.13232
2-3+0.440.26-
232
-
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MI intensity improvements with slip stacking
• MI currently running in “2+5” slip stacking mode> 2 MI bunches for pbar> 5 MI bunches for NuMI
• AD demonstrated “2+9” slip stacking mode> 2 MI bunches for pbar> 9 MI bunches for NuMI
• New record for beam in the MI set in April> 4.608E13 POT with good transport efficiency > Beam delivery limited to 4.0E13 POT until we have
a spare target in-hand (this summer)
• AD plans “2+9” as default after the shutdown> The intensity to be gradually increased from
2.4E13 POT> AD continuing preparations for the MI collimator
installation during the shutdown
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• Look for e appearance
> P(νμ→νe) ≈ sin2θ23 sin22θ13 sin2(1.27Δm231L/E)
(plus CP violation and matter effects)
• Look for events with compact shower and typical EM profile> Primary background from NC events
> Matter effects alter e yield by 20%
• Reach depends strongly on POT> Far Detector data for this
analysis is still blinded
> 4×1020 POT - can challenge the world’s best limit (CHOOZ)
> 16×1020 POT - can significantly improve limit and increase chance of discovery
→ e oscillation search
See poster by Tingjun Yang
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Tuned MC incl. systematic error
Neutral current (NC) events
• NC interactions> Unaffected by νμ ντ
oscillations• Can test for sterile neutrino
contributions
> Large cross-section uncertainty for E ~1 GeV
• Near detector NC energy spectrum> Far Detector data for this
analysis is still blinded > Currently working on
• Near/Far extrapolation
• FD systematic error evaluation
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Neutrino scattering in the near detector
• Intense NuMI beam offers opportunities for exploring cross-sections> Recorded 3×1020 POT> We have 5.5×106 CC interactions
in the fiducial volume• Some non-oscillation analyses
underway> Total CC differential cross-section> Flux extraction> DIS differential cross-section> Structure functions> Quasi elastic scattering> Coherent production cross-section
• A few examples of work in progress… MC
See poster by Minsuk Kim for more
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Deep Inelastic Scattering
• Largest component of the MINOS event sample> The measurement will be systematics
limited
• Can explore new kinematic regions> Connects to precision higher energy
experiments
MC
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Quasi elastic scattering(vn → μp)
• The QE-enhanced sample can be used to extract the flux for MA measurement> 3×1020 POT
~ 800,000 events> Look for
• Well-defined muon track
• Low shower energy
• Low W
• Main background> Single charged pions