Beyond the God Particle

by Leon M. Lederman

  The Tevatron could accelerate the particles from the Main Injector up to 980 GeV. The protons and antiprotons are accelerated in opposite directions, crossing paths in the CDF and DØ detectors to collide at 1.96 TeV. To hold the particles on track the Tevatron uses 774 niobium-titanium superconducting dipole magnets cooled in liquid helium producing 4.2 teslas. The field ramps over about 20 seconds as the particles are accelerated. Another 240 NbTi quadrupole magnets are used to focus the beam.

  The Tevatron confirmed the existence of several subatomic particles that were predicted by theoretical particle physics, or gave suggestions to their existence. In 1995, the CDF experiment and DØ experiment collaborations announced the discovery of the top quark, and by 2007 they measured its mass to a precision of nearly 1%. In 2006, the CDF collaboration reported the first measurement of Bs oscillations, and observation of two types of sigma baryons.

  23. See “Tevatron,” http://en.wikipedia.org/wiki/Tevatron (site last visited 6/21/13).

  24. The antiprotons are created in a system called the “Antiproton Source.” The Main Injector–accelerated 120 GeV protons collide with a nickel target, producing a spray of different subatomic particles, which includes antiprotons. These are collected and “cooled,” meaning that compact stable bunches are formed. They are then stored in the accumulator ring, and then passed back to the Main Injector, then ultimately into the Tevatron.

  25. See “Large Electron–Positron Collider,” http://en.wikipedia.org/wiki/Large_Electron%E2%80%93Positron_Collider (site last visited 3/26/2013).

  26. See “Large Hadron Collider,” http://en.wikipedia.org/wiki/Large_Hadron_Collider (site last visited 3/26/2013).

  27. See “Georges Charpak,” http://en.wikipedia.org/wiki/Charpak (site last visited 3/26/2013).

  28. See “International Linear Collider,” http://en.wikipedia.org/wiki/International_Linear_Collider and http://www.linearcollider.org/ (sites last visited 3/26/2013).

  CHAPTER 9. RARE PROCESSES

  1. “Wilhelm Conrad Röntgen,” http://www.nobelprize.org/nobel_prizes/physics/laureates/1901/rontgen-bio.html; see “Wilhelm Röntgen,” http://en.wikipedia.org/wiki/Wilhelm_Röntgen; “The Discovery of X-Rays,” http://www.ndt-ed.org/EducationResources/HighSchool/Radiography/discoveryxrays.htm (sites last visited 3/23/2013). Gottfried Landwehr, Röntgen Centennial: X-Rays in Natural and Life Sciences, ed. A. Hasse (Singapore: World Scientific Publishing Co., 1997), pp. 7–8.

  2. See “Henri Becquerel,” http://en.wikipedia.org/wiki/Henri_Becquerel. Quoting from the article:

  As often happens in science, radioactivity came close to being discovered nearly four decades earlier when, in 1857, Abel Niepce de Saint-Victor, who was investigating photography under Michel Eugène Chevreul, observed that uranium salts emitted radiation able to darken photographic emulsions. By 1861, Niepce de Saint-Victor realized that uranium salts produce a radiation that is invisible to our eyes. (Note that Niepce de Saint-Victor knew Edmond Becquerel, Henri Becquerel's father). See “Beta decay,” http://en.wikipedia.org/wiki/Beta_decay#History, “Marie Curie,” http://en.wikipedia.org/wiki/Marie_Curie, and “Pierre Curie,” http://en.wikipedia.org/wiki/Pierre_Curie (sites last visited 3/23/2013).

  3. “What Is Radioactivity?” http://www.oasisllc.com/abgx/radioactivity.htm. For a good historical summary on radioactivity, see http://www.chemteam.info/Radioactivity/Disc-of-Alpha&Beta.html and http://www.chemteam.info/Radioactivity/Disc-Alpha&Beta-Particles.html (sites last visited 3/23/2013).

  4. See “Ernest Rutherford,” http://en.wikipedia.org/wiki/Ernest_Rutherford (site last visited 3/23/2013).

  Half-life: In a certain time interval, called the “half life,” there will be exactly half as much of a radioactive material as one began with; in another half-life interval the amount will be reduced to half as much again, or a quarter of the initial amount, and so on; materials with short half-lives are very radioactive, e.g., technecium-99 used in most medical imaging has a 2-hour half-life and therefore requires a small dose; 235U, the weapons-grade isotope of uranium has a half-life of 700,000 years; 238U about 4 billion years.

  5. See “Positron emission tomography,” http://en.wikipedia.org/wiki/Positron_emission_tomography and http://www.webmd.com/a-to-z-guides/positron-emission-tomography (sites last visited 3/23/2013).

  6. See “Paul Dirac,” http://en.wikipedia.org/wiki/Paul_Dirac (site last visited 3/23/2013). Dirac was one of quantum theory's towering figures. For one thing, Dirac wrote the book on quantum physics, called The Principle of Quantum Mechanics, which became the standard reference. Dirac's original contributions to quantum physics are among the greatest of the twentieth century, anticipating modern topology with his “magnetic monopole” and Feynman's “path integral” formulation of quantum theory. Perhaps one of the most profound discoveries of foundational physics in the twentieth century, however, happened when Dirac combined the theory of the electron with Einstein's theory of special relativity and discovered antimatter some four years before it was discovered in experiments. See also Graham Farmelo, The Strangest Man: The Hidden Life of Paul Dirac, Mystic of the Atom (Basic Books; First Trade Paper Edition, 2011).

  7. The Pauli exclusion principle is discussed further in our book: Quantum Physics for Poets (Amherst, NY: Prometheus Books, 2011). The quantum orbital state of motion in an atom can actually have two electrons, but one must have spin up and the other spin down.

  8. We call this view of the vacuum the “Dirac sea.” The Dirac sea is not empty but rather is a completely filled “ocean” that metaphorically represents the infinity of filled negative energy levels.

  Now, usually when a high-energy gamma ray collides with a negative-energy electron in the vacuum, nothing happens. A single gamma ray hitting a negative-energy electron cannot raise it out of the vacuum because such a process wouldn't conserve all of the necessary quantities that physics demands be conserved, i.e., momentum, energy, angular momentum. However, if there are other particles also participating in the collision (like a nearby heavy atomic nucleus to recoil slightly and conserve the overall momentum, energy, and angular momentum of the participants in the collision; we call this a 3-body collision), then the electron could be ejected out of the Dirac sea into a state of positive energy. The gamma ray could then successfully eject an electron out of its negative energy state and into one of positive energy, and that could register in the physicist's instruments.

  9. See “Carl David Anderson,” http://en.wikipedia.org/wiki/Carl_David_Anderson and “Positron,” http://en.wikipedia.org/wiki/Positron (sites last visited 3/23/2013).

  10. The momenta of the outgoing electron and proton didn't add up to that of the neutron either, since neutrons at rest in the lab decayed into protons and electrons that were not seen to be emitted back-to-back; the reaction can also be “crossed” into p+ + e– → n+ (missing energy).

  11. See “Wolfgang Pauli,” http://en.wikipedia.org/wiki/Wolfgang_Pauli. The full letter is in the CERN Pauli Archive, which may be visited online at www.library.cern.ch/archives/pauli/pauliletter.html and is reproduced in our book Symmetry and the Beautiful Universe (Amherst, NY: Prometheus Books, 2007). We thank the CERN Pauli Archive Committee for permission to reproduce it.

  12. It also allows the angular momentum to be conserved if the neutrino has spin 1/2; Enrico Fermi gave the name “neutrino” to the invisible particle in the decay process. Pauli had used the name “neutron” for his new particle, the name we now use for the heavy neutral constituent of the nucleus. You will note that this is a slight variation of the process p+ + e– → n0 +ve, which causes a supernova. The squeezing together of a proton and electron can happen only at the extreme densities inside a massive star collapse. A neutron in free space decays into proton, electron, and neutrino a half-life of about 11 minutes by the related process of “beta decay,” .

  13. Fermi's theory involves an “interaction strength” that is GF. If we use the units in which = c = 1, then we find 175 .

  14. See “Frederick Rei
nes,” http://en.wikipedia.org/wiki/Frederick_Reines and “Clyde Cowan,” http://en.wikipedia.org/wiki/Clyde_Cowan (sites last visited 3/26/2013).

  15. For the Lederman, Schwartz, Steinberger experiment, see chap. 6, note 1. When a third heavy lepton was discovered, the τ, or “tau,” it was quickly realized that there was also a τ-neutrino. Today we know that there are three distinct kinds of neutrinos, electron neutrinos (ve), muon neutrinos (vµ), and tau neutrinos (vτ), each matching their charged lepton counterparts. This zoology of particles is further elaborated in the Appendix. The τ-neutrino was discovered at Fermilab in 2000, in the “DONUT experiment”; see “Tau neutrino,” http://en.wikipedia.org/wiki/Tau_neutrino.

  16. “Clue,” or “Cluedo,” is great preparation for a budding physicist. See http://en.wikipedia.org/wiki/Cluedo (site last visited 3/26/2013).

  17. Lederman and Hill, “Symmetry and the Beautiful Universe,” chap 8, note 2; T. D. Lee and C. N. Yang, “Question of Parity Conservation in Weak Interactions,” Physical Review 104 (1956); J. Bernstein, “Profiles: A Question of Parity,” New Yorker Magazine 38 (1962); M. Gardner, The New Ambidextrous Universe: Symmetry and Asymmetry, from Mirror Reflections to Superstrings (New York: W. H. Freeman and Co., 1991).

  18. Even a complex break shot, where a cue ball scatters the ten pool balls, could in principle occur in a time-reversed way, but it is simply extremely improbable that it could be arranged to occur—this is why complex systems look funny when they run backward in time—the reversed physical processes are allowed, but it would be virtually impossible to set everything in motion to make things happen that way. The evolution of life is such a process—it is governed by the laws of physics, but it happens very slowly over many, many “collisions” of large macromolecules under rare circumstances. Once certain self-replicating macromolecules are formed, the process can build greater complexity through “random selection.”

  19. In physics we always pose, and solve, “if-then” problems. Let's consider the following elementary physics question (Q1): If a particle at time t1 is located at x1 traveling at a velocity, V, then where will the particle be at time t2? The answer is x2 = x1 + V(t2 – t1). But even this simple result illustrates some deep philosophical issues as to how we describe nature.

  Consider now a time-reversed question (Q2): “If at time t1 the particle is located at x2 and traveling with velocity –V (velocities change sign when we reverse the direction of time, as you well know by running a DVD backward and seeing a car driving in reverse down the highway), then where will it be at time t2?” Now the answer, by common sense, must be x1. And indeed, we see, upon a little rearranging, that our previous formula gives us x1 = x2 – V(t2 – t1).

  This is indeed the correct answer for the time-reversed question, yet it came from the original problem's solution after a little rearranging of the math. The answer for the forward-in-time question contains the answer for the backward-in-time question—we get both from one in the same physics equation! Our physical description of this system is the same if time is running forward as when time is running backward. In the second question, Q2, we set up initial conditions that were the opposite to those in the first question, Q1, that is, in Q2 we put the particle at the location, x2, where it ended up in Q1, and we reversed the direction of motion, replacing V by –V. We find that after an equivalent time interval, the particle in Q2 gets to location x1, where it started in Q1. This shows that we can do time-reversed physics without actually reversing the flow of time. We need only reverse the directions of motions and swap the final destinations for the initial one.

  20. The particle K0 and the antiparticle actually oscillate back and forth between one another, K0 ↔ . If CP is an exact symmetry, then the oscillation phase from the K0 into the should be exactly the same as the reverse oscillation phase, from the into the K0. Experimentally, however, it is found that the oscillation phase to go from K0 ↔ is slightly different, at one part in a thousand, than the oscillation phase from ↔ K0. J. H. Christenson, J. W. Cronin, V. L. Fitch, and R. Turlay, “Evidence for the 2π Decay of the K(2)0 Meson,” Physical Review Letters 13 (1964): 138–40. This is not CP invariant. In refined experiments with neutral K-mesons, direct confirmation of the violation of T-symmetry has also been confirmed. The combined symmetry transformation, CPT, is a symmetry of the decays. CP violation is now turning up in other particles, called B-mesons, containing the heavy beauty quark. Search online for “CP violation.”

  CHAPTER 10. NEUTRINOS

  1. See “Supernova” and references therein, http://en.wikipedia.org/wiki/Supernova (site last visited 3/28/13). Or search online for “supernova” for some great images. We are mainly describing Type II supernovae in the text. There are several kinds of supernovae with differing evolutionary processes, as detailed in the article.

  2. See “Galaxy,” http://en.wikipedia.org/wiki/Galaxy (site last visited 3/28/13). Search online for “galaxies” for images.

  3. See “Eta Carinae,” http://en.wikipedia.org/wiki/Eta_carinae (site last visited 3/28/13). Under the heading “Possible Effects on Earth,” “It is possible that the Eta Carinae hypernova or supernova, when it occurs, could affect Earth, which is about 7,500 light years from the star…. a certain few [scientists] claim that radiation damage to the upper atmosphere would have catastrophic effects as well. At least one scientist has claimed that when the star explodes, ‘it would be so bright that you would see it during the day, and you could even read a book by its light at night.’” A supernova or hypernova produced by Eta Carinae would probably eject a gamma ray burst (GRB) out from both polar areas of its rotational axis. Calculations show that the deposited energy of such a GRB striking Earth's atmosphere would be equivalent to one kiloton of TNT per square kilometer over the entire hemisphere facing the star, with ionizing radiation depositing ten times the lethal whole body dose to the surface. This catastrophic burst would probably not hit Earth though, because the rotation axis does not currently point toward our solar system. If Eta Carinae is a binary system, this may affect the future intensity and orientation of the supernova explosion that it produces, depending on the circumstances.

  Our advice is that you hug your children and call your Mom and tell her you love her.

  4. See “Neutrino oscillation,” http://en.wikipedia.org/wiki/Neutrino_oscillation (site last visited 3/28/13).

  5. Recall from chapter 6: The L electron carries a weak charge, and R does not. Weak charge must also be conserved, but the Higgs field has filled the vacuum with a large reservoir of weak charge. So, L can convert to R by dumping its weak charge into the Higgs field reservoir; and R can convert to L by absorbing the weak charge back again out of the Higgs field reservoir, making L. But the Higgs field does not absorb or relinquish electric charge, so the L electron must have the same charge as the R electron; the R positron must have the same charge as the L positron.

  6. See “Ettore Majorana,” http://en.wikipedia.org/wiki/Ettore_Majorana (site last visited 3/26/2013). The term “Majorana particle” is now commonly used but is erroneous, because the particle is actually one with a “Majorana mass.” The term “Majorana particle” was historically reserved for spin-1/2 particles whose wave functions are real, which can only occur in special space-time dimensionalities, like 2, 6, 8, 10, etc.

  7. See “Neutrinoless double-beta decay,” http://en.wikipedia.org/wiki/Double_beta_decay#Neutrinoless_double-beta_decay (site last visited 3/26/2013).

  8. This is called the “neutrino seesaw mechanism,” http://en.wikipedia.org/wiki/Seesaw_mechanism (site last visited 3/26/2013).

  9. See “Leptogenesis (physics),” http://en.wikipedia.org/wiki/Leptogenesis_%28physics%29 (site last visited 3/26/2013). Quoting from the source:

  The Big Bang produced matter and antimatter directly, but in nearly equal amounts. Today, however, we see no antimatter left in the universe. The cosmic annihilation of matter and antimatter should have been almost complete, leaving not nearly enough leftover matter to form the billions o
f stars that we see today, and us. Where did all this matter come from? Or, where did all the antimatter go? The process of leptogenesis could be the answer. Neutrinos are very different from other kinds of matter, and may be the only matter particles that are their own antiparticles. Neutrinos also have very tiny masses which suggests that the origin of neutrino mass involves much shorter-range interactions with hypothesized superheavy neutrinos. This may provide an experimental window to leptogenesis. When theorists rerun the tape of the Big Bang introducing superheavy partner neutrinos with nonstandard CP symmetry, the result is leptogenesis. The heavy neutrinos fall apart into light neutrinos, producing an excess of matter over antimatter. In the hot environment of the early universe, this excess is quickly passed along to all the particles that we are made of. If the theory of leptogenesis is correct, we owe our existence to neutrinos from the big bang.

  10. See “Bruno Pontecorvo,” http://en.wikipedia.org/wiki/Bruno_Pontecorvo (site last visited 3/26/2013).

  11. See “Raymond Davis,” http://en.wikipedia.org/wiki/Raymond_Davis_Jr. and “Homestake experiment,” http://en.wikipedia.org/wiki/Davis_Experiment (sites last visited 3/26/2013).

  12. See “Masatoshi Koshiba,” http://en.wikipedia.org/wiki/Masatoshi_Koshiba (site last visited 3/26/2013).

  13. See “Super-Kamiokande,” http://en.wikipedia.org/wiki/Super_Kamiokande (site last visited 3/26/2013).

  14. “How Does NOnA Work?” http://www-nova.fnal.gov/how-nova-works.html. See “Neutrino oscillation,” http://en.wikipedia.org/wiki/Neutrino_oscillation (sites last visited 3/26/2013). It's important to realize that we did not dig a 500-mile-long tunnel from Fermilab to Soudan, Minnesota—the neutrinos propagate freely and unimpeded through the earth under Wisconsin (Go, Packers!).