Abstract

An equality of particle and antiparticle gravitational interactions holds in general relativity and is supported by indirect observations. Gravity dependence on rotation or spin direction is experimentally constrained for non-relativistic matter. Here, a method based on high-energy Compton scattering is developed to measure the gravitational interaction of accelerated charged particles. Within that formalism, the Compton spectra measured at HERA rule out the speculated anti-gravity possibility for antimatter at a confidence level close to 100%. The same data, however, imply a gravitational CP violation around 13 GeV energies, by a maximal amount of [Formula: see text] for the charge and [Formula: see text] for the space parity. The detected asymmetry hints for a stronger gravitational coupling to left helicity electrons relative to right helicity positrons.

Highlights

  • Extreme weakness of gravitation makes it the least experimentally investigated fundamental interaction at sub-atomic scales, with elementary particles

  • As can be seen from the plot, 6 GeV storage rings have low sensitivity while the higher energy colliders (HERA, SLC, LEP) have a great potential for detecting gravity related energy shifts. This is true for the HERA and SLC Compton polarimeters but not for the LEP polarimeter, which has generated and registered many photons per machine pulse.[38]

  • We turn to HERA, which has recorded Compton measurements for both the electrons and the positrons

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Summary

Introduction

Extreme weakness of gravitation makes it the least experimentally investigated fundamental interaction at sub-atomic scales, with elementary particles. Departures from perfect spin or particle–antiparticle symmetry are allowed in some quantum gravitation scenarios.[2] observations of antiparticle gravitation could serve as an experimental input for quantum gravity.[3] Additional motivations for such investigation are the still unexplained matter-dominant universe[4] and the connection of antimatter’s possible anti-gravity[5] to the accelerated expansion of the universe.[6] One can think about a possible particle–antiparticle gravitational asymmetry and helicity dependence from an analogy to electroweak interactions, where a photon’s massive partners, W and Z bosons, are considered responsible for space and charge parity violations.[7] possible massive or lower spin gravitons could introduce similar violations[8] that may remain hidden at low energies and will become detectable at high energies Another possibility to incorporate asymmetric space or charge gravitational interactions is a modification of vacuum properties described within the Standard Model Extension (SME)[9] by Lorentz violating terms in Lagrangian. Systematic effects and prospects for other tests will be discussed at the end

Refraction in Gravitational Field
The Compton Process Affected by Gravity
Conclusions
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