Effect of the N3LO three-nucleon contact interaction on p-d scattering observables

A unitary transformation allows to remove redundant terms in the two-nucleon (2N) contact interaction at the fourth order (N3LO) in the low-energy expansion of Chiral Effective Field Theory. In so doing a three-nucleon (3N) interaction is generated. We express its short-range component in terms of five combinations of low-energy constants (LECs) parametrizing the N3LO 2N contact Lagrangian. Within a hybrid approach, in which this interaction is considered in conjunction with the phenomenological AV18 2N potential, we show that the involved LECs can be used to fit very accurate data on polarization observables of low-energy $p-d$ scattering, in particular the $A_y$ asymmetry. The resulting interaction is of the right order of magnitude for a N3LO contribution.Comment: 9 pages, 2 figure

The X17 boson and the 3^3H(p,e+e−)4(p,e^+ e^-)^4He and 3^3He(n,e+e−)4(n,e^+ e^-)^4He processes: a theoretical analysis

The present work deals with $e^+$-$e^-$ pair production in the four-nucleon system. We first analyze the process as a purely electromagnetic one in the context of a state-of-the-art approach to nuclear strong-interaction dynamics and nuclear electromagnetic currents, derived from chiral effective field theory ($\chi$EFT). Next, we examine how the exchange of a hypothetical low-mass boson would impact the cross section for such a process. We consider several possibilities, that this boson is either a scalar, pseudoscalar, vector, or axial particle. The ab initio calculations use exact hyperspherical-harmonics methods to describe the bound state and low-energy spectrum of the $A\,$=$\,4$ continuum, and fully account for initial state interaction effects in the $3+1$ clusters. While electromagnetic interactions are treated to high orders in the chiral expansion, the interactions of the hypothetical boson with nucleons are modeled in leading-order $\chi$EFT (albeit, in some instances, selected subleading contributions are also accounted for). We also provide an overview of possible future experiments probing pair production in the $A\,$=$\,4$ system at a number of candidate facilities.facilities.Comment: 32 pages, 17 figures. Corrected version, having fixed a problem with a phase in the multipolar expansions. Only Figs. 4 and 10 change significantly, the rest only marginally. The conclusions are unchanged. We include also a number of improvements: 1) better wave functions, 2) the isoscalar pseudoscalar case, and 3) the comparison with the new ATOMKI data (see new Fig. 17

Religion, welfare regimes and attitudes toward government responsibility for citizens' welfare. A European comparative analysis

The article aims to investigate the relationship between individual religiosity and attitudes towards government responsibility for citizens' welfare. The rationale for such a relationship stems from the idea that religion and government spending can be intended as substitute mechanisms that may insure individuals against negative life events. We theorized the existence of an additional and opposite mechanism working in certain contexts: complementarity of responsibility. The local solutions provided by Church organizations and State interventions are not always perceived to be in opposition, but they can reinforce each other. In testing the relationship between religiosity and attitudes toward public support, we hypothesized a moderating impact of contextual features: The prevalent religious denomination in a country and the type of welfare state regime. Both may have indeed influence on citizens' opinions about the role of government responsibility because they contribute to shape individual preferences. To address these issues in a multilevel framework, we analyse the integrated European Value Study database for 31 European countries. Our results confirm that the different Christian doctrines, the various types of welfare state regimes, as well as the combinations of the two, shape differently the relationship between religiosity and attitudes toward government responsibility