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Current Status of the MiniBooNE Neutral Current  0 Analysis

Current Status of the MiniBooNE Neutral Current  0 Analysis. Heather Ray hray@fnal.gov Los Alamos National Lab. Outline. Current world measurements Event selection Reconstructed mass peak Kinematic variables Future Plans. Current Measurements. One absolute measurement : Gargamelle.

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Current Status of the MiniBooNE Neutral Current  0 Analysis

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  1. Current Status of the MiniBooNE Neutral Current 0 Analysis Heather Ray hray@fnal.gov Los Alamos National Lab

  2. Outline • Current world measurements • Event selection • Reconstructed mass peak • Kinematic variables • Future Plans H. Ray

  3. Current Measurements • Oneabsolute measurement : Gargamelle Cross section for  - p Cross section for  - n Hawker, Morfin, and Pohl : NuInt ‘02 H. Ray

  4. Current Measurements • Rest of measurements exist as NC/CC  ratios • (bubble, spark chambers) NC  / CC  = 0.064  0.001(stat)  0.007(syst) K2K, hep-ex/0408134 R0 = (0/ )data = 1.03  0.02(stat)  0.09(syst) (0/  )MC C. Mauger for K2K, Nucl.Proc.Suppl. 112 (2002) H. Ray

  5. Why Measure 0 Cross Sections? • MiniBooNE : dominant mis-id background for e appearance oscillation analysis • NC0  used to limit the sterile neutrino component present in atmospheric oscillations • crucial for distinguishing  from s • + angular distribution constrains mechanisms for NC 0 production H. Ray

  6. Event Selection candidate • Identify events using hit topology • Minimum tank hits, maximum veto hits, no decay electrons, 2 Cerenkov rings > 40 MeV each, opening angle cut, minimum allowed reconstructed mass • signal yield extracted from fit with bgd MC : fit assuming 2 rings • Collected ~2x1020 pot for this analysis ecandidate 0 candidate H. Ray

  7. NC 0 Candidate Events • Mass peak : 55% sample purity with 42% efficiency • Signal from NC resonant and coherent production • Resonant •  + (p/n)   +    (p/n)+ 0 • Background to e appearance • Coherent •  + C  + C + 0 • Background from all other events (some multi- and non-NC final state 0 expected) H. Ray

  8. NC 0 Kinematic Distributions Errors are shape errors Dark grey : flux errors Light grey : representative oil optical model variation bands • Fit to mass peak to extract signal yields in each kinematic bin • high purity! • Angular distribution of production as a function of reconstructed 0 direction relative to beam direction (Cos 0) • sensitive to production mechanism (coherent = forward, resonant = not so forward) H. Ray

  9. NC 0 Kinematic Distributions • 0 momentum = good data/mc agreement • Falloff at high momentum due to flux (less 0 at high momentum) • Cosine of COM angle • Important for appearance search : CCQE e has large values H. Ray

  10. Summary • Lack of cross section measurements in MiniBooNE energy range • On the way to analyzing the coherent contribution to production • Next step : NC 0 cross section! H. Ray

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