Impact of squark generation mixing on the search for squarks and gluinos at LHC

TL;DR

This paper investigates how squark-generation mixing in the MSSM can significantly affect squark and gluino production and decay at the LHC, leading to observable flavor-violating signals and distinctive mass distribution features.

Contribution

It demonstrates that squark-generation mixing can produce large flavor-violating decay branching ratios and unique invariant mass structures, despite strong experimental constraints.

Findings

QFV decay branching ratio of gluino can reach 50%

Multiple-edge structures in charm-top invariant mass distribution

Large branching ratios for squark decays into charm or top quarks

Abstract

We study the effect of squark-generation mixing on production and decays of squarks and gluinos at LHC in the Minimal Supersymmetric Standard Model (MSSM). We show that the mixing effects can be very large in a significant range of the squark-generation mixing parameters despite the very strong constraints on quark-flavour violation (QFV) from experimental data on B mesons. We find that under favourable conditions the QFV decay branching ratio B(gluino -> c bar{t} (t bar{c}) neutralino_1) can be as large as about 50%, which may lead to significant QFV signals at LHC. We also find that the squark generation mixing can result in a novel multiple-edge (3- or 4-edge) structure in the charm-top quark invariant mass distribution. Further we show that the two lightest up-type squarks ~u_{1,2} can have very large branching ratios for the decays ~u_i -> c neutralino_1 and ~u_i -> t neutralino_1 simultaneously due to the mixing effect, resulting in QFV signals 'pp -> c bar{t} (t bar{c}) + missing-E_T + X' at a significant rate at LHC. These remarkable signatures could provide a powerful test of supersymmetric QFV at LHC and could have an important impact on the search for squarks and gluinos and the determination of the MSSM parameters at LHC.