pion


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pion

pion (pīˈŏn) or pi meson, lightest of the meson family of elementary particles. The existence of the pion was predicted in 1935 by Hideki Yukawa, who theorized that it was responsible for the force of the strong interactions holding the atomic nucleus together. It was first detected in cosmic rays by C. F. Powell in 1947. The pion is actually a multiplet of three particles. The neutral pion, π0, has a mass about 264 times that of the electron. The charged pions, π+ and π, each have a mass about 273 times that of the electron. The neutral pion is its own antiparticle, while the negative pion is the antiparticle of the positive pion. It is now known that each pion (and, more generally, each meson) consists of a quark bound to an antiquark. Free pions are unstable. The charged pions decay with an average lifetime of 2.55 × 10−8 sec into a muon of like charge and a neutrino or antineutrino; the neutral pion decays in about 10−15 sec, usually into a pair of photons but occasionally into a positron-electron pair and a photon.
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pion

[′pī‚än]
(particle physics)
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.

pion

, pi meson
Physics a meson having a positive or negative charge and a rest mass 273.13 times that of the electron, or no charge and a rest mass 264.14 times that of the electron
Collins Discovery Encyclopedia, 1st edition © HarperCollins Publishers 2005
References in periodicals archive ?
Figure 3 depicts the variation of kaon to pion ratio with energy in case of pp collisions from 6.3 GeV to 7 TeV for experimental, UrQMD simulated, and DPMJETIII simulated events.
Our investigation of three events revealed that the maximum pion production indicating the maximum efficiency of proton acceleration was observed within the time interval of maximum energy release determined by [dI.sub.SXR]/dt.
This value of the momentum is much greater than the pion's mass.
OPERA's pions, made at CERN, have on average 3.5 times as much energy as their neutrino progeny.
PION is a rare condition in which there is infarction of the posterior portion of the optic nerve either following a hypotensive episode occurring intraoperatively or during a critical illness, when it is usually bilateral, or occurring spontaneously in the presence of atheromatous vascular disease or giant cell arteritis, when it typically affects just one eye.
Cecil Watson, a psychiatrist, began treating his patients through interactive video in the late 1950s (Nevins & Pion, 2000).
The field inspection is a three-step process, said Pion: "Identify, document and react to the loss." First, identify the overall condition of the building, he said.
The variance is caused by the stiffness of advertiser spine - or lack thereof." Pion sets the paper on Intertype and Ludlow machines.
Whereas Anderson's moun had all the properties of an electron except for its greater mass, so that it was a lepton, the pion shared certain properties with the more massive particles and was lumped with them as a hadron.
Marlborough, MA, October 10, 2018 --(PR.com)-- The Marlborough Economic Development Corporation (MEDC) elected Andrea Pion as its new Executive Chair.
In this paper, we present an analysis of the Coulomb effects on charged pion production in Au+Au collisions at RHIC-BES energies based on an analytic model developed in [15,16].