FCNC Processes from D-brane Instantons

TL;DR

This paper investigates how flavor-changing neutral current processes constrain low string scale models with D-branes, using instanton formalism to compute amplitudes and derive bounds relevant for collider physics.

Contribution

It introduces a D-brane instanton formalism for calculating FCNC amplitudes and explores the resulting constraints on the string scale in supersymmetric intersecting D-brane models.

Findings

FCNC processes set significant lower bounds on the string scale.

Both perturbative and non-perturbative effects influence these bounds.

Constraints are relevant for models testable at the LHC.

Abstract

Low string scale models might be tested at the LHC directly by their Regge resonances. For such models it is important to investigate the constraints of Standard Model precision measurements on the string scale. It is shown that highly suppressed FCNC processes like K0- bar K^0 oscillations or leptonic decays of the D0-meson provide non-negligible lower bounds on both the perturbatively and surprisingly also non-perturbatively induced string theory couplings. We present both the D-brane instanton formalism to compute such amplitudes and discuss various possible scenarios and their constraints on the string scale for (softly broken) supersymmetric intersecting D-brane models.