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Neutrino Nucleon Elastic Scattering in MiniBooNE

Outline Theory behind ν neutral current scattering & Δ s How NCE and CCQE are observed in MiniBooNE An idea to identify protons from NCE interactions. Neutrino Nucleon Elastic Scattering in MiniBooNE. ν p → ν p. — David Christopher Cox ( Indiana University ).

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Neutrino Nucleon Elastic Scattering in MiniBooNE

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  1. Outline Theory behind νneutral current scattering & Δs How NCE and CCQE are observed in MiniBooNE An idea to identify protons from NCE interactions Neutrino Nucleon Elastic Scattering in MiniBooNE ν p → ν p — David Christopher Cox (Indiana University)

  2. Vector form factors: F1, F2 ~ nucleon weak charge, magnetic moment Axial vector form factor G1 related to nucleon spins NC scattering allows contribution of strange quark (isoscalar) terms to f.f.’s For example: isospin sign from neutron β decay where Δs in Neutrino Nucleon Scattering Nucleon Weak Current: (assumes time and isospin invariance, pseudoscalar f.f. = 0)

  3. Differential cross section for ν and ν N NC and CC scattering: ν pelastic Δs in ν N Cross Sections G1 dominant at low Q2(proton KE) to first order 0.0 0.1 0.2 0.3 flux weighted cross section (10-38cm-1) Ratios reduce sensitivities to systematics, nuclear effects, etc. in study MiniBooNE & FINeSSE* 0.1 0.3 0.5 0.7 0.9 1.1 Q2 (GeV2) *Rex Tayloe BE007

  4. Basic ν N Scattering Events in MiniBooNE 250 kgal baby oil sphere constantly monitored by PMT’s (main & veto)* *Chris Green CG002 Charged Current Quasi-Elastic CCQE Neutral Current Elastic (NCE) Черенков scintillating some scint 7:1 Черенков : Scintillation Take advantage of different event structures…

  5. Monte Carlo Look at NCE Event Separation No decaying leptons (none in neutral current) Low light level in veto (eliminates punch through leptons) Low light level in main tank (eliminates high Evis events) Preliminary greatly reduces CCQEs Number of hit PMTs in main tank

  6. NCE events in the data Additional cut: data in beam window Preliminary sensitive to details ~200MeV p; 15MeV e- equiv Relatively normalized good shape agreement

  7. Identify NCE: distinguish protons/electrons/muons Protons below threshold (Q2~0.7GeV2)  scintillate Muons, electrons above threshold  (mainly) Черенков Predict different hit time distributions (include gauβ recon. “smearing”) Scintillation Черенков exponent (~20ns decay) δ-function (prompt) predicted time distribution (analytic) time (ns) time (ns) Hypothesize 100% pure Черенков, 100% pure Scintillation “particles” Use log likelihood analysis to match real particles to hypotheses Predicted time distributions  pdf’s

  8. Testing the model Generate single particle proton, electron events in MC Use combined power of log(L_scint) and log(L_Чер) with ratio: some separation between protons, electrons. encouraging— continue studies Preliminary

  9. Summary & Future Work Goal: measure Δs in MiniBooNE Use NCE vs CCQE different event structures Separate p/μ/e using time—distinguish NCE events Encouraging results Pursue further…include topology Scintillation Черенков isotropic (no shape) ring shaped

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