Geoffrey Mills Status of the Mini Boo NE

Geoffrey Mills Status of the Mini. Boo. NE Experiment Purpose Operation Survey of Processes Analysis Progress Outlook

Geoffrey Mills Neutrino Oscillation Primer

Geoffrey Mills Surprisingly… • Evidence for neutrino oscillations is observed in (too? ) many settings: – – in the sun in cosmic ray interactions in the atmosphere in reactors at accelerators

Purpose: Confirm or deny LSND (as oscillations) LSND found an excess of e events in a beam Geoffrey Mills 4. 1 s evidence for oscillations.

Geoffrey Mills If LSND is confirmed… • Some possible explanations – Light (variable mass? ) sterile neutrinos • Could explain dark matter and dark energy? hep-ph/0507235 • Could explain pulsar kicks? • Could explain SN synthesis of heavy elements – Lorentz invariance violation(? ? ) – Quantum decoherence(? ? ? ) – …

Geoffrey Mills Enter Mini. Boo. NE. . . Fermilab Batavia, IL

Geoffrey Mills The Mini. Boo. NE Neutrino Beam e?

Geoffrey Mills Fermilab 8 -Ge. V Booster

2. 5 KV 170 KA 143 s 5 Hz

The Mini. Boo. NE Detector Geoffrey Mills 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. Neutrino interactions in oil produce: • Prompt Čerenkov light • Delayed scintillation light Čerenkov: scintillation ~ 5: 1

Geoffrey Mills

Geoffrey Mills Mini. Boo. NE Operation • Began recording data on September 1, 2002 • Finished neutrino mode running in February, 2006 – Booster provided ~ 5. 6 E 20 protons on target – Recorded ~ 700, 000 contained CC interactions • Switched to anti-neutrino mode Feb. 2006 – Continuing to run this way until near detector Sci. Boo. NE/Mini. Boo. NE are ready to switch back to neutrino mode

Geoffrey Mills Neutrino Event Rates Contains everything interesting: oscillation physics, exotic event rates, cross sections, etc. One must understand all three factors in order to reach new physics

Geoffrey Mills Neutrino Event Rates Contains everything interesting: oscillation physics, exotic event rates, cross sections, etc.

Geoffrey Mills Neutrino Beam Fluxes • Neutrino beams are produced in the laboratory by the weak decays of nuclei, nucleons, and , , and K mesons. • The spectrum of neutrinos from these decays is known extremely well • The only significant flux uncertainty comes from the production cross section of the parent particle and its subsequent scattering in target materials (ignoring neutrino oscillation parameters that is!) • In decay-at-rest beams, this is simply an overall normalization factor. A single well-understood neutrino cross section is enough to completely determine the neutrino flux (e. g. e elastic process, or an inverse -decay transition) However, in decay-in-flight beams, the complete differential production cross sections of the parent particles are needed, along with their interactions in material along their flight paths

Geoffrey Mills Decay-in-Flight Beams • The calculation of secondary-production cross sections of and K mesons in proton-nucleus collisions is not reliable, although new data is challenging modelers to make improvements • Phenomenological parameterizations can be valid over limited energy and angle ranges, more useful at higher energies (> ~15 Ge. V) (e. g. Sanford. Wang or others) • There are large discrepancies in the various hadron production models used in MC generators (MARS, FLUKA, MCNP, GHEISHA, etc. ), although the situation is has been improving In order to predict fluxes with uncertainties less than ~10%, direct measurements in the appropriate energy and angular ranges are necessary

Geoffrey Mills Variation in MC Predictions of Flux (Mini. Boo. NE) (old) Conclusion: the neutrino beam is sensitive to poorly understood, forward (small angle), pion production rates

Geoffrey Mills Mitigation of the Problem • Experimental design helps in neutrino oscillation measurements (although not in cross section measurements) • near/far ratio (two detectors): (K 2 K/MINOS) – This is the simplest solution, although somewhat more costly. Useful in both appearance and disappearance measurements, a large signal helps! • e / “ratio”: (Mini. Boo. NE) – In appearance experiments, the source neutrino channel (usually ) can be used to measure the expected oscillated flux under a particular oscillation hypothesis. This assumes only “lepton-universality” in the reaction cross sections, but accurate background measurements are important. Nevertheless, flux uncertainties can result in much poorer experimental sensitivities and better flux predictions are warranted

Geoffrey Mills HARP hep-ex/0702024

Geoffrey Mills Neutrino Event Rates Contains everything interesting: oscillation physics, exotic event rates, cross sections, etc.

Geoffrey Mills Mini. Boo. NE Events (no beam) Tank is inner region (1280 tubes) "Veto is optically isolated outer region (240 tubes) " Cosmics enter outer veto region first " " " Rate consistent with known measurement. Check of veto efficiency Michel electrons decay from cosmic muons " Important tool for calibration " Well-understood. "

Geoffrey Mills

Geoffrey Mills Michel Decay Events for Calibration

0 Reconstruction: constrains important mis-ID background Neutral Current 0 C 0 X Geoffrey Mills

Geoffrey Mills

Geoffrey Mills Backgrounds • Misidentified neutral current 0 – 0 rate is well measured – background comes from events where single decay photon happens to go forward • Misidentified CC interactions – Have a large sample of Michel-tagged events to determine backrounds • Intrinsic e from kaon and muon decays – Daughter muon decays are directly linked to primary pion decays and hence constrained by CCQE event rates – Kaons are sufficiently constrained by measured high energy (>1. 5 Ge. V) interactions

Geoffrey Mills Mini. Boo. NE Conclusions • All the necessary ingredients are in place, flux, cross sections, backgrounds, detector response • We have constructed a “final fit” to our CCQE data ( and e ) for an appearance signal • We will proceed to “unblind” the data when we are satisfied that our systematic errors are understood • Stay tuned…