30
R. N. Mohapatra
their combinations. To be sure, there are some indirect tell-tale signs of quarks
in the very high energy particle collisions in the form of what is known as
jets (a jet is a spray of particles of known varieties such as pions and other
mesons, for instance), but no live quarks (unlike neutrons and protons) have
been seen yet. It is believed that this mysterious property of quarks is related
to the property of nuclear forces, embodied in a theory known as Quantum
Chromodynamics, invented by David Gross, Frank Wilczek, and H. David
Politzer, for which they got the Nobel Prize in 2004.
4.2 Baryons Have Their Own Markers, the
Baryon Number (B)
Another mystery of elementary particle theory is that in any particle reaction,
when a particle in one form of baryonic matter (p, n, ,..), disappears in
the initial state, there appears the original baryon itself or another form of
baryonic matter in the final state. We have never seen a baryon (say a proton)
vanish, leaving in its trail a bunch of mesons and no baryon. These kinds of
observations have led particle physicists to imagine ways which can prevent the
baryonic type matter like protons and neutrons from disappearing. One such
way is to assign a new quantum number for baryons which would have the
property of not changing in any elementary particle reaction. The quantum
number assigned for protons, neutrons, hyperons, and other similar particles
is called the baryon number, which is supposed to have the property of being
indestructible and works as a marker for their core property. Baryon number
remains unchanged in any elementary particle reaction. On the other hand,
the mesons such as pions, K-mesons, etc. are not supposed to have any such
quantum number that remains same before and after a reaction. A single
meson can transform to many mesons in a nuclear reaction or even just
disappear to other forms of particles. The baryon number never changes, and
is like a rule with a slogan T-shirt that says “I am a baryon and you cannot
destroy me—you can only change me to another baryon.” In other words,
you know a baryon when you see one.
Since all objects including planets, stars, mountains, plants, and animals
are full of protons, the fact that their identity continues to remain the
same during the history of the universe means that the baryon number is
crucial to the stability of matter. Because the protons and neutrons have this
indestructible attribute called baryon number, we all exist and are stable—
we will not suddenly (or over time) disappear. This property of the baryon
R. N. Mohapatra
their combinations. To be sure, there are some indirect tell-tale signs of quarks
in the very high energy particle collisions in the form of what is known as
jets (a jet is a spray of particles of known varieties such as pions and other
mesons, for instance), but no live quarks (unlike neutrons and protons) have
been seen yet. It is believed that this mysterious property of quarks is related
to the property of nuclear forces, embodied in a theory known as Quantum
Chromodynamics, invented by David Gross, Frank Wilczek, and H. David
Politzer, for which they got the Nobel Prize in 2004.
4.2 Baryons Have Their Own Markers, the
Baryon Number (B)
Another mystery of elementary particle theory is that in any particle reaction,
when a particle in one form of baryonic matter (p, n, ,..), disappears in
the initial state, there appears the original baryon itself or another form of
baryonic matter in the final state. We have never seen a baryon (say a proton)
vanish, leaving in its trail a bunch of mesons and no baryon. These kinds of
observations have led particle physicists to imagine ways which can prevent the
baryonic type matter like protons and neutrons from disappearing. One such
way is to assign a new quantum number for baryons which would have the
property of not changing in any elementary particle reaction. The quantum
number assigned for protons, neutrons, hyperons, and other similar particles
is called the baryon number, which is supposed to have the property of being
indestructible and works as a marker for their core property. Baryon number
remains unchanged in any elementary particle reaction. On the other hand,
the mesons such as pions, K-mesons, etc. are not supposed to have any such
quantum number that remains same before and after a reaction. A single
meson can transform to many mesons in a nuclear reaction or even just
disappear to other forms of particles. The baryon number never changes, and
is like a rule with a slogan T-shirt that says “I am a baryon and you cannot
destroy me—you can only change me to another baryon.” In other words,
you know a baryon when you see one.
Since all objects including planets, stars, mountains, plants, and animals
are full of protons, the fact that their identity continues to remain the
same during the history of the universe means that the baryon number is
crucial to the stability of matter. Because the protons and neutrons have this
indestructible attribute called baryon number, we all exist and are stable—
we will not suddenly (or over time) disappear. This property of the baryon