Current Status of the MiniBooNE Neutral Current ?0 Analysis

1
Current Status of the MiniBooNE Neutral Current
?0 Analysis

• Heather Ray
• hray_at_fnal.gov
• Los Alamos National Lab

2
Outline

• Current world measurements
• Event selection
• Reconstructed mass peak
• Kinematic variables
• Future Plans

3
Current Measurements

• One absolute measurement Gargamelle

Cross section for ? - p
Cross section for ? - n
Hawker, Morfin, and Pohl NuInt 02
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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)
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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

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Event Selection
? candidate

• Identify events using hit topology
• Minimum tank hits, maximum veto hits, no decay
  electrons, 2 Cerenkov rings gt 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

?0 candidate
e candidate
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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)

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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)

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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

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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!