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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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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)

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


Δs in Neutrino Nucleon Scattering

Nucleon Weak Current:

(assumes time and isospin invariance, pseudoscalar f.f. = 0)

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


0.1 0.3 0.5 0.7 0.9 1.1

Q2 (GeV2)

*Rex Tayloe BE007

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)



some scint

7:1 Черенков : Scintillation

Take advantage of different event structures…

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)


greatly reduces CCQEs

Number of hit PMTs in main tank

NCE events in the data

Additional cut: data in beam window



to details

~200MeV p; 15MeV e- equiv

Relatively normalized

good shape agreement

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”)



exponent (~20ns decay)

δ-function (prompt)





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

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,



continue studies


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



isotropic (no shape)

ring shaped