Hello I am new into jetphysics and I read here that 'Hadronic jets are amongst the most striking phenomena in high-energy physics'.

My small understanding of jets is that they are defined by the hadrons that are composed from the decay process. (Jets are shapes starting from a collision point up and the energy/radiation shower of hadrons that we can observer in the detector calorimeters).

I want to know if there are non-hadronic jets, and if so how are they defined. Or if something fundamental I miss. Any introducttonary textbook suggestions on the subject is very welcome. Thank you in advance

There exists a notion of jets in QED: one such definition of a jet arises due to the $$\sigma_{2\rightarrow2}$$ electron to muon scattering. Analysis of Feynman diagrams at the next order suggests the inclusion of the two radiative emission diagrams as well, allowing us to calculate $$\sigma_{2\rightarrow2}$$ as $$\sigma_{\rm total} - \sigma_{2\rightarrow3}$$, where $$\sigma_{2\rightarrow3}$$ is $$\sigma(e^+e^-\rightarrow\mu^+\mu^-\gamma)$$.
Now, in calculating $$\sigma_{2\rightarrow3}$$, we usually employ "experimental regularisation"$$^\dagger$$ to counter the IR divergence from the radiative corrections, and posit that the detectors can only detect photons with energy lower than some $$E_\gamma$$, and that they can only distinguish between the $$\mu$$ and $$\gamma$$ impact at an angle greater than $$\theta'$$. Thus the final two-body state will also be parameterised by $$E_\gamma$$ and $$\theta'$$, forming a Sterman-Weinberg jet.
$$^\dagger$$ Of course, theoretical particle physicists usually prefer to use a photon mass $$m_\gamma$$ as a regulator during calculations.