CPT Violation in String-Modified Quantum Mechanics and the Neutral Kaon System

TL;DR

This paper explores how string theory predicts a form of CPT violation in the neutral kaon system that does not violate energy conservation, potentially detectable with current or near-future experiments.

Contribution

It introduces a novel string-inspired modification to quantum mechanics that leads to CPT violation, constrained by experimental data on kaon decays.

Findings

CPT violation could be near current experimental sensitivity.

Stringy modifications to quantum mechanics can violate CPT without energy conservation.

Data allows for a non-zero CPT violation level accessible to future experiments.

Abstract

We show that $CPT$ is in general violated in a non-quantum-mechanical way in the effective low-energy theory derived from string theory, as a result of apparent world-sheet charge non-conservation induced by stringy monopoles corresponding to target-space black hole configurations. This modification of quantum mechanics does not violate energy conservation. The magnitude of this effective spontaneous violation of $CPT$ may not be be far from the present experimental sensitivity in the neutral kaon system. We demonstrate that our previously proposed stringy modifications to the quantum-mechanical description of the neutral kaon system violate $CPT$, although in a different way from that assumed in phenomenological analyses within conventional quantum mechanics. We constrain the novel $CPT$-violating parameters using available data on $K_L \rightarrow 2\pi$, $K_S \rightarrow 3\pi ^0$ and semileptonic $K_{L,S}$ decay asymmetries. We demonstrate that these data and an approximate treatment of interference effects in $K \rightarrow 2\pi $ decays are consistent with a {\it non-vanishing} amount of $CPT$ violation at a level accessible to a new round of experiments, and further data and/or analysis are required to exclude the extreme possibility that they dominate over $CP$ violation. Could non-quantum-field theoretical and non-quantum-mechanical $CPT$ violation usher in the long-awaited era of string phenomenology?}