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A Search for Sterile Neutrinos in MINOS

A Search for Sterile Neutrinos in MINOS. Thomas Osiecki University of Texas at Austin For the MINOS Collaboration. Motivation for Sterile Neutrinos Sterile Neutrino Signature in MINOS Experimental Challenges Sensitivity Outlook. Motivation For Sterile Neutrinos.

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A Search for Sterile Neutrinos in MINOS

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  1. A Search for Sterile Neutrinos in MINOS Thomas Osiecki University of Texas at Austin For the MINOS Collaboration • Motivation for Sterile Neutrinos • Sterile Neutrino Signature in MINOS • Experimental Challenges • Sensitivity • Outlook APS April 22, 2006 Session C12

  2. Motivation For Sterile Neutrinos Dm2sol + Dm2atmDm2LSND 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 also predicted by a number of theories APS April 22, 2006 Session C12

  3. m- nm W+ u d Sterile Neutrino Signature Using NC Predict Far Measure Near nmNC nX NC Conventional Oscillations X=e,m,t Evisible Evisible Sterile Oscillations CC NC nX NC X=e,m,t,sterile Evisible NC Deficit in Predicted energy spectrum is evidence of sterile oscillations APS April 22, 2006 Session C12

  4. Neutrino Interactions in MINOS Monte Carlo NC CC NC 1.8m 3.5m Transverse Direction CC E Resolution: Longitudinal Direction APS April 22, 2006 Session C12

  5. Oscillations Effect on NC Energy Take a Monte Carlo Far Detector NC energy spectrum with a CC background to study effects of sterile neutrinos fsterile = Fraction of Sterile Mixing Conventional Oscillations Sterile Oscillations NC (fsterile = 0) NC (fsterile = 0) (fsterile = 0.3) CC (No Osc.) (fsterile = 0.5) CC (Osc.) CC (Osc.) Dm2=0.003 eV2 Dm2=0.003 eV2 APS April 22, 2006 Session C12

  6. Experimental Challenges - Intensity Intense Neutrino Beam, Many Interactions Near Detector Data 1 neutrino spill=10 ms MINOS NC signal is at low energies. Have to properly identify Individual interactions Near Detector is crucial for Extrapolation to Far APS April 22, 2006 Session C12

  7. Experimental Challenges - CC/NC Separation 1-RMS in longitudinal direction from charge weighted center 2-Energy per Plane in the 2nd Half of the Event 3-Maximum Energy in a 4 Plane Window Can Construct PDFs from 1,2,3 Monte Carlo 1 3 2 CC dE/dx m NC [m] [ADC counts] [%] APS April 22, 2006 Session C12

  8. NC/CC Separation Select NC-like Spectrum from Particle ID (PID) Cut Percentage of NC Events Retained Percentage of Events that are Actually NC Monte Carlo CC NC PID Particle ID Particle ID APS April 22, 2006 Session C12

  9. Physics Reach Far Detector Mock Data with Dm2 = 0.00212 eV2 , fsterile = 0.11 Performed a Chi-squared Fit between “data” and prediction at Far 7.4e20 Protons on Target Monte Carlo Visible Energy (GeV) fsterile APS April 22, 2006 Session C12

  10. Outlook • 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. NC Background Y = Hadronic Energy Deposited / Total Neutrino Energy Monte Carlo CC NC CC Events with lots of Hadronic Activity look like NC Events APS April 22, 2006 Session C12

  13. SK Sterile Limit APS April 22, 2006 Session C12

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