L1ExtraFromMCTruthProd

Complete:

Contents:

Introduction
Description of Algorithm
Instructions for use

Introduction

Beginning in 17X, this package is no longer maintained.

This EDProducer (L1Trigger/L1ExtraFromMCTruthProd) generates L1Extra objects and a L1CMS.GlobalTriggerReadoutRecord based on MC particles at generator level, bypassing all the detector simulation and trigger emulation. It is intended to be a temporary tool for seeding HLT algorithms. Detector acceptance and resolution are very crudely simulated. The L1 triggers being emulated are those that were used for the PTDR vol. 2.

Description of Algorithm

The default parameters and the modules necessary for running this EDProducer are given in the file L1Trigger/L1ExtraFromMCTruthProd/data/l1extra-from-mctruth.cff, which includes l1extramctruth.cfi.

Resolution and acceptance

The trigger resolution is modeled by independent Gaussian smearing of f, h, and E for each particle. Although E_T, not E, is the relevant trigger variable, we do not smear this quantity directly because it is correlated with h. The smearing widths are separately specified by parameter for each particle type (e/g, jet, m), and these widths are fixed, independent of h and E_T. The default widths are the same for all particles: s_f = 0.1, s_h = 0.1, s_E = 5 GeV.

Detector acceptance is modeled as a simple h cut, also specified by parameter separately for the calorimeter (i.e. e/g and jets, default = 5.0) and the muon chambers (default = 2.5). The cut is applied to the smeared h values. For jets, the boundary between the central and forward regions is defined by parameter, and the default value is 1.5.

Jet finding

Jet finding for generated particles uses the same algorithms and EDProducers as for reconstructed particles; one simply inputs Candidate list made by HepMCCandidateProducer instead of reconstructed Candidate objects. The particular choice of jet finding algorithm is controlled by parameter (default = midPointCone5GenJets). In the above .cff file, we do not allow Candidate objects (and, thus, jets) to be made from electrons, muons, neutrinos, K⁰_Ls, and neutrons.

t jets in the central region are identified by matching the unsmeared jet direction to the generated t direction, with Df and Dh tolerances specified by parameter (default = 0.35 for both).

The remaining jets are sorted by h into forward or central regions. Central, forward, and t jets are ranked by E_T, and only the top 4 candidates of each type (maximum 12 total) are retained and inserted into the event. t jets are inserted as different collection from forward and central jets, and the two collections are distinguished by instance label ("Tau" and "ForCen", respectively).

e/g and m

Electron, photon, and muon candidates are taken from the list of stable generated particles. Electrons and photons within the calorimeter acceptance are sorted into isolated and non-isolated e/g candidate lists. Isolation is determined by the presence of nearby calorimeter energy deposits, and these are assumed to come from other e/g or jet objects. The f and h isolation windows are adjustable by parameter (default = +-0.35 for both). In evaluating Df, possible wraparound by 2p is accounted for. e/g candidates in each of the two categories (isolated and non-isolated) are ranked by E_T, and only the top 4 candidates in each category (maximum 8 total) are retained and inserted into the event.

Muons within their h acceptance are ranked by E_T, and only the top 4 candidates in the entire detector are retained and inserted into the event. All muons have their MIP bits set, and their isolation is determined as above for e/g, except f and h windows (default = +- 0.35 for both) can, in principle, be different from e/g isolation.

MET calculation

Unlike with jets, we do not obtain the MET vector from METProducer using generated 4-momenta as input. Rather, the MET calculation is performed inside L1ExtraFromMCTruthProd in order to make use of the smeared particle 4-momenta and to exclude particles outside the h acceptance. Because the L1 MET uses only calorimeter information, we do not include muons in the calculation. We sum transverse momentum vectors for all observed e/g and jet objects, not just the top 4 of each category.

Total E_T is determined from the same particles as for MET. Hadronic E_T is not straightforward to calculate from the generated particles, so it is set equal to the total E_T.

L1 trigger conditions

The above particle lists are meant to approximate the outputs of the GCT and GMT, which are input to the GT. For GT emulation, we evaluate the entries in the trigger menu (listed on the instructions pages below), and we construct a L1ParticleMapCollection with one L1ParticleMap for each trigger menu entry. For each entry, the index or position in the collection corresponds to the trigger type, as specified by the enum L1ParticleMap::L1TriggerType. The E_T threshold(s) or prescale of each trigger is adjustable by parameter, and the default values are those used in the PTDR vol. 2 (Table E.11). For H_T, we use the total E_T described above.

The global L1 decision is constructed by OR'ing all the trigger decisions. It is recorded in the L1CMS.GlobalTriggerReadoutRecord, which is inserted into the event.