Superpotential de-sequestering in string models

TL;DR

This paper investigates how non-perturbative effects in string compactifications can alter Yukawa couplings, potentially causing flavor-changing effects due to misaligned flavor structures in the visible sector.

Contribution

It provides a detailed calculation of non-perturbative corrections to Yukawa couplings in orbifold models, revealing conditions for their appearance and implications for flavor physics.

Findings

Non-perturbative effects can induce flavor-violating Yukawa corrections.

The flavor structure of these corrections generally misaligns with the original Yukawa couplings.

Distant D7-brane scalar VEVs can further modify Yukawa couplings with different flavor patterns.

Abstract

Non-perturbative superpotential cross-couplings between visible sector matter and K\"ahler moduli can lead to significant flavour-changing neutral currents in compactifications of type IIB string theory. Here, we compute corrections to Yukawa couplings in orbifold models with chiral matter localised on D3-branes and non-perturbative effects on distant D7-branes. By evaluating a threshold correction to the D7-brane gauge coupling, we determine conditions under which the non-perturbative corrections to the Yukawa couplings appear. The flavour structure of the induced Yukawa coupling generically fails to be aligned with the tree-flavour structure. We check our results by also evaluating a correlation function of two D7-brane gauginos and a D3-brane Yukawa coupling. Finally, by calculating a string amplitude between n hidden scalars and visible matter we show how non-vanishing vacuum expectation values of distant D7-brane scalars, if present, may correct visible Yukawa couplings with a flavour structure that differs from the tree-level flavour structure.