Quarkonium MadGraph

People

1. Pierre Artoisenet
2. Fabio Maltoni
3. Tim Stelzer

Aim of the project

Build an event generator for quarkonium physics.

Tools

• Madgraph/MadEvent v4 and StandAlone

Work

We have identified two phases:

1. Add to MadGraph the possibility of generating pairs of heavy quarks (same or different flavors) with given quantum numbers, of spin, total angular momentum, color: %$^{{2S+1}L_J[1,8]$%, for %$L=0,1$%.}
2. Interface it to MadEvent for event generation.

Physics results and papers writeup

The paper phase 1 is out! ​MadOnia paper

Preliminary code

The code phase 1 is done. The quarkonium amplitude generator has been interfaced with a basic phase space generator to produce cross sections and distributions. The code is available under request. In order to generate heavy quarkonium cross sections, you must:

1. Copy the directory Template into my_proc

2. Edit the proc_card.dat in my_proc/Card/proc_card.dat.

You have to enter the parton-level process

IMPORTANT: THE HEAVY QQ bar PAIR MUST BE PLACED AT THE END OF THE LINE DEFINING THE PROCESS !!

The quantum numbers of the QQ bar pair are written in squared brackets using the spectroscopic notation

[(2S+1)LJC] with S=spin, L=orbital momentum, J= total momentum, C=color

For example, type gg>gcc~[3S11] if you want to consider gg > g + charmonium with S=1, L=0 J=1, c=1 (J/psi production via a color-singlet transition)

see also an example of proc_card.dat in the Template.

3. go into my_proc/bin and type "./newprocess"

4. Fill in the two input files my_proc/Cards/param_card.dat and my_proc/Cards/run_card.dat

5. go to my_proc/SubProcesses/P???

P??? is a specific process that you have requested in the proc_card.dat.

6. type "make" and then ./cross_section

the PT and rapidity distributions of the quarkonium state are written in the file histogram.dat

Remarks:

• We use the BBL normalization for the long distance matrix elements.

MadOnia version II

11/2008: Phase 2 is done! MG_ME is been upgraded with the MadOnia implementation. Production of quarkonium unweighted events has been successfully tested.

-- Main.PierreArtoisenet - 25 Nov 2008