High-Energy Physics - Signal Processing Systems - page 146

Fig. 5 The energy of the largest particle accelerators has shown a trend of exponential increase
with time
interrelated, and both are directly affected by the rate of collision events being
produced in the experiments. The level of collisions being produced at differ-
ent particle accelerators is by no means the same, and is driven by the type of
accelerator and the goals of the experiments. Experiments that produce collisions
at very low rates—those studying neutrino interactions for example—typically have
relaxed requirements for their triggering systems [ 3 ] . However, the largest, most
complex, and most expensive accelerators that have been built are proton-anti-
proton, electron-positron, or heavy-ion colliders, such as the LHC, the Tevatron,
the Large Electron Positron Collider, and the Relativistic Heavy Ion Collider. These
accelerators have historically required triggering systems with low-latency and
high-bandwidth requirements that pushed the limits of the technology available at
the time of their design [ 2 , 19 , 41 ] .
Looking toward the future, the technical requirements of the LHC upgrades and
post-LHC accelerators are likely to pose even more significant challenges. Historical
trends show that particle accelerator collision energies have been increasing at an
exponential rate [ 59 ] , as seen in Fig. 5 . Higher energy collisions may correlate to
even shorter-lived particles and higher rates of interesting collision events. These
higher collision rates will likely be necessary, as even with extremely high collision
rates, some high-energy phenomena still occur very rarely. For example, despite
producing one billion collisions per second at the LHC, it is still predicted that a
Higgs boson, if it does exist, will only be produced at a rate of 0.1 Hz [ 48 ] . Higher
collision rates will put more pressure on the detector's local buffers, making it
unlikely that advances in memory density will eliminate the need for low-latency
triggering systems. Overcoming the technical signal processing challenges may be
one of the key aspects of making new accelerators feasible.