13 Neutrinos Oscillate and Hence They Weigh
93
particles were moving at extremely high speeds and the second when phenomena were taking place in atomic and sub-atomic distances. The full wonder
of quantum mechanics cannot be described within the limited space of this
book but in a nutshell, quantum mechanics [63] provides a dual description
of nature where both the discrete nature of particles and the continuous
nature of waves are used for description of the same phenomena. This wave–
particle duality grew out of attempts to explain phenomena in atomic spectra
that could not be understood on the basis of classical ideas of Newton’s
laws and Maxwell’s laws of electricity and magnetism. The observation of
discrete light spectra from atoms required physics beyond the old classical
laws and it led to Bohr’s groundbreaking suggestion of discrete atomic orbits
of Bohr’s and Einstein’s, together with Planck’s ideas of discreteness of light
energy, developed into a more elaborate description based on a new kind
of mathematics that eventually became quantum mechanics. As just noted,
according to quantum mechanics, physical phenomena at atomic and subatomic distances can have descriptions in terms of both waves and particles.
To reconcile the particle nature (particles are located at a point) with the
wave nature (waves may have infinite spread), the particles are assumed to
be described by wave packets. Those are collections of simple plain waves with
infinite spread, altogether making a finite size packet within which the particle
has a high probability of being found. With this much broad background, one
can think of neutrinos as follows: two neutrinos, one of which oscillates to the
other, are both described by two wave packets and roughly speaking, oscillation
becomes possible if the two wave packets overlap with each other and they get
confused about their identity as stated in Sect. 13.1. If they are separated from
one another, no oscillation is possible.
13.3 Detecting Neutrino Oscillations
What is the experimental manifestation of the oscillation of neutrino states?
As the name implies, due to oscillation phenomenon, one neutrino species
spontaneously converts to another neutrino species and then depending on the
oscillation period, it can convert back to the first neutrino, just like a swing
that goes back and forth. If we catch the neutrino state halfway through its
oscillation, the intensity of the initial neutrino beam will be less since some of
the original beam has oscillated away to the other neutrino. For example, if a
source emits ten neutrinos of one kind, five could have oscillated into another
kind. This would cause a depletion of the original beam. This is actually the
way neutrino oscillation is detected in nature.
93
particles were moving at extremely high speeds and the second when phenomena were taking place in atomic and sub-atomic distances. The full wonder
of quantum mechanics cannot be described within the limited space of this
book but in a nutshell, quantum mechanics [63] provides a dual description
of nature where both the discrete nature of particles and the continuous
nature of waves are used for description of the same phenomena. This wave–
particle duality grew out of attempts to explain phenomena in atomic spectra
that could not be understood on the basis of classical ideas of Newton’s
laws and Maxwell’s laws of electricity and magnetism. The observation of
discrete light spectra from atoms required physics beyond the old classical
laws and it led to Bohr’s groundbreaking suggestion of discrete atomic orbits
of Bohr’s and Einstein’s, together with Planck’s ideas of discreteness of light
energy, developed into a more elaborate description based on a new kind
of mathematics that eventually became quantum mechanics. As just noted,
according to quantum mechanics, physical phenomena at atomic and subatomic distances can have descriptions in terms of both waves and particles.
To reconcile the particle nature (particles are located at a point) with the
wave nature (waves may have infinite spread), the particles are assumed to
be described by wave packets. Those are collections of simple plain waves with
infinite spread, altogether making a finite size packet within which the particle
has a high probability of being found. With this much broad background, one
can think of neutrinos as follows: two neutrinos, one of which oscillates to the
other, are both described by two wave packets and roughly speaking, oscillation
becomes possible if the two wave packets overlap with each other and they get
confused about their identity as stated in Sect. 13.1. If they are separated from
one another, no oscillation is possible.
13.3 Detecting Neutrino Oscillations
What is the experimental manifestation of the oscillation of neutrino states?
As the name implies, due to oscillation phenomenon, one neutrino species
spontaneously converts to another neutrino species and then depending on the
oscillation period, it can convert back to the first neutrino, just like a swing
that goes back and forth. If we catch the neutrino state halfway through its
oscillation, the intensity of the initial neutrino beam will be less since some of
the original beam has oscillated away to the other neutrino. For example, if a
source emits ten neutrinos of one kind, five could have oscillated into another
kind. This would cause a depletion of the original beam. This is actually the
way neutrino oscillation is detected in nature.