# Knowledge of threshold

## Main Question or Discussion Point

I want to know about the thresholds of particles observed when colliding two matter particles together in fermilab or CERN i.e the pion production threshold is 290 MeV, what other thresholds are there?

What is the complete list of thresholds according to the energy provided? "Is there a threshold at 2 GeV"?

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Meir Achuz
Homework Helper
Gold Member
The threshold energy depends on what the masses of the incident and produced articles are, and whether it is a fixed target or colliding beam production. There are specific formulas for specific cases.
I doubt that a random number like 2 GeV is a threshold energy.

The threshold energy depends on what the masses of the incident and produced articles are, and whether it is a fixed target or colliding beam production. There are specific formulas for specific cases.
I doubt that a random number like 2 GeV is a threshold energy.
Yes but i have read that after the big bang, hadrons collided with each other (during hadron epoch) in conditions similar to that of particles colliding at 2 GeV (in our lab experiments).....how to fit the concept there?

fzero
Homework Helper
Gold Member
In the cosmological context, 2 GeV is a threshold for proton-antiproton pair production, for example through photon collisions

$$\gamma + \gamma \rightarrow p + \bar{p}.$$

This threshold is easy to calculate because the center-of-mass energy is easy to compute. As Meir told you, for a laboratory production threshold, there can be more inputs that need to be known.

In the cosmological context, 2 GeV is a threshold for proton-antiproton pair production, for example through photon collisions

$$\gamma + \gamma \rightarrow p + \bar{p}.$$

This threshold is easy to calculate because the center-of-mass energy is easy to compute. As Meir told you, for a laboratory production threshold, there can be more inputs that need to be known.
can u identify your source of information on this.....ive never heard of photon-photon collision before....please provide link or source