Stop searches in flavourful supersymmetry

TL;DR

This paper investigates how various decay modes of light stops affect LHC search sensitivities, revealing that existing bounds are robust against stop-scharm mixing and that large parameter regions are excluded regardless of mixing angles.

Contribution

It provides a model-independent analysis of stop decay channels and their interplay, clarifying the impact of stop-scharm mixing on LHC mass limits.

Findings

Large regions are excluded for any ${ ilde t_1} o c ilde u$ branching ratio.

Stop-scharm mixing only modestly affects allowed parameter space.

LHC bounds from ${ ilde c_1} o c ilde u$ searches are significant.

Abstract

Natural realisations of supersymmetry require light stops ${\tilde t}_1$, making them a prime target of LHC searches for physics beyond the Standard Model. Depending on the kinematic region, the main search channels are ${\tilde t_1}\to t \tilde \chi^0_1$, ${\tilde t_1}\to W b \tilde \chi^0_1$ and ${\tilde t_1}\to c \tilde \chi^0_1$. We first examine the interplay of these decay modes with ${\tilde c_1}\to c \tilde \chi^0_1$ in a model-independent fashion, revealing the existence of large regions in parameter space which are excluded for any ${\tilde t_1}\to c \tilde \chi^0_1$ branching ratio. This effect is then illustrated for scenarios with stop-scharm mixing in the right-handed sector, where it has previously been observed that the stop mass limits can be significantly weakened for large mixing. Our analysis shows that once the LHC bounds from ${\tilde c_1}\to c \tilde \chi^0_1$ searches are taken into account, non-zero stop-scharm mixing leads only to a modest increase in the allowed regions of parameter space, with large areas excluded for arbitrary mixing angles.