Episode 3: Physics - Feynman Diagrams

[amorenobr]

The Feynman package allows to draw Feynman diagrams using matplotlib. This could be included in this episode in order to show more examples and applications

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[amanmdesai]

I have a couple of scripts here (for Higgs-strahlung)

https://github.com/amanmdesai/Feynman-Diagrams/blob/master/higgs_strahlung.py

or this one if you want to show decays of Higgs

https://github.com/amanmdesai/Feynman-Diagrams/blob/master/higgs_cc.py

[amorenobr]

Yes Aman, that would be the idea...

[amanmdesai]

How about adding this:

import matplotlib.pyplot as plt
from feynman import Diagram

fig = plt.figure(figsize=(10.,10.))
ax = fig.add_axes([0,0,1,1], frameon=False)

diagram = Diagram(ax) 
diagram.text(.5,0.9,"Higgs Strahlung with H -> cc~ and Z decay to l+ l-", fontsize=20)
in1 = diagram.vertex(xy=(.05,.75), marker='') #quark starting point (left up); xy- vertex coordinates (x,y); marker
in2 = diagram.vertex(xy=(.05,.25), marker='') # anti-quark starting point (left down) 
v1 = diagram.vertex(xy=(.30,.5)) # Z boson starting point (left) 
v2 = diagram.vertex(xy=(.60,.5)) # Z boson starting point (right)
higgsout = diagram.vertex(xy=(.8,.65)) # higgs boson
zhout = diagram.vertex(xy=(.8,.35),marker='')  # produced Z boson in association with Higgs
c1 = diagram.vertex(xy=(.9,.75),marker='') # charm quark 
c2 = diagram.vertex(xy=(.9,.55),marker='') # charm antiquark
l1 = diagram.vertex(xy=(.9,.25),marker='') # lepton 1
l2 = diagram.vertex(xy=(.9,.45),marker='') # lepton 2

q1 = diagram.line(in1, v1) #quark 1; line joining the points 
q2 = diagram.line(v1, in2) #quark 2 
wz1 = diagram.line(v1, v2, style='wiggly',nwiggles=6) # wiggles to represent Z boson 
wz2 = diagram.line(v2, zhout, style='wiggly',nwiggles=6)
higgs = diagram.line(v2, higgsout, arrow=False, style='dashed') # dashed line to represent the higgs
charm1 = diagram.line(c1,higgsout)
charm2 = diagram.line(higgsout, c2)
lep1 = diagram.line(zhout, l1)
lep2 = diagram.line(zhout, l2)

# Text command adds text near the line

q1.text("q",fontsize=30)
q2.text(r"$\bar{\mathrm{q}}$",fontsize=30)
wz1.text("$Z$",t=0.5,y=0.1,fontsize=30)
wz2.text("$Z$",t=0.5,y=-0.15,fontsize=30)
higgs.text("H",fontsize=30)
charm2.text("c",fontsize=30)
charm1.text(r"$\bar{\mathrm{c}}$",fontsize=30)
lep2.text(r"$\mathcal{l}^{\pm}$",t=0.5,y=0.1,fontsize=30)
lep1.text(r"$\mathcal{l}^{\mp}$",t=0.5,y=-0.1,fontsize=30)
diagram.scale(0.6)
diagram.plot()
plt.savefig('zh_hcc.eps', format='eps')

Here is the code with comments

https://github.com/amanmdesai/Feynman-Diagrams/blob/master/higgs_ZH_production_hcc.py

[amorenobr]

That looks great Aman. I think it is important to make everything clear, as much as we can.

I don't know if you have had any problem with that, but in my case Feynman runs with python 2.

[amanmdesai]

I am using Python 3.10.4

[klieret]

Hi @amanmdesai @amorenobr Thanks a lot for starting this! I think we were discussing this a long time ago in one of our training meetings. I'm a bit wary of pushing too many "walls of code" on the students and I think that this will be more of a special use case of matplotlib.
But I think it would indeed be a fun bonus episode that can be included depending on the time budget of the workshop or for students who want more :)

[amorenobr]

I agree with you @klieret. Maybe we could add these codes in hidden sections right below every diagram in this episode, so if anybody is interested in learning something fun can take a look :)

[klieret]

Ah, I also really like that idea :)

[amanmdesai]

The idea sounds good. Codes to the Feynman diagrams could be found here:

https://github.com/GkAntonius/feynman/tree/master/examples/Particle_Physics

1 . plot_VBF.py
2. plot_VH.py
3. plot_ggF_SM.py
4. plot_ttH.py

[klieret]

We could simply wrap it in a HTML details element like so:

<details>
  <summary>See More</summary>
  This text will be hidden if your browser supports it.
</details>

So feel free to open a PR for that.

For consistency, please format your code with black

[amorenobr]

Thanks @klieret and @amanmdesai. I'll open a PR as soon as I can... :)

[stale]

This issue or pull request has been automatically marked as stale because it has not had recent activity. Please manually close it, if it is no longer relevant, or ask for help or support to help getting it unstuck. Let me bring this to the attention of @klieret @wdconinc @michmx for now.