MINOS+ Sterile Neutrino Studies
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Transcript of MINOS+ Sterile Neutrino Studies
MINOS+ Sterile Neutrino Studies
J.ThomasUCL
J.Evans (UCL), A.Gavrilenko (W&M), M.Matthis (W&M)A.Sousa(Harvard)
UCL
MINOS+ Precision Measurement
• ~3000 CC events/year between 4-10GeV (including energy resolution and efficiencies)
Sterile neutrino search
PAC requested update on this
Different experiments• Reactor experiments (ne disappearance): q14
• MiniBooNE and LSND (ne appearance):q14+q24
• MINOS (NC and nm disappearance) q24+ q34
• MiniBooNE and LSND, CDHS, CFFR (nm dis):q24
• MINOS+ (nm disappearance) : q24
• MINOS+ (NC disappearance) : q24+ q34
Improvements• MINOS+ Monte Carlo used for this analysis– Previous used reweighted LE events
• Oscillations at the Near Detector are incorporated
• A complete 4-flavour oscillation formula is used to allow lower reach in Dm2
43
– Down to where interference with atmospheric oscillations occurs (Dm2
43 = 2.5x10-3eV2)
MINOS+ advantages• MINOS+ will have very high statistics– Simulations here use 2 years of neutrinos or 2
years of anti-neutrinos• 2 detector experiment– Normalisation measurement at FD rather than
shape only (MiniBoone, CDHS, CCFR)– Two baselines : 1km and 735km
Some Mathematics
And helpful assumptions (but these not implemented in simulation)
Some Maths
Thought Simplifications • Dm2
21 dependence can be neglected at this L and E, so
q13 is small (set to 0)
Thought simplifications
• Reactor anomaly allows q14 < ~9o, (small)• so:• End up with:
• Above Dm243 of 10-1eV2 , sin2D41 and sin2D43≈0.5
• And Probability at FD:
The limits from last PAC
MINOS AND MINOS+
MINOS MINOS+(old)
Characteristics of Limits• 10-1<Dm2
34<1eV2 : FD in fast oscillation mode and mass squared term averages to ½, so no sensitivity to exact value of Dm2
34
• Dm234 > 1eV2 : Near Detector spectrum affected
leading to more structure to the exclusion region• Dm2
34 > 10eV2 : ND and FD both see fast oscillations, so comparison cancels sensitivity to the effect
FD sterile example
Both atmospheric and sterile dips apparent here
DM2 factor averages to 0.5
Near Detector Example
Systematic error is on ratio of numu to numubar
MINOS+ θ24
sin2D41≈sin2D43≈0.5 : FD effect
Atmospheric analysis assumed correct!
ND starts fast oscillation too
ND starts to see effect
Bottom Line
anti-neutrinos neutrinos
Summary• More careful job results in much larger reach• NC additional analysis not yet complete but
improvement expected between 10-2eV2 and 10-3eV2.
• MINOS+ has a world-beating sensitivity to this sterile search for both neutrinos and antineutrinos over large range of mass splitting