Search for pair production of massive particles decaying into three quarks with the ATLAS detector in $ \sqrt{s}=7\;\mathrm{TeV} $ pp collisions at the LHC

Abstract

A search is conducted for hadronic three-body decays of a new massive coloured particle in $ \sqrt{s}=7\;\mathrm{TeV} $ pp collisions at the LHC using an integrated luminosity of 4.6 fb−1 collected by the ATLAS detector. Supersymmetric gluino pair production in the context of a model with R-parity violation is used as a benchmark scenario. The analysis is divided into two search channels, each optimised separately for their sensitivity to high-mass and low-mass gluino production. The first search channel uses a stringent selection on the transverse momentum of the six leading jets and is performed as a counting experiment. The second search channel focuses on low-mass gluinos produced with a large boost. Large-radius jets are selected and the invariant mass of each of the two leading jets is used as a discriminant between the signal and the background. The results are found to be consistent with Standard Model expectations and limits are set on the allowed gluino mass.

Performance of jet substructure techniques for large-R jets in proton-proton collisions at $ \sqrt{s}=7 $ TeV using the ATLAS detector

“…Grooming algorithms are designed to retain the characteristic substructure within such a jet while reducing the impact of the fluctuations of the parton shower and the UE, thereby improving the mass resolution and mitigating the influence of pile-up. These features have only recently begun to be studied experimentally [24][25][26][27][28][29][30][31] and have been exploited heavily in recent studies of the phenomenological implications of such tools in searches for new physics [9,[32][33][34][35][36][37][38][39][40][41][42]. A groomed jet can also be a powerful tool to discriminate between the often dominant multi-jet background and the heavy-particle decay, which increases signal sensitivity.…”

Towards an understanding of jet substructure

“…10 It sets a fat-jet mass substantially larger than the final pruned mass, ρ fat ≫ ρ, while the emission that dominates the pruned mass still has θ > R prune . The above two expressions should capture terms α n s L 2n−1 and α n s L 2n−2 in Σ (Y-prune) (ρ).…”

“…Note that overall we have one power of L more than for Y-pruning. As 10 In integrating over z ′ we have replaced pgq(z…”

“…[4][5][6][7] for studies on QCD jets and refs. [8][9][10][11][12][13][14] for searches). The taggers' and groomers' action is twofold: they aim to suppress or reshape backgrounds, while retaining signal jets and enhancing their characteristic jet-mass peak at the W/Z/Higgs/top/etc.…”

Natural,R-parity violating supersymmetry, and horizontal flavor symmetries

“…[49] a pair-produced massive particle decaying to three jets was looked for: this topology can describe a decay chain of a gluino to three quarks, g ! qq !…”