Video Transcript
The diagram shows six baryons and
their quark content. Which of the diagrams do not
correctly represent possible quark combinations? How the quarks are colored in the
diagrams does not represent their electric charges.
Among these six baryons, we see
quarks and antiquarks, and all of them are colored either red or blue or green. We’re told that these colors do not
represent electric charges, but they do represent another kind of charge called
color charge. Red is one type of color charge,
green is another, and blue is a third. In this question overall, we’re on
the lookout for any diagrams that do not correctly represent possible quark
combinations. Since this diagram is meant to
represent six baryons, let’s recall the conditions for quarks coming together to
form one of these particles.
The first condition that a baryon
must satisfy is that every baryon is made of exactly three quarks. And second, the total color charge
of a baryon must be what’s called white. This means that the color charges
of the three quarks that combine to form the baryon must add together to form
white. If we think about red, green, and
blue as primary colors, then we know that if we add them together in equal amounts,
the color we’ll end up with is white. For the total color charge of a
baryon to be white then, that means it must be made up of equal parts, red, green,
and blue color charge. And therefore, each baryon must
have one red, one blue, and one green color charge quark. It doesn’t matter which quarks have
which particular color charge, but only that they balance out this way.
Considering these two conditions a
baryon must satisfy, let’s look again at our six options. We see that choices (ii) and (vi)
are both made up of antiquarks rather than quarks. This means that these particles are
not technically baryons but instead would be called antibaryons. Since we want to identify which of
these diagrams do not correctly represent possible quark combinations, we’ll put
options (ii) and (vi) in boxes. And now, let’s look at the second
condition a baryon must satisfy, that its total color charge must be white. We can see that options (i), (iii),
and (iv) all satisfy this condition in that one of the quarks has a red color
charge, one has a blue color charge, and one has a green. But option (v) does not; all of the
quarks here have the same red color charge. This means the total color charge
of this particle cannot be white, so it does not represent a possible quark
combination. The remaining three baryons do show
possible combinations.
