In nuclear physics and particle physics, isospin (I) is a quantum number related to the up- and down quark content of the particle.
Isospin is also known as isobaric spin or isotopic spin.
Isospin symmetry is a subset of the flavour symmetry seen more broadly in the interactions of baryons and mesons.
The name of the concept contains the term spin because its quantum mechanical description is mathematically similar to that of angular momentum (in particular, in the way it couples; for example, a proton–neutron pair can be coupled either in a state of total isospin 1 or in one of 0[1]). But unlike angular momentum, it is a dimensionless quantity and is not actually any type of spin.
Before the concept of quarks was introduced, particles that are affected equally by the strong force but had different charges (e.g. protons and neutrons) were considered different states of the same particle, but having isospin values related to the number of charge states.[2] A close examination of isospin symmetry ultimately led directly to the discovery and understanding of quarks and to the development of Yang–Mills theory. Isospin symmetry remains an important concept in particle physics.
^Povh, Bogdan; Klaus, Rith; Scholz, Christoph; Zetsche, Frank (2008) [1993]. "Chapter 2". Particles and Nuclei. Springer. p. 21. ISBN 978-3-540-79367-0.
^Cite error: The named reference Greiner was invoked but never defined (see the help page).
physics and particle physics, isospin (I) is a quantum number related to the up- and down quark content of the particle. Isospin is also known as isobaric...
with zero weak isospin do not. Weak isospin is a construct parallel to the idea of isospin under the strong interaction. Weak isospin is usually given...
interaction, weak isospin is conserved: The sum of the weak isospin numbers of the particles entering the interaction equals the sum of the weak isospin numbers...
In particle physics, isospin multiplets are families of hadrons with approximately equal masses. All particles within a multiplet, have the same spin...
particle, but in different isospin states. The mathematics of isospin was modeled after the mathematics of spin. Isospin projections varied in increments...
quarks. Under the isospin model, they were considered to be a single particle in different charged states. The mathematics of isospin was modeled after...
symmetry relating the proton and neutron is known as isospin and denoted I (or sometimes T). Isospin is an SU(2) symmetry, like ordinary spin, so is completely...
strong interactions, isospin symmetry remains a useful calculational tool, and its violation introduces corrections to the isospin-symmetric results. Because...
quantum number relating the electric charge and the third component of weak isospin. It is frequently denoted Y W {\displaystyle Y_{\mathsf {W}}} and corresponds...
without changing the dynamics of the system. These fields are the weak isospin fields W1, W2, and W3, and the weak hypercharge field B. This invariance...
as two states of the same nucleon, and together form an isospin doublet (I = 1/2). In isospin space, neutrons can be transformed into protons and conversely...
hypercharge provides a single charge operator that accounts for properties of isospin, electric charge, and flavour. The hypercharge is useful to classify hadrons;...
not only electric charge, but also charges such as color charge and weak isospin. Because of a phenomenon known as color confinement, a hadron cannot have...
antiparticle. Together, the pions form a triplet of isospin. Each pion has isospin (I = 1) and third-component isospin equal to its charge (Iz = +1, 0 or −1). The...
flavor symmetry. This classification scheme organized the hadrons into isospin multiplets, but the physical basis behind it was still unclear. In 1964...
( T = 1 / 2 ) of the weak isospin SU(2) gauge symmetry. This means that these particles are eigenstates of the isospin projection T3 with eigenvalues...
quarks each. The isospin analogy also applies to quarks, and is the source of the names up (as in "isospin up") and down (as in "isospin down") for the...
particle, but with different isospin quantum numbers; conventionally, the proton is isospin up, while the neutron is isospin down. The strong force is invariant...
called an isospin singlet, mathematically analogous to how a spin-0 particle behaves under ordinary rotation. In general, particles form isospin multiplets...
SU(3) flavor symmetry. This ordered hadrons into isospin multiplets. The physical basis behind both isospin and strangeness was only explained in 1964, when...
In particular, since χ ∈ L has weak isospin 1⁄2 like the Higgs field H, and η {\displaystyle \eta } has weak isospin 0, the mass parameter M can be generated...
distinguished from neutrinos by having opposite-signed lepton number and weak isospin, and right-handed instead of left-handed chirality. To conserve total lepton...
leptons involved, following the convention in use for the sign of weak isospin and the sign of strangeness quantum number (for quarks), both of which...
The Δ baryons have a mass of about 1232 MeV/c2; their third component of isospin I 3 = ± 1 2 o r ± 3 2 ; {\displaystyle \;I_{3}=\pm {\tfrac {1}{2}}~{\mathsf...
particle physics, a rho meson is a short-lived hadronic particle that is an isospin triplet whose three states are denoted as ρ+ , ρ0 and ρ− . Along with pions...
weak isospin SU(2) transformations the left-handed particles are weak-isospin doublets, whereas the right-handed are singlets – i.e. the weak isospin of...
changes, here labelled as the isospin. Up and down quarks have total isospin I = 1 2 {\textstyle I={\frac {1}{2}}} and isospin projections I z = { 1 2 up...
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