Jet substructure at the Tevatron and LHC: new results, new tools, new benchmarks

276

254

We propose a new method for pileup mitigation by implementing "pileup per particle identification" (PUPPI). For each particle we first define a local shape α which probes the collinear versus soft diffuse structure in the neighborhood of the particle. The former is indicative of particles originating from the hard scatter and the latter of particles originating from pileup interactions. The distribution of α for charged pileup, assumed as a proxy for all pileup, is used on an event-by-event basis to calculate a weight for each particle. The weights describe the degree to which particles are pileup-like and are used to rescale their four-momenta, superseding the need for jet-based corrections. Furthermore, the algorithm flexibly allows combination with other, possibly experimental, probabilistic information associated with particles such as vertexing and timing performance. We demonstrate the algorithm improves over existing methods by looking at jet p T and jet mass. We also find an improvement on non-jet quantities like missing transverse energy.

Section: Jhep10(2014)059mentioning

confidence: 99%

“…Here we show results for jet mass which is considered a reasonable proxy for generic jet shapes and is used in many applications such as boosted object tagging (see [34][35][36] and references therein). First we look at jet mass for central jets with 100 GeV < p T < 200 GeV.…”

Section: Jet Shapesmentioning

confidence: 99%

Pileup per particle identification

Bertolini

Harris

Low³

et al. 2014

276

254

“…It is well established that various jet grooming techniques increase the separation in jet mass between signal and QCD jets [31,32]. Figure 9 shows this comparison: while a 4-vector pileup correction alone (left) does not allow for separation between QCD and W jet, both trimming (center) and re-clustered jet trimming (right) allow for the successful discrimination of signal and background using the jet mass.…”

Section: Comparisons To Qcdmentioning

confidence: 96%

Jets from jets: re-clustering as a tool for large radius jet reconstruction and grooming at the LHC

Nachman

Nef

Schwartzman

et al. 2015

Jets with a large radius R 1 and grooming algorithms are widely used to fully capture the decay products of boosted heavy particles at the Large Hadron Collider (LHC). Unlike most discriminating variables used in such studies, the jet radius is usually not optimized for specific physics scenarios. This is because every jet configuration must be calibrated, insitu, to account for detector response and other experimental effects. One solution to enhance the availability of large-R jet configurations used by the LHC experiments is jet re-clustering. Jet re-clustering introduces an intermediate scale r < R at which jets are calibrated and used as the inputs to reconstruct large radius jets. In this paper we systematically study and propose new jet re-clustering configurations and show that re-clustered large radius jets have essentially the same jet mass performance as large radius groomed jets. Jet re-clustering has the benefit that no additional large-R calibration is necessary, allowing the re-clustered large radius parameter to be optimized in the context of specific precision measurements or searches for new physics.

“…Many available methods for boosted top tagging exist in the literature (see for instance refs. [15,16,18,[31][32][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47][48] and references therein). In addition, several interesting proposals for boosted W tagging appeared recetly in refs.…”

Section: Tagging Of Boosted Objectsmentioning

confidence: 99%

LHC top partner searches beyond the 2 TeV mass region

Backović

Flacke

Lee

et al. 2015

We propose a new search strategy for heavy top partners at the early stages of the LHC run-II, based on lepton-jet final states. Our results show that final states containing a boosted massive jet and a hard lepton, in addition to a top quark and possibly a forward jet, offer a new window to both detecting and measuring top partners of mass ∼ 2 TeV. Our resulting signal significance is comparable or superior to the same sign dilepton channels for top partner masses heavier than roughly 1 TeV. Unlike the di-lepton channel, the selection criteria we propose are sensitive both to 5/3 and 1/3 charge top partners and allow for full reconstruction of the resonance mass peak. Our search strategy utilizes a simplified b-tagging procedure and the Template Overlap Method to tag the massive boosted objects and reject the corresponding backgrounds. In addition, we propose a new, pileup insensitive method, to tag forward jets which characterize our signal events. We consider full effects of pileup contamination at 50 interactions per bunch crossing. We demonstrate that even in the most pessimistic pileup scenarios, the significance we obtain is sufficient to claim a discovery over a wide range of top partner parameters. While we focus on the minimal natural composite Higgs model, the results of this paper can be easily translated into bounds on any heavy partner with a ttW j final state topology.