Uncertainty for NPDGamma experiment in reaction

Pil-Neyo SeoU of Virginia/TUNL

HIGS2 Workshop, June 3-4, 2013

NPDGamma experiment

, where

NPDGamma experiment

Uncertainties in NPDGamma experiment-Statistical uncertainty

: associated with detected gamma rays, unavoidable: limit by beam intensity and detector solid angle : electronic noise and drift was small compared to counting statistics

LANSCE SNS

Uncertainties in NPDGamma experiment-Systematic uncertainty

: not associated with the beam: gain drift and additive couplings (mag field on detector gain, leakage of control signal into preamp, shift in main voltage when pwr supply on and off…) - additive couplings diagnosed by no beam for up-down asymmetry - gain drift by illuminating a detector with light - isolating PV signal from neutron spin flip

Main handle to control systematic uncertainty : frequent reversal of neutron polarization spin direction

in match with beam pulse frequency

B= 𝐴𝛾❑𝑚𝑒𝑎𝑠𝑢𝑟𝑒𝑑=

𝑈 ↑−𝐷↑−(𝑈 ↓−𝐷↓)𝑈 ↑+𝐷↑+(𝑈 ↓+𝐷↓)