About the towers in the default ATLAS, CMS, ... tcl files

[tangyilei]

I was reading the manual 1307.6346 and the default tcl files provided in the examples directory.
According to the manual, it seems that the energy deposit is assumed to happen in the geographical center of the tower cell and is smeared all over the area of the cell. Does that mean that for a definition in the delphes_card_CMS.tcl,

# 5 degrees towers
set PhiBins {}
for {set i -36} {$i <= 36} {incr i} {

add PhiBins [expr {$i * $pi/36.0}]

}
foreach eta {-1.566 -1.479 -1.392 -1.305 -1.218 -1.131 -1.044 -0.957 -0.87 -0.783 -0.696 -0.609 -0.522 -0.435 -0.348 -0.261 -0.174 -0.087 0 0.087 0.174 0.261 0.348 0.435 0.522 0.609 0.696 0.783 0.87 0.957 1.044 1.131 1.218 1.305 1.392 1.479 1.566 1.653} {

add EtaPhiBins $eta $PhiBins

}

means that for the position of a uncharged particle, only a precision of 5 degree along the phi-direction together with a precision of 0.087 along the eta direction can be reached?

However, according to the literature and the comments from some members of the experimental groups, the position precision can be much better than this number. For example, according to some literature, although one unit of ECal is spread through a 0.025*0.025 square in the eta-phi plane, and they can work in 3*3, 4*4 clusters, ..., however, by measuring the different responses of different units, the precision of position can be limited within ~2-3cm in the barrel surface. If the calorimeter is built from silicon-tungsten, the precision of position can be far beyond the 0.087*0.087 given by the delphes_card_FCC_basic.tcl...

So, I want to know the reference of the 0.087*0.087 data, and can I set a better resolution of these towers for a better precision on position?

[Michele Selvaggi]

Hi ,

sorry for the very late answer.
What you say is correct for the ECAL granularity. In the original cards we set ECAL = HCAL granularity for simplicity.
It is a good approximation unless you are interested in reconstructing photons with high precisions. Note that even in jets the angular resolution is dominated by the intrinsic QCD width of the jets.
This said, it is possible to define separate granularities for ECAL and HCAL. This is done with the SimpleCalorimeter module.
To have an example on how to set the workflow you can have a look at both the ILD and there FCC cards.

Michele