import numpy as np
import math
import matplotlib.pyplot as plt
from scipy.stats import argus
# The argus function is defined as
# f(x) ~ x * sqrt((1-x**2)) * exp(-chi*(1-x**2))
#
# For Upsilon(4S) physics we want x = 2*mass/sqrt(s)
#
#
sqrts = 10.5794 # mass of upsilon(4s) in GeV
chi=10
x = np.linspace(5.2, 5.3, 1000) # plot range
ax = plt.subplot(111)
y = argus.pdf(x, chi, scale=sqrts/2)
ax.plot(x, y)
ax.grid()
ax.set_xlim(5.2,5.3)
ax.set_ylim(0,2*np.amax(y))
(0.0, 18.206243585803207)