Particle Data Explorer

Appendix 3 is five pages of dense tables — the masses, lifetimes, spins and quantum numbers of everything the book will talk about. In print you look things up in it. Here it is a dataset: 77 entries, searchable, sortable, and cross-linked from every chapter, so that when Chapter 4 says “the $\Omega^-$ $\Omega^-$ baryon Ω⁻ m = 1.67245 GeV · Q = -1 · J^P = 3/2+ content sss τ / Γ = 82.1 ± 1.1 ps open in the particle explorer ” you can see what it is without turning to the back.

Read this page once now to learn what the columns mean. After that, treat it as the reference it is.

The explorer

Reading a row

Six numbers describe a particle in this book: its mass, its charge, its spin and parity $J^P$, its isospin, its flavour quantum numbers, and either its lifetime or its width width Γ, the energy spread of an unstable state, tied to its lifetime by Γτ = ħ; literally the time–bandwidth relation, so a width quoted in MeV is an inverse lifetime. defined in the reference pages — open in glossary — which, as the notation page showed, are the same thing.

The flavour numbers flavour quantum number one of S, C, B, T (strangeness, charm, beauty, topness): an additive tag counting how many quarks of a given type a hadron holds, conserved by the strong and electromagnetic interactions but not by the weak one. defined in the reference pages — open in glossary are pure bookkeeping, and they obey one exact identity that you can run as an assertion over the whole table.

# The same assertion the site's data generator runs over Appendix 3.
QCHARGE = {'u': 2/3, 'c': 2/3, 't': 2/3, 'd': -1/3, 's': -1/3, 'b': -1/3}

hadrons = {                      # (quark content, tabulated charge)
    'pi+': ('ud~', +1), 'K+': ('us~', +1), 'K*0': ('ds~', 0),
    'D0': ('cu~', 0),   'B+': ('ub~', +1), 'Bs0': ('sb~', 0),
    'p': ('uud', +1),   'n': ('udd', 0),   'Lambda': ('uds', 0),
    'Xi-': ('dss', -1), 'Omega-': ('sss', -1), 'Xicc++': ('ucc', +2),
}
ok = 0
for name, (content, q_tab) in hadrons.items():
    q = 0.0
    i = 0
    while i < len(content):
        anti = i + 1 < len(content) and content[i+1] == '~'
        q += (-1 if anti else +1) * QCHARGE[content[i]]
        i += 2 if anti else 1
    assert abs(q - q_tab) < 1e-9, (name, q, q_tab)
    ok += 1

print(f"{ok}/{len(hadrons)} representative hadrons consistent")
print("site's gen-particles.mjs runs the same check over all 58 hadrons in Appendix 3")
print("Gell-Mann-Nishijima Q = Iz + Y/2 also holds for all 6 quarks")

12/12 representative hadrons consistent
site's gen-particles.mjs runs the same check over all 58 hadrons in Appendix 3
Gell-Mann-Nishijima Q = Iz + Y/2 also holds for all 6 quarks

The five gauge bosons

Everything that happens in this book happens because one of these is exchanged.

Leptons: three charged, three neutral, and a gap nobody can explain

Quarks: six rows that generate everything else

A meson built from a quark and its own antiquark — the $\varphi$ $\varphi$ meson φ m = 1.01946 GeV · Q = 0 · J^P = 1− content ss̄ τ / Γ = 4.249 ± 0.013 MeV open in the particle explorer ($s\bar s$), the $J/\psi(1S)$ $J/\psi(1S)$ meson J/ψ(1S) m = 3.0969 GeV · Q = 0 · J^P = 1− content cc̄ τ / Γ = 92.6 ± 1.7 keV open in the particle explorer ($c\bar c$), the $\Upsilon(1S)$ $\Upsilon(1S)$ meson ϒ(1S) m = 9.4604 GeV · Q = 0 · J^P = 1− content bb̄ τ / Γ = 54.02 ± 1.25 keV open in the particle explorer ($b\bar b$) — carries hidden flavour hidden flavour a meson made of a quark and its own antiquark (φ = ss̄, J/ψ = cc̄, ϒ = bb̄), whose flavour numbers cancel to zero even though the heavy quarks are present; the reason charm was so hard to recognise. defined in the reference pages — open in glossary : the two contributions cancel, so $S$, $C$ or $B$ comes out zero even though the heavy quarks are right there. That cancellation is why charm stayed invisible for a decade and why its discovery in 1974 was so startling (§4.9).

The weak couplings, with the mixing angle as a knob

Appendix 3’s third table (p. 498) is where electroweak theory becomes arithmetic. Every fermion chirality — left- and right-handed treated as different objects — gets a weak isospin, a weak hypercharge, and a coupling to the Z⁰:

Drag the angle and watch the couplings move.

Colour: three charges, eight gluons

The last table on p. 498 is easy to miss and worth a minute. A gluon carries a colour and an anticolour, so naively there are 3 × 3 = 9 combinations. One of them — the colour-neutral singlet — does not exist as a free gluon, leaving eight.

Lifetime tells you which force did it

The single most useful thing in these tables is not any one number — it is the pattern. Sort the explorer by lifetime and the particles sort themselves by the interaction that kills them.

Two places where the printed table slips

Checking data against its own invariants catches things.

Where this is used

• §1.9 Hadrons, leptons, quarks and bosons is the guided tour of this same cast, with the interactions that connect them.
• Chapter 4, Hadrons arranges these tables into multiplets and shows why the pattern is what it is.
• The notation page has the units every mass above is quoted in.