N meson

Because both versions, which have been elaborated on in Ref. 5—one with muons and the other with pions—give almost identically good results of the analysis, the question arises as to which version prevails, and what arguments may help us reach such a conclusion. The important thing is that the new deuteron model proposed here implies the participation of mesons in the deuteron structure. Whether they are p mesons, that is muons, or n mesons, that is, pions, does not have any influence at all on any of the main computed magnitudes, which characterize the new deuteron model. What is really important is the fact that the newly proposed deuteron model offers a completely new insight into nuclear forces and nuclear structures in general. 

Photographic films with nuclear emulsions are used successfully in order to record very rare events induced by cosmic radiation. For this purpose, light-shielded packages of films have been carried by balloons to high altitudes. Some elementary particles, e.g. the positron and the n meson, have been detected by use of photographic emulsions. 

An analysis of the hot-spot model was attempted by Cemy and Kaufman [50], who irradiated several explosives with tt" mesons (pions). The decay of mesonic atoms formed by the capture of n mesons can result in the emission of 12-17 charged particles from a single lattice site. It was estimated that a temperature of IO" °C would be produced over a 10-A radius for 10 " sec. The calculations indicated that the temperature would decrease rapidly, but that the radius of a hot-spot site would increase to meet the criterion of Bowden. 

A detailed analysis of the hot spot model was attempted by Cerny and Kaufman (Ref 128) who irradiated several expls with n mesons (pions). High, local energy densities in rou y spherical shape can be formed from slow pion bombardment of solids... 

In the case of the photoproduction of neutral n mesons, some of the mesons are absorbed before they leave the nucleus. One could try to put a complex (real and imaginary) phase factor into the outgoing wave to take care of attenuation. However, it is also necessary to consider multiple collisions within the nucleus and the associated change in direction. The calculation is obviously no longer that of a simple form factor but a quite formidable undertaking. It becomes a many-body problem. Similar considerations are involved in the elastic scattering of nucleons from complex nuclei. 

Mesons. At the present time useful external beams of charged n mesons are available at proton accelerators. As an example", the (122 3) beam... 

Beams of fx mesons have been obtained from synchrocyclotrons the fx mesons arise from n mesons which decay in flight. Winsberg obtained approximately 10 ix mesons per second with an energy of (40 15) Mev. 

At the Berkeley Bevatron and the Brookhaven Cosmotron beams of charged K mesons are obtained (by K mesons we mean particles with a mass about 966 electron masses and a lifetime of about 10 sec). Unfortunately in the so-called meson beam there are actually about 20 times as many n mesons present as mesons. At Berkeley in the arrangement of Birge for every... 

Most laboratories with n meson beams have such investigations underway, and more effort is being devoted presently to studies of zr-mesic X-rays than to studies of [x-mesic X-rays. 

Proton-Proton-Streuquerschnitt bei hohen Energien, proton-proton scattering cross section at high energies 463-Protonquerschnitte bei nichtelastischer Streuung, nonelastic proton cross sections 260. 71-Meson s. Pion, n-meson see pion. 

According to quantum electrodynamics, the electromagnetic interaction is mediated by photons. For instance, one of the electric charges emits a photon, and the other one absorbs it. Yukawa (1935) supposed that the interaction between nucleons is also mediated by the exchange of field quanta, and the predicted rest energy of the field quantum (called meson) is 140 MeV. After the discovery of n mesons (Lattes et al. 1947) the quanta of the meson field have been identified with n mesons, which have approximately the same rest energy. 

According to experiments, the n mesons exist in three charge states Jt, Jt , n. From a pseudoscalar theory, taking into account all three charge states in a symmetric way, the following expression was obtained (see, e.g., Bohr and Mottelson 1969) for the asymptotic behavior of the so-called one-pion exchange nucleon-nucleon potential Vopep)-... 

The one-pion exchange potential (Vop p) is actually dominant only far from the core region (r > 2 fin). The numerical value of the potential can be determined from the analysis of the scattering of n mesons on nucleons. 

If two nucleons are close enough to each other, exchange of two or more n mesons, as well as exchange of heavier mesons (p, r, to) may occur between them, too. Beginning fiom the 1970s, meson field theoretical potentials have been deduced, which take into accormt these possibilities and give a better description of experimental data at small distances (r < 2 fin) than Vopep does. 

The lightest hadron, the n meson or pion has isospin 7=1 and, correspondingly, the three possible isospin states are characterized by 3 = — 1,0, +1 and it has three charge states, positive, neutral and negative. Thus the isospin became a basic quantum number in the classification of particles. 

Pions are n mesons, subnuclear particles with mass comparable to that of the muon, a particle about 200 times more massive than an electron. Pions were discovered in 1947 by C.G. Lattes, G.S.P. Occhiahni, and C.F. Powell. 

---