ATLAS pile-up card

[Simon Knapen]

Hello,

My colleagues and I were studying low mass diphoton resonances with Delphes, and we noticed a large difference in the m_\gamma\gamma invariant mass spectrum depending on whether we used the standard ATLAS cards with and without pile-up, even if the number of pile-up events is set to zero in the pile-up card. (See attached plot.) The syntax of the calorimeter definitions in both cards is rather different, which may relate to the issue. When we try the same procedure with CMS cards, we don't see this discrepancy.

In the attached plot:

• blue: CMS no pile-up card
• yellow: CMS pile-up card, setting nr of pile-up to zero
• green: ATLAS pile-up card, setting nr of pile-up to zero

Curve for ATLAS no pile-up card is not plotted, but looks very similar to the blue and yellow histograms.

Best,

Simon