Kinematic sensitivity to the Fierz term of $\beta$-decay differential spectra

Abstract

The current most stringent constraints on exotic scalar or tensor couplings in neutron and nuclear $\beta$ decay, involving left-handed neutrinos, are obtained from the Fierz interference term. The sensitivity to this term in a correlation coefficient is usually driven by an energy-averaged kinematic factor that increases monotonically toward smaller values of the $\beta$ endpoint energies. We first point out here that this property does not hold for certain differential observables that are directly sensitive to the Fierz term, such as the $\beta$ or the recoil energy spectrum. This observation is relevant for the selection of sensitive transitions in searches for exotic couplings through spectrum shape measurements. We then point out previous errors in the exploitation of measurements of the $\beta -\nu$ angular correlation coefficient and discuss their impact on the extraction of constraints on exotic couplings.

7 pages, 5 figures

References in corpus (5)

• Tests of the standard electroweak model in beta decay
• Precision Measurement of the Neutron Beta-Decay Asymmetry
• Measurement of the Beta-Neutrino Correlation of Sodium-21 using Shakeoff Electrons
• Tensor interaction constraints from beta decay recoil spin asymmetry of trapped atoms
• The use of Geant4 for simulations of a plastic beta-detector and its application to efficiency calibration

Cited by in corpus (11)

• Comprehensive analysis of beta decays within and beyond the Standard Model
• $\mathcal{F}t$ values of the mirror $\beta$ transitions and the weak magnetism induced current in allowed nuclear $\beta$ decay
• First direct constraints on Fierz interference in free neutron $\beta$ decay
• Using Nab to determine correlations in unpolarized neutron decay
• Constraints on subleading interactions in beta decay Lagrangian
• Opportunities and open questions in modern $\beta$ decay
• Multipole decomposition of tensor interactions of fermionic probes with composite particles and BSM signatures in nuclear reactions
• Gas electron tracking detector for beta decay experiments
• ${}^{23}$Ne Production at SARAF-I
• Nuclear ab initio calculations of 6He $\beta$-decay for beyond the Standard Model studies
• Testing effective field theory with the most general neutron decay correlations