Comparison of prompt long-lived charged particles in Chromo and CRMC

[jboelhauve]

Hi, Hans and I are working on a measurement of prompt production of long-lived charged particles and are comparing the double-differential cross-section in bins of pseudorapidity and transverse momentum with generator predictions. In the past, we accessed the generators via CRMC, while we use Chromo now.

We produced two comparison plots of the differential cross-sections in proton-proton collisions at 13 TeV from Chromo 0.5.1 and CRMC for QGSJet II.04 and Sibyll 2.3d, which you can find attached (the last subplot is empty due to a changed binning). For QGSJet, there is an offset of around 4 % in most bins. For Sibyll, the deviations are larger at low transverse momentum and vanish towards higher values. Do you have an idea where these differences may come from?

QGSJet.pdf
Sibyll.pdf

[afedynitch]

Hi!

it could be that this is an issue with the definition of stable particles. To debug this issue it would be nice, if you could make histrograms of particle counts for all particles that occur in the events.

Please look at this example to see what I mean.

https://github.com/impy-project/chromo/blob/main/examples/count_final_state_particles.ipynb

[jboelhauve]

Hi Anatoli,

For the predictions from CRMC, I only have the combined charged-particle counts, unfortunately. I didn't generate the events myself back then, so I cannot easily rerun them for a comparison...

I don't know how this is handled in CRMC, but if it uses the default prompt long-lived definition (via the 30 ps), shouldn't the list of stable particles be well defined?

When I was once comparing the differential cross-section between different Chromo versions, I also found larger deviations at low p_T. In that case, it was related to the pi^0, which was stable in an older version.