Paper detail

First results from the NPDGamma experiment at the Spallation Neutron Source

The NPDGamma experiment aims to measure the parity-odd correlation between the neutron spin and the direction of the emitted photon in neutron-proton capture. A parity violating asymmetry (to be measured to 10$^{-8}$) from this process can be directly related to the strength of the hadronic weak interaction between nucleons, specifically the $Δ$I=1 contribution. As part of the commissioning runs on the Fundamental Neutron Physics beamline at the Spallation Neutron Source (SNS) at ORNL, the gamma-ray asymmetries from the parity-violating capture of cold neutrons on $^{35}$Cl and $^{27}$Al were measured, to check for systematic effects, false asymmetries, and backgrounds. Early this year, the parahydrogen target for the production run of NPDGamma was commissioned. Preliminary results for the commissioning measurements with $^{35}$Cl and $^{27}$Al will be presented as well as first results of the hydrogen run.