Introduction

First (and second) paragraph:

A reference should also be made to the ”fast simulations” developed by CMS and ATLAS, which are two to three orders of magnitude faster than the GEANT-based simulations, while minimizing the loss of accuracy, and allowing the ”complex reconstruction algorithms” to be used.

(Andrea's temporary comment) I don't think it's very relevant, but just for the sake of compromise, we can do. For ATLAS, I know this reference: ​http://inspirehep.net/record/1196761 but it is only for tracking; a more generic one, although it is just a conference proceeding, is ​http://inspirehep.net/record/1211010 (I suggest to cite both, for completeness.) For CMS, the most recent and appropriate is: ​http://inspirehep.net/record/1214935 but there is the delicate point that there is not his name on it ;) So in addition one could also cite ​http://inspirehep.net/record/1117120 (but not this one alone, because some details are now obsolete, like the pileup treatment). Both are conference proceedings, but it is standard practice in CMS to cite them. And, still for CMS, one could argue that also this one should be cited, because it contains comparison to data: ​http://inspirehep.net/record/1230052 Please let me know if you think that these are too many citations.

(Michele) thanks for the references, I think we can include them all (see below in the suggested intro)

(CD) I agree. Still, I don't like the way you motivate the fast-sim, and I am sure that the referee will jump if we keep the text like this. Fast-sim is NOT ONLY for preliminary and inaccurate studies. It is tuned to reproduce fullsim and save CPU cycles. I would simply say "To face the limited computing resources and still allow the use of large samples (for example when scanning parameter spaces), LHC collaborations (...) "

Third paragraph:

L4: It’s not enough to say that the magnetic field is uniform (as this adjective qualifies only the absolute value in Tesla). The word ”axial” and the expression ”along the beam direction” could be used to the sake of clarity.

addressed (CD) please add "axial" as well, as requested.

L5: The energy smearing applies also to all other particles, not only to photons and electrons. Why are these two particles singled out here ?

addressed: photons and electrons have been replaced by

long-lived visible particles"

L6-7: ”Jets and missing energy can be computed with the particle-flow al- gorithm.” is an incorrect sentence. First ”the particle-flow algorithm” would probably need to be somehow defined, or at least given a reference. Sec- ond, ”the particle-flow algorithm” does not deliver jets and missing energy, it delivers a list of reconstructed and identified particle candidates. Jets and missing (transverse) energy can then be obtained from either calorimeter de- posits, or from these particle candidates. Both approaches are conceptually and technically identical for jets and missing energy. This misconception of the PF reconstruction appears in several places in the article, and most likely in several aspects of the simulation implementation too. A number of the comments that follow are related to this aspect.

addressed

We agree that the particle-flow algorithm should be defined. We now call our approach a "particle-flow-like emulation" in the new draft: we don't aim at re-implementing the PF algorithm itself, but at emulating its effects. This would make more clear why we only apply it to jets and MET: there is no PF-like approach that we can follow for muons, electrons, etc., as those are already perfectly identified objects in our simulation.

We'd rather call this energy-flow, since this is what we are doing. (CD) indeed, what we do is more an energy-flow. I would also cite CMS/ALEPH papers already in the introduction.

The suggestion regarding the last two comments is to explain that all particle energies are smeared according to parameterized detector resolutions, and that physics objects used in physics analyses (isolated leptons, isolated photons, jets, missing transverse energy, taus) are derived from these smeared energies. The concept of calorimeter and particle flow algorithm is to be kept for the next paragraph.

addressed

Paragraph 4:

L1: Add ”which was only simulating energy deposits in the calorimeters” or anything closer to the truth, after ”predecessor”.

it was actually bugged, and creating photons out of nowhere, but how can we say this to ref.?

(CD) I have no problem saying that to the referee. We can say in the text that the old version, while providing a good detector simulation, was providing a very simple (simplistic) approach to object reconstruction.

L3: Add ”to deliver a list of reconstructed and identified particles as close as possible to the true (generated) list.” after ”sub-detectors”

not relevant anymore. We use energy-flow for jets and missing energy.

L6: ”fully modular” would need some more explanation for the reader to understand it. But is it so important for a JHEP article ?

It is important to mention the modularity since it is crucial improvement with respect to the prior version. The modular aspects of Delphes are explained in the technical description part, which was moved in the appendix section. At this stage it is enough for the non-software expert reader to know that modular

implies greater flexibility.

(CD) I would add to the text that "(...) providing a greater flexibility to the user and allowing the integration of \DELPHES routines in other projects.

Paragraph 5:

L2/L3: Propose to drop. The software implementation is out of context.

Dropped the software description since it will be in the Appendix, but the use cases should be mentioned.

PAGE 3

Par 2:

L5/6/7: This sentence starts with ”As for the tracking efficiency”, but nothing was said about the tracking efficiency settings prior to this sentence. A mention of the fact that this efficiency can be user-defined should appear at the beginning of the paragraph, and replace ”(good)”.

addressed: "Charged particles have a user-defined probability to be seen as tracks"