Crystal ball function initial parameters

Newbie
,
1

ROOT Version: 6.18/00
Platform: Red Hat 8.5.0-16
Compiler: gcc version 8.5.0

Hello everyone,
I want to fit a histogram (see figure) with the crystal ball function following the code:

TF1 *fitFunction = new TF1("fitFunction", "crystalball", 84, 105);
fitFunction->SetParameters(p0, p1, p2, p3, p4);
hist->Fit("fitFunction");

But I am finding it hard to set the initial values p0…p4. First of, I am not sure what they refer to, since I couldn’t find the explicit definition of the “crystalball” function, and second, most examples I have seen fit around 0 so I am a bit confused.

I would appreciate it if you could help me understand and find the appropriate parameters, thank you!

energy_dist
energy_dist1652×967 17.4 KB

2

Try: fitFunction->Print();

3

Thank you!