Getting no.of background events in signal region

[Wile_E_Coyote]

Try to calculate the integral of your background function using, for example, something similar to (instead of “gaus” use the name of your “red dots” background function):

Entries under a gaussian?

std::cout << hspectrum->GetFunction("gaus")->Integral(2, 45) / hspectrum->GetBinWidth(1) << std::endl;