APS April 22, 2006 Session C12 1

A Search for Sterile Neutrinos in MINOS

Thomas OsieckiUniversity of Texas at AustinFor the MINOS Collaboration

• Motivation for Sterile Neutrinos • Sterile Neutrino Signature in MINOS• Experimental Challenges• Sensitivity• Outlook

APS April 22, 2006 Session C12 2

m2sol + m2

atm m2LSND

Implies the existence of more than 3 neutrinos!

LEP has measured three active neutrinos that couple to the Z boson.

If there were more than 3 neutrinos, they would not couple to the Z and are labelled “sterile”

Sterile Neutrinos are alsopredicted by a number of theories

APS April 22, 2006 Session C12 3

735 km735 km

Conventional Oscillations

d

u

W+

CC NC

NC Deficit in Predicted energy spectrum is evidence of sterile oscillations

Evisible

X NCX=e,

Evisible

NC

Sterile Oscillations

Evisible

X NCX=e,sterile

Measure Near Predict Far

APS April 22, 2006 Session C12 4

3.5m 1.8m

Monte Carlo

CC

NCCC

NC

Longitudinal Direction

Tra

nsvers

e D

irecti

on

E Resolution:

APS April 22, 2006 Session C12 5

NC (fsterile = 0)

CC (No Osc.)

CC (Osc.)

Conventional Oscillations Sterile Oscillations

NC (fsterile = 0)

(fsterile = 0.3)

(fsterile = 0.5)

m2=0.003 eV2

fsterile = Fraction of Sterile Mixing

CC (Osc.)m2=0.003 eV2

Take a Monte Carlo Far Detector NC energy spectrum with a CC background to study effects of sterile neutrinos

APS April 22, 2006 Session C12 6

Near Detector DataIntense Neutrino Beam, Many Interactions

MINOS NC signal is at low energies.

Have to properly identify Individual interactions

Near Detector is crucial for Extrapolation to Far

1 neutrino spill=10 s

APS April 22, 2006 Session C12 7

CC

NC

Monte Carlo

1 2 3

1-RMS in longitudinal direction from charge weighted center2-Energy per Plane in the 2nd Half of the Event3-Maximum Energy in a 4 Plane Window

dE/dx

[m] [ADC counts] [%]

Can Construct PDFs from 1,2,3

APS April 22, 2006 Session C12 8

Monte Carlo

))log()log(( NCPPPID

PID

CCNC

Percentage of NC Events Retained

Percentage of Events that are Actually NC

Particle IDParticle ID

Select NC-like Spectrum from Particle ID (PID) Cut

APS April 22, 2006 Session C12 9

Monte Carlo

Far Detector Mock Data with m2 = 0.00212 eV2 , fsterile = 0.11

Visible Energy (GeV)

Performed a Chi-squared Fit between “data” and prediction at Far

7.4e20 Protons on Target

fsterile

APS April 22, 2006 Session C12 10

MINOS is a 2 detector experiment where the first detector will predict a NC energy spectrum at the far detector

Current Work Includes Improve Reconstruction of NC events Improve NC/CC Separation Modeling of NC events Studies of systematics

MINOS will provide a sensitive measurement of sterile neutrinos

We currently have 1.4e20 Protons on Target and expect to have a sterile neutrino measurement later this fall

APS April 22, 2006 Session C12 11

Backup

Start backup

APS April 22, 2006 Session C12 12

Monte Carlo

CCNC

Y = Hadronic Energy Deposited / Total Neutrino Energy

CC Events with lots of Hadronic Activity look like NC Events

APS April 22, 2006 Session C12 13