Tests of the Equivalence Principle with Neutral Kaons

TL;DR

This paper tests the Equivalence Principle for particles and antiparticles using neutral kaon decay data, finding no correlation with gravitational potential variations and setting stringent limits on possible violations.

Contribution

It provides the first search for modulations in kaon decay parameters related to gravitational potential changes, establishing new bounds on equivalence principle violations for different interaction types.

Findings

No observed correlation between decay parameters and gravitational potential variations.

Limits on equivalence principle violations are set at 6.5, 4.3, and 1.8 x 10^{-9} for scalar, vector, and tensor interactions.

Upper bounds on gravitational coupling differences between K0 and K0bar are established.

Abstract

We test the Principle of Equivalence for particles and antiparticles, using CPLEAR data on tagged K0 and K0bar decays into pi^+ pi^-. For the first time, we search for possible annual, monthly and diurnal modulations of the observables |eta_{+-}| and phi_{+-}, that could be correlated with variations in astrophysical potentials. Within the accuracy of CPLEAR, the measured values of |eta_{+-}| and phi_{+-} are found not to be correlated with changes of the gravitational potential. We analyze data assuming effective scalar, vector and tensor interactions, and we conclude that the Principle of Equivalence between particles and antiparticles holds to a level of 6.5, 4.3 and 1.8 x 10^{-9}, respectively, for scalar, vector and tensor potentials originating from the Sun with a range much greater than the distance Earth-Sun. We also study energy-dependent effects that might arise from vector or tensor interactions. Finally, we compile upper limits on the gravitational coupling difference between K0 and K0bar as a function of the scalar, vector and tensor interaction range.