Discussion Overview
The discussion centers on the various thresholds of energy required for particle collisions, particularly in the context of experiments at facilities like Fermilab and CERN. Participants explore specific thresholds, such as the pion production threshold and the potential existence of a threshold at 2 GeV, while considering the implications of these thresholds in both laboratory and cosmological settings.
Discussion Character
- Exploratory
- Technical explanation
- Debate/contested
Main Points Raised
- One participant inquires about the complete list of thresholds for particle collisions, specifically mentioning the pion production threshold of 290 MeV and questioning the validity of a 2 GeV threshold.
- Another participant states that the threshold energy is dependent on the masses of the incident and produced particles, as well as the type of collision (fixed target vs. colliding beams), suggesting that a random number like 2 GeV is unlikely to be a threshold energy.
- A later reply references the hadron epoch after the Big Bang, proposing that conditions similar to those in laboratory experiments at 2 GeV may have existed during that time.
- One participant claims that in a cosmological context, 2 GeV is indeed a threshold for proton-antiproton pair production via photon collisions, providing a specific reaction equation.
- Another participant requests a source for the claim regarding photon-photon collisions, expressing unfamiliarity with the concept.
Areas of Agreement / Disagreement
Participants express differing views on the validity of a 2 GeV threshold, with some supporting its relevance in cosmological contexts while others challenge its significance in laboratory settings. The discussion remains unresolved regarding the specific thresholds and their implications.
Contextual Notes
The discussion highlights the dependence of threshold energies on various factors, including particle masses and collision types, which may not be fully addressed in the contributions. There are also unresolved questions regarding the sources of information on photon-photon collisions.