Efectul Compton

The force applied to ball 2 during collision from the side of the ball 1 is directed along the line joining the centers of the balls. So, after collision the ball 2 will move at angle θ as shown in the figure.
(r1 + r2) sin θ = δ 
During the collision the energy and momentum of the motion is constant:

From these equations we can find:

Considering m1=m2, the bi dimensional collision does not fit again with observed distribution of energy before and after collision.
If there is a ,,really” elastic collision, and photon mass equal with electron mass, a larger distribution of recoil electron energy and recoil photon should be counted. It should be observed cases when incident photon loose 50% of its initial energy even 75 % percent or even more.
This is not the end of nightmare for actual theoreticians.
The up presented discussion was made for a 0,66MeV photon.
In case of a 3,5MeV photon, the mass of this photon is:


By comparison with electron mass there is:

In this case the mass of photon is significantly greater then electron mass considered at rest.
Again from classical mechanics when a greater object collides with a smaller object at rest, it is impossible for the greater object to have recoil at 135 degree. So, in case of Compton effect as the incident photon energy increases, the signal for recoil photon at an angle greater then 90 degree should vanish. Does this happen in experiments? Maybe is the time for actual theoreticians to repeat some experiments before making comments.
Long time ago, but published in 2007, and also in a internet article, an alternative explanation for Compton effect was proposed. The explanation was based on a collision between a mass photon and a electron ,,at rest” in order to have a comparison with quantum mechanics. 
At the moment, in absence of another possibility to estimate the mass of a photon, it is very difficult to draw a clear conclusion for Compton effect. 

If the mass of a γ-ray photon is comparable with electron mass, the Compton effect is caused by collision of γ-ray photon with atomic nucleus.
If the mass of γ-ray photon is much smaller then electron mass, the Compton effect can be caused by both type of collisions: γ-ray photon with electrons and γ-ray photon with atomic nucleus.
In both cases the mathematical demonstration made in Atomic structure book and in the up presented link remains valid as principle. It is necessary to establish the ,,obstacle” which deviate the photon.
Both these possibilities blow up the actual explanation and quantum theory.
It is foreseen a further revision of Compton effect in physical-chemistry book.