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