Quarks With Charge 2 3 E example essay topic

What exactly is Quark? Quark: a fermion which is believed to be one of the fundamental constituents of matter. All quarks have a fractional electric charge 1. This pretty much means quarks have 1/2 spin (rotate two full rotations to get to place it started), apply to Pauli Exclusion Principle, is one of the things that make up all matter, and its electric charge is a fraction.

There are three different colors of quark; red, green, and blue. The colors always up to white. Also there are three different kinds of anti quark; cyan, yellow, and magenta. Quarks are at least 330 MeV. Quarks were first proposed in 1964.

It was named quark by Caltech theorist Murray Gell-Mann. He named them that from a quotation in a novel "Three quarks for Muster Mark, Sure he hasn't got much of a bark... ". 2 Gell-Mann said all mesons, baryons, and hadrons are made of quarks. He also said they are made of three types of quarks (up, down, and strange). That makes a total of nine types of quarks.

George Zweig called them aces. Not many people believed in it at this time. From 1968 to 1973 MIT bombarded protons and neutrons with electrons. Electrons ricocheted off protons and neutrons as if it hit a hard, tiny object.

The hard object was a quark. Over the years experiments and researches have led to a lot of indirect evidence that quarks exist. Despite all this indirect evidence they could not find a single free quark. No particle detector detected one. This led to a lot of non believers. As more proof has been shown that quarks exist it became more popular and less doubted.

Chapter 1: Over coming Skepticism Doubters did not believe in quarks. They thought of quarks just as a math equation that could explain a couple of things. They had good reason. The quark was never found free or even revealed itself. That was until 1974 when two discoveries occurred at the Brookhaven Laboratory and Stanford.

They had found a new particle. Stanford called it the psi and Brookhaven called it the J. The new particle had to be a new kind of quark. Two years later Harvard theorist Sheldon Glasgow named the new particle the charmed quark. This discovery shattered any doubts about the quark being real or not. The discovery also shattered the bootstrap model theory.

This theory said that protons, neutrons, and other particles were the smallest units. From 1964 to 1976 this theory was very popular. Research associate Michael Riordan said "Supposedly we had finally reached the innermost layer of the cosmic onion, the lowest rung of the quantum ladder, where every particle was built from all others"3. In 1973 theorists proposed a new force might explain how quarks are locked together. The theory was known as Quantum chromo dynamics. The theory gave a natural reason for why quarks seemed only to exist inside protons, neutrons, and other particles.

There was a problem with the first quark model. The original model meant that you had two exact quarks in the same quantum state. This violated the Pauli Exclusion Principle. O.W. Green burg proposed that there were 3 triplets of the fractionally charged para quarks. This meant you could build up baryons from three para quarks and not violate the Pauli Exclusion Principle. This was not well accepted. If quarks did exist people thought they would have to be really slow.

It also has to be very big. The uncertainty principle proposed that slow quarks could only fit in tiny spaces if they are big. People thought that it had to be 4 to 10 GeV. There was a problem with that. There a three quarks in a proton. This would make it 12 to 30 GeV for a single proton.

A proton only has a mass of less than 1 GeV. Quarks have to be packed tightly in protons. To take them apart there has to be lots of energy. Binding energy makes it negative towards the total mass. It represents energy that is needed to make quarks free. Binding energy has to be around -11 to negative -29 GeV.

This is probably why no one has seen a free quark. Chapter 2 Instruments to find Quarks There are many ways to detect quarks. There are chambers and other devices used in detecting quark. Some devices help in the search for quarks. In 1899 C.T. R Wilson at Cambridge found a way of measuring ionization.

It is a called a cloud chamber. Moist, dust free air is saturated with water vapor. A diaphragm expands the air in the chamber. The air cools and the water vapor condenses. Water droplets form on any ions present in the chamber. If too saturated water droplets will form anywhere.

If not saturated at all droplets will not form. When droplets grow big enough they can be photographed and counted. The bubble chamber is similar to the cloud chamber. It is a big vessel filled with a hot liquid. It detects ionized particles that pass through it. When a particle enters the pressure is decreased by a piston.

This heats the liquid. The particle boils along the path and forms a string of bubbles. A camera is on the top of the chamber and takes a picture. Charged particles travel in a twisted path.

The path is determined by the ratio of charge and mass of the particle. This means the mass can be measured. The pressure is returned to normal. Photographic emulsions make particle tracks visible. They are continuously sensitive though.

This is good for other things but not for finding quarks. It should be triggered only when a particle that could be a quark passes through. It would only detect quarks with charge 2/3 e. Anything smaller is too hard to spot. Neon flash tubes, invented by Marcello Converse, are very simple.

It is a long glass tube filled with neon. If it is between to electrodes it will glow when a high voltage pulse is applied to the electrodes after a charged particle has passed through the tube. The ionization produced by the particle makes the tube glow. If you have a lot of the tubes a two-dimensional layout of the path of a particle is shown and can be photographed by a camera at the end. It is good at singling out quarks. The neon tube detectors led to the invention of spark chambers.

A spark chamber has two parallel electrodes in an appropriate gas and pressure. If a high voltage pulse is applied across electrodes after a particle has passed, a spark will follow the ionized column of gas left by the particle. Can determine where spark is by photographing the chamber from two different angles. By using a few spark chambers spread out you can determine the course of a particle. The spark chamber is not good for figuring out the ionization made by a particle. It has been used though in quark searches to find out the path of the quark.

A scintillator measures the ionization of a particle. It is a combination of a block of scintillating material and a photomultiplier. The photomultiplier changes weak flashes of light into an electric pulse and it amplifies it. It can count single protons. It is a very fast particle counter. It can also tell the difference between particles with different ionization.

Chapter 3 How to Find Quarks The instruments in chapter 2 have to be used somewhere. Scientists and theorists look in specific places for them. There are a few methods of searching for quark. The first search for quarks in accelerators was in 1964.

An accelerator uses electric fields to propel charged particles to big energies. The CERN intersecting storage rings became available. This accelerator collides together to beams of protons moving in opposite directions. Two tubes carry the proton beams. The protons are bent into a circular path using magnets. The two beams then clash.

Experiments have had the accelerator at energies of 1500 to 2000 GeV. None of the new experiments found quarks either. Telescopes are placed to detect the quarks in these high energy interactions. The telescopes have scintillation counters. The counters are used to determine where the particles are as they pass the telescope. The courses of the particles are straight lines because no magnetic fields are used.

Two experiments were done using this method, one led by Fab jan and the other led by Antonio Zichichi, and they found two particles that could have been a quark. It had all the characteristics that a quark was supposed to have. But since it was only two events that might have found a free quark it was not that big of a deal. Scientists in the 1960's used a revised version of the Rutherford scattering experiment to search for quarks. Rutherford probed the atom using a beam of tiny entities.

The beam was changed into one of high energy electrons. This method was used with the Linear Accelerator at Stanford. Electrons travel on an electromagnetic wave. They collide with the protons and their scattering angles are measured. The last method is to look for new particles and see if the fitted the description for a quark.

A lot were found that did fit. When one did not fit the description of a quark but it could an extended model for a quark that contained different types of quarks they made a new model. Chapter 4 Unsuccessful Experiments Lots of experiments were tried to find a free quark. All of the experiments were unsuccessful. The two accelerators used were the CERN proton synchrotron and the Brookhaven synchrotron. They looked for quarks with a charge of 1/3 e or 2/3 e.

They did not find anything. A team of people from Columbia University led by Leon Lederman realized that if they took advantage of Fermi motion or internal motion of protons and neutrons they could make bigger particles. In 1965 they slammed proton beam into copper and studied the debris off a five degree angle. They looked for heavy particles and quarks with whole number charges.

All they found was evidence of an anti deuteron. If quarks did exist they had to be heavier than five GeV. In 1965 five CERN scientists led by An tonino Zichichi looked for fractionally charged quarks in cosmic rays. They built a cosmic-ray telescope to look for the quarks. It had six layers of plastic scintillator.

Each layer could be viewed by its own photocell. When a charged particle passed through a layer its trail of ions gave a light flash that the photocell turns into an electronic pulse. The pulse is in proportion with the square of the particles charge. In 1966 they ran the test for three months. In the end they did not find anything that looked like a quark.

They found out that if quarks did exist they fell at a rate less than one quark per square foot per day. They found one particle that could have been a quark. It had low pulses. None of the scientists thought it could be a quark. They tried to explain it but they could not find a good explanation so they continued the experiment. Three scientists at the Argonne National Laboratory looked for quarks in normal matter.

They searched for quarks in meteorites, sea water, air, and dust. They passed big volumes of air and water through electronic fields. The only thing they could found out is that there is less than one quark per kilogram of air or seawater. Giacomo Morpurgo, an Italian theorist at the University of Genoa, wrote a paper about quarks in 1965. He said quarks were real things. He gave a simple example of how quarks might be in hadrons.

"If the present ideas are valid, the quarks should exist, they should not be only mathematical entities". 4 He then did an experiment. He built a device that used magnetic fields to levitate granules of graphite. Then he measured charge on grain by observing its movement. The deflection told them the size of the charge. The direction told them if the grain was positive or negative.

They shinned ultraviolet light on the grain so they could take out the electrons and change its charge. If the grain has a fractional charge it would never hit zero. The deflection would give a measure of its fractional charge. This would give proof of quarks. They rejected a lot of the granules because they had too many extra electrons. They found five granules that fitted what they were looking for.

But the amount of graphite was too small. They spent ten more years running the experiment. They improved the device but still did not have any success. Chapter 5 The Fall of the Quark Model By 1966 there had been twenty experiments searching for the free quark.

All of these experiments have been in vain. The only way to explain this was that quarks did not exist as real particles. Quarks were just math equations, which is not rare in physics. In a speech Gell-Mann said "So we must face the likelihood that quarks are not real". 5 All baryons can be built from a combination of three quarks. The quark model placed limits on Baryons and Mesons and allowed physicists to calculate the magnetic attributes of a meson and neutron easily.

In 1966 the biannual Rochester Conference the S-matrix and bootstrap model theories were back. In the conference Giacomo Morpurgo gave in nine papers about quarks. Gell-Mann, who was one of the leading men ii particle physics made a speech to start the conference. In the speech he said how improbable quarks were. This speech gave by a top theorist had everyone doubting quarks existed. A group of theorists still believed in the quark.

There leader was Richard Dalitz. He developed a non realistic quark model. Dalitz had a talk at Berkeley on how mesons and baryons could be built from heavy quarks. A lot of the people were bored during it and most left. Chapter 6 The Resurrection of the Quark theory In 1966 the quark theory was in serious danger. It had no substance.

When it seemed like the quark theory had lost all hope a new generation of scientists and physicists brought it back. At the University of Tokyo's Institute for Nuclear Studies and the Yokohama National University the used an emulsion chamber to study high energy interactions of cosmic radiation. They used the last method I spoke about in chapter 3. The small chamber had 79 layers of nuclear emulsion and lead.

Twelve chambers were flown on a jet for 500 hours at 10,000 meters. This experiment lead to the making of the fourth flavor of quark; charm. It was named charm by Harvard theorist Sheldon Glas hov. In 1974 two US teams found a similar particle in accelerators. One group was lead by Samuel Ting in Brookhaven National Laboratory and the other one was at the Stanford Linear Accelerator (SLAC). SLAC was made in 1966.

It is the biggest atom smasher in the world. It is two miles long and cost $114 million. It is so big because Robert Hofstadtor suggested "Why not build one a mile long?" 6 There was a SLAC-MIT-Caltech collaboration but Caltech left and only SLAC and MIT were left. The c harmonium hypothesis supported idea of combination of quarks. Now twelve different types of quarks exist including their anti-quarks. SLAC looked for another quark.

After several years they found it. It was twice as big as a proton. In 1977 Fermilab discovered the bottom quark in proton collisions. In 1995 Fermilab also discovered the top quark in proton-antiproton annihilation. Chapter 7 The Searching for a Free Quark Even with all those discoveries a free quark was not seen. They expected to find quarks in cosmic radiation or left over from earlier stage of cosmos.

Some people thought that free quarks might not exist. Accelerator energies increased and not one was found. Cosmic radiation has energetic charged particles. In the 1960's most people looked for quarks in "low-energy"7 cosmic radiation which is 30 GeV to 3000 GeV. In University of Tokyo they made an experiment using 12 layers of scintillation counter and a stream chamber that makes the path of a particle visible. They ran their telescopes for 3500 hours.

They found one track that was expected of a quark's track. But it occurred after the streamer chamber was in action. They did not claim that they had found a free quark. In New Zealand, P.C. M York and his co-workers reported a few fractionally charged particles with a telescope. Brian Mccuscker led a cloud chamber experiment in Sydney.

He found 4 candidates to be a quark. All of them had defects though. He found a promising track though. It was lightly ionizing. In Berkley they tried to repeat the Sydney experiment only bigger.

They had 11 cloud chambers. None of the experiments found a quark track. You could quarks with a neon horoscope. It is a big device that had a big collection area. It has a stack of glass tubes filled with neon. After a charged particle passes through the stack it is photographed.

The Durham neon horoscope experiment had 11670 tubes. It ran for 15179 hours and had found two candidates. But their tracks could be caused by early random muons. Brian McCuscker found value for flux of quarks in air shower cores. This explained why a lot of the experiments on a larger scale than his did not see a quark. In 1962 there was a collaboration between Brazilian and Japanese scientists.

They made large emulsion chambers. They have two layers of lead and photographic emulsion split by layer of pitch, wood, and air gap. This requires lots of resources. In 1971 the collaboration reported an unusual event called the centaur o. They had found a large number of energetic y-rays in the lower part of the chamber but few on the upper part. This meant that in between the two parts of the chamber there was a lot of nuclear interactions.

A lot of energetic hadrons hit the top of the chamber. It did not produce a pion which was never seen before. In 1978 James Bjork en and J.S. McClerran proposed that the particle that caused the centaur o was a quark glob. The glob could penetrate 1/2 of atmosphere and produce 75 baryons and no pions. The glob had to have 225 quarks with no anti-quarks. If the number of quarks was divisible by three when the glob broke no quarks would be left because there are 3 quarks in a baryon.

The quark like tracks in the Sydney and Durham experiments were from left over quark a centaur o interaction. Other events fit the quark glob portrait. Evidence of free quark in high-energy cosmic radiation grew. Scientists looked for quark in normal matter. Millikan in 1910 might have been the first person to see quark. He used an oil drop method.

In Stanford a group led by William Fairbanks did an oil drop type of experiment except with superconducting levitation. In 1970 they reported their results. They found fractional charges of 1/3 e, which is expected for a quark to have. People criticized their results. They repeated the experiment and got the same results. Some people give credit to Fairbanks for being the first person to see a free quark.

No one found really found any convincing proof of that a free quark exists. Some scientist think it does exist some don't. Conclusion The search of quarks has encountered many highs and lows. Physicists have come across many hard parts in the quark model.

Many devices, machines, and instruments are used to search for the tiny particle that is quark. It has overcome a lot of skepticism. It has changed during the years since it was first proposed to include fifteen different types of quarks not including anti-quarks. Quarks come in six different flavors and three colors. The different flavors are; up, down, strange / sideways, charm, top and bottom. Free quarks have not been found and a lot of people think that quarks can not get out of hadrons.

Foot Notes 1. J.C. Polkinghorne, The Particle Play (University of Cambridge, 1979), p. 1322. James Joyce, Finnegan's Wake (London, 1939) 3. Michael Riordan, The Hunting of the Quark (New York, 1987), p. 10 4. G., Morpurgo, Physics, vol. 2 (1965), p. 103 5. Murray Gell-Mann, Elementary Particles, vol. 41 (1966), p. 1606. Robert Hofstadtor, quoted from interview (January 20 1984) 7. Brian McCuscker, The Quest for Quarks (Cambridge, 1983), p. 112.