Page 313 - Radiochemistry and nuclear chemistry

296 Radiochemistry and Nuclear Chemistry

Table 10.2. Classification and properties of elementary particles according to the Standard Model.

Basic Family Name and symbol Forces Charge Rest mass
nature involved
Basic Leptons: electron, e EM,W + 1 0.511 MeV
building I e-neutrino, J'e W 0 < 18 eV
blocks of Quarks: up EM,W,S +~ 1/s u
nature down EM,W,S - 1/s 1/s u
Leptons: muon, fl EM,W + 1 105.6 MeV
II p-neutrino, I,~, W 0 07
Formed in Quarks: charm EM,W,S
Big-Bang, strange EM,W,S
cosmic rays
and high-energy Leptons: tau, r EM,W -1-1
accelerators [] r-neutrino, J,, W 0 07
Quarks: top (or truth) EM,W,S
bottom (or beauty) EM,W,S

Carders of force" Photon, ? EM 0 0
bosons; Pion, x S 0,-1-1 137 MeV
s=0, 1, .. Gluon EM,W,S
Pauli print. W+,W',Z ~ W
not valid
EM = electromagnetic force, W = weak interaction, S = strong interaction.

where u and d represent the up and down quarks, respectively. The neutron decay (w
can be written according to the quark model:
e-1

I > ~ d'ln---->u*~ + e'l+ ~,

v e

i.e. a d-quark is transformed into a u-quark with the simultaneous emission of an electron
and an anti-neutrino.
In all reactions the lepton number must be conserved: the total number of leptons minus
antileptons on each side of a decay or reaction process must be the same. A similar law is
valid for the quarks. In the reaction above several quantum numbers are obeyed: (i) the
charge is the same on both side, (ii) the lepton number is zero on both sides (none =
electron minus anti-neutrino), (iii) the quark number is conserved. The elementary reactions
in Figure 10.4 can all be described in terms of lepton and quark transformations.
All hadrons contain 3 quarks, while all mesons are made up of 2 quarks or antiquarks.
The quarks move around in the nucleus, which makes it difficult to observe these minute
particles: if an atom had the size of the earth, the size of the quark would be about half a