Does deep inelastic scattering produce photon? I know that DIS produces hadron jets, which are formed from the intense energy of the interaction. But I wonder, are photons also produced? And if so, what are the processes that create these photons?
 A: Photons are seen in the final state in many cases.
The "final" products of any process include only stable particles (or at least those long-lived enough to not matter in the context of the detector you are using): electrons, protons, neutrons, neutrinos, and photons (plus possibly muons depending on the size of your detector system and the energies involved). All other product decay or re-interact after production. 
You get photons from 


*

*decay of unstable particles

*direct production of off charged particles involved in the vertex interactions of charged products with the medium of the detector (Bremsstrahulung)

*interactions of charged products with the medium of the detector

*annihilation of particles with their charge conjugation partners (i.e. matter-antimatter)


and other less common causes.
A: DIS was originally used to probe the insides of protons and neutrons and discover quarks. The energetic lepton knocks out a quark from the proton or neutron, and the exchange of energy between the lepton and the quarks is via virtual photons.
These virtual photons are off mass shell, and are not real photons. They are just a mathematical model to describe the process.

Also, note that in the perturbative approximation it is a high-energy virtual photon emitted from the lepton and absorbed by the target hadron which transfers energy to one of its constituent quarks, as in the adjacent diagram.

https://en.wikipedia.org/wiki/Deep_inelastic_scattering
If you are asking about isolated photons being produced by DIS, then here you can find some information.
https://arxiv.org/abs/1509.02905
