How to use a Pythia afterburner for O2

Cas · October 10, 2022, 9:40am

Dear O2 experts,

For my studies I need to add a pythia afterburner to the simulation.
This afterburner will calculate the amount of Internal bremsstrahlung created when a collision takes places. The amount of photons produced (and in particular soft photons) is predicted via the Gellman and Low’s theorem.

These photons will be added to the event (since they are soft, they will have a negligible impact on the production processes, so an afterburner seems to be the best option).

How do I integrate such an afterburner?
Do I make it like a user hook and place it in AliceO2/Generators/share/egconfig at dev · AliceO2Group/AliceO2 · GitHub ? Or is there a better way I can tackle this?

Kind regards,
Cas

swenzel · October 10, 2022, 12:41pm

Pinging @rpreghen as expert for generation.

rpreghen · October 10, 2022, 7:12pm

hi @Cas ,
the user hooks approach is IMO not the right one.
I would rather implement a custom event generator that inherits from Pythia.

an starting point can be this one

github.com

AliceO2Group/AliceO2/blob/dev/run/SimExamples/HF_Embedding_Pythia8/GeneratorHF.macro

/// \author R+Preghenella - July 2020

// Example of an implementation of an event generator
// that provides HF signals for embedding in background

#include "Pythia8/Pythia.h"

namespace o2 {
namespace eventgen {

class GeneratorHF : public GeneratorPythia8
{
  
public:

  GeneratorHF() : GeneratorPythia8() { };
  ~GeneratorHF() = default;

  // We initialise the local Pythia8 event where we store the particles
  // of the signal event that is the sum of multiple Pythia8 events

This file has been truncated. show original

an approach can be that you let Pythia generate the event like in the Bool_t generateEvent() override { function. You analyse the event when generated and add particles to the Pythia stack as per your needs.

Cheers,
Roberto