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ρ is calculated using kt R=0.4 jets reconstructed from locally calibrated (LCW) topoclusters within |η|<2. The density calculation is with respect to the Voronoi area of the jets as defined in JHEP 0804 (2008) 005. Topoclusters are an attempt to reconstruct three-dimensional energy deposits in the calorimeter and are built using a nearest-neighbor algorithm that clusters calorimeter cells with energy significance (|Ecell|/σ) >4 for the seed, >2 for neighbors, and >0 at the boundary. Ecell is calibrated using informaton derived from test beam and detailed GEANT4 simulatons (EM scale) and σ is the sum in quadrature of the electronic and expected pileup noise, as described in Sec. 10.5.2 of JINST 3 (2008) S08003. Topoclusters can be further calibrated using local information (LCW) as described in Nucl. Instrum. Meth. A 531 (2004) 481. The value of the pileup noise (σnoisepile-up) used in the topoclustering is optimized for each value of pileup. Pileup is simulated by overlaying GEANT4 simulated events from PYTHIA (v6.4) including non-diffractive and diffractive events.

Trimming is implemented (as in arXiv:1306.4945) by re-clustering the jet into subjets of radius R=0.3. The clusters belonging to subjets that carry at least 5% of the original jet pT are kept, and those clusters in subjets with less than 5% of the original jet pT are discarded.


Major updates:
-- MichaelBegel - 07-Aug-2013

Responsible: Main.unknown
Subject: public

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Topic revision: r1 - 2013-08-07 - unknown
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