QCD the game
is a fun way to learn about particle physics. Players match colors to learn how
quarks combine to form protons, neutrons, mesons, and other particles.
There are a variety of games that can be played with a deck of QCD cards, including Quark Rummy,
. (See the How to Play
for details). The table below shows the concepts involved in each game.
|Concept ||Rummy ||Poker ||Accelerator
|Quark flavors || X || X || X
|Strangeness and charm || X || X || X
|Strong and weak nuclear forces || X || || X
|Color charge and color neutrality || X || X || X
|Intermediate vector bosons || X || || X
|Transmutation || X || || X
|Disintegration, or radioactive decay || X || ||
|Antimatter || X || X || X
|Mass-energy equivalence || X || || X
|Matter-antimatter annihilation || X || || X
|Baryons, anti-baryons and mesons || X || X || X
|Quark content of protons, neutrons,
deltas, pions and kaons
| X || || X
|Pentaquarks || || X ||
Not every aspect of particle physics could be included in the rules of QCD The Game. Here are some
additional topics which you might share with students.
- The concept of electric charge has not been incorporated into the game. Students may be interested to know
that color-neutral particles automatically have electic charges that are integral multiples of the electron
charge. This important fact allows atoms to be electrically neutral.
- Gluons are not mentioned, however they are represented on the face of each quark card as little springs
reflectig the fact that the strong nuclear force which binds quarks together gets stronger as the quarks
get farther apart.
- Simple Feynman diagrams are represented on each card face with no explanation. Students may be interested
to know that the arrows represent quarks moving through time, and that the anti-quarks are represented as
regular quarks that move backward through time.
- There are no leptons (electrons or neutrinos) in the game. This may appear reasonable since leptons do not
possess color charge, and so do not participate in the strong nuclear force. They do however participate
in the weak interaction. Transmutation of one quark to another via the weak interaction would in reality be
accompanied by lepton production.
- The word hadron is not used, but simply refers to any particle containing quarks, including all baryons and mesons.
- Top and bottom quarks were omitted to enhance the playability of the game. Comparatively few particles have been
measured that contain top or bottom quarks, and their stupendous mass would render the light particles
irrelevant for scoring purposes. Inclusion of these heavy quarks would also unacceptably inflate the size of the deck.
- Superposition states in the makeup of pions and kaons are ignored. For exapmple, the
π0 should be a superposition of up/anti-up with down/anti-down,
but is represented in the game as either up/anti-up OR down/anti-down.
- Neutral-current interractions mediated by the Z boson are absent. While flavor-changing events mediated by the Z
is a subject of ongoing research, it may be said that such events are rare at best when compared with the normal
charged-current interractions mediated by the W boson.
- The concept of spin has not been incorporated. Thus, particle energy is awarded solely on the basis of quark content.
- The rules allude to the fact that the half life of the delta is ten-billion
times shorter than that of "most other particles". The same might be said regarding the Phi and J/Psi mesons,
however only the delta is offered as an example of a particle having a significantly different half life.
- The energies associated with each quark reflect the quark's contribution to the meson or baryon energy rather than
the intrinsic rest energy of the quark. Along with special rules for scoring pions and kaons, this approach allows
reasonably accurate energy values to be assigned to each quark combination. As the following table shows, only the
delta particle has an awarded energy that is off by more than 20%, and except for the charmed sigma and neutral
pion, the other particle energies are accurate to better than 10%.
Approximately half the particles are within 5% of their accepted rest energy.
π−||150 MeV||+ 7.5%
K−||500 MeV||+ 0.5%
||500 MeV||+ 1.3%
|Proton||P||900 MeV||- 4.1%
|Neutron||N||900 MeV||- 4.2%
|Phi meson||φ||1000 MeV||- 1.9%
||1100 MeV||- 7.5%
||1100 MeV||- 7.8%
||1100 MeV||- 8.1%
||1300 MeV||- 1.6%
||1300 MeV||- 1.1%
D−||1800 MeV||- 3.7%
||1800 MeV||- 3.5%
|Strange D meson||
||2000 MeV||+ 1.6%
|Charmed Xi Cascade||
||2300 MeV||- 6.8%
||2300 MeV||- 6.9%
||2500 MeV||- 7.2%
|J/Psi||J/Ψ ||3000 MeV||- 3.1%
|Doubly Charmed Xi ||
||3300 MeV||- 6.2%
|Doubly Charmed Omega||
|Triply Charmed Omega||