Unexpected increase in muon range

[pkalaczynski]

Hi!

I wanted to test what muon range can I expect from PROPOSAL 6.1.5, so I shot muons through 100km of sea water to be sure they will stop before exiting. I plotted the reached distance as a function of the initial muon energy:

What I found surprising and possibly unphysical is the rise at the highest energies (~10^11GeV). Is there any reason why the range slope could increase there? I'd rather expect it to further decrease, if anything.

Cheers,
Piotr

[Jean1995]

Hello Piotr!

Per default, PROPOSAL builds all interpolation tables up to energy of 1e14 MeV. For energies above, PROPOSAL would extrapolate the tables, which could cause such errors.

If you didn't change this upper limit of the interpolation tables in PROPOSAL, I would advise you to do so and check whether this already solves the issue.

If you work with a configuration file, you need to add an max_node_energy element to the interpolation field, so it looks something like this:

		"interpolation":
		{
			"do_interpolation" : true,
			"path_to_tables" : ["resources/tables"],
			"path_to_tables_readonly" : ["resources/tables"],
			"do_binary_tables" : false,
			"just_use_readonly_path" : false,
                        "max_node_energy": 1e15
		},

Note that the energy is in MeV. You should set the max_node_energy to the highest muon energies that you have in your simulation.

[asandrock]

At such extremely high energies, the Landau-Pomeranchuk-Migdal effect and the Ter-Mikaelian effect decrease the Bremsstrahlung cross section noticeably. If you plot the average energy loss divided by the energy, it becomes clear:

[maxnoe]

What are those horizontal stripes in your histogram?

[pkalaczynski]

What are those horizontal stripes in your histogram?

It's my sampling: I've been propagating in 100m (10^-1km) steps

[pkalaczynski]

interpolation

max_node_energy

Thanks @Jean1995 , I indeed have "max_node_energy" : 1e14,. I do not really expect that high muon energies, so I suppose I'll just clip at 1e14 MeV.

[pkalaczynski]

At such extremely high energies, the Landau-Pomeranchuk-Migdal effect and the Ter-Mikaelian effect decrease the Bremsstrahlung cross section noticeably. If you plot the average energy loss divided by the energy, it becomes clear:

Oh, so one could actually expect an increase in the slope after all. Thank you, that's quite interesting. Also, I have not heard about Ter-Mikaelian effect before, so I learned something new :)

[pkalaczynski]

Thank you all for swift replies, I think I'm already satisfied with the answers, so I'll close the issue.