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

Jonathan Link, Columbia ICFP05 Neutrino Phenomenology If neutrinos have mass then they may oscillate between flavors. For oscillations involving just two neutrino mass eigenstates the oscillation probability simplifies to With three neutrinos the mixing is governed by the MNS matrix which relates the mass eigenstates ( 1, 2 and 3 ) to the flavor eigenstates. → Schrödinger's Eq.

October 4, 2005Jonathan Link, Columbia ICFP05 First observed by Ray Davis. Nailed down by Super-K, SNO and KamLAND. Presumed to be dominated by mixing between states 1and 2 (or  12 ) Seen by Super-K and confirmed by many including K2K. (  23 ) Unconfirmed observation by LSND. Neutrino Oscillation Data

October 4, 2005Jonathan Link, Columbia ICFP05 The LSND Experiment LSND took data from The full dataset represents nearly 49,000 Coulombs of protons on target The full dataset represents nearly 49,000 Coulombs of protons on target. Baseline of 30 meters Energy range of 20 to 55 MeV L/E of about 1m/MeV LSND’s Signature 2.2 MeV neutron capture Čerenkov Scintillation  +   +  e +  e e  p  e + n n+H→D+γ

October 4, 2005Jonathan Link, Columbia ICFP05 The LSND Signal They looked for an excess of e events in a  beam They found 87.9 ± 22.4 ± 6.0 events over expectation. With an oscillation probability of (0.264 ± ± 0.045)%. Decay in flight analysis (   e ) oscillation probability of (0.10 ± 0.16 ± 0.04) %

October 4, 2005Jonathan Link, Columbia ICFP05 Why is this Result Interesting? LEP found that there are only 3 light neutrinos that interact weakly. ν3ν3 ν2ν2 ν1ν1 m22m22 m12m12  m 3 2 =  m  m 2 2 Three neutrinos allow only 2 independent  m 2 scales. But there are experimental results at 3 different  m 2 scales!?!

October 4, 2005Jonathan Link, Columbia ICFP05 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  m 2 scales Best fits to the data require at least two sterile The Usual 3 ν Model mass

October 4, 2005Jonathan Link, Columbia ICFP05 A Conclusive Experiment is Needed With High Significance With High Significance – At least 3  over the entire LSND region (including systematic and statistical uncertainties) – Able to demonstrate energy dependence for oscillation Low and Different Systematics (Change the signature) Low and Different Systematics (Change the signature) – Change the beam to higher energy – Optimize detector for new signature High Statistics High Statistics – Significantly more events than LSND The Mini Booster Neutrino Experiment, MiniBooNE, was formed. The collaboration consists of about 60 scientists from 14 institutions.

October 4, 2005Jonathan Link, Columbia ICFP05 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  ±  ± . K ±   e ± e, K L  ± e  e and  ±  e ± e contribute e ’s to background. A toroidal field horn focuses the charged particles on the detector. Initially positive particles will be focused selecting. The horn current can be reversed to select. 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.   e ? The MiniBooNE Neutrino Beam

October 4, 2005Jonathan Link, Columbia ICFP05 Neutrino Flux at the Detector From beam simulations, the expected intrinsic e flux is small compared to the  flux. The L/E is designed to be a good match to LSND at ~1 m/MeV. But the intrinsic e flux is comparable in size to an LSND-like signal.

October 4, 2005Jonathan Link, Columbia ICFP05 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.

October 4, 2005Jonathan Link, Columbia ICFP05 Intrinsic ν e (from K&μ decay) : 236 events Other  ν μ mis-ID: 140 events π 0 mis-ID: 294 events (Neutral Current Interaction) LSND-like   e signal: 300 events Approximate number of events and Background expected in MiniBooNE   Charged Current, Quasi-elastic   Charged Current, Quasi-elastic 500,000 events 500,000 events Background Signal

October 4, 2005Jonathan Link, Columbia ICFP05 Neutrino interactions in oil produce: Prompt Čerenkov light in a cone centered on the track. Prompt Čerenkov light in a cone centered on the track. Delayed scintillation light distributed isotropically. 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.  0 look like 2 electrons (usually) Particle Identification: , e, and  0 Short Exiting

October 4, 2005Jonathan Link, Columbia ICFP05 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. 1.6 μs

October 4, 2005Jonathan Link, Columbia ICFP05 Progress on Date Taking Data Taking begain in September We need at least 5×10 20 protons on target (pot)… We want 1×10 21 pot We’ve got 6.3×10 20 so far Minos Start-up

October 4, 2005Jonathan Link, Columbia ICFP05 Progress on the Analysis The minimum data required for the analysis is in the bag, but no 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)

October 4, 2005Jonathan Link, Columbia ICFP05 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.

October 4, 2005Jonathan Link, Columbia ICFP05 Projected Coverage Here we see the projected limits for a null result with 1×10 21 pot Even with 7×10 21 pot we should still cover the entire 90% CL region from LSND at 3σ This sensitivity depends on understanding the background from intrinsic ν e to 10% and the background from mis-ID π 0 to 5%

October 4, 2005Jonathan Link, Columbia ICFP05 Signal Mis-ID Intrinsic ν e Δm 2 = 1 ev 2 Δm 2 = 0.4 ev 2 Sensitivity to a Signal The LSND question will soon be resolved

October 4, 2005Jonathan Link, Columbia ICFP05 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!

October 4, 2005Jonathan Link, Columbia ICFP05 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.

October 4, 2005Jonathan Link, Columbia ICFP05 Conclusions and Outlook We have over 6  protons on target in  mode. We have over 6  protons on target in  mode. With this data we will confirm or rule out the full high  m 2 oscillation range of LSND (CP conserving). Results Soon. With this data we will confirm or rule out the full high  m 2 oscillation range of LSND (CP conserving). Results Soon. If no signal is seen in mode, running is needed to investigate possible 3+2 CP violating modles. If no signal is seen in mode, running is needed to investigate possible 3+2 CP violating modles. We are working towards several interesting cross section results We are working towards several interesting cross section results – Charged current π + – Neutral Current π 0 Anti-neutrino run approved for Initially to study cross sections but can be extended to do oscillations. Anti-neutrino run approved for Initially to study cross sections but can be extended to do oscillations. Possible upgrade to BooNE, a two detector experiment to carefully measure  m 2 and look for  disappearance. Possible upgrade to BooNE, a two detector experiment to carefully measure  m 2 and look for  disappearance.

October 4, 2005Jonathan Link, Columbia ICFP05 The BooNE Collaboration

October 4, 2005Jonathan Link, Columbia ICFP05 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. Inside the MiniBooNE Detector

October 4, 2005Jonathan Link, Columbia ICFP05 Beam Survey Experiments Experiments E910 at Brookhaven and HARP at CERN are studying K and  production with medium energy proton beams on beryllium. The HARP Experiment at CERN 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.

October 4, 2005Jonathan Link, Columbia ICFP05 Other Related Data Allowed Region from Joint Karmen and LSND fit The most restrictive limits come from the Karmen Experiment. From Church, Eitel, Mills, & Steidl hep-ex/ Several other experiments have looked for oscillations in this region.

October 4, 2005Jonathan Link, Columbia ICFP05 scintillator cube 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. Calibration Systems

October 4, 2005Jonathan Link, Columbia ICFP05 Other Calibration Studies With 8%   capture on carbon, expected  lifetime in oil is 2.13  s Cosmic Muons  = 2.12 ± 0.05  s e Energy from  Decay Preliminary  0 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

October 4, 2005Jonathan Link, Columbia ICFP05 CCπ +

October 4, 2005Jonathan Link, Columbia ICFP05 CCπ +

October 4, 2005Jonathan Link, Columbia ICFP05 The Little Muon Counter (LMC) Detects muons at an angle of 7° from the beam center. Detects muons at an angle of 7° from the beam center. At this angle all muons are from kaon decays. At this angle all muons are from kaon decays. Gives us an important data point on kaons in our own beam line. Gives us an important data point on kaons in our own beam line. The LMC drift pipe during construction