A charged particle crossing a uniform magnetic field B follows a circular arc whose radius comes straight from the Lorentz force balancing the centripetal requirement, in the practical accelerator-physics form (p in GeV/c, B in tesla, r in metres, q in elementary charges):
r = p / (0.3 · |q| · B) → p = 0.3 · |q| · B · r
That radius depends only on momentum and charge — not on mass. So at a fixed beam kinetic energy T, electron/muon/proton get different momenta (E = T + m, p = √(E² − m²)) and therefore visibly different curvature, but a bare tracker measurement alone can never tell you the mass of an unknown track: two different particles with the same momentum curve identically.
Real detectors break that degeneracy with a second, independent measurement — time of flight or ionisation energy loss (dE/dx). Here the "mystery" track is timed over its measured arc length to a fixed wall; measured velocity β = L/(c·t) combined with the tracker's momentum solves for the mass:
m = p · √(1/β² − 1)
The Timing resolution slider adds realistic jitter to that clock — push it high enough and the mass hypotheses start to overlap, exactly like a real TOF detector losing separating power at high momentum.