# Missing energy is reasonable?

Dear User Forum,

About the missing energy, I have a similar question as in e.g. "Missing energy" in output file.

However, I want to understand if my case is reasonable or not.
I am calculating the energy deposited by a proton beam of of 2.5 GeV in a beam dump of Cu, 25 cm radius and 120 cm long. The missing energy is 0.424 GeV per primary, i.e. 17%.
Considering the nuclear binding energy is about 8 MeV per nucleon in Cu, this seems a bit high, or? The number of stars is about 12 per primary meaning 35 MeV “lost” as binding energy per star. How can this be understood? Is it due to the inelastic interactions by the secondaries? E.g. can I read out how many secondary nuclear inelastic interactions are produced?

See the energy balance and events per region below.

Best regards,
Björn

From Run Summary
2.5000E+00 (100.%) GeV available per beam particle divided into
1.1835E+00 (47.3%) 0.0000E+00 ( 0.0%) GeV hadron and muon dE/dx
5.6439E-01 (22.6%) 0.0000E+00 ( 0.0%) GeV electro-magnetic showers
2.0871E-02 ( 0.8%) 0.0000E+00 ( 0.0%) GeV nuclear recoils and heavy fragments
0.0000E+00 ( 0.0%) 0.0000E+00 ( 0.0%) GeV particles below threshold
0.0000E+00 ( 0.0%) 0.0000E+00 ( 0.0%) GeV residual excitation energy
1.8153E-02 ( 0.7%) 0.0000E+00 ( 0.0%) GeV low energy neutrons
2.5276E-01 (10.1%) 0.0000E+00 ( 0.0%) GeV particles escaping the system
3.6295E-02 ( 1.5%) 0.0000E+00 ( 0.0%) GeV particles discarded
0.0000E+00 ( 0.0%) 0.0000E+00 ( 0.0%) GeV particles out of time limit
4.2407E-01 (17.0%) GeV missing

It’s helpful to raise the question, since it gives the opportunity to point out that, at the indicated proton beam energy, the “missing” energy does not account only for binding breaking (nucleon freeing), but also for creation of new particles, such as pions (and kaons), whose mass is taken from the initial kinetic energy.

As for the number of inelastic interactions (aka stars), the detailed information is also printed towards the end the output file, in the run summary:
`Number of stars generated per beam particle:`
as a function of the type of the particle inducing the reaction.
Note that, by definition of inelastic interaction, a beam particle can undergo at most one star.

Right after, you find the
`Number of secondaries generated in inelastic interactions per beam particle:`

I will look more into the .out files. I can see now that I have created some pions…

So, in short, do you think that the lost energy of 17% is reasonable?

4.0360E-01 ( 3.3%) 0.0000E+00 ( 0.0%) generated by PION+
6.1910E-01 ( 5.1%) 0.0000E+00 ( 0.0%) generated by PION-

Best regards,
Björn

So, in short, do you think that the lost energy of 17% is reasonable?

Yes, for the considered beam energy I do.

Ok, thank you!
Björn