Particle Physics Topical Packet




Bonuses               Toss-Ups







1) Identify the following types of decay, for six points each.


a) An unstable nucleus ejects an energetic electron and an antineutrino, and a neutron becomes a proton. The atomic number of the resulting atom is one greater, while the mass number is the same. For example, hydrogen-3 decays to helium-3.

Answer: electron emission or negative beta decay (prompt on just beta decay)


b) An unstable nucleus ejects a particle consisting of two positive charges and four atomic mass units. The atomic number of the resulting atom is two less, while the mass number is four less. For example, polonium-210 decays to lead-206.

Answer: alpha decay


c) An electron orbiting around the nucleus combines with a nuclear proton to produce a neutron and a neutrino, which is ejected. The atomic number of the resulting atom is one less, and the mass number remains the same.

Answer: electron capture or K-capture (prompt on beta decay)


d) Unstable nuclei resulting from either of the other major types of decay can dissipate excess energy by undergoing this additional type of decay. In one type, photons are radiated. In another type, called internal conversion, excess energy in a nucleus is transferred to one of its own orbiting electrons, which is ejected. In a third type, called internal pair production, excess energy is converted into an electron and a positron which are emitted together.

Answer: gamma decay


e) A proton decays into a neutron and ejects a positron and a neutrino. The atomic number of the resulting atom is one less, while the mass number is the same.

Answer: positron emission or positive beta decay (prompt on just beta decay)



2) Give the nation or, if it is in the United States, the state in which each of the following laboratories important in the development of particle physics is located, for three points each. For an additional 4.5 points each, also give the city.


a) CERN - the European Laboratory for Particle Physics

Answer: Geneva, Switzerland


b) Cavendish Laboratory

Answer: Cambridge, England (accept UK, etc.)


c) Fermilab

Answer: Batavia, Illinois


d) Brookhaven Laboratory

Answer: Upton, New York



3) FFPE, list the four fundamental forces in increasing order of strength. For an additional ten points, then give the ratio of the strength of the weakest to the strongest, within three orders of magnitude.


Answer: gravity, weak nuclear, electromagnetic, strong nuclear; 10-39 (accept 10-36 to 10-42)



4) Given information about the substance and time of their work, as well as their nationality, identify the following people who have contributed to particle physics, FFPE.


a) English, 17th Century, formulated the law of universal gravitation

Answer: Isaac Newton


b) Danish, 1913, incorporated the ideas of quantization in his atomic model

Answer: Niels Bohr


c) Italian-American, 1934, incorporated the neutrino in his description of beta decay

Answer: Enrico Fermi


d) one American and one Israeli, 1962, proposed SU(3) symmetry for hadrons

Answer: Murray Gell-Mann and Yural Ne'eman


e) American, 1964-1965, introduced the idea of colour

Answer: Oscar Greenberg



5) Given a subatomic particle and the year of its discovery or postulation, identify the discoverer or postulator, FFPE.


a) electron, discovered 1897

Answer: JJ Thompson


b) proton, discovered 1911

Answer: Ernest Rutherford


c) neutrino, postulated 1931

Answer: Wolfgang Pauli


d) neutron, discovered 1932

Answer: James Chadwick


e) positron, discovered 1932

Answer: Carl Anderson


f) pion, postulated 1935

Answer: Yukawa Hideki



6) Each of the following statements applies to exactly two of the fundamental forces. Name those two, all or nothing, FTPE.


a) Strength of the force is inversely related to the square of the distance between two particles

Answer: gravity and electromagnetic


b) Affect neutrinos

Answer: weak nuclear and gravity


c) The first two forces to be described by a single unified theory

Answer: electromagnetic and weak nuclear



7) In this bonus, we will construct a hierarchical chart of all particles. Pencil and paper ready. Sixteen total answers will be required, worth 1.875 points each.


a) All particles can be classified into one of two major categories. The first consists of all particles of matter and is characterized by half-integral spins and obedience to the Pauli exclusion principle. The second consists of all particles which carry force and is characterized by whole-integral spins. Name these two categories, in the order described.

Answer: fermions and bosons


b) We will now expand the bosons category. Name, in order, the bosons associated with the electromagnetic, strong nuclear, gravitational, and weak nuclear forces. Note that the existence of the boson for gravity has not yet been experimentally verified, and that there are three bosons associated with the weak nuclear force - all or nothing.

Answer: photon, gluon, graviton, W+ / W- / Z


c) We will now expand the fermions category. All fermions can be classified into one of two major categories. The first consists of particles composed of quarks and which are affected by the strong nuclear force. The second consists of particles which do not seem to be further divisible and are not affected by the strong nuclear force. Name these two categories, in the order described.

Answer: hadrons and leptons


d) We will now expand the leptons category. There are six types of leptons, three charged and three uncharged, each of which has a corresponding antilepton. Name the six leptons.

Answer: electron, muon, tau, electron neutrino, muon neutrino, tau neutrino


e) We will now expand the hadrons category. All hadrons can be classified into one of two major categories. The first consists of particles made of three quarks, such as the proton and neutron. The second consists of particles made of a quark and an antiquark, such as pions and kaons. Name these two categories, in the order described.

Answer: baryons and mesons


f) All hadrons are composed of quarks. But that is the subject of another bonus.



8) Given information about the substance and time of their work, as well as their nationality, identify the following people who have contributed to particle physics, FFPE.


a) French, 18th Century, formulated a law of electrostatic force similar to the law of universal gravitation

Answer: Charles Coulomb


b) two Americans, 1964, introduced the idea of quarks

Answers: Murray Gell-Mann and George Zweig


c) two Americans and one English, 1979, won Nobel Prize for their work in developing electroweak theory, introducing massive bosons and using SU(2) * U(1) symmetry

Answer: Sheldon Glashow, Abdus Salam, Steven Weinberg



9) Answer the following concerning quarks.


a) For two points each, name the six flavours of quarks.

Answer: up, down, strange, charm, bottom (or beauty), top (or truth) (in any order)


b) For three points each, now arrange them in increasing order of mass.

Answer: up, down, strange, charm, bottom (or beauty), top (or truth) (in that order)



10) Given its component quarks, identify the hadron, FFPE.


a) up, up, down

Answer: proton


b) up, antidown

Answer: positive pion (prompt on just pion)


c) down, down, up

Answer: neutron


d) down, antiup

Answer: negative pion (prompt on just pion)


e) up, charm, down

Answer: lambda-c


f) up and antiup or down and antidown

Answer: neutral pion (prompt on just pion)



11) Identify the following attempts at comprehensive theories in particle physics, FTPE.


a) Our current understanding combines electroweak theory and quantum chromodynamics. It divides matter into quarks and leptons, and describes the four known types of interactions among them. No experimental results actually conflict with this theory, although it has a large number of unsatisfactory features which raise a number of questions.

Answer: Standard Model


b) Most examples of this type of theory are based on the mathematical symmetry group SU(5) and suggest that quarks and leptons can be interconverted through new X gauge bosons. They are inspired by evidence that the strong force is weaker at shorter distances, suggesting that the strengths of three of the fundamental forces may become the same at high energies. They seek to unify the strong nuclear force with electroweak theory.

Answer: GUTs (grand unified theories)


c) This type of theory, the dream of theoretical physicists, would unify all four fundamental forces, including gravity.

Answer: TOE (theory of everything)



12) Given information about the substance and time of their work, as well as their nationality, identify the following people who have contributed to particle physics, FFPE.


a) Scottish, 1850s, described the relations of electric and magnetic fields to the forces that produce them in a set of four basic equations, including Gauss's, Ampere's, and Faraday's equations

Answer: James Maxwell


b) French, 1896, discovered radioactivity

Answer: Henri Becquerel


c) German, early 1900s, theorized that electromagnetic radiation, such as light, occurs in discrete bundles, or "quanta," of energy known as photons

Answer: Max Planck


d) German, 1927 and 1932, proposed his uncertainty principle and proposed that neutrons and protons are the same type of particle, held together by electron exchange particles

Answer: Werner Heisenberg


e) English, 1927 and 1928, proposed the first quantum field theory for electromagnetism, and put forth the relativistic electron theory, which predicted the existence of positrons

Answer: PAM Dirac


f) Swedish, 1930s, proposed a weak force carrier with a spin of one

Answer: Oskar Klein



13) One of the most popular theories of everything currently under consideration brings together two ideas which originated in the 1970s. Identify the following about this theory, FTPE.


a) One of the two ideas was that, in order for the strengths of the strong, weak, and electromagnetic interactions to converge properly, this type of symmetry must be included. It is the symmetry between fermions and the gauge bosons that mediate their interactions, and it predicts that every known particle should have a partner with a different spin.

Answer: supersymmetry


b) The second idea was to regard all particles, including quarks, leptons, and bosons, not as points in space, as in conventional field theories, but as extended one-dimensional objects known as these.

Answer: strings


c) The combined theory, known by this name and developed in the mid-1980s, predicts the existence of gravitons, and is entirely self-consistent.

Answer: superstring theory



14) Answer the following about particle physics terms which are related to College Bowl players for ten points each.


a) In 1947, it was found that particles 800 times more massive than electrons were created in strong interactions within cosmic rays and lived for a relatively long time without themselves interacting strongly with matter. This behavior was explained by the introduction of this property, which is conserved in strong nuclear reactions, and all particles were assigned a quantum number for this property. The pion, proton, and neutron have a value of zero for this number, but, if they were subatomic particles, most College Bowl players would have large integral values.

Answer: strangeness


b) These hypothetical particles could only interact with matter through the gravitational and weak nuclear forces. They are a possible explanation for the dark matter, so they would have to be very massive, but they must also interact very weakly with matter, or else they would already have been discovered. Some, however, might say that they already can be easily found on most College Bowl teams.

Answer: WIMPs (weakly interacting massive particles)


c) Academic Decathletes may remember from 1997 SuperQuiz that the term quark comes from this James Joyce novel.

Answer: Finnegans Wake



15) Given information about the substance and time of their work, as well as their nationality, identify the following people who have contributed to particle physics, FFPE.


a) one American and one Japanese, 1953, proposed strangeness property

Answer: Murray Gell-Mann and Nishijima Kazuhiko


b) two Americans, 1958, proposed vector minus axial vector theory, providing the mathematical structure of weak interactions and incorporating parity violations

Answer: Richard Feynman and Murray Gell-Mann


c) one English and one American, 1980s, developed superstring theory

Answer: Michael Green and John Schwartz



16) Given information about the substance and time of their work, as well as their nationality, identify the following people who have contributed to particle physics, FFPE.


a) English, 1938, proposed the idea of isotopic spin

Answer: Nicolas Kenmer


b) English, 1964, proposed hidden symmetry, a mechanism for "breaking" symmetry in electroweak theory

Answer: Peter Higgs


c) two Americans and one Japanese, 1965, renormalized quantum electrodynamics to eliminate embarrassing infinities

Answer: Richard Feynman, Julian Schwinger, Tomonaga Shin'ichiro


d) Dutch, 1971, proved that the Higgs mechanism could be renormalized

Answer: Gerard 't Hooft






1) When Einstein's special theory of relativity was introduced into quantum mechanics in order to describe the behavior of an electron in an electromagnetic field, physicists were surprised to find that the equations yielded two solutions for the allowable energies of an electron, one negative and one positive. In 1932, a particle was discovered which resolved this mystery. FTP, identify this particle, which has the same mass and spin as an electron but the opposite electric charge.


Answer: positron


2) Although this class of subatomic particle contains over 200 known members, most exist for less than 10-23 seconds, and only one is known to be stable. Its name comes from the Greek for "strong" because these particles experience the strong nuclear force. FTP, identify this group, whose members are built from quarks, and whose best known examples include the neutron and proton.


Answer: hadrons


3) Those for each of the four fundamental forces all exhibit gauge symmetry, meaning that certain changes can be made that do not affect their basic structure, and that the relevant physical laws are the same in different regions of space and time. Since the 1930s, physicists have recognized that they can use these to model all four fundamental forces. Mathematically, they describe something that varies continuously through space and time. FTP, identify these constructs, which map the way force varies in strength and direction, and whose strength for magnets can be calculated using the Biot-Savart Law.


Answer: fields


4) The enormous energy of cosmic rays converts into matter according to the E=mc2 equation, producing pairs of positrons and electrons, which exist until they come close enough to each other to be converted back into energy. Atoms can exist only because there is an excess of electrons and protons in the everyday world, with no corresponding positrons and antiprotons. FTP, identify this term for the act of mutual destruction in which a particle and its antiparticle are converted into energy.


Answer: annihilation


5) Unlike quarks and leptons, they have integral spin quantum numbers. They act as a private, invisible messenger between particles, influencing their behavior with the information they convey, rather as a ball influences the action of children playing catch. FTP, identify this type of subatomic particle which, in a sense, carries force.


Answer: gauge bosons (prompt on just bosons)


6) It has never been directly observed, so all of its assumed properties are based solely on the theory of general relativity. It must have a spin quantum number of two, and it must have no mass, only energy. FTP, identify this gauge boson, the hypothetical force carrier for gravity.


Answer: graviton


7) When a neutron transmutes into a proton, this gauge boson, one of the four described by electroweak theory, is emitted. In this case, the boson is virtual because, at 80.33 GeV, it is much more massive than the neutron, so its existence must be fleetingly short. FTP, identify this particle, which immediately transforms into an electron and an antineutrino, whose name is given by its charge and a letter of the alphabet.


Answer: W- gauge boson (prompt on just W)


8) At the instant one particle emits a photon and another particle absorbs it, energy is not conserved. A discrepancy in energy may exist for a short time provided that the product of delta E and delta t is less than the value of Planck's constant divided by two pi. These photons, which effective "borrow" energy, are known as virtual photons. This temporary violation of energy and momentum conservation is allowable under the conditions of, FTP, what theory, proposed in 1927, which states that it is impossible, even in principle, to know all the details, such as position and momentum, about a particular quantum system.


Answer: Heisenberg's Uncertainty Principle


9) In 1938, it was realized that the strong force recognizes no difference between protons and neutrons. To model this symmetry, protons and neutrons can be seen as different states of a single basic nucleon, differentiated by an internal property with a value of plus or minus one-half. FTP, identify this property, analogous to the property which distinguishes two electrons in the same orbital.


Answer: isospin (or isotopic spin; prompt on just spin although you really shouldn't)


10) It contains subgroups of objects that are related to each other by symmetric transformations, rather as a group describing the rotations of a square through ninety degrees contains the four symmetric positions of the square. Hadrons are naturally grouped in sets of eights or tens in a manner consistent with this type of symmetry, a fact recognized in 1962. FTP, identify this mathematical symmetry, often abbreviated as SU(3).


Answer: special unitary group in three dimensions (accept rough equivalents and early SU(3))


11) Physicists long assumed that this operation would make no difference to the laws of physics. However, in 1956 Chinese-American physicists Tsung-Dao Lee and Chen Ning Yang discovered that the decay of strange particles could only be understood if the weak force violated this operation, a fact that was later experimentally confirmed. FTP, identify this operation which negates the values of a point's x, y, and z coordinates, much like reflecting something in a mirror, and in a different context, has served as a source of complaint for many NFL fans dissatisfied with the inability of any team to form a dynasty reminiscent of the '70s Steelers or '80s 49ers in recent years.


Answer: parity


12) The existence of these particles is predicted by a theory of the same name which breaks symmetry. According to the mechanism, it is as if the universe lies at the bottom of a wine bottle. The symmetry of the bottle's base is clear from the top of the dimple in the center, but it is hidden from any point in the valley surrounding the central dimple. These particles would carry the additional fields needed for the symmetry breaking, have zero spin because they exist in a scalar field, and have higher energy when the field is zero than when it is nonzero. FTP, identify these carrier particles which can endow mass on elementary particles through its interactions with them.


Answer: Higgs bosons


13) According to this theory, developed in the 1970s, quarks are bound together by exchanging gauge bosons and carry a property called colour. FTP, identify this theory which describes the strong nuclear force, and, except that it is based on a three-charge system of red, green, and blue rather than the two-charge system of positive and negative, is analogous to the theory describing the electromagnetic force, known as quantum electrodynamics.


Answer: quantum chromodynamics


14) Like photons, they are massless and have a spin quantum number of one. However, unlike photons, they can interact with each other, which limits the range of their effectiveness. They carry charge in the form of a colour and an anticolour. FTP, identify this type of gauge boson, the exchange particle for the strong nuclear force, named for its ability to "glue" quarks together.


Answer: gluons


15) It decays after an average lifetime of 2.2 microseconds into an electron, a neutrino, and an antineutrino via the weak nuclear force. It has a mass of 106 MeV, 200 times greater than that of an electron but 17 times less than that of a tau. FTP, identify this subatomic particle, one of the three principle types of charged leptons.


Answer: muon


16) Massive neutrinos, supersymmetric particles, and matter that has failed to ignite as stars are all possible explanations for it, although most theories favor more exotic explanations, introducing new kinds of particles. It has not been observed through radiation of any kind, but it must exist if the motions of stars and galaxies are to be understood. FTP, identify this type of nonluminous matter, believed to constitute more than ninety percent of the universe.


Answer: dark matter


17) These hadrons decay via the strong force in the amount of time it takes light to cross the particle. By colliding particles with a net energy that is just sufficient to create the rest mass of the new particle, the system absorbs more energy than usual because the energy is being supplied at the system's own natural frequency, and the particle can therefore be observed. FTP, identify this type of subatomic particle, named for the phenomenon by which they are observed, analogous to the theory which describes the stability of many chemical compounds, such as benzene.


Answer: resonances


18) As it stood in the 1930s, quantum electrodynamics gave the wrong answers for quite simple problems. It said that the emission and reabsorption of the same photon would occur with an infinite probability, which led to infinities occurring in many situations. It even predicted that the mass of a single electron was infinite. In the late 1940s, a group of physicists ridded the theory of its embarrassing infinities by acknowledging all possible infinities and allowing the positive infinites to cancel the negative ones. FTP, identify this process, which transformed QED from a problematic theory to the most accurate quantum field theory scientists now have a their disposal.


Answer: renormalization


19) Its existence was first proposed in Japan, and it was discovered in 1937 in cosmic rays. Consisting of a quark and an antiquark, it can decay into a penetrating muon. Its mass is 200 times that of an electron, and it is chiefly responsible for the strong interactions between protons and neutrons in atomic nuclei. FTP, identify this particle, the lightest meson.


Answer: pion (or pi meson)


20) When divided by two pi, it is known as Dirac's constant, and is used to calculate pure numbers, a unitless quantity used to compare the strengths of the fundamental forces. It is often defined as the elementary quantum of action, since its dimension is the product of energy and time. FTP, identify this constant which relates frequency to energy and has a value of 6.62*10-34 joule-seconds.


Answer: Planck's Constant