Concepts and Plans towards fast large scale Monte Carlo production for the ATLAS Experiment

E Ritsch

doi:10.1088/1742-6596/523/1/012035

Abstract

The huge success of the physics program of the ATLAS experiment at the Large Hadron Collider (LHC) during Run 1 relies upon a great number of simulated Monte Carlo events. This Monte Carlo production takes the biggest part of the computing resources being in use by ATLAS as of now. In this document we describe the plans to overcome the computing resource limitations for large scale Monte Carlo production in the ATLAS Experiment for Run 2, and beyond. A number of fast detector simulation, digitization and reconstruction techniques are being discussed, based upon a new flexible detector simulation framework. To optimally benefit from these developments, a redesigned ATLAS MC production chain is presented at the end of this document.

Highlights

The current ATLAS Monte Carlo production chain has proven very successful over the past years of data taking with the ATLAS experiment [1]
Fast simulation methods have been bundled in an Integrated Simulation Framework (ISF)
The ATLAS Monte Carlo production chain [2], as it is currently in use, is best described by five main steps, which are depicted in figure 1: Event Generation concerns the simulation of truth-level particle collision processes which are stored in the event generator (EVGEN) output format

Summary

Introduction

The current ATLAS Monte Carlo production chain (further described in section 2) has proven very successful over the past years of data taking with the ATLAS experiment [1]. The ATLAS Monte Carlo production chain [2], as it is currently in use, is best described by five main steps, which are depicted in figure 1: Event Generation concerns the simulation of truth-level particle collision processes which are stored in the EVGEN output format. Secondaries stemming from such interactions are treated in the same way as primary particles coming from the event generator This approach is the most time consuming simulation method. The Integrated Simulation Framework allows to combine various simulators (full and fast) for different particles within each event This way fully accurate simulators can be chosen for particles of interest for a particular physics analysis (e.g. signal (efficiency/fakes) physics object event reconstruction high

ACCURACY creation

Standard Reconstruction

Findings

Conclusions