Hi @chris_pav ,
I’ll do my best with this one, but I’m not sure what your physics background is, so I hope you’re ok with my guessing here — ask if I use terminology you don’t know, or let me know if you already know all this.
The full answer to your question is rather complicated; in a nutshell, the question is “what exactly do you calibrate and how?” Our calorimeter measures currents which we attribute to the drift of ions in a strong electric field (in the case of CMS, light which they attribute to showers in crystals), and we have to understand (with quite a lot of work) how the currents we measure map into the energies of particles. An electron is a rather “simple” case: we measure a signal in the calorimeter — each individual area that we can read a signal from is called a “cell” — and then correct for the fraction of the detector that is capable of measuring a signal (known as the sampling fraction). We then have a rather complex calibration that takes the energies of cells that are nearby one another and associated with an object that looks like an electron (has a track that behaves in the expected way in the inner detector, does not deposit much energy in the hadronic calorimeter, has a fairly narrow shower in the electromagnetic part of the calorimeter) and tries to estimate the energy of the original electron, using a number of different steps. There is a paper on the subject we wrote here:
https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/EGAM-2021-02/
and you can look at Figure 3 for the calibration flow diagram. Based on that energy and its position in the detector relative to the position of the original proton-proton collision from which the electron came), we have the eta and phi coordinates of the electron. Indeed, for electrons, we assume the mass. Those four measurements then give you the full kinematics of the electron.
For a jet, the mass is induced by the spread of energy through the calorimeter. A jet is not a single object, but a collection of particles. For a jet, we calibrate the entire 4-vector, which you can read about in this paper:
https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/JETM-2018-05/
pT and energy are only independent measurements when they are measured with different systems of the detector. An electron, for example, has a pT measured from its track momentum and the energy in the calorimeter. Both must be calibrated — differences can arise from normal physics processes like Bremsstrahlung. If measurements have to be independent, then they cannot be cross-calibrated — otherwise you would introduce a bias (by correcting one based on the other). This is in fact a tricky issue when we measure things like fragmentation (the fraction of charged particles) in jets, since our jet calibration depends on the charged particles, and so we have a bias that we must understand and correct for.
What makes you think that you need “two calorimeter measured variables”, and what do you expect these would teach you?
Cheers,
Zach