Fast Detector Simulation Specification and Usage

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(Review of Software Requirements (integration into tool chain))
(Comparison/Validation against internal detector simulations)
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** Tevatron, HERA, LEP...?
** Tevatron, HERA, LEP...?
** Default LHC detector parametrisations?
** Default LHC detector parametrisations?
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Delphes has been validated with respect to CMS. The resolution for electrons/photons/muons is insured by the fast-simulation process itself (i.e. smearing). The jet energy resolution and the MET resolution are based on calorimetric towers and FastJet algorithms. The smearing is performed at the tower level, before applying the reconstruction algorithm, so the agreement would not be a priori straightforward. The resolution for jets and MET in a very good agreement with the results in the (public) Physics TDR of CMS. Simular procedures (using 10 bins in jet p_T for pp -> ggX events) as in the TDR are used for this direct comparison. See the paper for more details. The simulation of the very forward detectors is performed by HECTOR (used by Delphes) and this has already been validated for the LHC beamlines around ATLAS and CMS. The missing piece for ATLAS validation is the comparison of resolutions for jets and missing transverse energy, which is not yet checked. Delphes has never been used outside LHC, but in principle this can be done.
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http://www.fynu.ucl.ac.be/delphes.html
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Maybe a cross-check of ATLFastI or AcerDET and Delphes could be worth.

Revision as of 11:54, 15 June 2009

Interested people (session 1) Simon Dean, Jon Butterworth, Peter Loch, Samir Ferrag, Frank-Peter Schilling, Fabio Maltoni, Matthew Schwartz, Steve Mrenna, Andy Buckley, Joanna Weng


While in general it is to hoped that experiments will correct for detector effects, producing particle-level measurements valid within some systematic uncertainty, this is not always the case. Some key measurements only exist in uncorrected form, and a detector smearing or acceptance needs to be applied to theoretical/MC results before they can be compared to the data. Also, in some phenomenological evaluations of possible new measurements, it is desirable to have a rough simulation to estimate their robustness against detector effect.

We propose to evaluate tools in this area, and examine the requirements they might need to meet. A key issue is likely to be a standard output format for "reconstructed" objects such as jets, missing transverse energy etc.

  • Possible physics requirements
    • Acceptance, resolution, trigger and reconstruction efficiency
    • Granularity
    • Magnetic field
    • B-tagging

Review of Software Requirements (integration into tool chain)

  • Standardized input from generators

The discussion in Session 1 recommended that the input format be HepMC. Detector simulation should be generator independent and so should restrict itself to looking at final state (status code 1) particles.

  • Standardized output to Rivet and/or user code

The discussion in Session 1 suggested ideas based on "Reconstructed Objects" which would be a 4-vector with optional list of numbers for efficiency, isolation etc. How specified should these things be? Do jets point to constituents? Strong preference for keeping it simple.

We should define use cases, when is it a good idea for theorists to worry about detector simulation etc.

Would be useful to define some key plots which maybe could be used to check external sims against the detector in-house versions?


Comparison/Validation against internal detector simulations

Delphes has been validated with respect to CMS. The resolution for electrons/photons/muons is insured by the fast-simulation process itself (i.e. smearing). The jet energy resolution and the MET resolution are based on calorimetric towers and FastJet algorithms. The smearing is performed at the tower level, before applying the reconstruction algorithm, so the agreement would not be a priori straightforward. The resolution for jets and MET in a very good agreement with the results in the (public) Physics TDR of CMS. Simular procedures (using 10 bins in jet p_T for pp -> ggX events) as in the TDR are used for this direct comparison. See the paper for more details. The simulation of the very forward detectors is performed by HECTOR (used by Delphes) and this has already been validated for the LHC beamlines around ATLAS and CMS. The missing piece for ATLAS validation is the comparison of resolutions for jets and missing transverse energy, which is not yet checked. Delphes has never been used outside LHC, but in principle this can be done. http://www.fynu.ucl.ac.be/delphes.html

Maybe a cross-check of ATLFastI or AcerDET and Delphes could be worth.

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