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
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