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Which of the elementary particles in particular are called ‘Bosons’? It is a trivial knowledge that electrons are Fermions obeying Fermi-Dirac statistics. Fermions follow Pauli Exclusion Principle as per which no two elementary particle in atom can have same set of quantum numbers. So two such particles in same energy state must have +1/2 or -1/2 spin(anticlockwise or clockwise) or magnetic quantum number. But Bosons have integral spin meaning thereby two particles can have same set of all quantum numbers. Bosons subscribe to Bose-Einstein statistics. It owes its name to an Indian scientist Satyen Bose who proposed the statistics in parallel to that of Einstein.

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The following elementary particles are bosons.

Higgs boson: spin 0

Photon, gluon, W bosons, and Z boson: spin 1

Graviton (?): spin 2

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Note that in the case of 2 fermions "having opposite spin" is somewhat of a classical colloquialism, since the antisymmetric state of which you speak is:

$$ |0,0\rangle =\frac 1 {\sqrt 2}[|\uparrow_1\downarrow_2\rangle - |\downarrow_1\uparrow_2\rangle] $$

in which particle one and two are both spin up and spin down, which is the same as in the forbidden symmetric state:

$$ |1,0\rangle=\frac 1 {\sqrt 2}[|\uparrow_1\downarrow_2\rangle + |\downarrow_1\uparrow_2\rangle] $$

So the particle don't have definite spins, though the states are combinations of state with definite and opposite spins, which say nothing about their symmetry and only guarantees $M=0$ in complete state.

Moreover, fermions can have additional internal quantum numbers that need to be considered before making definitive statements about all pairs of fermions.

Note also that any pure state with integer spin is a boson (e.g. helium-4), no matter how large, but if you include "elementary" as a condition, G. Smith's answer is complete.

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  • $\begingroup$ What you say at the beginning applies to identical fermions, but two different particles can have opposite spins and join. $\endgroup$
    – FGSUZ
    Jan 19 '19 at 0:08

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