Mono-top Signature from Supersymmetric $t \bar t H$ Channel

TL;DR

This paper identifies a unique mono-top signature in Natural SUSY scenarios with nearly degenerate scalar top-quarks and higgsinos, proposing a search strategy to probe the stop and neutralino sectors at the LHC.

Contribution

It introduces a novel mono-top signature from supersymmetric $t ar t H$ processes as a direct probe of the stop and higgsino sectors, with an optimized search method.

Findings

High luminosity LHC can probe stop masses up to 380 GeV.

The channel is sensitive to the higgsino components in neutralinos.

A new kinematic variable can measure stop mixing.

Abstract

We point out that a distinctive mono-top signature is present in Natural SUSY scenarios when a scalar top-quark and higgsinos are almost mass degenerate. This signature originates from a supersymmetric counter part of the $t \bar t H$ process, i.e. $pp \to \tilde t t \tilde h$. Unlike mono-jet signatures exploiting initial state radiation, this channel can be regarded as a smoking gun signature of a light stop and higgsinos, allowing a direct probe of the stop and neutralino sectors. The production rate of this channel largely depends on the up-type higgsino components in the neutralinos while the stop sector is sensitive to angular distributions of top-quark's decay products. We develop an optimal search strategy to capture the supersymmetric $t \bar t H$ process and find that a high luminosity LHC can probe the stop and higgsino sectors with $m_{\tilde t_1} \lesssim 380$ GeV and $m_{\tilde t_1} - m_{\tilde \chi_1^0} \lesssim m_W$. Additionally, we propose a kinematic variable with which one can measure the stop mixing in this channel.