The phrase "a pion" is correct and usable in written English.
It can be used when referring to a type of subatomic particle in the context of physics or particle physics discussions.
Example: "In particle physics, a pion is a meson that mediates the strong force between nucleons."
Alternatives: "one pion" or "a pi meson".
The vast majority of neutrinos produced when a pion decays are so-called "muon neutrinos".
Taking a pion as an example, all we can say is that the up and anti-up quarks inside the pion must be the same color at all times.
As one measure of how high the ante has been raised, a pion has about one-seventh the weight of a proton, while a Higgs boson -- a particle the hadron collider will chase -- is thought to have a weight that is 100 to 200 times as great as a proton's and to be much harder to identify.
One of the prototypes has been tested in a pion beam at the CERN SPS.
Because the proton's gammas actually come from pions, each gamma ray must have at least half the energy of a pion.
The researchers also studied the decay of a related particle called a B+ meson into a K meson and a pion and compared it with its antimatter counterpart.
The simplest example is the deuteron, the nucleus of heavy hydrogen, which consists either of a proton and a neutron or of two neutrons bound by a positive pion (a meson that has a mass 273 times that of an electron when in the free state).
Mesic atom, atom in which one electron is replaced by a negative muon or a negative pion (pi meson).
In the data, they found evidence for gamma rays that had come from the decay of a type of particle, called a neutral pion, which is created when cosmic rays interact with the material surrounding a supernova.
For example, a neutral pion (which decays electromagnetically) has a life of about 10−16 seconds, while a charged pion (which decays through the weak interaction) lives about 10−8 seconds, a hundred million times longer.
When the high-speed proton collides with one of its low-speed cousins in the interstellar medium, their interaction often spawns an elementary particle called a neutral pion.
