Q&As on Higgs search article in Parade magazine
This Sunday, Parade - the 16-page magazine inserted into more than 30 million copies of Sunday newspapers - featured an article on the search for the elusive Higgs boson at the Fermi National Accelerator Laboratory in Illinois. This blog provides links to some background information and a list of Q&As related to the Parade article.
The article's author, Stephen Fried, an adjunct professor at Columbia University Graduate School of Journalism and a writer for national magazines, visited Fermilab in April to interview scientists and take a tour of the laboratory. A few weeks before his visit, Fermilab had announced in a press release its most stringent constraints on the mass of the Higgs particle. Scientists expect that either the Tevatron particle collider at Fermilab or the Large Hadron Collider at the European laboratory CERN will produce a signal for the Higgs particle in the next couple of years.
Fried had the chance to see the LHC Remote Operations Center at Fermilab, where more than 300 people gathered for a pajama party the night of September 9-10 to celebrate and watch via video conference the startup of the LHC accelerator in Europe. He toured the CDF and DZero collider experiments at Fermilab and interviewed Fermilab Director Pier Oddone. He saw the laboratory's Main Control Room and learned about the applications of particle physics technology in medicine and industry.
His article "The Race for the Secret of the Universe" is a superb example of how one can tell an exciting particle physics story in less than 1300 words without skimping on the details.
In response to the Parade article, people have submitted questions to Fermilab. Here are the answers. I'll post more as they come in.
Q: Why is the Higgs boson called "the God particle"?
A: In the early 1990s, Nobel laureate Leon Lederman wrote a book on particle physics and the search for the Higgs boson. According to Lederman, his publisher came up with the title "The God Particle" for the book, hoping it would attract more attention than a conventional particle physics title. Well, it worked. But among scientists, the nickname is frowned upon.
Q: How does a Higgs boson make matter?
A: In addition to a Higgs boson, there is a Higgs field. The field permeates the entire universe. In physics, that concept is nothing unusual. Physicists also know of gravitational fields, electromagnetic fields, etc. The Higgs field gives mass to elementary particles such as electrons and quarks. I like to think of the Higgs field as an invisible fog that fills the universe, and the Higgs bosons are tiny droplets - condensation - in the fog. Elementary particles such as electrons interact with the Higgs field by just being surrounded by it. Different particles interact with the Higgs field with different strength. That's why an electron is much lighter than a top quark.
Q: What is a Higgs boson made of?
A: A Higgs boson does not contain smaller particles, according to our current understanding. Instead, the Higgs boson is the localization of a tiny amount of energy in space. Scientists also call it a resonance. It is a resonance of the Higgs field and it requires a specific amount of energy to be produced. (That's why it is called a resonance.) Albert Einstein discovered that energy and mass are equivalent: E=mc2. Hence energy can produce particles (resonances), and particles can convert back into energy. When a particle collision sets free the right amount of energy, it can produce a Higgs boson. The energy is transformed into the mass of the Higgs boson. But low-energy collisions such as the collisions of molecules in a gas don't have enough energy to produce the Higgs boson. They won't do the trick. Scientists must use high-energy particle accelerators to produce high-energy particle collisions. Scientists think that particle accelerators such as Fermilab's Tevatron and CERN's Large Hadron Collider can produce particle collisions that have enough energy to produce a Higgs particle. Once a Higgs boson is produced, it decays quickly into lighter particles, converting some of its mass back into the mass and kinetic energy of lighter particles.
Q: How small is a Higgs boson?
A: The theoretical framework that accurately describes the behavior of all particles, known as the Standard Model of particles and their interactions, requires elementary particles such as quarks, leptons and bosons to be point-like particles. They have zero diameter. This might seem weird, but after all, these elementary particles do not contain any smaller building blocks. In contrast, composite particles - such as the proton - have a finite, non-zero diameter. In the case of the proton it is 10-15 meters. That is tiny, but it provides plenty of space for the (zero-diameter) quarks inside a proton.
Q: What are leptons and quarks?
A: Scientists know of six quarks and six leptons. They are elementary particles (that means they contain no smaller particles as far as we know). They are the most fundamental building blocks of all matter on Earth. Their names are:
up quark, down quark, strange quark, charm quark, bottom quark, top quark;
electron, electron neutrino, muon, muon neutrino, tau, tau neutrino.
The Standard Model of particles and interactions describes how quarks and leptons interact with each other through the exchange of bosons. For more information, check out the Particle Adventure.
Q: Are quarks and leptons part of an atom?
A: Yes. An atom is made of electrons (which are a type of lepton) and an atomic nucleus made of protons and neutrons. Those protons and neutrons are made of quarks. Hence an atom contains both quarks and leptons. An atom is larger than a proton, and a proton is larger than a quark.
Q: What is the Big Bang theory?
A: Based on the measurements of the motion of stars and galaxies, scientists know that the universe is expanding. Examining the history of the universe and - like an archeologist - discovering older and older galaxies and other cosmic objects and phenomena, scientists found that all matter in the universe came from a single outburst of energy larger than anyone can imagine - the Big Bang. Here is a NASA Web site that explains in more detail what the Big Bang theory is and it lists in great detail all the experimental observations that again and again have confirmed the Big Bang theory. Today's telescopes and measurements are so precise that scientists have determined that the Big Bang occurred 13.7 billion years ago. But what triggered the Big Bang and what was before the Big Bang are unknown.
Q: How is the Higgs boson related to the Big Bang theory?
A: The Big Bang was an enormous outburst of particles and radiation (energy). The Higgs field endowed elementary particles such as quarks and leptons with mass. As the universe expanded and cooled, particles started to clump together, eventually forming simple atoms such as hydrogen and helium. If there were no Higgs field (or something else that gives elementary particles mass), the electron would have no mass and atoms would not form. There would be no chemical bonding, no stable structures, no Earth and no physicists.
Q: Does the Higgs make atoms?
A: No, other forces are responsible for making atoms. But without the Higgs, the electron would have no mass and atoms could not form. Since electrons do have mass, they are slow enough to be captured by atomic nuclei via the electromagnetic force and form atoms.
Q: Could there be more to an atom than many scientists think, or have all possibilities been explored?
A: Science is about making measurements and observations, finding explanations, predicting the outcome of new experiments based on those explanations, and carrying out experiments to test the predictions and, if necessary, make changes to the explanations. Scientists are always looking for new ways to test the makeup and behavior of atoms. So far, experiments again and again have confirmed our current understanding of what an atom is and what it is made. But some day an experiment could, for example, show that electrons - one of the building blocks of all atoms - are made of even smaller building blocks themselves. Then scientists would need to refine the current theory and develop an explanation that explains everything that is already known and the new observation. Developing better experimental tools and designing clever experiments is the only way to find out whether our current explanations are not yet complete.