SWGuideL1ExtraFromMCTruth < CMSPublic

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---+!! !L1ExtraFromMCTruthProd
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---++ 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*Beginning in 17X, this package is no longer maintained.*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 <font face="Symbol">f</font>, <font face="Symbol">h</font>, and E for each particle.  Although E<sub>T</sub>, not E, is the relevant trigger variable, we do not smear this quantity directly because it is correlated with <font face="Symbol">h</font>.  The smearing widths are separately specified by parameter for each particle type (e/<font face="Symbol">g</font>, jet, <font face="Symbol">m</font>), and these widths are fixed, independent of <font face="Symbol">h</font> and E<sub>T</sub>.  The default widths are the same for all particles: <font face="Symbol">s<sub>f</sub></font> = 0.1, <font face="Symbol">s<sub>h</sub></font> = 0.1, <font face="Symbol">s<sub>E</sub></font> = 5 !GeV.

Detector acceptance is modeled as a simple <font face="Symbol">h</font> cut, also specified by parameter separately for the calorimeter (i.e. e/<font face="Symbol">g</font> and jets, default = 5.0) and the muon chambers (default = 2.5).  The cut is applied to the smeared <font face="Symbol">h</font> 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, K<sup>0</sup><sub>L</sub>s, and neutrons.

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

The remaining jets are sorted by <font face="Symbol">h</font> into forward or central regions.  Central, forward, and <font face="Symbol">t</font> jets are ranked by E<sub>T</sub>, and only the top 4 candidates of each type (maximum 12 total) are retained and inserted into the event.  <font face="Symbol">t</font> 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/<font face="Symbol">g</font> and <font face="Symbol">m</font>

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/<font face="Symbol">g</font> candidate lists.  Isolation is determined by the presence of nearby calorimeter energy deposits, and these are assumed to come from other e/<font face="Symbol">g</font> or jet objects.  The <font face="Symbol">f</font> and <font face="Symbol">h</font> isolation windows are adjustable by parameter (default = +-0.35 for both).  In evaluating <font face="Symbol">Df</font>, possible wraparound by 2<font face="Symbol">p</font> is accounted for.  e/<font face="Symbol">g</font> candidates in each of the two categories (isolated and non-isolated) are ranked by E<sub>T</sub>, and only the top 4 candidates in each category (maximum 8 total) are retained and inserted into the event.

Muons within their <font face="Symbol">h</font> acceptance are ranked by E<sub>T</sub>, 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/<font face="Symbol">g</font>, except <font face="Symbol">f</font> and <font face="Symbol">h</font> windows (default = +- 0.35 for both) can, in principle, be different from e/<font face="Symbol">g</font> 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 <font face="Symbol">h</font> 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/<font face="Symbol">g</font> and jet objects, not just the top 4 of each category.

Total E<sub>T</sub> is determined from the same particles as for MET.  Hadronic E<sub>T</sub> is not straightforward to calculate from the generated particles, so it is set equal to the total E<sub>T</sub>.

---+++ 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<sub>T</sub> 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<sub>T</sub>, we use the total E<sub>T</sub> 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.

---++ Instructions for use

For =CMSSW_0_9_0_pre2= through =CMSSW_1_0_0=, see [[CMS.L1ExtraFromMCTruth090pre2][here]]

For =CMSSW_1_1_0_pre1= through =CMSSW_1_2_1=, see [[CMS.L1ExtraFromMCTruth110pre1][here]]

For =CMSSW_1_2_2= onward, see [[CMS.L1ExtraFromMCTruth122][here]]

The trigger tables implemented are identical to those for =L1ExtraParticleMapProd=.  View the release-by-release tables
[[SWGuideL1Extra][here]].

#ReviewStatus
---++!! Review Status

| *Editor/Review and date* | *Comments* |
| Main.wsun - 04 Aug 2006 | page author |


%RESPONSIBLE% Main.wsun %BR%
%REVIEW%