Eta meson

η

η '

The η -meson ( eta meson ) and the η' meson (read: " Eta -prime meson " ) are mesons. They are subject to the strong interaction and thus belong to the hadrons.

Description

In the quark model are η and η 'is a mixture of the three quark- antiquark states uu, dd and ss the Up, Down, and strange quarks. Both states η and η 'have a hypercharge and an isospin multiplet and are in the pseudoscalar mesons in the same place like the neutral pion.

The three mutually orthogonal linear combinations of the above-mentioned Quark-anti- quark states are thereby identified as follows:

The physical (mass) states η and η ' arise again as linear combinations of η8 and η1:

The thus introduced mixing angle has an experimental value, which is highly model-dependent and between -10 ° and -20 °. The η -meson therefore corresponds to almost the octet state η8, with an admixture of a few percent of the singlet state η1; when η' meson it is accordingly reversed:

The η meson was first detected in 1961 at the Lawrence Radiation Laboratory in pion - deuteron reactions.

The Flavours Charm and beauty also occur pseudoscalar mesons, the c- and b- quarks mix but because of the large mass of only little with the light quark states. The? C and? B are therefore practically pure quarkonium states cc or bb.

Decay channels

The η meson can decay through various channels; most common are the decay into three pions ( π π - π0 or π0 3 ) with around 55 % and the decay into two photons with 39%. The decay into two pions is forbidden, because it would violate the parity and the CP- invariance.

The main decay channels of the η ' with a share of around 65 % of the decay in an η -meson and two pions ( π π - η or π0π0η ) and with 29% of decay into π π - ρ0γ or γ.