Analysis of aCORN Data J. E. Adelman*, M. S. Dewey†, F. Wietfeldt‡, G. Darius‡, G.L. Jones*, B. Collett*, and R. Kosar* August 2012 * Hamilton College, Clinton NY † The National Institute of Standards and Technology, Gaithersburg, MD ‡ Tulane University, New Orleans, LA.

Background: Neutron Decays Free neutrons undergo beta decay Standard Model: Two constants characterize this decay – g A : axial coupling – g V : vector coupling

Neutron decay has several correlation coefficients – Know any two, get g V, g A. – Know any three – test standard model a is the electron-antineutrino correlation coefficient – Current value: ± 0.004

veve Background II: The aCORN Project To get a, measure antineutrino and electron momentum – Proton used to infer ν ē Experiment designed to give two groups – “Fast” and “Slow” protons p+ veve e- p+ Electron Detector Proton Detector Group 1 “Fast” Group 2 “Slow”

Group Separation depends on electron energy – Result: “Wishbone” data shape “Slow” Group “Fast” Group

The aCORN Apparatus Analysis focused on four apparatus parameters 1. Electrostatic mirror voltage 2. Electron detector trim coil current 3. Proton detector size and focusing grid 4. Electron detector gain

Current State of aCORN Apparatus assembled on NCNR’s NG-6 beamline January – March 2011: Data collection – Raw data distilled and reduced prior to analysis Another round with the beam – February 2012

Goals: 1.Introduce a new calibration paradigm 2.Perform series by series analysis on outstanding data 3.Note the effects of parameter changes on calculated asymmetries 4.Offer suggestions for next round of data collection

Part I: Calibration Bi and Sn sources Points of Analysis: – Resolutions – Are three Gaussians better than one? – Effect of apparatus parameters on resolutions Channel Number Counts

Results Resolutions still below expectations – Need ~ 20% Three Gaussian: – 1% better on Sn – 2% better on Bi 975 Curve correlated to run parameters New Bi source shows promise of improved

Part II: Series Analysis Goal: extract values for “pseudo-a”, wishbone rate, and background rate for all outstanding data.

Part III: Analysis Original Goal: Algebraic isolation of individual effects by pairwise examination – Problem: Splitting series in half gives values beyond the calculated error bars Fallback: Single-factor Analysis of Variance (ANOVA) – f-test to find correlations – Difficult to discern contributions from multiple effects

ANOVA Results Algebraic analysis indicated effects on the order of pseudo a Evidence is consistent with a problem detecting protons

Series Summary

Part IV: Unanswered Questions Missing Rate Shape to Rate vs. Time Graph

Acknowledgement I would like to thank NIST, the SURF advisors, my mentor Scott Dewey, the members of the aCORN consortium, PML’s Neutron Research group, and everyone else who helped foster an enjoyable and productive summer