Vertex Smearing

Complete: 5

Internal vertex smearing (in FamosSimHits and in FamosPileUp)

Because the same vertex smearing is applied to pile-up events and to signal events, an internal vertex smearing has to be used. Indeed, the official vertex smearing (through the module VtxSmeared, described below) smears only the signal event HepMCProduct, because the pileup events used in the full simulation are supposed to be simulated ahead of time (hence with a given vertex smearing), and read back to be mixed with the simulated signal events.

A complete documentation of the internal vertex smearing can be found here.

Vertex smearing (VtxSmeared)

Although not recommended for use in FastSimulation when pile-up is to be simulated, the official vertex smearing module can be used in the absence of pile-up. A complete documentation on how to enable it can be found in the WorkBook as well.

The random number initialization for this step is included as follows,

     untracked uint32 VtxSmeared = 98765

together with one of the following .cfi include files, for Realistic, Gaussian and Flat vertex smearing, respectively. (The relevant parameters can be modified with the "replace" command.)

#include "IOMC/EventVertexGenerators/data/VtxSmearedEarlyCollision.cfi"
#include "IOMC/EventVertexGenerators/data/VtxSmearedGauss.cfi"
#include "IOMC/EventVertexGenerators/data/VtxSmearedFlat.cfi"

Finally, the module "VtxSmeared" must be added in the "path", before the Famos sequence, e.g.,

path p1 = { 

Note: As mentioned above, the FastSimulation is fully equipped with its own internal (recommended) vertex smearing, but the latter is not run on the signal events when the VtxSmeared module has been called beforehand. The internal vertex smearing is run only for pile-up events. It is important to synchronize the configuration of both smearing engine.

Review status

Reviewer/Editor and Date (copy from screen) Comments
PatrickJanot - 08 Feb 2008 Update documentation
PatrickJanot - 08 May 2007 Add two notes on the use of VtxSmeared
PatrickJanot - 26 Apr 2007 Documentation complete
JennyWilliams - 23 Mar 2007 created template page

Responsible: AndreaPerrotta

Last reviewed by: Reviewer

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Topic revision: r7 - 2011-05-03 - AndreaPerrotta

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