Search for massive supersymmetric particles decaying to many jets using the ATLAS detector in $pp$ collisions at $\sqrt{s} = 8$ TeV

TL;DR

This paper reports a search for supersymmetric particles decaying into many jets using ATLAS data at 8 TeV, setting limits on gluino masses with no significant deviations from the Standard Model observed.

Contribution

It introduces a novel analysis method focusing on high jet multiplicities and topological variables to search for R-parity-violating gluino decays in fully hadronic final states.

Findings

Excluded gluino masses below 1 TeV for certain decay modes.

No significant excess over Standard Model backgrounds observed.

Set new limits on gluino and neutralino masses in RPV SUSY models.

Abstract

Results of a search for decays of massive particles to fully hadronic final states are presented. This search uses 20.3 fb$^{-1}$ of data collected by the ATLAS detector in $\sqrt{s} = 8$ TeV proton--proton collisions at the LHC. Signatures based on high jet multiplicities without requirements on the missing transverse momentum are used to search for $R$-parity-violating supersymmetric gluino pair production with subsequent decays to quarks. The analysis is performed using a requirement on the number of jets, in combination with separate requirements on the number of $b$-tagged jets, as well as a topological observable formed from the scalar sum of the mass values of large-radius jets in the event. Results are interpreted in the context of all possible branching ratios of direct gluino decays to various quark flavors. No significant deviation is observed from the expected Standard Model backgrounds estimated using jet-counting as well as data-driven templates of the total-jet-mass spectra. Gluino pair decays to ten or more quarks via intermediate neutralinos are excluded for a gluino with mass $m_{\tilde{g}} < 1$ TeV for a neutralino mass $m_{\tilde{\chi}^0_1} = 500$ GeV. Direct gluino decays to six quarks are excluded for $m_{\tilde{g}} < 917$ GeV for light-flavor final states, and results for various flavor hypotheses are presented.