Corrections for the polarization-dependent efficiency and new neutron-proton analyzing power data at 7.6 MeV

Abstract

We present new corrections for the polarization-dependent efficiency (PDE), which introduces a false asymmetry into measurements of n-p analyzing power A y (θ) caused by double scattering in the neutron side detectors. To accomplish this, we created a new database of 12 C( n,n) A y (θ) by using a combination of fits to data, phase-shift analysis, and R-matrix analysis. Our recorrection for PDE of previously reported n-p A y (θ) data at 7.6 and 12.0 MeV and new data at 7.6 MeV indicate that we have achieved a superior representation of 12 C( n,n). Our results continue to suggest a possible charge dependence of the pion-nucleon coupling constant.The motivation for collecting high-precision neutronproton (n-p) analyzing power A y (θ ) data is to test the accuracy of nucleon-nucleon (NN) phase-shift analysis (PSA) predictions for this observable. At low energy, n-p A y (θ ) depends greatly on the 3 P 0 , 3 P 1 , and 3 P 2 phase shifts and good-quality data can be useful in constraining these parameters. Nearly two decades ago, Triangle Universities Nuclear Laboratory (TUNL) collected n-p A y (θ ) data at E n = 7.6, 12.0, 14.0, 16.0, and 18.0 MeV [1]. In terms of uncertainties, these data were of similar quality as earlier measurements by Holslin and co-workers [2] at E n = 10.03 MeV. None of these data were of adequate precision to show clear discrepancies with the Nijmegen PSA predictions [3]. Reference [1] also found that data from 14 to 20 MeV probably would not be able to demonstrate discrepancies with NN predictions, since there is less difference between the various theoretical models in this energy range.

Precise determination of charge-dependent pion-nucleon-nucleon coupling constants

“…The problem was re-analyzed theoretically in ref. [59], and motivated the reanalysis of the data [60] and the disentanglement between systematic and statistical errors. Actually, in ref.…”