Difference: PythiattH (7 vs. 8)

Revision 82010-11-01 - GavinKirby

Line: 1 to 1
 
META TOPICPARENT name="PythiattH"
-- GavinKirby - 2010-09-29
Line: 27 to 27
  14000D0 5000 10 500 p p
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In this case, 14000 is the centre of mass energy (in GeV), 5000 is the number of events to generate, 10 is the number of events to printout at the start of the run, 500 is the subsequent printout interval, and "p p" is the initial state appropriate to the LHC.
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In this case, 14000 is the centre of mass energy (in GeV), 5000 is the number of events to generate, 10 is the number of events to printout at the start of the run, 500 is the subsequent printout interval, and "p p" is the initial state appropriate to the LHC (e.g. p pbar would be used for Tevatron runs).
 

Pythia Code

Line: 49 to 49
 

Changes from VBF

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The code was initially designed to generate vector boson (WW) fusion events, and it has been adapted in stages to generate ttH instead, with some additional modifications. In particular, the histogramming aspect of the initial VBF code (which used the Pythia data to prepare an hbook file) has been disabled.
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The code was initially designed to generate vector boson (WW) fusion events, and it has been adapted in stages to generate ttH events instead, with some additional modifications. In particular, the histogramming aspect of the initial VBF code (which used the Pythia data to prepare an hbook file) has been disabled, with a view to amending the code to produce a text output file containing the necessary information (in the appropriate format) to prepare root ntuples for histogramming and analysis.
 

Particle Number Checking

Changed:
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It is important to check that the numbers of particles of each kind in an event are correct. For semileptonic ttH we expect to find one top, one tbar, one each of Wplus and Wminus (or two, for H->bbar), one lepton and its associated neutrino (or three leptons, for H->leptons), one (or two) each of b and bbar.
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The code uses a number of independent checks to ensure that the events that Pythia is generating have the appropriate structure. In particular, it is important to check that the numbers of particles of each kind in an event are correct. For semileptonic ttH we expect to find one top, one tbar, one each of Wplus and Wminus (or two, for H->bbar), one lepton and its associated neutrino (or three leptons, for H->leptons), one (or two) each of b and bbar.
 

Particle Parentage Checking

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Added:
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It is also important to check that the particles in each event correspond to the expected pattern of decays (i.e. parent/daughter particles). For instance, one expects the lepton in a semileptonic ttH process to appear as a result of the weak decay of a W (or from H->ll) and this condition can be imposed on events, so together with the independent counting of particles it is possible to impose the condition (for example) that any acceptable event must contain exactly one lepton with a W parent (of appropriate charge).
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