Isotopic spin

In Physical of the particles, the isotopic spin (isotopic contraction of spin ) is a symmetry of the strong Interaction which is mathematically similar to the Spin. It is also said that it is a quantum Nombre.

History

The isotopic spin was suggested by Werner Heisenberg in 1932 to show that the proton and the neutron can be treated like two distinct particles constituting the nucleon. Indeed, the proton and the neutron have very similar properties, put besides their difference in load. Heisenberg introduced the isopsin to explain the fact that the intensity of the strong Interaction between two Proton S is appreciably equal to that between two Neutron S or a proton and a neutron, with the difference close the electromagnetic Interaction depends on the electric Charge of the particles which interact.

The idea of Heisenberg was that the protons and the neutrons were two physical statuses of the same particle, the Nucléon , in the same way that a Fermion presents two states of different Spin, high and low. Even by disregarding electromagnetic interaction, the proton and the neutron are not perfectly symmetrical, the isotopic spin is thus not a perfect symmetry of the strong interaction.

Symmetry

Within the framework of the standard model, the invariance of isotopic spin of the strong interaction is due to the fact that the particles low differ only by the exchange from a Quark high by a quark or vice versa. They behave appreciably in the same way from the point of view of this interaction, and this independently of the savor of the particle. It is not the case of the electromagnetic Interaction and the weak Interaction which depend on the savor of the quarks.

KNOWN (2)

The mathematical description of the isotopic spin is the same one as that of the Spin, from which the name isotopic spin comes. To be more precise, the symmetry of isotopic spin is given by the invariance of the Hamiltonian of the strong interaction under the action of the group of Dregs KNOWN (2). The Neutron and the Proton are associated with the doublet (similar to spin 1/2) of KNOWN (2), and the pawns are associated with the triplet (similar to spin 1) of KNOWN (2).

Constuction of the states of a nucleon-nucleon system similar to the addition of 2 spins 1/2:

$\ begin {boxes} \ green I=1, I_3=1 \ rangle = p$

\ \ \ green I=1, I_3=0 \ rangle = \ sqrt \ frac12 (pn +np) \ \ \ green I=1, I_3=-1 \ rangle = N \ end {boxes}

\ green I=1, I_3=0 \ rangle = \ sqrt \ frac12 (pn +np)

See too

References

Introduction, university level second cycle

Donald H. Perkins, Introduction to High Energy Physics , Cambridge University Close, 4. edition, 2000,440 pages, (ISBN 0521621968) and (ISBN-13: 978-0521621960)
Francis Halzen and Alan D. Martin, Quarks & Leptons: Year Introductory Race in Modern Particle Physics , Wiley, 1984,416 pages, (ISBN-10: 0471887412)
Povh, Rith, Scholz and Zetsche, Teilchen und Kerne, eine Einführung in die physikalischen Konzepte , Springer, Berlin Heidelberg, 7. edition, 2006,417 pages, (ISBN-10: 3540366857) and (ISBN-13: 978-3540366850)

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