# Citizen Science Entry 2

Here's my entry for @lemouth's citizen science program, [episode 2](https://stemgeeks.net/hive-196387/@lemouth/citizen-science-on-hive-simulating-top-quark-production-at-cern-s-large-hadron-collider). Glad to be back :).

Before starting MadGraph, I picked apart the acronyms in the name of the package: 'MadGraph5_aMC@NLO'. Specifically, I wanted to know what the 'aMC' and 'NLO' terms meant. After some searching, here's what I concluded:

* aMC: adjoint Monte Carlo.
* NLO: Next-to-Leading-Order.

I was most interested in the 'aMC' acronym since 'aMC' appears prominently in the MadGraph5 prompt. So it's gotta be important!

Now for the meat-n-potatoes: simulating 10000 proton-proton collisions where each individual collision yields one top quark and one top antiquark. Following lemouth's lead in episode 2, here's the commands I entered.



```
$ ./bin/mg5_aMC
MG5_aMC>generate p p > t t~   # Task 1. Defines the collider process of interest.
MG5_aMC>display diagrams      # Task 1. Writes diagrams to /tmp/ in my container.
MG5_aMC>output pp_tt          # Task 2. Set output directory and build Fortran code.
MG5_aMC>launch pp_tt          # Task 3. Run simulation and compute top anti-top production rates.
```
<br>

Note the presence of '#' at the end of the MG5 commands above. Through trial and error, I found that '#' indicates a comment in MadGraph's REPL. For example, `generate p p > t t~ # Collider process` is a valid command.

## An aside on filesystems

Initially I ran the simulation on a shared filesystem (/host/c). That was slow. So I tried both a container-local filesystem and a filesystem mounted in RAM (ramfs). For comparison, I measured the elapsed time of the 'launch' command (minus menu interactions). Here are the results:

* Shared filesystem (/host/c/temp/pp_tt): 14m29s
* Container filesystem (./pp_tt): 6m31s
* RAM filesystem (~/ramfs/pp_tt): 5m47s

The learning: don't use a shared filesystem like I did :(. It was more than 2 times slower. And ramfs helps, but not too significantly. The minor effect of ramfs makes sense as the simulation is likely compute bound.

Since I'm running MadGraph in a container, there is no interactive display session. It's (nearly) headless. So I'm forced to copy graphical results (like images) to the host machine before viewing. That does incur some overhead.


## Production Rates and Verification

A screenshot of my final output:


![LeMouth02-MadGraph.PNG](https://images.hive.blog/DQmdnVbSojoFbZttw2hT135TjF1GNdLqGZQDBLMTFSrLsJD/LeMouth02-MadGraph.PNG)


My cross-section is: 505.8 +- 0.8 pb, which yields the same production rate @lemouth determined. Assuming 140/fb has two significant figures.

I verified parton showering, hadronisation, and decay.

That's about it. Looking forward to the next episode and seeing you folks around!

#citizenscience

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