Status of MiniBooNE Short Baseline Neutrino Oscillation Experiment

1. Status of MiniBooNE Short Baseline Neutrino Oscillation Experiment Jonathan Link Columbia University International Conference on Flavor Physics October 4, 2005

2. Neutrino Phenomenology If neutrinos have mass then they may oscillate between flavors. → Schrödinger's Eq. With three neutrinos the mixing is governed by the MNS matrix which relates the mass eigenstates (n1, n2 andn3) to the flavor eigenstates. For oscillations involving just two neutrino mass eigenstates the oscillation probability simplifies to Jonathan Link, Columbia ICFP05

3. Neutrino Oscillation Data Unconfirmed observation by LSND. Seen by Super-K and confirmed by many including K2K. (q23) First observed by Ray Davis. Nailed down by Super-K, SNO and KamLAND. Presumed to be dominated by mixing between states 1and 2 (or q12) Jonathan Link, Columbia ICFP05

4. The LSND Experiment LSND took data from 1993-98 The full dataset represents nearly 49,000 Coulombs of protons on target. p+ m+ nm Baseline of 30 meters Energy range of 20 to 55 MeV L/E of about 1m/MeV nep e+ n e+ nmne n+H→D+γ LSND’s Signature Scintillation Čerenkov 2.2 MeV neutron capture Jonathan Link, Columbia ICFP05

5. The LSND Signal They looked for an excess of ne events in a nm beam They found 87.9 ± 22.4 ± 6.0 events over expectation. With an oscillation probability of (0.264 ± 0.067 ± 0.045)%. Decay in flight analysis (nmne) oscillation probability of (0.10± 0.16 ± 0.04) % Jonathan Link, Columbia ICFP05

6. ν3 Dm22 ν2 Dm12 ν1 Why is this Result Interesting? LEP found that there are only 3 light neutrinos that interact weakly. Three neutrinos allow only 2 independent Dm2 scales. Dm32=Dm12+ Dm22 But there are experimental results at 3 different Dm2 scales!?! Jonathan Link, Columbia ICFP05

7. What Does it Mean? • First, One or more of the experiments may be wrong LSND being the leading candidate, has to be checked → MiniBooNE • Otherwise, add one or more sterile neutrinos… Giving you more independent Dm2 scales • Best fits to the data require at least two sterile The Usual 3 ν Model mass Jonathan Link, Columbia ICFP05

8. A Conclusive Experiment is Needed • With High Significance • At least 3s over the entire LSND region (including systematic and statistical uncertainties) • Able to demonstrate energy dependence for oscillation • Low and Different Systematics (Change the signature) • Change the beam to higher energy • Optimize detector for new signature • High Statistics • Significantly more events than LSND The MiniBooster Neutrino Experiment, MiniBooNE, was formed. The collaboration consists of about 60 scientists from 14 institutions. Jonathan Link, Columbia ICFP05

9. The MiniBooNE Neutrino Beam nmne? • Start with an intense 8 GeV proton beam from the Booster. • In the Be target primarily pions are produced, but also some kaons. • Charged pions decay almost exclusively as p±m±nm. • K±p0e±ne, KLp±ene and m±e±ne contribute ne’s to background. • A toroidal field horn focuses the charged particles on the detector. • Initially positive particles will be focused selecting n. • The horn current can be reversed to select n. • Increases neutrino intensity by a factor of 5. • The horn is followed by a decay region. • The decay region is followed by an absorber and 450 m of dirt, beyond which only the neutrino component of the beam survives. Jonathan Link, Columbia ICFP05

10. Neutrino Flux at the Detector The L/E is designed to be a good match to LSND at ~1 m/MeV. From beam simulations, the expected intrinsic ne flux is small compared to the nm flux. But the intrinsic ne flux is comparable in size to an LSND-like signal. Jonathan Link, Columbia ICFP05

11. The MiniBooNE Detector • 12 meter diameter sphere • Filled with 950,000 liters of pure mineral oil — 20+ meter attenuation length • Light tight inner region with 1280 photomultiplier tubes • Outer veto region with 240 PMTs. Jonathan Link, Columbia ICFP05

12. Approximate number of events and Background expected in MiniBooNE nmCharged Current, Quasi-elastic 500,000 events Intrinsic νe (from K&μ decay) : 236 events Background π0 mis-ID: 294 events (Neutral Current Interaction) Otherνμmis-ID: 140 events Signal LSND-like nmne signal: 300 events Jonathan Link, Columbia ICFP05

13. Particle Identification: m, e, and p0 • Neutrino interactions in oil produce: • Prompt Čerenkov light in a cone centered on the track. • Delayed scintillation light distributed isotropically. • Čerenkov to scintillation ratio ~ 4 to 1 • Particle ID is based on ring fuzziness, track length, ratio of prompt/late light. • Fuzzy rings distinguish electrons from muons. • p0 look like 2 electrons (usually) Short Exiting Jonathan Link, Columbia ICFP05

14. 1.6 μs Beam Events Simple trigger: takes 20 μs about each beam spill. The spill is 1.6 μs wide. Cutting on less than 6 veto hits removes all primary cosmic rays. Requiring 200 tank hits removes all μ decay, or “Michel”, electrons leaving only primary beam events. Jonathan Link, Columbia ICFP05

15. Progress on Date Taking Minos Start-up Data Taking begain in September 2002. We need at least 5×1020 protons on target (pot)… We want 1×1021 pot We’ve got 6.3×1020 so far Jonathan Link, Columbia ICFP05

16. Progress on the Analysis • The minimum data required for the analysis is in the bag, butno oscillation analysis before the end of the year. • We still need… • Improved data on meson production (π and K) in proton beam • We have preliminary result from HARP on p-Be π thin target production (Agrees well with Brookhaven E910) • We’ve had a first look at thick target data • (at most a small effect) • We are still waiting for HARP charged K cross sections. • Neutral kaons have to come from somewhere else (E910 analysis underway) Jonathan Link, Columbia ICFP05

17. Progress on the Analysis (continued) • Work continues to improve the optical model… • Without a near detector we have no choice but to demand outstanding agreement between data and monte carlo. • We have many ex situ measurements of the oil properties. • This work has converged significantly in the last few months, but it is not done yet. Jonathan Link, Columbia ICFP05

18. Projected Coverage Here we see the projected limits for a null result with 1×1021 pot Even with 7×1021 pot we should still cover the entire 90% CL region from LSND at 3σ This sensitivity depends on understanding the background from intrinsic νe to 10% and the background from mis-ID π0 to 5% Jonathan Link, Columbia ICFP05

19. Sensitivity to a Signal Signal Mis-ID Intrinsic νe Δm2 = 1 ev2 Δm2 = 0.4 ev2 The LSND question will soon be resolved Jonathan Link, Columbia ICFP05

20. Cross Section Physics Region with MiniBooNE Coverage Great opportunity to contribute to neutrino interaction cross sections in the MiniBooNE Energy Range. Even less data on anti-neutrino cross sections! Jonathan Link, Columbia ICFP05

21. Charged Current π+ Cross Section Nice triple coincident signature Absolute cross section is calculated relative to the theoretical charged current quasi-elastic (ν+C → μ++C) cross section. Jonathan Link, Columbia ICFP05

22. Conclusions and Outlook • We have over 61020 protons on target in n mode. • With this data we will confirm or rule out the full high Dm2oscillation range of LSND (CP conserving). Results Soon. • If no signal is seen in n mode, n running is needed to investigate possible 3+2 CP violating modles. • We are working towards several interesting cross section results • Charged current π+ • Neutral Current π0 • Anti-neutrino run approved for 2006. Initially to study cross sections but can be extended to do oscillations. • Possible upgrade to BooNE, a two detector experiment to carefully measure Dm2 and look for nm disappearance. Jonathan Link, Columbia ICFP05

23. The BooNE Collaboration Jonathan Link, Columbia ICFP05

24. Inside the MiniBooNE Detector PMTs at the bottom of the detector just before sealing up the inner region. View of the Veto Region as the first oil is added to the detector. Jonathan Link, Columbia ICFP05

25. Beam Survey Experiments Experiments E910 at Brookhaven and HARP at CERN are studying K and p production with medium energy proton beams on beryllium. HARP took data using our target with 8 GeV protons. These data sets are still being analyzed. The results will be the primary input to our neutrino flux simulations. The HARP Experiment at CERN Jonathan Link, Columbia ICFP05

26. Other Related Data Several other experiments have looked for oscillations in this region. Allowed Region from Joint Karmen and LSND fit From Church, Eitel, Mills, & Steidl hep-ex/0203023 The most restrictive limits come from the Karmen Experiment. Jonathan Link, Columbia ICFP05

27. scintillator cube Calibration Systems Laser flasks provide PMT charge and timing calibration and a means to monitor the oil attenuation length in situ. Muon tracker above detector and 7 optically isolated scintillator cubes in the detector provide cross checks for energy estimation and reconstruction algorithms. Jonathan Link, Columbia ICFP05

28. Other Calibration Studies Cosmic Muons t = 2.12 ± 0.05 ms With 8% m- capture on carbon, expected m lifetime in oil is2.13 ms Preliminary e Energy from m Decay p0 Mass Can be used to check energy calibration at the relevant energy scale. >200 hits in Tank <6 hits in Veto >10 p.e. in each ring Jonathan Link, Columbia ICFP05

29. CCπ+ Jonathan Link, Columbia ICFP05

30. CCπ+ CCπ+ Jonathan Link, Columbia ICFP05

31. The Little Muon Counter (LMC) • Detects muons at an angle of 7° from the beam center. • At this angle all muons are from kaon decays. • Gives us an important data point on kaons in our own beam line. The LMC drift pipe during construction Jonathan Link, Columbia ICFP05