24
R. N. Mohapatra
Over the years, colliders proved invaluable in exploring the sub-atomic
world and discovering new particles. This provided a deeper understanding
of what was known about sub-atomic particles. To go deeper, the speed of
the colliding proton or electron had to get larger. That meant devising clever
schemes without taking too much space and spending too much resources.
People used linear colliders to avoid having to use extremely high magnetic
fields to bend energetic beams of electrons. Bending very high energy electrons
would also cause huge energy loss, since electrons lose energy by radiating
light as they bend. A classic linear collider machine was the Stanford Linear
Accelerator. At the same time, a circular electron positron collider was built at
CERN in Geneva, Switzerland. Proton accelerating higher energy machines
were also built in Brookhaven National Laboratory and Fermilab. The most
energetic such machine is the famed Large Hadron Collider (LHC) at CERN
Geneva. The LHC spans 17 miles in circumference and uses a huge amount of
electricity when it is running. That is why it is made to stop running during
cold weather when there is need for more electricity for public use. Built at a
cost of nearly seven billion dollars, this machine represents true international
collaboration in science. Only 2 ng of hydrogen are used each day to make
intense and energetic proton beams, one from each side, and they collide at
four intersection points around the machine. At the point of collision, the
fleeting temperature is 100,000 times the temperature in the core of the Sun.
The protons travel at very close to the speed of light. The discovery of the
Higgs boson (see later) is one of its shining achievements.
3.2 Particles from Cosmic Rays
The magnetic and electric fields that are naturally present in space can
accelerate particles with electric charge and produce new energetic beams of
them as they fly in from distant astrophysical sources to Earth. They are known
as cosmic rays. Victor Hess won the 1936 Nobel Prize for his discovery of
the cosmic rays, although others made comparably significant contribution to
this discovery. Theodor Wulf may have been the first to make the discovery
in 1910 [11]. Cosmic rays come from Sun, but mostly they originate in our
galaxy and outside of it. They could be coming from stellar explosion, known
as supernovae, or possibly from other sources, such as active galactic nuclei at
the center of the galaxy. It is not clear yet what the actual sources are for cosmic
rays. What we know is that they come and collide with the atoms and nuclei
in the Earth’s atmosphere to generate cascades of other particles (see Fig. 3.2)
which are observed at the Earth’s surface and also in sky-borne detectors.
R. N. Mohapatra
Over the years, colliders proved invaluable in exploring the sub-atomic
world and discovering new particles. This provided a deeper understanding
of what was known about sub-atomic particles. To go deeper, the speed of
the colliding proton or electron had to get larger. That meant devising clever
schemes without taking too much space and spending too much resources.
People used linear colliders to avoid having to use extremely high magnetic
fields to bend energetic beams of electrons. Bending very high energy electrons
would also cause huge energy loss, since electrons lose energy by radiating
light as they bend. A classic linear collider machine was the Stanford Linear
Accelerator. At the same time, a circular electron positron collider was built at
CERN in Geneva, Switzerland. Proton accelerating higher energy machines
were also built in Brookhaven National Laboratory and Fermilab. The most
energetic such machine is the famed Large Hadron Collider (LHC) at CERN
Geneva. The LHC spans 17 miles in circumference and uses a huge amount of
electricity when it is running. That is why it is made to stop running during
cold weather when there is need for more electricity for public use. Built at a
cost of nearly seven billion dollars, this machine represents true international
collaboration in science. Only 2 ng of hydrogen are used each day to make
intense and energetic proton beams, one from each side, and they collide at
four intersection points around the machine. At the point of collision, the
fleeting temperature is 100,000 times the temperature in the core of the Sun.
The protons travel at very close to the speed of light. The discovery of the
Higgs boson (see later) is one of its shining achievements.
3.2 Particles from Cosmic Rays
The magnetic and electric fields that are naturally present in space can
accelerate particles with electric charge and produce new energetic beams of
them as they fly in from distant astrophysical sources to Earth. They are known
as cosmic rays. Victor Hess won the 1936 Nobel Prize for his discovery of
the cosmic rays, although others made comparably significant contribution to
this discovery. Theodor Wulf may have been the first to make the discovery
in 1910 [11]. Cosmic rays come from Sun, but mostly they originate in our
galaxy and outside of it. They could be coming from stellar explosion, known
as supernovae, or possibly from other sources, such as active galactic nuclei at
the center of the galaxy. It is not clear yet what the actual sources are for cosmic
rays. What we know is that they come and collide with the atoms and nuclei
in the Earth’s atmosphere to generate cascades of other particles (see Fig. 3.2)
which are observed at the Earth’s surface and also in sky-borne detectors.