Eur. Phys. J. A (2017) 53: 168
https://doi.org/10.1140/epja/i2017-12357-7

Regular Article - Theoretical Physics

Uncertainties in constraining low-energy constants from ³H decay

¹ Institut für Kernphysik, Technische Universität Darmstadt, 64289, Darmstadt, Germany
² ExtreMe Matter Institute EMMI, GSI Helmholtzzentrum für Schwerionenforschung GmbH, 64291, Darmstadt, Germany
³ Department of Physics, University of Tokyo, Hongo, 113-0033, Tokyo, Japan
⁴ Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, 69117, Heidelberg, Germany

^* e-mail: pklos@theorie.ikp.physik.tu-darmstadt.de

Received: 17 July 2017
Accepted: 25 July 2017
Published online: 25 August 2017

Abstract

We discuss the uncertainties in constraining low-energy constants of chiral effective field theory from ³H decay. The half-life is very precisely known, so that the Gamow-Teller matrix element has been used to fit the coupling of the axial-vector current to a short-range two-nucleon pair. Because the same coupling also describes the leading one-pion-exchange three-nucleon force, this in principle provides a very constraining fit, uncorrelated with the ³H binding energy fit used to constrain another low-energy coupling in three-nucleon forces. However, so far such ³H half-life fits have only been performed at a fixed cutoff value. We show that the cutoff dependence due to the regulators in the axial-vector two-body current can significantly affect the Gamow-Teller matrix elements and consequently also the extracted values for the coupling constant. The degree of the cutoff dependence is correlated with the softness of the employed NN interaction. As a result, present three-nucleon forces based on a fit to ³H decay underestimate the uncertainty in . We explore a range of values that is compatible within cutoff variation with the experimental ³H half-life and estimate the resulting uncertainties for many-body systems by performing calculations of symmetric nuclear matter.